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ae43cab6ba
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
Alp Toker ae43cab6ba Fix known typos 
Sweep the codebase for common typos. Includes some changes to visible function
names that were misspelt.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200018 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-24 17:20:08 +00:00

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//===- LoopVectorize.cpp - A Loop Vectorizer ------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
// and generates target-independent LLVM-IR.
// The vectorizer uses the TargetTransformInfo analysis to estimate the costs
// of instructions in order to estimate the profitability of vectorization.
//
// The loop vectorizer combines consecutive loop iterations into a single
// 'wide' iteration. After this transformation the index is incremented
// by the SIMD vector width, and not by one.
//
// This pass has three parts:
// 1. The main loop pass that drives the different parts.
// 2. LoopVectorizationLegality - A unit that checks for the legality
// of the vectorization.
// 3. InnerLoopVectorizer - A unit that performs the actual
// widening of instructions.
// 4. LoopVectorizationCostModel - A unit that checks for the profitability
// of vectorization. It decides on the optimal vector width, which
// can be one, if vectorization is not profitable.
//
//===----------------------------------------------------------------------===//
//
// The reduction-variable vectorization is based on the paper:
// D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
//
// Variable uniformity checks are inspired by:
// Karrenberg, R. and Hack, S. Whole Function Vectorization.
//
// Other ideas/concepts are from:
// A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
//
// S. Maleki, Y. Gao, M. Garzaran, T. Wong and D. Padua. An Evaluation of
// Vectorizing Compilers.
//
//===----------------------------------------------------------------------===//
#define LV_NAME "loop-vectorize"
#define DEBUG_TYPE LV_NAME
#include "llvm/Transforms/Vectorize.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopIterator.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/PatternMatch.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <map>
using namespace llvm;
using namespace llvm::PatternMatch;
static cl::opt<unsigned>
VectorizationFactor("force-vector-width", cl::init(0), cl::Hidden,
cl::desc("Sets the SIMD width. Zero is autoselect."));
static cl::opt<unsigned>
VectorizationUnroll("force-vector-unroll", cl::init(0), cl::Hidden,
cl::desc("Sets the vectorization unroll count. "
"Zero is autoselect."));
static cl::opt<bool>
EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden,
cl::desc("Enable if-conversion during vectorization."));
/// We don't vectorize loops with a known constant trip count below this number.
static cl::opt<unsigned>
TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16),
cl::Hidden,
cl::desc("Don't vectorize loops with a constant "
"trip count that is smaller than this "
"value."));
/// This enables versioning on the strides of symbolically striding memory
/// accesses in code like the following.
/// for (i = 0; i < N; ++i)
/// A[i * Stride1] += B[i * Stride2] ...
///
/// Will be roughly translated to
/// if (Stride1 == 1 && Stride2 == 1) {
/// for (i = 0; i < N; i+=4)
/// A[i:i+3] += ...
/// } else
/// ...
static cl::opt<bool> EnableMemAccessVersioning(
"enable-mem-access-versioning", cl::init(true), cl::Hidden,
cl::desc("Enable symblic stride memory access versioning"));
/// We don't unroll loops with a known constant trip count below this number.
static const unsigned TinyTripCountUnrollThreshold = 128;
/// When performing memory disambiguation checks at runtime do not make more
/// than this number of comparisons.
static const unsigned RuntimeMemoryCheckThreshold = 8;
/// Maximum simd width.
static const unsigned MaxVectorWidth = 64;
/// Maximum vectorization unroll count.
static const unsigned MaxUnrollFactor = 16;
/// The cost of a loop that is considered 'small' by the unroller.
static const unsigned SmallLoopCost = 20;
namespace {
// Forward declarations.
class LoopVectorizationLegality;
class LoopVectorizationCostModel;
/// InnerLoopVectorizer vectorizes loops which contain only one basic
/// block to a specified vectorization factor (VF).
/// This class performs the widening of scalars into vectors, or multiple
/// scalars. This class also implements the following features:
/// * It inserts an epilogue loop for handling loops that don't have iteration
/// counts that are known to be a multiple of the vectorization factor.
/// * It handles the code generation for reduction variables.
/// * Scalarization (implementation using scalars) of un-vectorizable
/// instructions.
/// InnerLoopVectorizer does not perform any vectorization-legality
/// checks, and relies on the caller to check for the different legality
/// aspects. The InnerLoopVectorizer relies on the
/// LoopVectorizationLegality class to provide information about the induction
/// and reduction variables that were found to a given vectorization factor.
class InnerLoopVectorizer {
public:
InnerLoopVectorizer(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
DominatorTree *DT, DataLayout *DL,
const TargetLibraryInfo *TLI, unsigned VecWidth,
unsigned UnrollFactor)
: OrigLoop(OrigLoop), SE(SE), LI(LI), DT(DT), DL(DL), TLI(TLI),
VF(VecWidth), UF(UnrollFactor), Builder(SE->getContext()), Induction(0),
OldInduction(0), WidenMap(UnrollFactor), Legal(0) {}
// Perform the actual loop widening (vectorization).
void vectorize(LoopVectorizationLegality *L) {
Legal = L;
// Create a new empty loop. Unlink the old loop and connect the new one.
createEmptyLoop();
// Widen each instruction in the old loop to a new one in the new loop.
// Use the Legality module to find the induction and reduction variables.
vectorizeLoop();
// Register the new loop and update the analysis passes.
updateAnalysis();
}
virtual ~InnerLoopVectorizer() {}
protected:
/// A small list of PHINodes.
typedef SmallVector<PHINode*, 4> PhiVector;
/// When we unroll loops we have multiple vector values for each scalar.
/// This data structure holds the unrolled and vectorized values that
/// originated from one scalar instruction.
typedef SmallVector<Value*, 2> VectorParts;
// When we if-convert we need create edge masks. We have to cache values so
// that we don't end up with exponential recursion/IR.
typedef DenseMap<std::pair<BasicBlock*, BasicBlock*>,
VectorParts> EdgeMaskCache;
/// \brief Add code that checks at runtime if the accessed arrays overlap.
///
/// Returns a pair of instructions where the first element is the first
/// instruction generated in possibly a sequence of instructions and the
/// second value is the final comparator value or NULL if no check is needed.
std::pair<Instruction *, Instruction *> addRuntimeCheck(Instruction *Loc);
/// \brief Add checks for strides that where assumed to be 1.
///
/// Returns the last check instruction and the first check instruction in the
/// pair as (first, last).
std::pair<Instruction *, Instruction *> addStrideCheck(Instruction *Loc);
/// Create an empty loop, based on the loop ranges of the old loop.
void createEmptyLoop();
/// Copy and widen the instructions from the old loop.
virtual void vectorizeLoop();
/// \brief The Loop exit block may have single value PHI nodes where the
/// incoming value is 'Undef'. While vectorizing we only handled real values
/// that were defined inside the loop. Here we fix the 'undef case'.
/// See PR14725.
void fixLCSSAPHIs();
/// A helper function that computes the predicate of the block BB, assuming
/// that the header block of the loop is set to True. It returns the *entry*
/// mask for the block BB.
VectorParts createBlockInMask(BasicBlock *BB);
/// A helper function that computes the predicate of the edge between SRC
/// and DST.
VectorParts createEdgeMask(BasicBlock *Src, BasicBlock *Dst);
/// A helper function to vectorize a single BB within the innermost loop.
void vectorizeBlockInLoop(BasicBlock *BB, PhiVector *PV);
/// Vectorize a single PHINode in a block. This method handles the induction
/// variable canonicalization. It supports both VF = 1 for unrolled loops and
/// arbitrary length vectors.
void widenPHIInstruction(Instruction *PN, VectorParts &Entry,
unsigned UF, unsigned VF, PhiVector *PV);
/// Insert the new loop to the loop hierarchy and pass manager
/// and update the analysis passes.
void updateAnalysis();
/// This instruction is un-vectorizable. Implement it as a sequence
/// of scalars.
virtual void scalarizeInstruction(Instruction *Instr);
/// Vectorize Load and Store instructions,
virtual void vectorizeMemoryInstruction(Instruction *Instr);
/// Create a broadcast instruction. This method generates a broadcast
/// instruction (shuffle) for loop invariant values and for the induction
/// value. If this is the induction variable then we extend it to N, N+1, ...
/// this is needed because each iteration in the loop corresponds to a SIMD
/// element.
virtual Value *getBroadcastInstrs(Value *V);
/// This function adds 0, 1, 2 ... to each vector element, starting at zero.
/// If Negate is set then negative numbers are added e.g. (0, -1, -2, ...).
/// The sequence starts at StartIndex.
virtual Value *getConsecutiveVector(Value* Val, int StartIdx, bool Negate);
/// When we go over instructions in the basic block we rely on previous
/// values within the current basic block or on loop invariant values.
/// When we widen (vectorize) values we place them in the map. If the values
/// are not within the map, they have to be loop invariant, so we simply
/// broadcast them into a vector.
VectorParts &getVectorValue(Value *V);
/// Generate a shuffle sequence that will reverse the vector Vec.
virtual Value *reverseVector(Value *Vec);
/// This is a helper class that holds the vectorizer state. It maps scalar
/// instructions to vector instructions. When the code is 'unrolled' then
/// then a single scalar value is mapped to multiple vector parts. The parts
/// are stored in the VectorPart type.
struct ValueMap {
/// C'tor. UnrollFactor controls the number of vectors ('parts') that
/// are mapped.
ValueMap(unsigned UnrollFactor) : UF(UnrollFactor) {}
/// \return True if 'Key' is saved in the Value Map.
bool has(Value *Key) const { return MapStorage.count(Key); }
/// Initializes a new entry in the map. Sets all of the vector parts to the
/// save value in 'Val'.
/// \return A reference to a vector with splat values.
VectorParts &splat(Value *Key, Value *Val) {
VectorParts &Entry = MapStorage[Key];
Entry.assign(UF, Val);
return Entry;
}
///\return A reference to the value that is stored at 'Key'.
VectorParts &get(Value *Key) {
VectorParts &Entry = MapStorage[Key];
if (Entry.empty())
Entry.resize(UF);
assert(Entry.size() == UF);
return Entry;
}
private:
/// The unroll factor. Each entry in the map stores this number of vector
/// elements.
unsigned UF;
/// Map storage. We use std::map and not DenseMap because insertions to a
/// dense map invalidates its iterators.
std::map<Value *, VectorParts> MapStorage;
};
/// The original loop.
Loop *OrigLoop;
/// Scev analysis to use.
ScalarEvolution *SE;
/// Loop Info.
LoopInfo *LI;
/// Dominator Tree.
DominatorTree *DT;
/// Data Layout.
DataLayout *DL;
/// Target Library Info.
const TargetLibraryInfo *TLI;
/// The vectorization SIMD factor to use. Each vector will have this many
/// vector elements.
unsigned VF;
protected:
/// The vectorization unroll factor to use. Each scalar is vectorized to this
/// many different vector instructions.
unsigned UF;
/// The builder that we use
IRBuilder<> Builder;
// --- Vectorization state ---
/// The vector-loop preheader.
BasicBlock *LoopVectorPreHeader;
/// The scalar-loop preheader.
BasicBlock *LoopScalarPreHeader;
/// Middle Block between the vector and the scalar.
BasicBlock *LoopMiddleBlock;
///The ExitBlock of the scalar loop.
BasicBlock *LoopExitBlock;
///The vector loop body.
BasicBlock *LoopVectorBody;
///The scalar loop body.
BasicBlock *LoopScalarBody;
/// A list of all bypass blocks. The first block is the entry of the loop.
SmallVector<BasicBlock *, 4> LoopBypassBlocks;
/// The new Induction variable which was added to the new block.
PHINode *Induction;
/// The induction variable of the old basic block.
PHINode *OldInduction;
/// Holds the extended (to the widest induction type) start index.
Value *ExtendedIdx;
/// Maps scalars to widened vectors.
ValueMap WidenMap;
EdgeMaskCache MaskCache;
LoopVectorizationLegality *Legal;
};
class InnerLoopUnroller : public InnerLoopVectorizer {
public:
InnerLoopUnroller(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
DominatorTree *DT, DataLayout *DL,
const TargetLibraryInfo *TLI, unsigned UnrollFactor) :
InnerLoopVectorizer(OrigLoop, SE, LI, DT, DL, TLI, 1, UnrollFactor) { }
private:
virtual void scalarizeInstruction(Instruction *Instr);
virtual void vectorizeMemoryInstruction(Instruction *Instr);
virtual Value *getBroadcastInstrs(Value *V);
virtual Value *getConsecutiveVector(Value* Val, int StartIdx, bool Negate);
virtual Value *reverseVector(Value *Vec);
};
/// \brief Look for a meaningful debug location on the instruction or it's
/// operands.
static Instruction *getDebugLocFromInstOrOperands(Instruction *I) {
if (!I)
return I;
DebugLoc Empty;
if (I->getDebugLoc() != Empty)
return I;
for (User::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) {
if (Instruction *OpInst = dyn_cast<Instruction>(*OI))
if (OpInst->getDebugLoc() != Empty)
return OpInst;
}
return I;
}
/// \brief Set the debug location in the builder using the debug location in the
/// instruction.
static void setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr) {
if (const Instruction *Inst = dyn_cast_or_null<Instruction>(Ptr))
B.SetCurrentDebugLocation(Inst->getDebugLoc());
else
B.SetCurrentDebugLocation(DebugLoc());
}
/// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
/// to what vectorization factor.
/// This class does not look at the profitability of vectorization, only the
/// legality. This class has two main kinds of checks:
/// * Memory checks - The code in canVectorizeMemory checks if vectorization
/// will change the order of memory accesses in a way that will change the
/// correctness of the program.
/// * Scalars checks - The code in canVectorizeInstrs and canVectorizeMemory
/// checks for a number of different conditions, such as the availability of a
/// single induction variable, that all types are supported and vectorize-able,
/// etc. This code reflects the capabilities of InnerLoopVectorizer.
/// This class is also used by InnerLoopVectorizer for identifying
/// induction variable and the different reduction variables.
class LoopVectorizationLegality {
public:
LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, DataLayout *DL,
DominatorTree *DT, TargetLibraryInfo *TLI)
: TheLoop(L), SE(SE), DL(DL), DT(DT), TLI(TLI),
Induction(0), WidestIndTy(0), HasFunNoNaNAttr(false),
MaxSafeDepDistBytes(-1U) {}
/// This enum represents the kinds of reductions that we support.
enum ReductionKind {
RK_NoReduction, ///< Not a reduction.
RK_IntegerAdd, ///< Sum of integers.
RK_IntegerMult, ///< Product of integers.
RK_IntegerOr, ///< Bitwise or logical OR of numbers.
RK_IntegerAnd, ///< Bitwise or logical AND of numbers.
RK_IntegerXor, ///< Bitwise or logical XOR of numbers.
RK_IntegerMinMax, ///< Min/max implemented in terms of select(cmp()).
RK_FloatAdd, ///< Sum of floats.
RK_FloatMult, ///< Product of floats.
RK_FloatMinMax ///< Min/max implemented in terms of select(cmp()).
};
/// This enum represents the kinds of inductions that we support.
enum InductionKind {
IK_NoInduction, ///< Not an induction variable.
IK_IntInduction, ///< Integer induction variable. Step = 1.
IK_ReverseIntInduction, ///< Reverse int induction variable. Step = -1.
IK_PtrInduction, ///< Pointer induction var. Step = sizeof(elem).
IK_ReversePtrInduction ///< Reverse ptr indvar. Step = - sizeof(elem).
};
// This enum represents the kind of minmax reduction.
enum MinMaxReductionKind {
MRK_Invalid,
MRK_UIntMin,
MRK_UIntMax,
MRK_SIntMin,
MRK_SIntMax,
MRK_FloatMin,
MRK_FloatMax
};
/// This struct holds information about reduction variables.
struct ReductionDescriptor {
ReductionDescriptor() : StartValue(0), LoopExitInstr(0),
Kind(RK_NoReduction), MinMaxKind(MRK_Invalid) {}
ReductionDescriptor(Value *Start, Instruction *Exit, ReductionKind K,
MinMaxReductionKind MK)
: StartValue(Start), LoopExitInstr(Exit), Kind(K), MinMaxKind(MK) {}
// The starting value of the reduction.
// It does not have to be zero!
TrackingVH<Value> StartValue;
// The instruction who's value is used outside the loop.
Instruction *LoopExitInstr;
// The kind of the reduction.
ReductionKind Kind;
// If this a min/max reduction the kind of reduction.
MinMaxReductionKind MinMaxKind;
};
/// This POD struct holds information about a potential reduction operation.
struct ReductionInstDesc {
ReductionInstDesc(bool IsRedux, Instruction *I) :
IsReduction(IsRedux), PatternLastInst(I), MinMaxKind(MRK_Invalid) {}
ReductionInstDesc(Instruction *I, MinMaxReductionKind K) :
IsReduction(true), PatternLastInst(I), MinMaxKind(K) {}
// Is this instruction a reduction candidate.
bool IsReduction;
// The last instruction in a min/max pattern (select of the select(icmp())
// pattern), or the current reduction instruction otherwise.
Instruction *PatternLastInst;
// If this is a min/max pattern the comparison predicate.
MinMaxReductionKind MinMaxKind;
};
/// This struct holds information about the memory runtime legality
/// check that a group of pointers do not overlap.
struct RuntimePointerCheck {
RuntimePointerCheck() : Need(false) {}
/// Reset the state of the pointer runtime information.
void reset() {
Need = false;
Pointers.clear();
Starts.clear();
Ends.clear();
IsWritePtr.clear();
DependencySetId.clear();
}
/// Insert a pointer and calculate the start and end SCEVs.
void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr,
unsigned DepSetId, ValueToValueMap &Strides);
/// This flag indicates if we need to add the runtime check.
bool Need;
/// Holds the pointers that we need to check.
SmallVector<TrackingVH<Value>, 2> Pointers;
/// Holds the pointer value at the beginning of the loop.
SmallVector<const SCEV*, 2> Starts;
/// Holds the pointer value at the end of the loop.
SmallVector<const SCEV*, 2> Ends;
/// Holds the information if this pointer is used for writing to memory.
SmallVector<bool, 2> IsWritePtr;
/// Holds the id of the set of pointers that could be dependent because of a
/// shared underlying object.
SmallVector<unsigned, 2> DependencySetId;
};
/// A struct for saving information about induction variables.
struct InductionInfo {
InductionInfo(Value *Start, InductionKind K) : StartValue(Start), IK(K) {}
InductionInfo() : StartValue(0), IK(IK_NoInduction) {}
/// Start value.
TrackingVH<Value> StartValue;
/// Induction kind.
InductionKind IK;
};
/// ReductionList contains the reduction descriptors for all
/// of the reductions that were found in the loop.
typedef DenseMap<PHINode*, ReductionDescriptor> ReductionList;
/// InductionList saves induction variables and maps them to the
/// induction descriptor.
typedef MapVector<PHINode*, InductionInfo> InductionList;
/// Returns true if it is legal to vectorize this loop.
/// This does not mean that it is profitable to vectorize this
/// loop, only that it is legal to do so.
bool canVectorize();
/// Returns the Induction variable.
PHINode *getInduction() { return Induction; }
/// Returns the reduction variables found in the loop.
ReductionList *getReductionVars() { return &Reductions; }
/// Returns the induction variables found in the loop.
InductionList *getInductionVars() { return &Inductions; }
/// Returns the widest induction type.
Type *getWidestInductionType() { return WidestIndTy; }
/// Returns True if V is an induction variable in this loop.
bool isInductionVariable(const Value *V);
/// Return true if the block BB needs to be predicated in order for the loop
/// to be vectorized.
bool blockNeedsPredication(BasicBlock *BB);
/// Check if this pointer is consecutive when vectorizing. This happens
/// when the last index of the GEP is the induction variable, or that the
/// pointer itself is an induction variable.
/// This check allows us to vectorize A[idx] into a wide load/store.
/// Returns:
/// 0 - Stride is unknown or non-consecutive.
/// 1 - Address is consecutive.
/// -1 - Address is consecutive, and decreasing.
int isConsecutivePtr(Value *Ptr);
/// Returns true if the value V is uniform within the loop.
bool isUniform(Value *V);
/// Returns true if this instruction will remain scalar after vectorization.
bool isUniformAfterVectorization(Instruction* I) { return Uniforms.count(I); }
/// Returns the information that we collected about runtime memory check.
RuntimePointerCheck *getRuntimePointerCheck() { return &PtrRtCheck; }
/// This function returns the identity element (or neutral element) for
/// the operation K.
static Constant *getReductionIdentity(ReductionKind K, Type *Tp);
unsigned getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
bool hasStride(Value *V) { return StrideSet.count(V); }
bool mustCheckStrides() { return !StrideSet.empty(); }
SmallPtrSet<Value *, 8>::iterator strides_begin() {
return StrideSet.begin();
}
SmallPtrSet<Value *, 8>::iterator strides_end() { return StrideSet.end(); }
private:
/// Check if a single basic block loop is vectorizable.
/// At this point we know that this is a loop with a constant trip count
/// and we only need to check individual instructions.
bool canVectorizeInstrs();
/// When we vectorize loops we may change the order in which
/// we read and write from memory. This method checks if it is
/// legal to vectorize the code, considering only memory constrains.
/// Returns true if the loop is vectorizable
bool canVectorizeMemory();
/// Return true if we can vectorize this loop using the IF-conversion
/// transformation.
bool canVectorizeWithIfConvert();
/// Collect the variables that need to stay uniform after vectorization.
void collectLoopUniforms();
/// Return true if all of the instructions in the block can be speculatively
/// executed. \p SafePtrs is a list of addresses that are known to be legal
/// and we know that we can read from them without segfault.
bool blockCanBePredicated(BasicBlock *BB, SmallPtrSet<Value *, 8>& SafePtrs);
/// Returns True, if 'Phi' is the kind of reduction variable for type
/// 'Kind'. If this is a reduction variable, it adds it to ReductionList.
bool AddReductionVar(PHINode *Phi, ReductionKind Kind);
/// Returns a struct describing if the instruction 'I' can be a reduction
/// variable of type 'Kind'. If the reduction is a min/max pattern of
/// select(icmp()) this function advances the instruction pointer 'I' from the
/// compare instruction to the select instruction and stores this pointer in
/// 'PatternLastInst' member of the returned struct.
ReductionInstDesc isReductionInstr(Instruction *I, ReductionKind Kind,
ReductionInstDesc &Desc);
/// Returns true if the instruction is a Select(ICmp(X, Y), X, Y) instruction
/// pattern corresponding to a min(X, Y) or max(X, Y).
static ReductionInstDesc isMinMaxSelectCmpPattern(Instruction *I,
ReductionInstDesc &Prev);
/// Returns the induction kind of Phi. This function may return NoInduction
/// if the PHI is not an induction variable.
InductionKind isInductionVariable(PHINode *Phi);
/// \brief Collect memory access with loop invariant strides.
///
/// Looks for accesses like "a[i * StrideA]" where "StrideA" is loop
/// invariant.
void collectStridedAcccess(Value *LoadOrStoreInst);
/// The loop that we evaluate.
Loop *TheLoop;
/// Scev analysis.
ScalarEvolution *SE;
/// DataLayout analysis.
DataLayout *DL;
/// Dominators.
DominatorTree *DT;
/// Target Library Info.
TargetLibraryInfo *TLI;
// --- vectorization state --- //
/// Holds the integer induction variable. This is the counter of the
/// loop.
PHINode *Induction;
/// Holds the reduction variables.
ReductionList Reductions;
/// Holds all of the induction variables that we found in the loop.
/// Notice that inductions don't need to start at zero and that induction
/// variables can be pointers.
InductionList Inductions;
/// Holds the widest induction type encountered.
Type *WidestIndTy;
/// Allowed outside users. This holds the reduction
/// vars which can be accessed from outside the loop.
SmallPtrSet<Value*, 4> AllowedExit;
/// This set holds the variables which are known to be uniform after
/// vectorization.
SmallPtrSet<Instruction*, 4> Uniforms;
/// We need to check that all of the pointers in this list are disjoint
/// at runtime.
RuntimePointerCheck PtrRtCheck;
/// Can we assume the absence of NaNs.
bool HasFunNoNaNAttr;
unsigned MaxSafeDepDistBytes;
ValueToValueMap Strides;
SmallPtrSet<Value *, 8> StrideSet;
};
/// LoopVectorizationCostModel - estimates the expected speedups due to
/// vectorization.
/// In many cases vectorization is not profitable. This can happen because of
/// a number of reasons. In this class we mainly attempt to predict the
/// expected speedup/slowdowns due to the supported instruction set. We use the
/// TargetTransformInfo to query the different backends for the cost of
/// different operations.
class LoopVectorizationCostModel {
public:
LoopVectorizationCostModel(Loop *L, ScalarEvolution *SE, LoopInfo *LI,
LoopVectorizationLegality *Legal,
const TargetTransformInfo &TTI,
DataLayout *DL, const TargetLibraryInfo *TLI)
: TheLoop(L), SE(SE), LI(LI), Legal(Legal), TTI(TTI), DL(DL), TLI(TLI) {}
/// Information about vectorization costs
struct VectorizationFactor {
unsigned Width; // Vector width with best cost
unsigned Cost; // Cost of the loop with that width
};
/// \return The most profitable vectorization factor and the cost of that VF.
/// This method checks every power of two up to VF. If UserVF is not ZERO
/// then this vectorization factor will be selected if vectorization is
/// possible.
VectorizationFactor selectVectorizationFactor(bool OptForSize,
unsigned UserVF);
/// \return The size (in bits) of the widest type in the code that
/// needs to be vectorized. We ignore values that remain scalar such as
/// 64 bit loop indices.
unsigned getWidestType();
/// \return The most profitable unroll factor.
/// If UserUF is non-zero then this method finds the best unroll-factor
/// based on register pressure and other parameters.
/// VF and LoopCost are the selected vectorization factor and the cost of the
/// selected VF.
unsigned selectUnrollFactor(bool OptForSize, unsigned UserUF, unsigned VF,
unsigned LoopCost);
/// \brief A struct that represents some properties of the register usage
/// of a loop.
struct RegisterUsage {
/// Holds the number of loop invariant values that are used in the loop.
unsigned LoopInvariantRegs;
/// Holds the maximum number of concurrent live intervals in the loop.
unsigned MaxLocalUsers;
/// Holds the number of instructions in the loop.
unsigned NumInstructions;
};
/// \return information about the register usage of the loop.
RegisterUsage calculateRegisterUsage();
private:
/// Returns the expected execution cost. The unit of the cost does
/// not matter because we use the 'cost' units to compare different
/// vector widths. The cost that is returned is *not* normalized by
/// the factor width.
unsigned expectedCost(unsigned VF);
/// Returns the execution time cost of an instruction for a given vector
/// width. Vector width of one means scalar.
unsigned getInstructionCost(Instruction *I, unsigned VF);
/// A helper function for converting Scalar types to vector types.
/// If the incoming type is void, we return void. If the VF is 1, we return
/// the scalar type.
static Type* ToVectorTy(Type *Scalar, unsigned VF);
/// Returns whether the instruction is a load or store and will be a emitted
/// as a vector operation.
bool isConsecutiveLoadOrStore(Instruction *I);
/// The loop that we evaluate.
Loop *TheLoop;
/// Scev analysis.
ScalarEvolution *SE;
/// Loop Info analysis.
LoopInfo *LI;
/// Vectorization legality.
LoopVectorizationLegality *Legal;
/// Vector target information.
const TargetTransformInfo &TTI;
/// Target data layout information.
DataLayout *DL;
/// Target Library Info.
const TargetLibraryInfo *TLI;
};
/// Utility class for getting and setting loop vectorizer hints in the form
/// of loop metadata.
struct LoopVectorizeHints {
/// Vectorization width.
unsigned Width;
/// Vectorization unroll factor.
unsigned Unroll;
/// Vectorization forced (-1 not selected, 0 force disabled, 1 force enabled)
int Force;
LoopVectorizeHints(const Loop *L, bool DisableUnrolling)
: Width(VectorizationFactor)
, Unroll(DisableUnrolling ? 1 : VectorizationUnroll)
, Force(-1)
, LoopID(L->getLoopID()) {
getHints(L);
// The command line options override any loop metadata except for when
// width == 1 which is used to indicate the loop is already vectorized.
if (VectorizationFactor.getNumOccurrences() > 0 && Width != 1)
Width = VectorizationFactor;
if (VectorizationUnroll.getNumOccurrences() > 0)
Unroll = VectorizationUnroll;
DEBUG(if (DisableUnrolling && Unroll == 1)
dbgs() << "LV: Unrolling disabled by the pass manager\n");
}
/// Return the loop vectorizer metadata prefix.
static StringRef Prefix() { return "llvm.vectorizer."; }
MDNode *createHint(LLVMContext &Context, StringRef Name, unsigned V) {
SmallVector<Value*, 2> Vals;
Vals.push_back(MDString::get(Context, Name));
Vals.push_back(ConstantInt::get(Type::getInt32Ty(Context), V));
return MDNode::get(Context, Vals);
}
/// Mark the loop L as already vectorized by setting the width to 1.
void setAlreadyVectorized(Loop *L) {
LLVMContext &Context = L->getHeader()->getContext();
Width = 1;
// Create a new loop id with one more operand for the already_vectorized
// hint. If the loop already has a loop id then copy the existing operands.
SmallVector<Value*, 4> Vals(1);
if (LoopID)
for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i)
Vals.push_back(LoopID->getOperand(i));
Vals.push_back(createHint(Context, Twine(Prefix(), "width").str(), Width));
Vals.push_back(createHint(Context, Twine(Prefix(), "unroll").str(), 1));
MDNode *NewLoopID = MDNode::get(Context, Vals);
// Set operand 0 to refer to the loop id itself.
NewLoopID->replaceOperandWith(0, NewLoopID);
L->setLoopID(NewLoopID);
if (LoopID)
LoopID->replaceAllUsesWith(NewLoopID);
LoopID = NewLoopID;
}
private:
MDNode *LoopID;
/// Find hints specified in the loop metadata.
void getHints(const Loop *L) {
if (!LoopID)
return;
// First operand should refer to the loop id itself.
assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
const MDString *S = 0;
SmallVector<Value*, 4> Args;
// The expected hint is either a MDString or a MDNode with the first
// operand a MDString.
if (const MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i))) {
if (!MD || MD->getNumOperands() == 0)
continue;
S = dyn_cast<MDString>(MD->getOperand(0));
for (unsigned i = 1, ie = MD->getNumOperands(); i < ie; ++i)
Args.push_back(MD->getOperand(i));
} else {
S = dyn_cast<MDString>(LoopID->getOperand(i));
assert(Args.size() == 0 && "too many arguments for MDString");
}
if (!S)
continue;
// Check if the hint starts with the vectorizer prefix.
StringRef Hint = S->getString();
if (!Hint.startswith(Prefix()))
continue;
// Remove the prefix.
Hint = Hint.substr(Prefix().size(), StringRef::npos);
if (Args.size() == 1)
getHint(Hint, Args[0]);
}
}
// Check string hint with one operand.
void getHint(StringRef Hint, Value *Arg) {
const ConstantInt *C = dyn_cast<ConstantInt>(Arg);
if (!C) return;
unsigned Val = C->getZExtValue();
if (Hint == "width") {
if (isPowerOf2_32(Val) && Val <= MaxVectorWidth)
Width = Val;
else
DEBUG(dbgs() << "LV: ignoring invalid width hint metadata\n");
} else if (Hint == "unroll") {
if (isPowerOf2_32(Val) && Val <= MaxUnrollFactor)
Unroll = Val;
else
DEBUG(dbgs() << "LV: ignoring invalid unroll hint metadata\n");
} else if (Hint == "enable") {
if (C->getBitWidth() == 1)
Force = Val;
else
DEBUG(dbgs() << "LV: ignoring invalid enable hint metadata\n");
} else {
DEBUG(dbgs() << "LV: ignoring unknown hint " << Hint << '\n');
}
}
};
/// The LoopVectorize Pass.
struct LoopVectorize : public LoopPass {
/// Pass identification, replacement for typeid
static char ID;
explicit LoopVectorize(bool NoUnrolling = false, bool AlwaysVectorize = true)
: LoopPass(ID),
DisableUnrolling(NoUnrolling),
AlwaysVectorize(AlwaysVectorize) {
initializeLoopVectorizePass(*PassRegistry::getPassRegistry());
}
ScalarEvolution *SE;
DataLayout *DL;
LoopInfo *LI;
TargetTransformInfo *TTI;
DominatorTree *DT;
TargetLibraryInfo *TLI;
bool DisableUnrolling;
bool AlwaysVectorize;
virtual bool runOnLoop(Loop *L, LPPassManager &LPM) {
// We only vectorize innermost loops.
if (!L->empty())
return false;
SE = &getAnalysis<ScalarEvolution>();
DL = getAnalysisIfAvailable<DataLayout>();
LI = &getAnalysis<LoopInfo>();
TTI = &getAnalysis<TargetTransformInfo>();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
// If the target claims to have no vector registers don't attempt
// vectorization.
if (!TTI->getNumberOfRegisters(true))
return false;
if (DL == NULL) {
DEBUG(dbgs() << "LV: Not vectorizing: Missing data layout\n");
return false;
}
DEBUG(dbgs() << "LV: Checking a loop in \"" <<
L->getHeader()->getParent()->getName() << "\"\n");
LoopVectorizeHints Hints(L, DisableUnrolling);
if (Hints.Force == 0) {
DEBUG(dbgs() << "LV: Not vectorizing: #pragma vectorize disable.\n");
return false;
}
if (!AlwaysVectorize && Hints.Force != 1) {
DEBUG(dbgs() << "LV: Not vectorizing: No #pragma vectorize enable.\n");
return false;
}
if (Hints.Width == 1 && Hints.Unroll == 1) {
DEBUG(dbgs() << "LV: Not vectorizing: Disabled/already vectorized.\n");
return false;
}
// Check if it is legal to vectorize the loop.
LoopVectorizationLegality LVL(L, SE, DL, DT, TLI);
if (!LVL.canVectorize()) {
DEBUG(dbgs() << "LV: Not vectorizing: Cannot prove legality.\n");
return false;
}
// Use the cost model.
LoopVectorizationCostModel CM(L, SE, LI, &LVL, *TTI, DL, TLI);
// Check the function attributes to find out if this function should be
// optimized for size.
Function *F = L->getHeader()->getParent();
Attribute::AttrKind SzAttr = Attribute::OptimizeForSize;
Attribute::AttrKind FlAttr = Attribute::NoImplicitFloat;
unsigned FnIndex = AttributeSet::FunctionIndex;
bool OptForSize = Hints.Force != 1 &&
F->getAttributes().hasAttribute(FnIndex, SzAttr);
bool NoFloat = F->getAttributes().hasAttribute(FnIndex, FlAttr);
if (NoFloat) {
DEBUG(dbgs() << "LV: Can't vectorize when the NoImplicitFloat"
"attribute is used.\n");
return false;
}
// Select the optimal vectorization factor.
LoopVectorizationCostModel::VectorizationFactor VF;
VF = CM.selectVectorizationFactor(OptForSize, Hints.Width);
// Select the unroll factor.
unsigned UF = CM.selectUnrollFactor(OptForSize, Hints.Unroll, VF.Width,
VF.Cost);
DEBUG(dbgs() << "LV: Found a vectorizable loop ("<< VF.Width << ") in "<<
F->getParent()->getModuleIdentifier() << '\n');
DEBUG(dbgs() << "LV: Unroll Factor is " << UF << '\n');
if (VF.Width == 1) {
DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
if (UF == 1)
return false;
DEBUG(dbgs() << "LV: Trying to at least unroll the loops.\n");
// We decided not to vectorize, but we may want to unroll.
InnerLoopUnroller Unroller(L, SE, LI, DT, DL, TLI, UF);
Unroller.vectorize(&LVL);
} else {
// If we decided that it is *legal* to vectorize the loop then do it.
InnerLoopVectorizer LB(L, SE, LI, DT, DL, TLI, VF.Width, UF);
LB.vectorize(&LVL);
}
// Mark the loop as already vectorized to avoid vectorizing again.
Hints.setAlreadyVectorized(L);
DEBUG(verifyFunction(*L->getHeader()->getParent()));
return true;
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
LoopPass::getAnalysisUsage(AU);
AU.addRequiredID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfo>();
AU.addRequired<ScalarEvolution>();
AU.addRequired<TargetTransformInfo>();
AU.addPreserved<LoopInfo>();
AU.addPreserved<DominatorTreeWrapperPass>();
}
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Implementation of LoopVectorizationLegality, InnerLoopVectorizer and
// LoopVectorizationCostModel.
//===----------------------------------------------------------------------===//
static Value *stripIntegerCast(Value *V) {
if (CastInst *CI = dyn_cast<CastInst>(V))
if (CI->getOperand(0)->getType()->isIntegerTy())
return CI->getOperand(0);
return V;
}
///\brief Replaces the symbolic stride in a pointer SCEV expression by one.
///
/// If \p OrigPtr is not null, use it to look up the stride value instead of
/// \p Ptr.
static const SCEV *replaceSymbolicStrideSCEV(ScalarEvolution *SE,
ValueToValueMap &PtrToStride,
Value *Ptr, Value *OrigPtr = 0) {
const SCEV *OrigSCEV = SE->getSCEV(Ptr);
// If there is an entry in the map return the SCEV of the pointer with the
// symbolic stride replaced by one.
ValueToValueMap::iterator SI = PtrToStride.find(OrigPtr ? OrigPtr : Ptr);
if (SI != PtrToStride.end()) {
Value *StrideVal = SI->second;
// Strip casts.
StrideVal = stripIntegerCast(StrideVal);
// Replace symbolic stride by one.
Value *One = ConstantInt::get(StrideVal->getType(), 1);
ValueToValueMap RewriteMap;
RewriteMap[StrideVal] = One;
const SCEV *ByOne =
SCEVParameterRewriter::rewrite(OrigSCEV, *SE, RewriteMap, true);
DEBUG(dbgs() << "LV: Replacing SCEV: " << *OrigSCEV << " by: " << *ByOne
<< "\n");
return ByOne;
}
// Otherwise, just return the SCEV of the original pointer.
return SE->getSCEV(Ptr);
}
void LoopVectorizationLegality::RuntimePointerCheck::insert(
ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr, unsigned DepSetId,
ValueToValueMap &Strides) {
// Get the stride replaced scev.
const SCEV *Sc = replaceSymbolicStrideSCEV(SE, Strides, Ptr);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Sc);
assert(AR && "Invalid addrec expression");
const SCEV *Ex = SE->getBackedgeTakenCount(Lp);
const SCEV *ScEnd = AR->evaluateAtIteration(Ex, *SE);
Pointers.push_back(Ptr);
Starts.push_back(AR->getStart());
Ends.push_back(ScEnd);
IsWritePtr.push_back(WritePtr);
DependencySetId.push_back(DepSetId);
}
Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
// We need to place the broadcast of invariant variables outside the loop.
Instruction *Instr = dyn_cast<Instruction>(V);
bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
// Place the code for broadcasting invariant variables in the new preheader.
IRBuilder<>::InsertPointGuard Guard(Builder);
if (Invariant)
Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
// Broadcast the scalar into all locations in the vector.
Value *Shuf = Builder.CreateVectorSplat(VF, V, "broadcast");
return Shuf;
}
Value *InnerLoopVectorizer::getConsecutiveVector(Value* Val, int StartIdx,
bool Negate) {
assert(Val->getType()->isVectorTy() && "Must be a vector");
assert(Val->getType()->getScalarType()->isIntegerTy() &&
"Elem must be an integer");
// Create the types.
Type *ITy = Val->getType()->getScalarType();
VectorType *Ty = cast<VectorType>(Val->getType());
int VLen = Ty->getNumElements();
SmallVector<Constant*, 8> Indices;
// Create a vector of consecutive numbers from zero to VF.
for (int i = 0; i < VLen; ++i) {
int64_t Idx = Negate ? (-i) : i;
Indices.push_back(ConstantInt::get(ITy, StartIdx + Idx, Negate));
}
// Add the consecutive indices to the vector value.
Constant *Cv = ConstantVector::get(Indices);
assert(Cv->getType() == Val->getType() && "Invalid consecutive vec");
return Builder.CreateAdd(Val, Cv, "induction");
}
/// \brief Find the operand of the GEP that should be checked for consecutive
/// stores. This ignores trailing indices that have no effect on the final
/// pointer.
static unsigned getGEPInductionOperand(DataLayout *DL,
const GetElementPtrInst *Gep) {
unsigned LastOperand = Gep->getNumOperands() - 1;
unsigned GEPAllocSize = DL->getTypeAllocSize(
cast<PointerType>(Gep->getType()->getScalarType())->getElementType());
// Walk backwards and try to peel off zeros.
while (LastOperand > 1 && match(Gep->getOperand(LastOperand), m_Zero())) {
// Find the type we're currently indexing into.
gep_type_iterator GEPTI = gep_type_begin(Gep);
std::advance(GEPTI, LastOperand - 1);
// If it's a type with the same allocation size as the result of the GEP we
// can peel off the zero index.
if (DL->getTypeAllocSize(*GEPTI) != GEPAllocSize)
break;
--LastOperand;
}
return LastOperand;
}
int LoopVectorizationLegality::isConsecutivePtr(Value *Ptr) {
assert(Ptr->getType()->isPointerTy() && "Unexpected non-ptr");
// Make sure that the pointer does not point to structs.
if (Ptr->getType()->getPointerElementType()->isAggregateType())
return 0;
// If this value is a pointer induction variable we know it is consecutive.
PHINode *Phi = dyn_cast_or_null<PHINode>(Ptr);
if (Phi && Inductions.count(Phi)) {
InductionInfo II = Inductions[Phi];
if (IK_PtrInduction == II.IK)
return 1;
else if (IK_ReversePtrInduction == II.IK)
return -1;
}
GetElementPtrInst *Gep = dyn_cast_or_null<GetElementPtrInst>(Ptr);
if (!Gep)
return 0;
unsigned NumOperands = Gep->getNumOperands();
Value *GpPtr = Gep->getPointerOperand();
// If this GEP value is a consecutive pointer induction variable and all of
// the indices are constant then we know it is consecutive. We can
Phi = dyn_cast<PHINode>(GpPtr);
if (Phi && Inductions.count(Phi)) {
// Make sure that the pointer does not point to structs.
PointerType *GepPtrType = cast<PointerType>(GpPtr->getType());
if (GepPtrType->getElementType()->isAggregateType())
return 0;
// Make sure that all of the index operands are loop invariant.
for (unsigned i = 1; i < NumOperands; ++i)
if (!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
return 0;
InductionInfo II = Inductions[Phi];
if (IK_PtrInduction == II.IK)
return 1;
else if (IK_ReversePtrInduction == II.IK)
return -1;
}
unsigned InductionOperand = getGEPInductionOperand(DL, Gep);
// Check that all of the gep indices are uniform except for our induction
// operand.
for (unsigned i = 0; i != NumOperands; ++i)
if (i != InductionOperand &&
!SE->isLoopInvariant(SE->getSCEV(Gep->getOperand(i)), TheLoop))
return 0;
// We can emit wide load/stores only if the last non-zero index is the
// induction variable.
const SCEV *Last = 0;
if (!Strides.count(Gep))
Last = SE->getSCEV(Gep->getOperand(InductionOperand));
else {
// Because of the multiplication by a stride we can have a s/zext cast.
// We are going to replace this stride by 1 so the cast is safe to ignore.
//
// %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
// %0 = trunc i64 %indvars.iv to i32
// %mul = mul i32 %0, %Stride1
// %idxprom = zext i32 %mul to i64 << Safe cast.
// %arrayidx = getelementptr inbounds i32* %B, i64 %idxprom
//
Last = replaceSymbolicStrideSCEV(SE, Strides,
Gep->getOperand(InductionOperand), Gep);
if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(Last))
Last =
(C->getSCEVType() == scSignExtend || C->getSCEVType() == scZeroExtend)
? C->getOperand()
: Last;
}
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Last)) {
const SCEV *Step = AR->getStepRecurrence(*SE);
// The memory is consecutive because the last index is consecutive
// and all other indices are loop invariant.
if (Step->isOne())
return 1;
if (Step->isAllOnesValue())
return -1;
}
return 0;
}
bool LoopVectorizationLegality::isUniform(Value *V) {
return (SE->isLoopInvariant(SE->getSCEV(V), TheLoop));
}
InnerLoopVectorizer::VectorParts&
InnerLoopVectorizer::getVectorValue(Value *V) {
assert(V != Induction && "The new induction variable should not be used.");
assert(!V->getType()->isVectorTy() && "Can't widen a vector");
// If we have a stride that is replaced by one, do it here.
if (Legal->hasStride(V))
V = ConstantInt::get(V->getType(), 1);
// If we have this scalar in the map, return it.
if (WidenMap.has(V))
return WidenMap.get(V);
// If this scalar is unknown, assume that it is a constant or that it is
// loop invariant. Broadcast V and save the value for future uses.
Value *B = getBroadcastInstrs(V);
return WidenMap.splat(V, B);
}
Value *InnerLoopVectorizer::reverseVector(Value *Vec) {
assert(Vec->getType()->isVectorTy() && "Invalid type");
SmallVector<Constant*, 8> ShuffleMask;
for (unsigned i = 0; i < VF; ++i)
ShuffleMask.push_back(Builder.getInt32(VF - i - 1));
return Builder.CreateShuffleVector(Vec, UndefValue::get(Vec->getType()),
ConstantVector::get(ShuffleMask),
"reverse");
}
void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr) {
// Attempt to issue a wide load.
LoadInst *LI = dyn_cast<LoadInst>(Instr);
StoreInst *SI = dyn_cast<StoreInst>(Instr);
assert((LI || SI) && "Invalid Load/Store instruction");
Type *ScalarDataTy = LI ? LI->getType() : SI->getValueOperand()->getType();
Type *DataTy = VectorType::get(ScalarDataTy, VF);
Value *Ptr = LI ? LI->getPointerOperand() : SI->getPointerOperand();
unsigned Alignment = LI ? LI->getAlignment() : SI->getAlignment();
// An alignment of 0 means target abi alignment. We need to use the scalar's
// target abi alignment in such a case.
if (!Alignment)
Alignment = DL->getABITypeAlignment(ScalarDataTy);
unsigned AddressSpace = Ptr->getType()->getPointerAddressSpace();
unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ScalarDataTy);
unsigned VectorElementSize = DL->getTypeStoreSize(DataTy)/VF;
if (ScalarAllocatedSize != VectorElementSize)
return scalarizeInstruction(Instr);
// If the pointer is loop invariant or if it is non-consecutive,
// scalarize the load.
int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
bool Reverse = ConsecutiveStride < 0;
bool UniformLoad = LI && Legal->isUniform(Ptr);
if (!ConsecutiveStride || UniformLoad)
return scalarizeInstruction(Instr);
Constant *Zero = Builder.getInt32(0);
VectorParts &Entry = WidenMap.get(Instr);
// Handle consecutive loads/stores.
GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
if (Gep && Legal->isInductionVariable(Gep->getPointerOperand())) {
setDebugLocFromInst(Builder, Gep);
Value *PtrOperand = Gep->getPointerOperand();
Value *FirstBasePtr = getVectorValue(PtrOperand)[0];
FirstBasePtr = Builder.CreateExtractElement(FirstBasePtr, Zero);
// Create the new GEP with the new induction variable.
GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
Gep2->setOperand(0, FirstBasePtr);
Gep2->setName("gep.indvar.base");
Ptr = Builder.Insert(Gep2);
} else if (Gep) {
setDebugLocFromInst(Builder, Gep);
assert(SE->isLoopInvariant(SE->getSCEV(Gep->getPointerOperand()),
OrigLoop) && "Base ptr must be invariant");
// The last index does not have to be the induction. It can be
// consecutive and be a function of the index. For example A[I+1];
unsigned NumOperands = Gep->getNumOperands();
unsigned InductionOperand = getGEPInductionOperand(DL, Gep);
// Create the new GEP with the new induction variable.
GetElementPtrInst *Gep2 = cast<GetElementPtrInst>(Gep->clone());
for (unsigned i = 0; i < NumOperands; ++i) {
Value *GepOperand = Gep->getOperand(i);
Instruction *GepOperandInst = dyn_cast<Instruction>(GepOperand);
// Update last index or loop invariant instruction anchored in loop.
if (i == InductionOperand ||
(GepOperandInst && OrigLoop->contains(GepOperandInst))) {
assert((i == InductionOperand ||
SE->isLoopInvariant(SE->getSCEV(GepOperandInst), OrigLoop)) &&
"Must be last index or loop invariant");
VectorParts &GEPParts = getVectorValue(GepOperand);
Value *Index = GEPParts[0];
Index = Builder.CreateExtractElement(Index, Zero);
Gep2->setOperand(i, Index);
Gep2->setName("gep.indvar.idx");
}
}
Ptr = Builder.Insert(Gep2);
} else {
// Use the induction element ptr.
assert(isa<PHINode>(Ptr) && "Invalid induction ptr");
setDebugLocFromInst(Builder, Ptr);
VectorParts &PtrVal = getVectorValue(Ptr);
Ptr = Builder.CreateExtractElement(PtrVal[0], Zero);
}
// Handle Stores:
if (SI) {
assert(!Legal->isUniform(SI->getPointerOperand()) &&
"We do not allow storing to uniform addresses");
setDebugLocFromInst(Builder, SI);
// We don't want to update the value in the map as it might be used in
// another expression. So don't use a reference type for "StoredVal".
VectorParts StoredVal = getVectorValue(SI->getValueOperand());
for (unsigned Part = 0; Part < UF; ++Part) {
// Calculate the pointer for the specific unroll-part.
Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
if (Reverse) {
// If we store to reverse consecutive memory locations then we need
// to reverse the order of elements in the stored value.
StoredVal[Part] = reverseVector(StoredVal[Part]);
// If the address is consecutive but reversed, then the
// wide store needs to start at the last vector element.
PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
}
Value *VecPtr = Builder.CreateBitCast(PartPtr,
DataTy->getPointerTo(AddressSpace));
Builder.CreateStore(StoredVal[Part], VecPtr)->setAlignment(Alignment);
}
return;
}
// Handle loads.
assert(LI && "Must have a load instruction");
setDebugLocFromInst(Builder, LI);
for (unsigned Part = 0; Part < UF; ++Part) {
// Calculate the pointer for the specific unroll-part.
Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
if (Reverse) {
// If the address is consecutive but reversed, then the
// wide store needs to start at the last vector element.
PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
}
Value *VecPtr = Builder.CreateBitCast(PartPtr,
DataTy->getPointerTo(AddressSpace));
Value *LI = Builder.CreateLoad(VecPtr, "wide.load");
cast<LoadInst>(LI)->setAlignment(Alignment);
Entry[Part] = Reverse ? reverseVector(LI) : LI;
}
}
void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr) {
assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
// Holds vector parameters or scalars, in case of uniform vals.
SmallVector<VectorParts, 4> Params;
setDebugLocFromInst(Builder, Instr);
// Find all of the vectorized parameters.
for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
Value *SrcOp = Instr->getOperand(op);
// If we are accessing the old induction variable, use the new one.
if (SrcOp == OldInduction) {
Params.push_back(getVectorValue(SrcOp));
continue;
}
// Try using previously calculated values.
Instruction *SrcInst = dyn_cast<Instruction>(SrcOp);
// If the src is an instruction that appeared earlier in the basic block
// then it should already be vectorized.
if (SrcInst && OrigLoop->contains(SrcInst)) {
assert(WidenMap.has(SrcInst) && "Source operand is unavailable");
// The parameter is a vector value from earlier.
Params.push_back(WidenMap.get(SrcInst));
} else {
// The parameter is a scalar from outside the loop. Maybe even a constant.
VectorParts Scalars;
Scalars.append(UF, SrcOp);
Params.push_back(Scalars);
}
}
assert(Params.size() == Instr->getNumOperands() &&
"Invalid number of operands");
// Does this instruction return a value ?
bool IsVoidRetTy = Instr->getType()->isVoidTy();
Value *UndefVec = IsVoidRetTy ? 0 :
UndefValue::get(VectorType::get(Instr->getType(), VF));
// Create a new entry in the WidenMap and initialize it to Undef or Null.
VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
// For each vector unroll 'part':
for (unsigned Part = 0; Part < UF; ++Part) {
// For each scalar that we create:
for (unsigned Width = 0; Width < VF; ++Width) {
Instruction *Cloned = Instr->clone();
if (!IsVoidRetTy)
Cloned->setName(Instr->getName() + ".cloned");
// Replace the operands of the cloned instructions with extracted scalars.
for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
Value *Op = Params[op][Part];
// Param is a vector. Need to extract the right lane.
if (Op->getType()->isVectorTy())
Op = Builder.CreateExtractElement(Op, Builder.getInt32(Width));
Cloned->setOperand(op, Op);
}
// Place the cloned scalar in the new loop.
Builder.Insert(Cloned);
// If the original scalar returns a value we need to place it in a vector
// so that future users will be able to use it.
if (!IsVoidRetTy)
VecResults[Part] = Builder.CreateInsertElement(VecResults[Part], Cloned,
Builder.getInt32(Width));
}
}
}
static Instruction *getFirstInst(Instruction *FirstInst, Value *V,
Instruction *Loc) {
if (FirstInst)
return FirstInst;
if (Instruction *I = dyn_cast<Instruction>(V))
return I->getParent() == Loc->getParent() ? I : 0;
return 0;
}
std::pair<Instruction *, Instruction *>
InnerLoopVectorizer::addStrideCheck(Instruction *Loc) {
Instruction *tnullptr = 0;
if (!Legal->mustCheckStrides())
return std::pair<Instruction *, Instruction *>(tnullptr, tnullptr);
IRBuilder<> ChkBuilder(Loc);
// Emit checks.
Value *Check = 0;
Instruction *FirstInst = 0;
for (SmallPtrSet<Value *, 8>::iterator SI = Legal->strides_begin(),
SE = Legal->strides_end();
SI != SE; ++SI) {
Value *Ptr = stripIntegerCast(*SI);
Value *C = ChkBuilder.CreateICmpNE(Ptr, ConstantInt::get(Ptr->getType(), 1),
"stride.chk");
// Store the first instruction we create.
FirstInst = getFirstInst(FirstInst, C, Loc);
if (Check)
Check = ChkBuilder.CreateOr(Check, C);
else
Check = C;
}
// We have to do this trickery because the IRBuilder might fold the check to a
// constant expression in which case there is no Instruction anchored in a
// the block.
LLVMContext &Ctx = Loc->getContext();
Instruction *TheCheck =
BinaryOperator::CreateAnd(Check, ConstantInt::getTrue(Ctx));
ChkBuilder.Insert(TheCheck, "stride.not.one");
FirstInst = getFirstInst(FirstInst, TheCheck, Loc);
return std::make_pair(FirstInst, TheCheck);
}
std::pair<Instruction *, Instruction *>
InnerLoopVectorizer::addRuntimeCheck(Instruction *Loc) {
LoopVectorizationLegality::RuntimePointerCheck *PtrRtCheck =
Legal->getRuntimePointerCheck();
Instruction *tnullptr = 0;
if (!PtrRtCheck->Need)
return std::pair<Instruction *, Instruction *>(tnullptr, tnullptr);
unsigned NumPointers = PtrRtCheck->Pointers.size();
SmallVector<TrackingVH<Value> , 2> Starts;
SmallVector<TrackingVH<Value> , 2> Ends;
LLVMContext &Ctx = Loc->getContext();
SCEVExpander Exp(*SE, "induction");
Instruction *FirstInst = 0;
for (unsigned i = 0; i < NumPointers; ++i) {
Value *Ptr = PtrRtCheck->Pointers[i];
const SCEV *Sc = SE->getSCEV(Ptr);
if (SE->isLoopInvariant(Sc, OrigLoop)) {
DEBUG(dbgs() << "LV: Adding RT check for a loop invariant ptr:" <<
*Ptr <<"\n");
Starts.push_back(Ptr);
Ends.push_back(Ptr);
} else {
DEBUG(dbgs() << "LV: Adding RT check for range:" << *Ptr << '\n');
unsigned AS = Ptr->getType()->getPointerAddressSpace();
// Use this type for pointer arithmetic.
Type *PtrArithTy = Type::getInt8PtrTy(Ctx, AS);
Value *Start = Exp.expandCodeFor(PtrRtCheck->Starts[i], PtrArithTy, Loc);
Value *End = Exp.expandCodeFor(PtrRtCheck->Ends[i], PtrArithTy, Loc);
Starts.push_back(Start);
Ends.push_back(End);
}
}
IRBuilder<> ChkBuilder(Loc);
// Our instructions might fold to a constant.
Value *MemoryRuntimeCheck = 0;
for (unsigned i = 0; i < NumPointers; ++i) {
for (unsigned j = i+1; j < NumPointers; ++j) {
// No need to check if two readonly pointers intersect.
if (!PtrRtCheck->IsWritePtr[i] && !PtrRtCheck->IsWritePtr[j])
continue;
// Only need to check pointers between two different dependency sets.
if (PtrRtCheck->DependencySetId[i] == PtrRtCheck->DependencySetId[j])
continue;
unsigned AS0 = Starts[i]->getType()->getPointerAddressSpace();
unsigned AS1 = Starts[j]->getType()->getPointerAddressSpace();
assert((AS0 == Ends[j]->getType()->getPointerAddressSpace()) &&
(AS1 == Ends[i]->getType()->getPointerAddressSpace()) &&
"Trying to bounds check pointers with different address spaces");
Type *PtrArithTy0 = Type::getInt8PtrTy(Ctx, AS0);
Type *PtrArithTy1 = Type::getInt8PtrTy(Ctx, AS1);
Value *Start0 = ChkBuilder.CreateBitCast(Starts[i], PtrArithTy0, "bc");
Value *Start1 = ChkBuilder.CreateBitCast(Starts[j], PtrArithTy1, "bc");
Value *End0 = ChkBuilder.CreateBitCast(Ends[i], PtrArithTy1, "bc");
Value *End1 = ChkBuilder.CreateBitCast(Ends[j], PtrArithTy0, "bc");
Value *Cmp0 = ChkBuilder.CreateICmpULE(Start0, End1, "bound0");
FirstInst = getFirstInst(FirstInst, Cmp0, Loc);
Value *Cmp1 = ChkBuilder.CreateICmpULE(Start1, End0, "bound1");
FirstInst = getFirstInst(FirstInst, Cmp1, Loc);
Value *IsConflict = ChkBuilder.CreateAnd(Cmp0, Cmp1, "found.conflict");
FirstInst = getFirstInst(FirstInst, IsConflict, Loc);
if (MemoryRuntimeCheck) {
IsConflict = ChkBuilder.CreateOr(MemoryRuntimeCheck, IsConflict,
"conflict.rdx");
FirstInst = getFirstInst(FirstInst, IsConflict, Loc);
}
MemoryRuntimeCheck = IsConflict;
}
}
// We have to do this trickery because the IRBuilder might fold the check to a
// constant expression in which case there is no Instruction anchored in a
// the block.
Instruction *Check = BinaryOperator::CreateAnd(MemoryRuntimeCheck,
ConstantInt::getTrue(Ctx));
ChkBuilder.Insert(Check, "memcheck.conflict");
FirstInst = getFirstInst(FirstInst, Check, Loc);
return std::make_pair(FirstInst, Check);
}
void InnerLoopVectorizer::createEmptyLoop() {
/*
In this function we generate a new loop. The new loop will contain
the vectorized instructions while the old loop will continue to run the
scalar remainder.
[ ] <-- vector loop bypass (may consist of multiple blocks).
/ |
/ v
| [ ] <-- vector pre header.
| |
| v
| [ ] \
| [ ]_| <-- vector loop.
| |
\ v
>[ ] <--- middle-block.
/ |
/ v
| [ ] <--- new preheader.
| |
| v
| [ ] \
| [ ]_| <-- old scalar loop to handle remainder.
\ |
\ v
>[ ] <-- exit block.
...
*/
BasicBlock *OldBasicBlock = OrigLoop->getHeader();
BasicBlock *BypassBlock = OrigLoop->getLoopPreheader();
BasicBlock *ExitBlock = OrigLoop->getExitBlock();
assert(ExitBlock && "Must have an exit block");
// Some loops have a single integer induction variable, while other loops
// don't. One example is c++ iterators that often have multiple pointer
// induction variables. In the code below we also support a case where we
// don't have a single induction variable.
OldInduction = Legal->getInduction();
Type *IdxTy = Legal->getWidestInductionType();
// Find the loop boundaries.
const SCEV *ExitCount = SE->getBackedgeTakenCount(OrigLoop);
assert(ExitCount != SE->getCouldNotCompute() && "Invalid loop count");
// The exit count might have the type of i64 while the phi is i32. This can
// happen if we have an induction variable that is sign extended before the
// compare. The only way that we get a backedge taken count is that the
// induction variable was signed and as such will not overflow. In such a case
// truncation is legal.
if (ExitCount->getType()->getPrimitiveSizeInBits() >
IdxTy->getPrimitiveSizeInBits())
ExitCount = SE->getTruncateOrNoop(ExitCount, IdxTy);
ExitCount = SE->getNoopOrZeroExtend(ExitCount, IdxTy);
// Get the total trip count from the count by adding 1.
ExitCount = SE->getAddExpr(ExitCount,
SE->getConstant(ExitCount->getType(), 1));
// Expand the trip count and place the new instructions in the preheader.
// Notice that the pre-header does not change, only the loop body.
SCEVExpander Exp(*SE, "induction");
// Count holds the overall loop count (N).
Value *Count = Exp.expandCodeFor(ExitCount, ExitCount->getType(),
BypassBlock->getTerminator());
// The loop index does not have to start at Zero. Find the original start
// value from the induction PHI node. If we don't have an induction variable
// then we know that it starts at zero.
Builder.SetInsertPoint(BypassBlock->getTerminator());
Value *StartIdx = ExtendedIdx = OldInduction ?
Builder.CreateZExt(OldInduction->getIncomingValueForBlock(BypassBlock),
IdxTy):
ConstantInt::get(IdxTy, 0);
assert(BypassBlock && "Invalid loop structure");
LoopBypassBlocks.push_back(BypassBlock);
// Split the single block loop into the two loop structure described above.
BasicBlock *VectorPH =
BypassBlock->splitBasicBlock(BypassBlock->getTerminator(), "vector.ph");
BasicBlock *VecBody =
VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body");
BasicBlock *MiddleBlock =
VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block");
BasicBlock *ScalarPH =
MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
// Create and register the new vector loop.
Loop* Lp = new Loop();
Loop *ParentLoop = OrigLoop->getParentLoop();
// Insert the new loop into the loop nest and register the new basic blocks
// before calling any utilities such as SCEV that require valid LoopInfo.
if (ParentLoop) {
ParentLoop->addChildLoop(Lp);
ParentLoop->addBasicBlockToLoop(ScalarPH, LI->getBase());
ParentLoop->addBasicBlockToLoop(VectorPH, LI->getBase());
ParentLoop->addBasicBlockToLoop(MiddleBlock, LI->getBase());
} else {
LI->addTopLevelLoop(Lp);
}
Lp->addBasicBlockToLoop(VecBody, LI->getBase());
// Use this IR builder to create the loop instructions (Phi, Br, Cmp)
// inside the loop.
Builder.SetInsertPoint(VecBody->getFirstNonPHI());
// Generate the induction variable.
setDebugLocFromInst(Builder, getDebugLocFromInstOrOperands(OldInduction));
Induction = Builder.CreatePHI(IdxTy, 2, "index");
// The loop step is equal to the vectorization factor (num of SIMD elements)
// times the unroll factor (num of SIMD instructions).
Constant *Step = ConstantInt::get(IdxTy, VF * UF);
// This is the IR builder that we use to add all of the logic for bypassing
// the new vector loop.
IRBuilder<> BypassBuilder(BypassBlock->getTerminator());
setDebugLocFromInst(BypassBuilder,
getDebugLocFromInstOrOperands(OldInduction));
// We may need to extend the index in case there is a type mismatch.
// We know that the count starts at zero and does not overflow.
if (Count->getType() != IdxTy) {
// The exit count can be of pointer type. Convert it to the correct
// integer type.
if (ExitCount->getType()->isPointerTy())
Count = BypassBuilder.CreatePointerCast(Count, IdxTy, "ptrcnt.to.int");
else
Count = BypassBuilder.CreateZExtOrTrunc(Count, IdxTy, "cnt.cast");
}
// Add the start index to the loop count to get the new end index.
Value *IdxEnd = BypassBuilder.CreateAdd(Count, StartIdx, "end.idx");
// Now we need to generate the expression for N - (N % VF), which is
// the part that the vectorized body will execute.
Value *R = BypassBuilder.CreateURem(Count, Step, "n.mod.vf");
Value *CountRoundDown = BypassBuilder.CreateSub(Count, R, "n.vec");
Value *IdxEndRoundDown = BypassBuilder.CreateAdd(CountRoundDown, StartIdx,
"end.idx.rnd.down");
// Now, compare the new count to zero. If it is zero skip the vector loop and
// jump to the scalar loop.
Value *Cmp = BypassBuilder.CreateICmpEQ(IdxEndRoundDown, StartIdx,
"cmp.zero");
BasicBlock *LastBypassBlock = BypassBlock;
// Generate the code to check that the strides we assumed to be one are really
// one. We want the new basic block to start at the first instruction in a
// sequence of instructions that form a check.
Instruction *StrideCheck;
Instruction *FirstCheckInst;
tie(FirstCheckInst, StrideCheck) =
addStrideCheck(BypassBlock->getTerminator());
if (StrideCheck) {
// Create a new block containing the stride check.
BasicBlock *CheckBlock =
BypassBlock->splitBasicBlock(FirstCheckInst, "vector.stridecheck");
if (ParentLoop)
ParentLoop->addBasicBlockToLoop(CheckBlock, LI->getBase());
LoopBypassBlocks.push_back(CheckBlock);
// Replace the branch into the memory check block with a conditional branch
// for the "few elements case".
Instruction *OldTerm = BypassBlock->getTerminator();
BranchInst::Create(MiddleBlock, CheckBlock, Cmp, OldTerm);
OldTerm->eraseFromParent();
Cmp = StrideCheck;
LastBypassBlock = CheckBlock;
}
// Generate the code that checks in runtime if arrays overlap. We put the
// checks into a separate block to make the more common case of few elements
// faster.
Instruction *MemRuntimeCheck;
tie(FirstCheckInst, MemRuntimeCheck) =
addRuntimeCheck(LastBypassBlock->getTerminator());
if (MemRuntimeCheck) {
// Create a new block containing the memory check.
BasicBlock *CheckBlock =
LastBypassBlock->splitBasicBlock(MemRuntimeCheck, "vector.memcheck");
if (ParentLoop)
ParentLoop->addBasicBlockToLoop(CheckBlock, LI->getBase());
LoopBypassBlocks.push_back(CheckBlock);
// Replace the branch into the memory check block with a conditional branch
// for the "few elements case".
Instruction *OldTerm = LastBypassBlock->getTerminator();
BranchInst::Create(MiddleBlock, CheckBlock, Cmp, OldTerm);
OldTerm->eraseFromParent();
Cmp = MemRuntimeCheck;
LastBypassBlock = CheckBlock;
}
LastBypassBlock->getTerminator()->eraseFromParent();
BranchInst::Create(MiddleBlock, VectorPH, Cmp,
LastBypassBlock);
// We are going to resume the execution of the scalar loop.
// Go over all of the induction variables that we found and fix the
// PHIs that are left in the scalar version of the loop.
// The starting values of PHI nodes depend on the counter of the last
// iteration in the vectorized loop.
// If we come from a bypass edge then we need to start from the original
// start value.
// This variable saves the new starting index for the scalar loop.
PHINode *ResumeIndex = 0;
LoopVectorizationLegality::InductionList::iterator I, E;
LoopVectorizationLegality::InductionList *List = Legal->getInductionVars();
// Set builder to point to last bypass block.
BypassBuilder.SetInsertPoint(LoopBypassBlocks.back()->getTerminator());
for (I = List->begin(), E = List->end(); I != E; ++I) {
PHINode *OrigPhi = I->first;
LoopVectorizationLegality::InductionInfo II = I->second;
Type *ResumeValTy = (OrigPhi == OldInduction) ? IdxTy : OrigPhi->getType();
PHINode *ResumeVal = PHINode::Create(ResumeValTy, 2, "resume.val",
MiddleBlock->getTerminator());
// We might have extended the type of the induction variable but we need a
// truncated version for the scalar loop.
PHINode *TruncResumeVal = (OrigPhi == OldInduction) ?
PHINode::Create(OrigPhi->getType(), 2, "trunc.resume.val",
MiddleBlock->getTerminator()) : 0;
Value *EndValue = 0;
switch (II.IK) {
case LoopVectorizationLegality::IK_NoInduction:
llvm_unreachable("Unknown induction");
case LoopVectorizationLegality::IK_IntInduction: {
// Handle the integer induction counter.
assert(OrigPhi->getType()->isIntegerTy() && "Invalid type");
// We have the canonical induction variable.
if (OrigPhi == OldInduction) {
// Create a truncated version of the resume value for the scalar loop,
// we might have promoted the type to a larger width.
EndValue =
BypassBuilder.CreateTrunc(IdxEndRoundDown, OrigPhi->getType());
// The new PHI merges the original incoming value, in case of a bypass,
// or the value at the end of the vectorized loop.
for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
TruncResumeVal->addIncoming(II.StartValue, LoopBypassBlocks[I]);
TruncResumeVal->addIncoming(EndValue, VecBody);
// We know what the end value is.
EndValue = IdxEndRoundDown;
// We also know which PHI node holds it.
ResumeIndex = ResumeVal;
break;
}
// Not the canonical induction variable - add the vector loop count to the
// start value.
Value *CRD = BypassBuilder.CreateSExtOrTrunc(CountRoundDown,
II.StartValue->getType(),
"cast.crd");
EndValue = BypassBuilder.CreateAdd(CRD, II.StartValue , "ind.end");
break;
}
case LoopVectorizationLegality::IK_ReverseIntInduction: {
// Convert the CountRoundDown variable to the PHI size.
Value *CRD = BypassBuilder.CreateSExtOrTrunc(CountRoundDown,
II.StartValue->getType(),
"cast.crd");
// Handle reverse integer induction counter.
EndValue = BypassBuilder.CreateSub(II.StartValue, CRD, "rev.ind.end");
break;
}
case LoopVectorizationLegality::IK_PtrInduction: {
// For pointer induction variables, calculate the offset using
// the end index.
EndValue = BypassBuilder.CreateGEP(II.StartValue, CountRoundDown,
"ptr.ind.end");
break;
}
case LoopVectorizationLegality::IK_ReversePtrInduction: {
// The value at the end of the loop for the reverse pointer is calculated
// by creating a GEP with a negative index starting from the start value.
Value *Zero = ConstantInt::get(CountRoundDown->getType(), 0);
Value *NegIdx = BypassBuilder.CreateSub(Zero, CountRoundDown,
"rev.ind.end");
EndValue = BypassBuilder.CreateGEP(II.StartValue, NegIdx,
"rev.ptr.ind.end");
break;
}
}// end of case
// The new PHI merges the original incoming value, in case of a bypass,
// or the value at the end of the vectorized loop.
for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I) {
if (OrigPhi == OldInduction)
ResumeVal->addIncoming(StartIdx, LoopBypassBlocks[I]);
else
ResumeVal->addIncoming(II.StartValue, LoopBypassBlocks[I]);
}
ResumeVal->addIncoming(EndValue, VecBody);
// Fix the scalar body counter (PHI node).
unsigned BlockIdx = OrigPhi->getBasicBlockIndex(ScalarPH);
// The old inductions phi node in the scalar body needs the truncated value.
if (OrigPhi == OldInduction)
OrigPhi->setIncomingValue(BlockIdx, TruncResumeVal);
else
OrigPhi->setIncomingValue(BlockIdx, ResumeVal);
}
// If we are generating a new induction variable then we also need to
// generate the code that calculates the exit value. This value is not
// simply the end of the counter because we may skip the vectorized body
// in case of a runtime check.
if (!OldInduction){
assert(!ResumeIndex && "Unexpected resume value found");
ResumeIndex = PHINode::Create(IdxTy, 2, "new.indc.resume.val",
MiddleBlock->getTerminator());
for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
ResumeIndex->addIncoming(StartIdx, LoopBypassBlocks[I]);
ResumeIndex->addIncoming(IdxEndRoundDown, VecBody);
}
// Make sure that we found the index where scalar loop needs to continue.
assert(ResumeIndex && ResumeIndex->getType()->isIntegerTy() &&
"Invalid resume Index");
// Add a check in the middle block to see if we have completed
// all of the iterations in the first vector loop.
// If (N - N%VF) == N, then we *don't* need to run the remainder.
Value *CmpN = CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, IdxEnd,
ResumeIndex, "cmp.n",
MiddleBlock->getTerminator());
BranchInst::Create(ExitBlock, ScalarPH, CmpN, MiddleBlock->getTerminator());
// Remove the old terminator.
MiddleBlock->getTerminator()->eraseFromParent();
// Create i+1 and fill the PHINode.
Value *NextIdx = Builder.CreateAdd(Induction, Step, "index.next");
Induction->addIncoming(StartIdx, VectorPH);
Induction->addIncoming(NextIdx, VecBody);
// Create the compare.
Value *ICmp = Builder.CreateICmpEQ(NextIdx, IdxEndRoundDown);
Builder.CreateCondBr(ICmp, MiddleBlock, VecBody);
// Now we have two terminators. Remove the old one from the block.
VecBody->getTerminator()->eraseFromParent();
// Get ready to start creating new instructions into the vectorized body.
Builder.SetInsertPoint(VecBody->getFirstInsertionPt());
// Save the state.
LoopVectorPreHeader = VectorPH;
LoopScalarPreHeader = ScalarPH;
LoopMiddleBlock = MiddleBlock;
LoopExitBlock = ExitBlock;
LoopVectorBody = VecBody;
LoopScalarBody = OldBasicBlock;
LoopVectorizeHints Hints(Lp, true);
Hints.setAlreadyVectorized(Lp);
}
/// This function returns the identity element (or neutral element) for
/// the operation K.
Constant*
LoopVectorizationLegality::getReductionIdentity(ReductionKind K, Type *Tp) {
switch (K) {
case RK_IntegerXor:
case RK_IntegerAdd:
case RK_IntegerOr:
// Adding, Xoring, Oring zero to a number does not change it.
return ConstantInt::get(Tp, 0);
case RK_IntegerMult:
// Multiplying a number by 1 does not change it.
return ConstantInt::get(Tp, 1);
case RK_IntegerAnd:
// AND-ing a number with an all-1 value does not change it.
return ConstantInt::get(Tp, -1, true);
case RK_FloatMult:
// Multiplying a number by 1 does not change it.
return ConstantFP::get(Tp, 1.0L);
case RK_FloatAdd:
// Adding zero to a number does not change it.
return ConstantFP::get(Tp, 0.0L);
default:
llvm_unreachable("Unknown reduction kind");
}
}
static Intrinsic::ID checkUnaryFloatSignature(const CallInst &I,
Intrinsic::ID ValidIntrinsicID) {
if (I.getNumArgOperands() != 1 ||
!I.getArgOperand(0)->getType()->isFloatingPointTy() ||
I.getType() != I.getArgOperand(0)->getType() ||
!I.onlyReadsMemory())
return Intrinsic::not_intrinsic;
return ValidIntrinsicID;
}
static Intrinsic::ID checkBinaryFloatSignature(const CallInst &I,
Intrinsic::ID ValidIntrinsicID) {
if (I.getNumArgOperands() != 2 ||
!I.getArgOperand(0)->getType()->isFloatingPointTy() ||
!I.getArgOperand(1)->getType()->isFloatingPointTy() ||
I.getType() != I.getArgOperand(0)->getType() ||
I.getType() != I.getArgOperand(1)->getType() ||
!I.onlyReadsMemory())
return Intrinsic::not_intrinsic;
return ValidIntrinsicID;
}
static Intrinsic::ID
getIntrinsicIDForCall(CallInst *CI, const TargetLibraryInfo *TLI) {
// If we have an intrinsic call, check if it is trivially vectorizable.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
switch (II->getIntrinsicID()) {
case Intrinsic::sqrt:
case Intrinsic::sin:
case Intrinsic::cos:
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::log:
case Intrinsic::log10:
case Intrinsic::log2:
case Intrinsic::fabs:
case Intrinsic::copysign:
case Intrinsic::floor:
case Intrinsic::ceil:
case Intrinsic::trunc:
case Intrinsic::rint:
case Intrinsic::nearbyint:
case Intrinsic::round:
case Intrinsic::pow:
case Intrinsic::fma:
case Intrinsic::fmuladd:
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
return II->getIntrinsicID();
default:
return Intrinsic::not_intrinsic;
}
}
if (!TLI)
return Intrinsic::not_intrinsic;
LibFunc::Func Func;
Function *F = CI->getCalledFunction();
// We're going to make assumptions on the semantics of the functions, check
// that the target knows that it's available in this environment and it does
// not have local linkage.
if (!F || F->hasLocalLinkage() || !TLI->getLibFunc(F->getName(), Func))
return Intrinsic::not_intrinsic;
// Otherwise check if we have a call to a function that can be turned into a
// vector intrinsic.
switch (Func) {
default:
break;
case LibFunc::sin:
case LibFunc::sinf:
case LibFunc::sinl:
return checkUnaryFloatSignature(*CI, Intrinsic::sin);
case LibFunc::cos:
case LibFunc::cosf:
case LibFunc::cosl:
return checkUnaryFloatSignature(*CI, Intrinsic::cos);
case LibFunc::exp:
case LibFunc::expf:
case LibFunc::expl:
return checkUnaryFloatSignature(*CI, Intrinsic::exp);
case LibFunc::exp2:
case LibFunc::exp2f:
case LibFunc::exp2l:
return checkUnaryFloatSignature(*CI, Intrinsic::exp2);
case LibFunc::log:
case LibFunc::logf:
case LibFunc::logl:
return checkUnaryFloatSignature(*CI, Intrinsic::log);
case LibFunc::log10:
case LibFunc::log10f:
case LibFunc::log10l:
return checkUnaryFloatSignature(*CI, Intrinsic::log10);
case LibFunc::log2:
case LibFunc::log2f:
case LibFunc::log2l:
return checkUnaryFloatSignature(*CI, Intrinsic::log2);
case LibFunc::fabs:
case LibFunc::fabsf:
case LibFunc::fabsl:
return checkUnaryFloatSignature(*CI, Intrinsic::fabs);
case LibFunc::copysign:
case LibFunc::copysignf:
case LibFunc::copysignl:
return checkBinaryFloatSignature(*CI, Intrinsic::copysign);
case LibFunc::floor:
case LibFunc::floorf:
case LibFunc::floorl:
return checkUnaryFloatSignature(*CI, Intrinsic::floor);
case LibFunc::ceil:
case LibFunc::ceilf:
case LibFunc::ceill:
return checkUnaryFloatSignature(*CI, Intrinsic::ceil);
case LibFunc::trunc:
case LibFunc::truncf:
case LibFunc::truncl:
return checkUnaryFloatSignature(*CI, Intrinsic::trunc);
case LibFunc::rint:
case LibFunc::rintf:
case LibFunc::rintl:
return checkUnaryFloatSignature(*CI, Intrinsic::rint);
case LibFunc::nearbyint:
case LibFunc::nearbyintf:
case LibFunc::nearbyintl:
return checkUnaryFloatSignature(*CI, Intrinsic::nearbyint);
case LibFunc::round:
case LibFunc::roundf:
case LibFunc::roundl:
return checkUnaryFloatSignature(*CI, Intrinsic::round);
case LibFunc::pow:
case LibFunc::powf:
case LibFunc::powl:
return checkBinaryFloatSignature(*CI, Intrinsic::pow);
}
return Intrinsic::not_intrinsic;
}
/// This function translates the reduction kind to an LLVM binary operator.
static unsigned
getReductionBinOp(LoopVectorizationLegality::ReductionKind Kind) {
switch (Kind) {
case LoopVectorizationLegality::RK_IntegerAdd:
return Instruction::Add;
case LoopVectorizationLegality::RK_IntegerMult:
return Instruction::Mul;
case LoopVectorizationLegality::RK_IntegerOr:
return Instruction::Or;
case LoopVectorizationLegality::RK_IntegerAnd:
return Instruction::And;
case LoopVectorizationLegality::RK_IntegerXor:
return Instruction::Xor;
case LoopVectorizationLegality::RK_FloatMult:
return Instruction::FMul;
case LoopVectorizationLegality::RK_FloatAdd:
return Instruction::FAdd;
case LoopVectorizationLegality::RK_IntegerMinMax:
return Instruction::ICmp;
case LoopVectorizationLegality::RK_FloatMinMax:
return Instruction::FCmp;
default:
llvm_unreachable("Unknown reduction operation");
}
}
Value *createMinMaxOp(IRBuilder<> &Builder,
LoopVectorizationLegality::MinMaxReductionKind RK,
Value *Left,
Value *Right) {
CmpInst::Predicate P = CmpInst::ICMP_NE;
switch (RK) {
default:
llvm_unreachable("Unknown min/max reduction kind");
case LoopVectorizationLegality::MRK_UIntMin:
P = CmpInst::ICMP_ULT;
break;
case LoopVectorizationLegality::MRK_UIntMax:
P = CmpInst::ICMP_UGT;
break;
case LoopVectorizationLegality::MRK_SIntMin:
P = CmpInst::ICMP_SLT;
break;
case LoopVectorizationLegality::MRK_SIntMax:
P = CmpInst::ICMP_SGT;
break;
case LoopVectorizationLegality::MRK_FloatMin:
P = CmpInst::FCMP_OLT;
break;
case LoopVectorizationLegality::MRK_FloatMax:
P = CmpInst::FCMP_OGT;
break;
}
Value *Cmp;
if (RK == LoopVectorizationLegality::MRK_FloatMin ||
RK == LoopVectorizationLegality::MRK_FloatMax)
Cmp = Builder.CreateFCmp(P, Left, Right, "rdx.minmax.cmp");
else
Cmp = Builder.CreateICmp(P, Left, Right, "rdx.minmax.cmp");
Value *Select = Builder.CreateSelect(Cmp, Left, Right, "rdx.minmax.select");
return Select;
}
namespace {
struct CSEDenseMapInfo {
static bool canHandle(Instruction *I) {
return isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) ||
isa<ShuffleVectorInst>(I) || isa<GetElementPtrInst>(I);
}
static inline Instruction *getEmptyKey() {
return DenseMapInfo<Instruction *>::getEmptyKey();
}
static inline Instruction *getTombstoneKey() {
return DenseMapInfo<Instruction *>::getTombstoneKey();
}
static unsigned getHashValue(Instruction *I) {
assert(canHandle(I) && "Unknown instruction!");
return hash_combine(I->getOpcode(), hash_combine_range(I->value_op_begin(),
I->value_op_end()));
}
static bool isEqual(Instruction *LHS, Instruction *RHS) {
if (LHS == getEmptyKey() || RHS == getEmptyKey() ||
LHS == getTombstoneKey() || RHS == getTombstoneKey())
return LHS == RHS;
return LHS->isIdenticalTo(RHS);
}
};
}
///\brief Perform cse of induction variable instructions.
static void cse(BasicBlock *BB) {
// Perform simple cse.
SmallDenseMap<Instruction *, Instruction *, 4, CSEDenseMapInfo> CSEMap;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
Instruction *In = I++;
if (!CSEDenseMapInfo::canHandle(In))
continue;
// Check if we can replace this instruction with any of the
// visited instructions.
if (Instruction *V = CSEMap.lookup(In)) {
In->replaceAllUsesWith(V);
In->eraseFromParent();
continue;
}
CSEMap[In] = In;
}
}
void InnerLoopVectorizer::vectorizeLoop() {
//===------------------------------------------------===//
//
// Notice: any optimization or new instruction that go
// into the code below should be also be implemented in
// the cost-model.
//
//===------------------------------------------------===//
Constant *Zero = Builder.getInt32(0);
// In order to support reduction variables we need to be able to vectorize
// Phi nodes. Phi nodes have cycles, so we need to vectorize them in two
// stages. First, we create a new vector PHI node with no incoming edges.
// We use this value when we vectorize all of the instructions that use the
// PHI. Next, after all of the instructions in the block are complete we
// add the new incoming edges to the PHI. At this point all of the
// instructions in the basic block are vectorized, so we can use them to
// construct the PHI.
PhiVector RdxPHIsToFix;
// Scan the loop in a topological order to ensure that defs are vectorized
// before users.
LoopBlocksDFS DFS(OrigLoop);
DFS.perform(LI);
// Vectorize all of the blocks in the original loop.
for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
be = DFS.endRPO(); bb != be; ++bb)
vectorizeBlockInLoop(*bb, &RdxPHIsToFix);
// At this point every instruction in the original loop is widened to
// a vector form. We are almost done. Now, we need to fix the PHI nodes
// that we vectorized. The PHI nodes are currently empty because we did
// not want to introduce cycles. Notice that the remaining PHI nodes
// that we need to fix are reduction variables.
// Create the 'reduced' values for each of the induction vars.
// The reduced values are the vector values that we scalarize and combine
// after the loop is finished.
for (PhiVector::iterator it = RdxPHIsToFix.begin(), e = RdxPHIsToFix.end();
it != e; ++it) {
PHINode *RdxPhi = *it;
assert(RdxPhi && "Unable to recover vectorized PHI");
// Find the reduction variable descriptor.
assert(Legal->getReductionVars()->count(RdxPhi) &&
"Unable to find the reduction variable");
LoopVectorizationLegality::ReductionDescriptor RdxDesc =
(*Legal->getReductionVars())[RdxPhi];
setDebugLocFromInst(Builder, RdxDesc.StartValue);
// We need to generate a reduction vector from the incoming scalar.
// To do so, we need to generate the 'identity' vector and override
// one of the elements with the incoming scalar reduction. We need
// to do it in the vector-loop preheader.
Builder.SetInsertPoint(LoopBypassBlocks.front()->getTerminator());
// This is the vector-clone of the value that leaves the loop.
VectorParts &VectorExit = getVectorValue(RdxDesc.LoopExitInstr);
Type *VecTy = VectorExit[0]->getType();
// Find the reduction identity variable. Zero for addition, or, xor,
// one for multiplication, -1 for And.
Value *Identity;
Value *VectorStart;
if (RdxDesc.Kind == LoopVectorizationLegality::RK_IntegerMinMax ||
RdxDesc.Kind == LoopVectorizationLegality::RK_FloatMinMax) {
// MinMax reduction have the start value as their identify.
if (VF == 1) {
VectorStart = Identity = RdxDesc.StartValue;
} else {
VectorStart = Identity = Builder.CreateVectorSplat(VF,
RdxDesc.StartValue,
"minmax.ident");
}
} else {
// Handle other reduction kinds:
Constant *Iden =
LoopVectorizationLegality::getReductionIdentity(RdxDesc.Kind,
VecTy->getScalarType());
if (VF == 1) {
Identity = Iden;
// This vector is the Identity vector where the first element is the
// incoming scalar reduction.
VectorStart = RdxDesc.StartValue;
} else {
Identity = ConstantVector::getSplat(VF, Iden);
// This vector is the Identity vector where the first element is the
// incoming scalar reduction.
VectorStart = Builder.CreateInsertElement(Identity,
RdxDesc.StartValue, Zero);
}
}
// Fix the vector-loop phi.
// We created the induction variable so we know that the
// preheader is the first entry.
BasicBlock *VecPreheader = Induction->getIncomingBlock(0);
// Reductions do not have to start at zero. They can start with
// any loop invariant values.
VectorParts &VecRdxPhi = WidenMap.get(RdxPhi);
BasicBlock *Latch = OrigLoop->getLoopLatch();
Value *LoopVal = RdxPhi->getIncomingValueForBlock(Latch);
VectorParts &Val = getVectorValue(LoopVal);
for (unsigned part = 0; part < UF; ++part) {
// Make sure to add the reduction stat value only to the
// first unroll part.
Value *StartVal = (part == 0) ? VectorStart : Identity;
cast<PHINode>(VecRdxPhi[part])->addIncoming(StartVal, VecPreheader);
cast<PHINode>(VecRdxPhi[part])->addIncoming(Val[part], LoopVectorBody);
}
// Before each round, move the insertion point right between
// the PHIs and the values we are going to write.
// This allows us to write both PHINodes and the extractelement
// instructions.
Builder.SetInsertPoint(LoopMiddleBlock->getFirstInsertionPt());
VectorParts RdxParts;
setDebugLocFromInst(Builder, RdxDesc.LoopExitInstr);
for (unsigned part = 0; part < UF; ++part) {
// This PHINode contains the vectorized reduction variable, or
// the initial value vector, if we bypass the vector loop.
VectorParts &RdxExitVal = getVectorValue(RdxDesc.LoopExitInstr);
PHINode *NewPhi = Builder.CreatePHI(VecTy, 2, "rdx.vec.exit.phi");
Value *StartVal = (part == 0) ? VectorStart : Identity;
for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
NewPhi->addIncoming(StartVal, LoopBypassBlocks[I]);
NewPhi->addIncoming(RdxExitVal[part], LoopVectorBody);
RdxParts.push_back(NewPhi);
}
// Reduce all of the unrolled parts into a single vector.
Value *ReducedPartRdx = RdxParts[0];
unsigned Op = getReductionBinOp(RdxDesc.Kind);
setDebugLocFromInst(Builder, ReducedPartRdx);
for (unsigned part = 1; part < UF; ++part) {
if (Op != Instruction::ICmp && Op != Instruction::FCmp)
ReducedPartRdx = Builder.CreateBinOp((Instruction::BinaryOps)Op,
RdxParts[part], ReducedPartRdx,
"bin.rdx");
else
ReducedPartRdx = createMinMaxOp(Builder, RdxDesc.MinMaxKind,
ReducedPartRdx, RdxParts[part]);
}
if (VF > 1) {
// VF is a power of 2 so we can emit the reduction using log2(VF) shuffles
// and vector ops, reducing the set of values being computed by half each
// round.
assert(isPowerOf2_32(VF) &&
"Reduction emission only supported for pow2 vectors!");
Value *TmpVec = ReducedPartRdx;
SmallVector<Constant*, 32> ShuffleMask(VF, 0);
for (unsigned i = VF; i != 1; i >>= 1) {
// Move the upper half of the vector to the lower half.
for (unsigned j = 0; j != i/2; ++j)
ShuffleMask[j] = Builder.getInt32(i/2 + j);
// Fill the rest of the mask with undef.
std::fill(&ShuffleMask[i/2], ShuffleMask.end(),
UndefValue::get(Builder.getInt32Ty()));
Value *Shuf =
Builder.CreateShuffleVector(TmpVec,
UndefValue::get(TmpVec->getType()),
ConstantVector::get(ShuffleMask),
"rdx.shuf");
if (Op != Instruction::ICmp && Op != Instruction::FCmp)
TmpVec = Builder.CreateBinOp((Instruction::BinaryOps)Op, TmpVec, Shuf,
"bin.rdx");
else
TmpVec = createMinMaxOp(Builder, RdxDesc.MinMaxKind, TmpVec, Shuf);
}
// The result is in the first element of the vector.
ReducedPartRdx = Builder.CreateExtractElement(TmpVec,
Builder.getInt32(0));
}
// Now, we need to fix the users of the reduction variable
// inside and outside of the scalar remainder loop.
// We know that the loop is in LCSSA form. We need to update the
// PHI nodes in the exit blocks.
for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
if (!LCSSAPhi) break;
// All PHINodes need to have a single entry edge, or two if
// we already fixed them.
assert(LCSSAPhi->getNumIncomingValues() < 3 && "Invalid LCSSA PHI");
// We found our reduction value exit-PHI. Update it with the
// incoming bypass edge.
if (LCSSAPhi->getIncomingValue(0) == RdxDesc.LoopExitInstr) {
// Add an edge coming from the bypass.
LCSSAPhi->addIncoming(ReducedPartRdx, LoopMiddleBlock);
break;
}
}// end of the LCSSA phi scan.
// Fix the scalar loop reduction variable with the incoming reduction sum
// from the vector body and from the backedge value.
int IncomingEdgeBlockIdx =
(RdxPhi)->getBasicBlockIndex(OrigLoop->getLoopLatch());
assert(IncomingEdgeBlockIdx >= 0 && "Invalid block index");
// Pick the other block.
int SelfEdgeBlockIdx = (IncomingEdgeBlockIdx ? 0 : 1);
(RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, ReducedPartRdx);
(RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
}// end of for each redux variable.
fixLCSSAPHIs();
// Remove redundant induction instructions.
cse(LoopVectorBody);
}
void InnerLoopVectorizer::fixLCSSAPHIs() {
for (BasicBlock::iterator LEI = LoopExitBlock->begin(),
LEE = LoopExitBlock->end(); LEI != LEE; ++LEI) {
PHINode *LCSSAPhi = dyn_cast<PHINode>(LEI);
if (!LCSSAPhi) break;
if (LCSSAPhi->getNumIncomingValues() == 1)
LCSSAPhi->addIncoming(UndefValue::get(LCSSAPhi->getType()),
LoopMiddleBlock);
}
}
InnerLoopVectorizer::VectorParts
InnerLoopVectorizer::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) {
assert(std::find(pred_begin(Dst), pred_end(Dst), Src) != pred_end(Dst) &&
"Invalid edge");
// Look for cached value.
std::pair<BasicBlock*, BasicBlock*> Edge(Src, Dst);
EdgeMaskCache::iterator ECEntryIt = MaskCache.find(Edge);
if (ECEntryIt != MaskCache.end())
return ECEntryIt->second;
VectorParts SrcMask = createBlockInMask(Src);
// The terminator has to be a branch inst!
BranchInst *BI = dyn_cast<BranchInst>(Src->getTerminator());
assert(BI && "Unexpected terminator found");
if (BI->isConditional()) {
VectorParts EdgeMask = getVectorValue(BI->getCondition());
if (BI->getSuccessor(0) != Dst)
for (unsigned part = 0; part < UF; ++part)
EdgeMask[part] = Builder.CreateNot(EdgeMask[part]);
for (unsigned part = 0; part < UF; ++part)
EdgeMask[part] = Builder.CreateAnd(EdgeMask[part], SrcMask[part]);
MaskCache[Edge] = EdgeMask;
return EdgeMask;
}
MaskCache[Edge] = SrcMask;
return SrcMask;
}
InnerLoopVectorizer::VectorParts
InnerLoopVectorizer::createBlockInMask(BasicBlock *BB) {
assert(OrigLoop->contains(BB) && "Block is not a part of a loop");
// Loop incoming mask is all-one.
if (OrigLoop->getHeader() == BB) {
Value *C = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 1);
return getVectorValue(C);
}
// This is the block mask. We OR all incoming edges, and with zero.
Value *Zero = ConstantInt::get(IntegerType::getInt1Ty(BB->getContext()), 0);
VectorParts BlockMask = getVectorValue(Zero);
// For each pred:
for (pred_iterator it = pred_begin(BB), e = pred_end(BB); it != e; ++it) {
VectorParts EM = createEdgeMask(*it, BB);
for (unsigned part = 0; part < UF; ++part)
BlockMask[part] = Builder.CreateOr(BlockMask[part], EM[part]);
}
return BlockMask;
}
void InnerLoopVectorizer::widenPHIInstruction(Instruction *PN,
InnerLoopVectorizer::VectorParts &Entry,
unsigned UF, unsigned VF, PhiVector *PV) {
PHINode* P = cast<PHINode>(PN);
// Handle reduction variables:
if (Legal->getReductionVars()->count(P)) {
for (unsigned part = 0; part < UF; ++part) {
// This is phase one of vectorizing PHIs.
Type *VecTy = (VF == 1) ? PN->getType() :
VectorType::get(PN->getType(), VF);
Entry[part] = PHINode::Create(VecTy, 2, "vec.phi",
LoopVectorBody-> getFirstInsertionPt());
}
PV->push_back(P);
return;
}
setDebugLocFromInst(Builder, P);
// Check for PHI nodes that are lowered to vector selects.
if (P->getParent() != OrigLoop->getHeader()) {
// We know that all PHIs in non-header blocks are converted into
// selects, so we don't have to worry about the insertion order and we
// can just use the builder.
// At this point we generate the predication tree. There may be
// duplications since this is a simple recursive scan, but future
// optimizations will clean it up.
unsigned NumIncoming = P->getNumIncomingValues();
// Generate a sequence of selects of the form:
// SELECT(Mask3, In3,
// SELECT(Mask2, In2,
// ( ...)))
for (unsigned In = 0; In < NumIncoming; In++) {
VectorParts Cond = createEdgeMask(P->getIncomingBlock(In),
P->getParent());
VectorParts &In0 = getVectorValue(P->getIncomingValue(In));
for (unsigned part = 0; part < UF; ++part) {
// We might have single edge PHIs (blocks) - use an identity
// 'select' for the first PHI operand.
if (In == 0)
Entry[part] = Builder.CreateSelect(Cond[part], In0[part],
In0[part]);
else
// Select between the current value and the previous incoming edge
// based on the incoming mask.
Entry[part] = Builder.CreateSelect(Cond[part], In0[part],
Entry[part], "predphi");
}
}
return;
}
// This PHINode must be an induction variable.
// Make sure that we know about it.
assert(Legal->getInductionVars()->count(P) &&
"Not an induction variable");
LoopVectorizationLegality::InductionInfo II =
Legal->getInductionVars()->lookup(P);
switch (II.IK) {
case LoopVectorizationLegality::IK_NoInduction:
llvm_unreachable("Unknown induction");
case LoopVectorizationLegality::IK_IntInduction: {
assert(P->getType() == II.StartValue->getType() && "Types must match");
Type *PhiTy = P->getType();
Value *Broadcasted;
if (P == OldInduction) {
// Handle the canonical induction variable. We might have had to
// extend the type.
Broadcasted = Builder.CreateTrunc(Induction, PhiTy);
} else {
// Handle other induction variables that are now based on the
// canonical one.
Value *NormalizedIdx = Builder.CreateSub(Induction, ExtendedIdx,
"normalized.idx");
NormalizedIdx = Builder.CreateSExtOrTrunc(NormalizedIdx, PhiTy);
Broadcasted = Builder.CreateAdd(II.StartValue, NormalizedIdx,
"offset.idx");
}
Broadcasted = getBroadcastInstrs(Broadcasted);
// After broadcasting the induction variable we need to make the vector
// consecutive by adding 0, 1, 2, etc.
for (unsigned part = 0; part < UF; ++part)
Entry[part] = getConsecutiveVector(Broadcasted, VF * part, false);
return;
}
case LoopVectorizationLegality::IK_ReverseIntInduction:
case LoopVectorizationLegality::IK_PtrInduction:
case LoopVectorizationLegality::IK_ReversePtrInduction:
// Handle reverse integer and pointer inductions.
Value *StartIdx = ExtendedIdx;
// This is the normalized GEP that starts counting at zero.
Value *NormalizedIdx = Builder.CreateSub(Induction, StartIdx,
"normalized.idx");
// Handle the reverse integer induction variable case.
if (LoopVectorizationLegality::IK_ReverseIntInduction == II.IK) {
IntegerType *DstTy = cast<IntegerType>(II.StartValue->getType());
Value *CNI = Builder.CreateSExtOrTrunc(NormalizedIdx, DstTy,
"resize.norm.idx");
Value *ReverseInd = Builder.CreateSub(II.StartValue, CNI,
"reverse.idx");
// This is a new value so do not hoist it out.
Value *Broadcasted = getBroadcastInstrs(ReverseInd);
// After broadcasting the induction variable we need to make the
// vector consecutive by adding ... -3, -2, -1, 0.
for (unsigned part = 0; part < UF; ++part)
Entry[part] = getConsecutiveVector(Broadcasted, -(int)VF * part,
true);
return;
}
// Handle the pointer induction variable case.
assert(P->getType()->isPointerTy() && "Unexpected type.");
// Is this a reverse induction ptr or a consecutive induction ptr.
bool Reverse = (LoopVectorizationLegality::IK_ReversePtrInduction ==
II.IK);
// This is the vector of results. Notice that we don't generate
// vector geps because scalar geps result in better code.
for (unsigned part = 0; part < UF; ++part) {
if (VF == 1) {
int EltIndex = (part) * (Reverse ? -1 : 1);
Constant *Idx = ConstantInt::get(Induction->getType(), EltIndex);
Value *GlobalIdx;
if (Reverse)
GlobalIdx = Builder.CreateSub(Idx, NormalizedIdx, "gep.ridx");
else
GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx,
"next.gep");
Entry[part] = SclrGep;
continue;
}
Value *VecVal = UndefValue::get(VectorType::get(P->getType(), VF));
for (unsigned int i = 0; i < VF; ++i) {
int EltIndex = (i + part * VF) * (Reverse ? -1 : 1);
Constant *Idx = ConstantInt::get(Induction->getType(), EltIndex);
Value *GlobalIdx;
if (!Reverse)
GlobalIdx = Builder.CreateAdd(NormalizedIdx, Idx, "gep.idx");
else
GlobalIdx = Builder.CreateSub(Idx, NormalizedIdx, "gep.ridx");
Value *SclrGep = Builder.CreateGEP(II.StartValue, GlobalIdx,
"next.gep");
VecVal = Builder.CreateInsertElement(VecVal, SclrGep,
Builder.getInt32(i),
"insert.gep");
}
Entry[part] = VecVal;
}
return;
}
}
void InnerLoopVectorizer::vectorizeBlockInLoop(BasicBlock *BB, PhiVector *PV) {
// For each instruction in the old loop.
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
VectorParts &Entry = WidenMap.get(it);
switch (it->getOpcode()) {
case Instruction::Br:
// Nothing to do for PHIs and BR, since we already took care of the
// loop control flow instructions.
continue;
case Instruction::PHI:{
// Vectorize PHINodes.
widenPHIInstruction(it, Entry, UF, VF, PV);
continue;
}// End of PHI.
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
case Instruction::FSub:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
// Just widen binops.
BinaryOperator *BinOp = dyn_cast<BinaryOperator>(it);
setDebugLocFromInst(Builder, BinOp);
VectorParts &A = getVectorValue(it->getOperand(0));
VectorParts &B = getVectorValue(it->getOperand(1));
// Use this vector value for all users of the original instruction.
for (unsigned Part = 0; Part < UF; ++Part) {
Value *V = Builder.CreateBinOp(BinOp->getOpcode(), A[Part], B[Part]);
// Update the NSW, NUW and Exact flags. Notice: V can be an Undef.
BinaryOperator *VecOp = dyn_cast<BinaryOperator>(V);
if (VecOp && isa<OverflowingBinaryOperator>(BinOp)) {
VecOp->setHasNoSignedWrap(BinOp->hasNoSignedWrap());
VecOp->setHasNoUnsignedWrap(BinOp->hasNoUnsignedWrap());
}
if (VecOp && isa<PossiblyExactOperator>(VecOp))
VecOp->setIsExact(BinOp->isExact());
Entry[Part] = V;
}
break;
}
case Instruction::Select: {
// Widen selects.
// If the selector is loop invariant we can create a select
// instruction with a scalar condition. Otherwise, use vector-select.
bool InvariantCond = SE->isLoopInvariant(SE->getSCEV(it->getOperand(0)),
OrigLoop);
setDebugLocFromInst(Builder, it);
// The condition can be loop invariant but still defined inside the
// loop. This means that we can't just use the original 'cond' value.
// We have to take the 'vectorized' value and pick the first lane.
// Instcombine will make this a no-op.
VectorParts &Cond = getVectorValue(it->getOperand(0));
VectorParts &Op0 = getVectorValue(it->getOperand(1));
VectorParts &Op1 = getVectorValue(it->getOperand(2));
Value *ScalarCond = (VF == 1) ? Cond[0] :
Builder.CreateExtractElement(Cond[0], Builder.getInt32(0));
for (unsigned Part = 0; Part < UF; ++Part) {
Entry[Part] = Builder.CreateSelect(
InvariantCond ? ScalarCond : Cond[Part],
Op0[Part],
Op1[Part]);
}
break;
}
case Instruction::ICmp:
case Instruction::FCmp: {
// Widen compares. Generate vector compares.
bool FCmp = (it->getOpcode() == Instruction::FCmp);
CmpInst *Cmp = dyn_cast<CmpInst>(it);
setDebugLocFromInst(Builder, it);
VectorParts &A = getVectorValue(it->getOperand(0));
VectorParts &B = getVectorValue(it->getOperand(1));
for (unsigned Part = 0; Part < UF; ++Part) {
Value *C = 0;
if (FCmp)
C = Builder.CreateFCmp(Cmp->getPredicate(), A[Part], B[Part]);
else
C = Builder.CreateICmp(Cmp->getPredicate(), A[Part], B[Part]);
Entry[Part] = C;
}
break;
}
case Instruction::Store:
case Instruction::Load:
vectorizeMemoryInstruction(it);
break;
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::FPExt:
case Instruction::PtrToInt:
case Instruction::IntToPtr:
case Instruction::SIToFP:
case Instruction::UIToFP:
case Instruction::Trunc:
case Instruction::FPTrunc:
case Instruction::BitCast: {
CastInst *CI = dyn_cast<CastInst>(it);
setDebugLocFromInst(Builder, it);
/// Optimize the special case where the source is the induction
/// variable. Notice that we can only optimize the 'trunc' case
/// because: a. FP conversions lose precision, b. sext/zext may wrap,
/// c. other casts depend on pointer size.
if (CI->getOperand(0) == OldInduction &&
it->getOpcode() == Instruction::Trunc) {
Value *ScalarCast = Builder.CreateCast(CI->getOpcode(), Induction,
CI->getType());
Value *Broadcasted = getBroadcastInstrs(ScalarCast);
for (unsigned Part = 0; Part < UF; ++Part)
Entry[Part] = getConsecutiveVector(Broadcasted, VF * Part, false);
break;
}
/// Vectorize casts.
Type *DestTy = (VF == 1) ? CI->getType() :
VectorType::get(CI->getType(), VF);
VectorParts &A = getVectorValue(it->getOperand(0));
for (unsigned Part = 0; Part < UF; ++Part)
Entry[Part] = Builder.CreateCast(CI->getOpcode(), A[Part], DestTy);
break;
}
case Instruction::Call: {
// Ignore dbg intrinsics.
if (isa<DbgInfoIntrinsic>(it))
break;
setDebugLocFromInst(Builder, it);
Module *M = BB->getParent()->getParent();
CallInst *CI = cast<CallInst>(it);
Intrinsic::ID ID = getIntrinsicIDForCall(CI, TLI);
assert(ID && "Not an intrinsic call!");
switch (ID) {
case Intrinsic::lifetime_end:
case Intrinsic::lifetime_start:
scalarizeInstruction(it);
break;
default:
for (unsigned Part = 0; Part < UF; ++Part) {
SmallVector<Value *, 4> Args;
for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i) {
VectorParts &Arg = getVectorValue(CI->getArgOperand(i));
Args.push_back(Arg[Part]);
}
Type *Tys[] = {CI->getType()};
if (VF > 1)
Tys[0] = VectorType::get(CI->getType()->getScalarType(), VF);
Function *F = Intrinsic::getDeclaration(M, ID, Tys);
Entry[Part] = Builder.CreateCall(F, Args);
}
break;
}
break;
}
default:
// All other instructions are unsupported. Scalarize them.
scalarizeInstruction(it);
break;
}// end of switch.
}// end of for_each instr.
}
void InnerLoopVectorizer::updateAnalysis() {
// Forget the original basic block.
SE->forgetLoop(OrigLoop);
// Update the dominator tree information.
assert(DT->properlyDominates(LoopBypassBlocks.front(), LoopExitBlock) &&
"Entry does not dominate exit.");
for (unsigned I = 1, E = LoopBypassBlocks.size(); I != E; ++I)
DT->addNewBlock(LoopBypassBlocks[I], LoopBypassBlocks[I-1]);
DT->addNewBlock(LoopVectorPreHeader, LoopBypassBlocks.back());
DT->addNewBlock(LoopVectorBody, LoopVectorPreHeader);
DT->addNewBlock(LoopMiddleBlock, LoopBypassBlocks.front());
DT->addNewBlock(LoopScalarPreHeader, LoopMiddleBlock);
DT->changeImmediateDominator(LoopScalarBody, LoopScalarPreHeader);
DT->changeImmediateDominator(LoopExitBlock, LoopMiddleBlock);
DEBUG(DT->verifyDomTree());
}
/// \brief Check whether it is safe to if-convert this phi node.
///
/// Phi nodes with constant expressions that can trap are not safe to if
/// convert.
static bool canIfConvertPHINodes(BasicBlock *BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
PHINode *Phi = dyn_cast<PHINode>(I);
if (!Phi)
return true;
for (unsigned p = 0, e = Phi->getNumIncomingValues(); p != e; ++p)
if (Constant *C = dyn_cast<Constant>(Phi->getIncomingValue(p)))
if (C->canTrap())
return false;
}
return true;
}
bool LoopVectorizationLegality::canVectorizeWithIfConvert() {
if (!EnableIfConversion)
return false;
assert(TheLoop->getNumBlocks() > 1 && "Single block loops are vectorizable");
// A list of pointers that we can safely read and write to.
SmallPtrSet<Value *, 8> SafePointes;
// Collect safe addresses.
for (Loop::block_iterator BI = TheLoop->block_begin(),
BE = TheLoop->block_end(); BI != BE; ++BI) {
BasicBlock *BB = *BI;
if (blockNeedsPredication(BB))
continue;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (LoadInst *LI = dyn_cast<LoadInst>(I))
SafePointes.insert(LI->getPointerOperand());
else if (StoreInst *SI = dyn_cast<StoreInst>(I))
SafePointes.insert(SI->getPointerOperand());
}
}
// Collect the blocks that need predication.
BasicBlock *Header = TheLoop->getHeader();
for (Loop::block_iterator BI = TheLoop->block_begin(),
BE = TheLoop->block_end(); BI != BE; ++BI) {
BasicBlock *BB = *BI;
// We don't support switch statements inside loops.
if (!isa<BranchInst>(BB->getTerminator()))
return false;
// We must be able to predicate all blocks that need to be predicated.
if (blockNeedsPredication(BB)) {
if (!blockCanBePredicated(BB, SafePointes))
return false;
} else if (BB != Header && !canIfConvertPHINodes(BB))
return false;
}
// We can if-convert this loop.
return true;
}
bool LoopVectorizationLegality::canVectorize() {
// We must have a loop in canonical form. Loops with indirectbr in them cannot
// be canonicalized.
if (!TheLoop->getLoopPreheader())
return false;
// We can only vectorize innermost loops.
if (TheLoop->getSubLoopsVector().size())
return false;
// We must have a single backedge.
if (TheLoop->getNumBackEdges() != 1)
return false;
// We must have a single exiting block.
if (!TheLoop->getExitingBlock())
return false;
// We need to have a loop header.
DEBUG(dbgs() << "LV: Found a loop: " <<
TheLoop->getHeader()->getName() << '\n');
// Check if we can if-convert non-single-bb loops.
unsigned NumBlocks = TheLoop->getNumBlocks();
if (NumBlocks != 1 && !canVectorizeWithIfConvert()) {
DEBUG(dbgs() << "LV: Can't if-convert the loop.\n");
return false;
}
// ScalarEvolution needs to be able to find the exit count.
const SCEV *ExitCount = SE->getBackedgeTakenCount(TheLoop);
if (ExitCount == SE->getCouldNotCompute()) {
DEBUG(dbgs() << "LV: SCEV could not compute the loop exit count.\n");
return false;
}
// Do not loop-vectorize loops with a tiny trip count.
BasicBlock *Latch = TheLoop->getLoopLatch();
unsigned TC = SE->getSmallConstantTripCount(TheLoop, Latch);
if (TC > 0u && TC < TinyTripCountVectorThreshold) {
DEBUG(dbgs() << "LV: Found a loop with a very small trip count. " <<
"This loop is not worth vectorizing.\n");
return false;
}
// Check if we can vectorize the instructions and CFG in this loop.
if (!canVectorizeInstrs()) {
DEBUG(dbgs() << "LV: Can't vectorize the instructions or CFG\n");
return false;
}
// Go over each instruction and look at memory deps.
if (!canVectorizeMemory()) {
DEBUG(dbgs() << "LV: Can't vectorize due to memory conflicts\n");
return false;
}
// Collect all of the variables that remain uniform after vectorization.
collectLoopUniforms();
DEBUG(dbgs() << "LV: We can vectorize this loop" <<
(PtrRtCheck.Need ? " (with a runtime bound check)" : "")
<<"!\n");
// Okay! We can vectorize. At this point we don't have any other mem analysis
// which may limit our maximum vectorization factor, so just return true with
// no restrictions.
return true;
}
static Type *convertPointerToIntegerType(DataLayout &DL, Type *Ty) {
if (Ty->isPointerTy())
return DL.getIntPtrType(Ty);
// It is possible that char's or short's overflow when we ask for the loop's
// trip count, work around this by changing the type size.
if (Ty->getScalarSizeInBits() < 32)
return Type::getInt32Ty(Ty->getContext());
return Ty;
}
static Type* getWiderType(DataLayout &DL, Type *Ty0, Type *Ty1) {
Ty0 = convertPointerToIntegerType(DL, Ty0);
Ty1 = convertPointerToIntegerType(DL, Ty1);
if (Ty0->getScalarSizeInBits() > Ty1->getScalarSizeInBits())
return Ty0;
return Ty1;
}
/// \brief Check that the instruction has outside loop users and is not an
/// identified reduction variable.
static bool hasOutsideLoopUser(const Loop *TheLoop, Instruction *Inst,
SmallPtrSet<Value *, 4> &Reductions) {
// Reduction instructions are allowed to have exit users. All other
// instructions must not have external users.
if (!Reductions.count(Inst))
//Check that all of the users of the loop are inside the BB.
for (Value::use_iterator I = Inst->use_begin(), E = Inst->use_end();
I != E; ++I) {
Instruction *U = cast<Instruction>(*I);
// This user may be a reduction exit value.
if (!TheLoop->contains(U)) {
DEBUG(dbgs() << "LV: Found an outside user for : " << *U << '\n');
return true;
}
}
return false;
}
bool LoopVectorizationLegality::canVectorizeInstrs() {
BasicBlock *PreHeader = TheLoop->getLoopPreheader();
BasicBlock *Header = TheLoop->getHeader();
// Look for the attribute signaling the absence of NaNs.
Function &F = *Header->getParent();
if (F.hasFnAttribute("no-nans-fp-math"))
HasFunNoNaNAttr = F.getAttributes().getAttribute(
AttributeSet::FunctionIndex,
"no-nans-fp-math").getValueAsString() == "true";
// For each block in the loop.
for (Loop::block_iterator bb = TheLoop->block_begin(),
be = TheLoop->block_end(); bb != be; ++bb) {
// Scan the instructions in the block and look for hazards.
for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
++it) {
if (PHINode *Phi = dyn_cast<PHINode>(it)) {
Type *PhiTy = Phi->getType();
// Check that this PHI type is allowed.
if (!PhiTy->isIntegerTy() &&
!PhiTy->isFloatingPointTy() &&
!PhiTy->isPointerTy()) {
DEBUG(dbgs() << "LV: Found an non-int non-pointer PHI.\n");
return false;
}
// If this PHINode is not in the header block, then we know that we
// can convert it to select during if-conversion. No need to check if
// the PHIs in this block are induction or reduction variables.
if (*bb != Header) {
// Check that this instruction has no outside users or is an
// identified reduction value with an outside user.
if(!hasOutsideLoopUser(TheLoop, it, AllowedExit))
continue;
return false;
}
// We only allow if-converted PHIs with more than two incoming values.
if (Phi->getNumIncomingValues() != 2) {
DEBUG(dbgs() << "LV: Found an invalid PHI.\n");
return false;
}
// This is the value coming from the preheader.
Value *StartValue = Phi->getIncomingValueForBlock(PreHeader);
// Check if this is an induction variable.
InductionKind IK = isInductionVariable(Phi);
if (IK_NoInduction != IK) {
// Get the widest type.
if (!WidestIndTy)
WidestIndTy = convertPointerToIntegerType(*DL, PhiTy);
else
WidestIndTy = getWiderType(*DL, PhiTy, WidestIndTy);
// Int inductions are special because we only allow one IV.
if (IK == IK_IntInduction) {
// Use the phi node with the widest type as induction. Use the last
// one if there are multiple (no good reason for doing this other
// than it is expedient).
if (!Induction || PhiTy == WidestIndTy)
Induction = Phi;
}
DEBUG(dbgs() << "LV: Found an induction variable.\n");
Inductions[Phi] = InductionInfo(StartValue, IK);
// Until we explicitly handle the case of an induction variable with
// an outside loop user we have to give up vectorizing this loop.
if (hasOutsideLoopUser(TheLoop, it, AllowedExit))
return false;
continue;
}
if (AddReductionVar(Phi, RK_IntegerAdd)) {
DEBUG(dbgs() << "LV: Found an ADD reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_IntegerMult)) {
DEBUG(dbgs() << "LV: Found a MUL reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_IntegerOr)) {
DEBUG(dbgs() << "LV: Found an OR reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_IntegerAnd)) {
DEBUG(dbgs() << "LV: Found an AND reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_IntegerXor)) {
DEBUG(dbgs() << "LV: Found a XOR reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_IntegerMinMax)) {
DEBUG(dbgs() << "LV: Found a MINMAX reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_FloatMult)) {
DEBUG(dbgs() << "LV: Found an FMult reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_FloatAdd)) {
DEBUG(dbgs() << "LV: Found an FAdd reduction PHI."<< *Phi <<"\n");
continue;
}
if (AddReductionVar(Phi, RK_FloatMinMax)) {
DEBUG(dbgs() << "LV: Found an float MINMAX reduction PHI."<< *Phi <<
"\n");
continue;
}
DEBUG(dbgs() << "LV: Found an unidentified PHI."<< *Phi <<"\n");
return false;
}// end of PHI handling
// We still don't handle functions. However, we can ignore dbg intrinsic
// calls and we do handle certain intrinsic and libm functions.
CallInst *CI = dyn_cast<CallInst>(it);
if (CI && !getIntrinsicIDForCall(CI, TLI) && !isa<DbgInfoIntrinsic>(CI)) {
DEBUG(dbgs() << "LV: Found a call site.\n");
return false;
}
// Check that the instruction return type is vectorizable.
// Also, we can't vectorize extractelement instructions.
if ((!VectorType::isValidElementType(it->getType()) &&
!it->getType()->isVoidTy()) || isa<ExtractElementInst>(it)) {
DEBUG(dbgs() << "LV: Found unvectorizable type.\n");
return false;
}
// Check that the stored type is vectorizable.
if (StoreInst *ST = dyn_cast<StoreInst>(it)) {
Type *T = ST->getValueOperand()->getType();
if (!VectorType::isValidElementType(T))
return false;
if (EnableMemAccessVersioning)
collectStridedAcccess(ST);
}
if (EnableMemAccessVersioning)
if (LoadInst *LI = dyn_cast<LoadInst>(it))
collectStridedAcccess(LI);
// Reduction instructions are allowed to have exit users.
// All other instructions must not have external users.
if (hasOutsideLoopUser(TheLoop, it, AllowedExit))
return false;
} // next instr.
}
if (!Induction) {
DEBUG(dbgs() << "LV: Did not find one integer induction var.\n");
if (Inductions.empty())
return false;
}
return true;
}
///\brief Remove GEPs whose indices but the last one are loop invariant and
/// return the induction operand of the gep pointer.
static Value *stripGetElementPtr(Value *Ptr, ScalarEvolution *SE,
DataLayout *DL, Loop *Lp) {
GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr);
if (!GEP)
return Ptr;
unsigned InductionOperand = getGEPInductionOperand(DL, GEP);
// Check that all of the gep indices are uniform except for our induction
// operand.
for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i)
if (i != InductionOperand &&
!SE->isLoopInvariant(SE->getSCEV(GEP->getOperand(i)), Lp))
return Ptr;
return GEP->getOperand(InductionOperand);
}
///\brief Look for a cast use of the passed value.
static Value *getUniqueCastUse(Value *Ptr, Loop *Lp, Type *Ty) {
Value *UniqueCast = 0;
for (Value::use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end(); UI != UE;
++UI) {
CastInst *CI = dyn_cast<CastInst>(*UI);
if (CI && CI->getType() == Ty) {
if (!UniqueCast)
UniqueCast = CI;
else
return 0;
}
}
return UniqueCast;
}
///\brief Get the stride of a pointer access in a loop.
/// Looks for symbolic strides "a[i*stride]". Returns the symbolic stride as a
/// pointer to the Value, or null otherwise.
static Value *getStrideFromPointer(Value *Ptr, ScalarEvolution *SE,
DataLayout *DL, Loop *Lp) {
const PointerType *PtrTy = dyn_cast<PointerType>(Ptr->getType());
if (!PtrTy || PtrTy->isAggregateType())
return 0;
// Try to remove a gep instruction to make the pointer (actually index at this
// point) easier analyzable. If OrigPtr is equal to Ptr we are analzying the
// pointer, otherwise, we are analyzing the index.
Value *OrigPtr = Ptr;
// The size of the pointer access.
int64_t PtrAccessSize = 1;
Ptr = stripGetElementPtr(Ptr, SE, DL, Lp);
const SCEV *V = SE->getSCEV(Ptr);
if (Ptr != OrigPtr)
// Strip off casts.
while (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(V))
V = C->getOperand();
const SCEVAddRecExpr *S = dyn_cast<SCEVAddRecExpr>(V);
if (!S)
return 0;
V = S->getStepRecurrence(*SE);
if (!V)
return 0;
// Strip off the size of access multiplication if we are still analyzing the
// pointer.
if (OrigPtr == Ptr) {
DL->getTypeAllocSize(PtrTy->getElementType());
if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(V)) {
if (M->getOperand(0)->getSCEVType() != scConstant)
return 0;
const APInt &APStepVal =
cast<SCEVConstant>(M->getOperand(0))->getValue()->getValue();
// Huge step value - give up.
if (APStepVal.getBitWidth() > 64)
return 0;
int64_t StepVal = APStepVal.getSExtValue();
if (PtrAccessSize != StepVal)
return 0;
V = M->getOperand(1);
}
}
// Strip off casts.
Type *StripedOffRecurrenceCast = 0;
if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(V)) {
StripedOffRecurrenceCast = C->getType();
V = C->getOperand();
}
// Look for the loop invariant symbolic value.
const SCEVUnknown *U = dyn_cast<SCEVUnknown>(V);
if (!U)
return 0;
Value *Stride = U->getValue();
if (!Lp->isLoopInvariant(Stride))
return 0;
// If we have stripped off the recurrence cast we have to make sure that we
// return the value that is used in this loop so that we can replace it later.
if (StripedOffRecurrenceCast)
Stride = getUniqueCastUse(Stride, Lp, StripedOffRecurrenceCast);
return Stride;
}
void LoopVectorizationLegality::collectStridedAcccess(Value *MemAccess) {
Value *Ptr = 0;
if (LoadInst *LI = dyn_cast<LoadInst>(MemAccess))
Ptr = LI->getPointerOperand();
else if (StoreInst *SI = dyn_cast<StoreInst>(MemAccess))
Ptr = SI->getPointerOperand();
else
return;
Value *Stride = getStrideFromPointer(Ptr, SE, DL, TheLoop);
if (!Stride)
return;
DEBUG(dbgs() << "LV: Found a strided access that we can version");
DEBUG(dbgs() << " Ptr: " << *Ptr << " Stride: " << *Stride << "\n");
Strides[Ptr] = Stride;
StrideSet.insert(Stride);
}
void LoopVectorizationLegality::collectLoopUniforms() {
// We now know that the loop is vectorizable!
// Collect variables that will remain uniform after vectorization.
std::vector<Value*> Worklist;
BasicBlock *Latch = TheLoop->getLoopLatch();
// Start with the conditional branch and walk up the block.
Worklist.push_back(Latch->getTerminator()->getOperand(0));
while (Worklist.size()) {
Instruction *I = dyn_cast<Instruction>(Worklist.back());
Worklist.pop_back();
// Look at instructions inside this loop.
// Stop when reaching PHI nodes.
// TODO: we need to follow values all over the loop, not only in this block.
if (!I || !TheLoop->contains(I) || isa<PHINode>(I))
continue;
// This is a known uniform.
Uniforms.insert(I);
// Insert all operands.
Worklist.insert(Worklist.end(), I->op_begin(), I->op_end());
}
}
namespace {
/// \brief Analyses memory accesses in a loop.
///
/// Checks whether run time pointer checks are needed and builds sets for data
/// dependence checking.
class AccessAnalysis {
public:
/// \brief Read or write access location.
typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
/// \brief Set of potential dependent memory accesses.
typedef EquivalenceClasses<MemAccessInfo> DepCandidates;
AccessAnalysis(DataLayout *Dl, DepCandidates &DA) :
DL(Dl), DepCands(DA), AreAllWritesIdentified(true),
AreAllReadsIdentified(true), IsRTCheckNeeded(false) {}
/// \brief Register a load and whether it is only read from.
void addLoad(Value *Ptr, bool IsReadOnly) {
Accesses.insert(MemAccessInfo(Ptr, false));
if (IsReadOnly)
ReadOnlyPtr.insert(Ptr);
}
/// \brief Register a store.
void addStore(Value *Ptr) {
Accesses.insert(MemAccessInfo(Ptr, true));
}
/// \brief Check whether we can check the pointers at runtime for
/// non-intersection.
bool canCheckPtrAtRT(LoopVectorizationLegality::RuntimePointerCheck &RtCheck,
unsigned &NumComparisons, ScalarEvolution *SE,
Loop *TheLoop, ValueToValueMap &Strides,
bool ShouldCheckStride = false);
/// \brief Goes over all memory accesses, checks whether a RT check is needed
/// and builds sets of dependent accesses.
void buildDependenceSets() {
// Process read-write pointers first.
processMemAccesses(false);
// Next, process read pointers.
processMemAccesses(true);
}
bool isRTCheckNeeded() { return IsRTCheckNeeded; }
bool isDependencyCheckNeeded() { return !CheckDeps.empty(); }
void resetDepChecks() { CheckDeps.clear(); }
MemAccessInfoSet &getDependenciesToCheck() { return CheckDeps; }
private:
typedef SetVector<MemAccessInfo> PtrAccessSet;
typedef DenseMap<Value*, MemAccessInfo> UnderlyingObjToAccessMap;
/// \brief Go over all memory access or only the deferred ones if
/// \p UseDeferred is true and check whether runtime pointer checks are needed
/// and build sets of dependency check candidates.
void processMemAccesses(bool UseDeferred);
/// Set of all accesses.
PtrAccessSet Accesses;
/// Set of access to check after all writes have been processed.
PtrAccessSet DeferredAccesses;
/// Map of pointers to last access encountered.
UnderlyingObjToAccessMap ObjToLastAccess;
/// Set of accesses that need a further dependence check.
MemAccessInfoSet CheckDeps;
/// Set of pointers that are read only.
SmallPtrSet<Value*, 16> ReadOnlyPtr;
/// Set of underlying objects already written to.
SmallPtrSet<Value*, 16> WriteObjects;
DataLayout *DL;
/// Sets of potentially dependent accesses - members of one set share an
/// underlying pointer. The set "CheckDeps" identfies which sets really need a
/// dependence check.
DepCandidates &DepCands;
bool AreAllWritesIdentified;
bool AreAllReadsIdentified;
bool IsRTCheckNeeded;
};
} // end anonymous namespace
/// \brief Check whether a pointer can participate in a runtime bounds check.
static bool hasComputableBounds(ScalarEvolution *SE, ValueToValueMap &Strides,
Value *Ptr) {
const SCEV *PtrScev = replaceSymbolicStrideSCEV(SE, Strides, Ptr);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
if (!AR)
return false;
return AR->isAffine();
}
/// \brief Check the stride of the pointer and ensure that it does not wrap in
/// the address space.
static int isStridedPtr(ScalarEvolution *SE, DataLayout *DL, Value *Ptr,
const Loop *Lp, ValueToValueMap &StridesMap);
bool AccessAnalysis::canCheckPtrAtRT(
LoopVectorizationLegality::RuntimePointerCheck &RtCheck,
unsigned &NumComparisons, ScalarEvolution *SE, Loop *TheLoop,
ValueToValueMap &StridesMap, bool ShouldCheckStride) {
// Find pointers with computable bounds. We are going to use this information
// to place a runtime bound check.
unsigned NumReadPtrChecks = 0;
unsigned NumWritePtrChecks = 0;
bool CanDoRT = true;
bool IsDepCheckNeeded = isDependencyCheckNeeded();
// We assign consecutive id to access from different dependence sets.
// Accesses within the same set don't need a runtime check.
unsigned RunningDepId = 1;
DenseMap<Value *, unsigned> DepSetId;
for (PtrAccessSet::iterator AI = Accesses.begin(), AE = Accesses.end();
AI != AE; ++AI) {
const MemAccessInfo &Access = *AI;
Value *Ptr = Access.getPointer();
bool IsWrite = Access.getInt();
// Just add write checks if we have both.
if (!IsWrite && Accesses.count(MemAccessInfo(Ptr, true)))
continue;
if (IsWrite)
++NumWritePtrChecks;
else
++NumReadPtrChecks;
if (hasComputableBounds(SE, StridesMap, Ptr) &&
// When we run after a failing dependency check we have to make sure we
// don't have wrapping pointers.
(!ShouldCheckStride ||
isStridedPtr(SE, DL, Ptr, TheLoop, StridesMap) == 1)) {
// The id of the dependence set.
unsigned DepId;
if (IsDepCheckNeeded) {
Value *Leader = DepCands.getLeaderValue(Access).getPointer();
unsigned &LeaderId = DepSetId[Leader];
if (!LeaderId)
LeaderId = RunningDepId++;
DepId = LeaderId;
} else
// Each access has its own dependence set.
DepId = RunningDepId++;
RtCheck.insert(SE, TheLoop, Ptr, IsWrite, DepId, StridesMap);
DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *Ptr << '\n');
} else {
CanDoRT = false;
}
}
if (IsDepCheckNeeded && CanDoRT && RunningDepId == 2)
NumComparisons = 0; // Only one dependence set.
else {
NumComparisons = (NumWritePtrChecks * (NumReadPtrChecks +
NumWritePtrChecks - 1));
}
// If the pointers that we would use for the bounds comparison have different
// address spaces, assume the values aren't directly comparable, so we can't
// use them for the runtime check. We also have to assume they could
// overlap. In the future there should be metadata for whether address spaces
// are disjoint.
unsigned NumPointers = RtCheck.Pointers.size();
for (unsigned i = 0; i < NumPointers; ++i) {
for (unsigned j = i + 1; j < NumPointers; ++j) {
// Only need to check pointers between two different dependency sets.
if (RtCheck.DependencySetId[i] == RtCheck.DependencySetId[j])
continue;
Value *PtrI = RtCheck.Pointers[i];
Value *PtrJ = RtCheck.Pointers[j];
unsigned ASi = PtrI->getType()->getPointerAddressSpace();
unsigned ASj = PtrJ->getType()->getPointerAddressSpace();
if (ASi != ASj) {
DEBUG(dbgs() << "LV: Runtime check would require comparison between"
" different address spaces\n");
return false;
}
}
}
return CanDoRT;
}
static bool isFunctionScopeIdentifiedObject(Value *Ptr) {
return isNoAliasArgument(Ptr) || isNoAliasCall(Ptr) || isa<AllocaInst>(Ptr);
}
void AccessAnalysis::processMemAccesses(bool UseDeferred) {
// We process the set twice: first we process read-write pointers, last we
// process read-only pointers. This allows us to skip dependence tests for
// read-only pointers.
PtrAccessSet &S = UseDeferred ? DeferredAccesses : Accesses;
for (PtrAccessSet::iterator AI = S.begin(), AE = S.end(); AI != AE; ++AI) {
const MemAccessInfo &Access = *AI;
Value *Ptr = Access.getPointer();
bool IsWrite = Access.getInt();
DepCands.insert(Access);
// Memorize read-only pointers for later processing and skip them in the
// first round (they need to be checked after we have seen all write
// pointers). Note: we also mark pointer that are not consecutive as
// "read-only" pointers (so that we check "a[b[i]] +="). Hence, we need the
// second check for "!IsWrite".
bool IsReadOnlyPtr = ReadOnlyPtr.count(Ptr) && !IsWrite;
if (!UseDeferred && IsReadOnlyPtr) {
DeferredAccesses.insert(Access);
continue;
}
bool NeedDepCheck = false;
// Check whether there is the possibility of dependency because of
// underlying objects being the same.
typedef SmallVector<Value*, 16> ValueVector;
ValueVector TempObjects;
GetUnderlyingObjects(Ptr, TempObjects, DL);
for (ValueVector::iterator UI = TempObjects.begin(), UE = TempObjects.end();
UI != UE; ++UI) {
Value *UnderlyingObj = *UI;
// If this is a write then it needs to be an identified object. If this a
// read and all writes (so far) are identified function scope objects we
// don't need an identified underlying object but only an Argument (the
// next write is going to invalidate this assumption if it is
// unidentified).
// This is a micro-optimization for the case where all writes are
// identified and we have one argument pointer.
// Otherwise, we do need a runtime check.
if ((IsWrite && !isFunctionScopeIdentifiedObject(UnderlyingObj)) ||
(!IsWrite && (!AreAllWritesIdentified ||
!isa<Argument>(UnderlyingObj)) &&
!isIdentifiedObject(UnderlyingObj))) {
DEBUG(dbgs() << "LV: Found an unidentified " <<
(IsWrite ? "write" : "read" ) << " ptr: " << *UnderlyingObj <<
"\n");
IsRTCheckNeeded = (IsRTCheckNeeded ||
!isIdentifiedObject(UnderlyingObj) ||
!AreAllReadsIdentified);
if (IsWrite)
AreAllWritesIdentified = false;
if (!IsWrite)
AreAllReadsIdentified = false;
}
// If this is a write - check other reads and writes for conflicts. If
// this is a read only check other writes for conflicts (but only if there
// is no other write to the ptr - this is an optimization to catch "a[i] =
// a[i] + " without having to do a dependence check).
if ((IsWrite || IsReadOnlyPtr) && WriteObjects.count(UnderlyingObj))
NeedDepCheck = true;
if (IsWrite)
WriteObjects.insert(UnderlyingObj);
// Create sets of pointers connected by shared underlying objects.
UnderlyingObjToAccessMap::iterator Prev =
ObjToLastAccess.find(UnderlyingObj);
if (Prev != ObjToLastAccess.end())
DepCands.unionSets(Access, Prev->second);
ObjToLastAccess[UnderlyingObj] = Access;
}
if (NeedDepCheck)
CheckDeps.insert(Access);
}
}
namespace {
/// \brief Checks memory dependences among accesses to the same underlying
/// object to determine whether there vectorization is legal or not (and at
/// which vectorization factor).
///
/// This class works under the assumption that we already checked that memory
/// locations with different underlying pointers are "must-not alias".
/// We use the ScalarEvolution framework to symbolically evalutate access
/// functions pairs. Since we currently don't restructure the loop we can rely
/// on the program order of memory accesses to determine their safety.
/// At the moment we will only deem accesses as safe for:
/// * A negative constant distance assuming program order.
///
/// Safe: tmp = a[i + 1]; OR a[i + 1] = x;
/// a[i] = tmp; y = a[i];
///
/// The latter case is safe because later checks guarantuee that there can't
/// be a cycle through a phi node (that is, we check that "x" and "y" is not
/// the same variable: a header phi can only be an induction or a reduction, a
/// reduction can't have a memory sink, an induction can't have a memory
/// source). This is important and must not be violated (or we have to
/// resort to checking for cycles through memory).
///
/// * A positive constant distance assuming program order that is bigger
/// than the biggest memory access.
///
/// tmp = a[i] OR b[i] = x
/// a[i+2] = tmp y = b[i+2];
///
/// Safe distance: 2 x sizeof(a[0]), and 2 x sizeof(b[0]), respectively.
///
/// * Zero distances and all accesses have the same size.
///
class MemoryDepChecker {
public:
typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
MemoryDepChecker(ScalarEvolution *Se, DataLayout *Dl, const Loop *L)
: SE(Se), DL(Dl), InnermostLoop(L), AccessIdx(0),
ShouldRetryWithRuntimeCheck(false) {}
/// \brief Register the location (instructions are given increasing numbers)
/// of a write access.
void addAccess(StoreInst *SI) {
Value *Ptr = SI->getPointerOperand();
Accesses[MemAccessInfo(Ptr, true)].push_back(AccessIdx);
InstMap.push_back(SI);
++AccessIdx;
}
/// \brief Register the location (instructions are given increasing numbers)
/// of a write access.
void addAccess(LoadInst *LI) {
Value *Ptr = LI->getPointerOperand();
Accesses[MemAccessInfo(Ptr, false)].push_back(AccessIdx);
InstMap.push_back(LI);
++AccessIdx;
}
/// \brief Check whether the dependencies between the accesses are safe.
///
/// Only checks sets with elements in \p CheckDeps.
bool areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
MemAccessInfoSet &CheckDeps, ValueToValueMap &Strides);
/// \brief The maximum number of bytes of a vector register we can vectorize
/// the accesses safely with.
unsigned getMaxSafeDepDistBytes() { return MaxSafeDepDistBytes; }
/// \brief In same cases when the dependency check fails we can still
/// vectorize the loop with a dynamic array access check.
bool shouldRetryWithRuntimeCheck() { return ShouldRetryWithRuntimeCheck; }
private:
ScalarEvolution *SE;
DataLayout *DL;
const Loop *InnermostLoop;
/// \brief Maps access locations (ptr, read/write) to program order.
DenseMap<MemAccessInfo, std::vector<unsigned> > Accesses;
/// \brief Memory access instructions in program order.
SmallVector<Instruction *, 16> InstMap;
/// \brief The program order index to be used for the next instruction.
unsigned AccessIdx;
// We can access this many bytes in parallel safely.
unsigned MaxSafeDepDistBytes;
/// \brief If we see a non-constant dependence distance we can still try to
/// vectorize this loop with runtime checks.
bool ShouldRetryWithRuntimeCheck;
/// \brief Check whether there is a plausible dependence between the two
/// accesses.
///
/// Access \p A must happen before \p B in program order. The two indices
/// identify the index into the program order map.
///
/// This function checks whether there is a plausible dependence (or the
/// absence of such can't be proved) between the two accesses. If there is a
/// plausible dependence but the dependence distance is bigger than one
/// element access it records this distance in \p MaxSafeDepDistBytes (if this
/// distance is smaller than any other distance encountered so far).
/// Otherwise, this function returns true signaling a possible dependence.
bool isDependent(const MemAccessInfo &A, unsigned AIdx,
const MemAccessInfo &B, unsigned BIdx,
ValueToValueMap &Strides);
/// \brief Check whether the data dependence could prevent store-load
/// forwarding.
bool couldPreventStoreLoadForward(unsigned Distance, unsigned TypeByteSize);
};
} // end anonymous namespace
static bool isInBoundsGep(Value *Ptr) {
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr))
return GEP->isInBounds();
return false;
}
/// \brief Check whether the access through \p Ptr has a constant stride.
static int isStridedPtr(ScalarEvolution *SE, DataLayout *DL, Value *Ptr,
const Loop *Lp, ValueToValueMap &StridesMap) {
const Type *Ty = Ptr->getType();
assert(Ty->isPointerTy() && "Unexpected non-ptr");
// Make sure that the pointer does not point to aggregate types.
const PointerType *PtrTy = cast<PointerType>(Ty);
if (PtrTy->getElementType()->isAggregateType()) {
DEBUG(dbgs() << "LV: Bad stride - Not a pointer to a scalar type" << *Ptr <<
"\n");
return 0;
}
const SCEV *PtrScev = replaceSymbolicStrideSCEV(SE, StridesMap, Ptr);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PtrScev);
if (!AR) {
DEBUG(dbgs() << "LV: Bad stride - Not an AddRecExpr pointer "
<< *Ptr << " SCEV: " << *PtrScev << "\n");
return 0;
}
// The accesss function must stride over the innermost loop.
if (Lp != AR->getLoop()) {
DEBUG(dbgs() << "LV: Bad stride - Not striding over innermost loop " <<
*Ptr << " SCEV: " << *PtrScev << "\n");
}
// The address calculation must not wrap. Otherwise, a dependence could be
// inverted.
// An inbounds getelementptr that is a AddRec with a unit stride
// cannot wrap per definition. The unit stride requirement is checked later.
// An getelementptr without an inbounds attribute and unit stride would have
// to access the pointer value "0" which is undefined behavior in address
// space 0, therefore we can also vectorize this case.
bool IsInBoundsGEP = isInBoundsGep(Ptr);
bool IsNoWrapAddRec = AR->getNoWrapFlags(SCEV::NoWrapMask);
bool IsInAddressSpaceZero = PtrTy->getAddressSpace() == 0;
if (!IsNoWrapAddRec && !IsInBoundsGEP && !IsInAddressSpaceZero) {
DEBUG(dbgs() << "LV: Bad stride - Pointer may wrap in the address space "
<< *Ptr << " SCEV: " << *PtrScev << "\n");
return 0;
}
// Check the step is constant.
const SCEV *Step = AR->getStepRecurrence(*SE);
// Calculate the pointer stride and check if it is consecutive.
const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
if (!C) {
DEBUG(dbgs() << "LV: Bad stride - Not a constant strided " << *Ptr <<
" SCEV: " << *PtrScev << "\n");
return 0;
}
int64_t Size = DL->getTypeAllocSize(PtrTy->getElementType());
const APInt &APStepVal = C->getValue()->getValue();
// Huge step value - give up.
if (APStepVal.getBitWidth() > 64)
return 0;
int64_t StepVal = APStepVal.getSExtValue();
// Strided access.
int64_t Stride = StepVal / Size;
int64_t Rem = StepVal % Size;
if (Rem)
return 0;
// If the SCEV could wrap but we have an inbounds gep with a unit stride we
// know we can't "wrap around the address space". In case of address space
// zero we know that this won't happen without triggering undefined behavior.
if (!IsNoWrapAddRec && (IsInBoundsGEP || IsInAddressSpaceZero) &&
Stride != 1 && Stride != -1)
return 0;
return Stride;
}
bool MemoryDepChecker::couldPreventStoreLoadForward(unsigned Distance,
unsigned TypeByteSize) {
// If loads occur at a distance that is not a multiple of a feasible vector
// factor store-load forwarding does not take place.
// Positive dependences might cause troubles because vectorizing them might
// prevent store-load forwarding making vectorized code run a lot slower.
// a[i] = a[i-3] ^ a[i-8];
// The stores to a[i:i+1] don't align with the stores to a[i-3:i-2] and
// hence on your typical architecture store-load forwarding does not take
// place. Vectorizing in such cases does not make sense.
// Store-load forwarding distance.
const unsigned NumCyclesForStoreLoadThroughMemory = 8*TypeByteSize;
// Maximum vector factor.
unsigned MaxVFWithoutSLForwardIssues = MaxVectorWidth*TypeByteSize;
if(MaxSafeDepDistBytes < MaxVFWithoutSLForwardIssues)
MaxVFWithoutSLForwardIssues = MaxSafeDepDistBytes;
for (unsigned vf = 2*TypeByteSize; vf <= MaxVFWithoutSLForwardIssues;
vf *= 2) {
if (Distance % vf && Distance / vf < NumCyclesForStoreLoadThroughMemory) {
MaxVFWithoutSLForwardIssues = (vf >>=1);
break;
}
}
if (MaxVFWithoutSLForwardIssues< 2*TypeByteSize) {
DEBUG(dbgs() << "LV: Distance " << Distance <<
" that could cause a store-load forwarding conflict\n");
return true;
}
if (MaxVFWithoutSLForwardIssues < MaxSafeDepDistBytes &&
MaxVFWithoutSLForwardIssues != MaxVectorWidth*TypeByteSize)
MaxSafeDepDistBytes = MaxVFWithoutSLForwardIssues;
return false;
}
bool MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
const MemAccessInfo &B, unsigned BIdx,
ValueToValueMap &Strides) {
assert (AIdx < BIdx && "Must pass arguments in program order");
Value *APtr = A.getPointer();
Value *BPtr = B.getPointer();
bool AIsWrite = A.getInt();
bool BIsWrite = B.getInt();
// Two reads are independent.
if (!AIsWrite && !BIsWrite)
return false;
const SCEV *AScev = replaceSymbolicStrideSCEV(SE, Strides, APtr);
const SCEV *BScev = replaceSymbolicStrideSCEV(SE, Strides, BPtr);
int StrideAPtr = isStridedPtr(SE, DL, APtr, InnermostLoop, Strides);
int StrideBPtr = isStridedPtr(SE, DL, BPtr, InnermostLoop, Strides);
const SCEV *Src = AScev;
const SCEV *Sink = BScev;
// If the induction step is negative we have to invert source and sink of the
// dependence.
if (StrideAPtr < 0) {
//Src = BScev;
//Sink = AScev;
std::swap(APtr, BPtr);
std::swap(Src, Sink);
std::swap(AIsWrite, BIsWrite);
std::swap(AIdx, BIdx);
std::swap(StrideAPtr, StrideBPtr);
}
const SCEV *Dist = SE->getMinusSCEV(Sink, Src);
DEBUG(dbgs() << "LV: Src Scev: " << *Src << "Sink Scev: " << *Sink
<< "(Induction step: " << StrideAPtr << ")\n");
DEBUG(dbgs() << "LV: Distance for " << *InstMap[AIdx] << " to "
<< *InstMap[BIdx] << ": " << *Dist << "\n");
// Need consecutive accesses. We don't want to vectorize
// "A[B[i]] += ..." and similar code or pointer arithmetic that could wrap in
// the address space.
if (!StrideAPtr || !StrideBPtr || StrideAPtr != StrideBPtr){
DEBUG(dbgs() << "Non-consecutive pointer access\n");
return true;
}
const SCEVConstant *C = dyn_cast<SCEVConstant>(Dist);
if (!C) {
DEBUG(dbgs() << "LV: Dependence because of non-constant distance\n");
ShouldRetryWithRuntimeCheck = true;
return true;
}
Type *ATy = APtr->getType()->getPointerElementType();
Type *BTy = BPtr->getType()->getPointerElementType();
unsigned TypeByteSize = DL->getTypeAllocSize(ATy);
// Negative distances are not plausible dependencies.
const APInt &Val = C->getValue()->getValue();
if (Val.isNegative()) {
bool IsTrueDataDependence = (AIsWrite && !BIsWrite);
if (IsTrueDataDependence &&
(couldPreventStoreLoadForward(Val.abs().getZExtValue(), TypeByteSize) ||
ATy != BTy))
return true;
DEBUG(dbgs() << "LV: Dependence is negative: NoDep\n");
return false;
}
// Write to the same location with the same size.
// Could be improved to assert type sizes are the same (i32 == float, etc).
if (Val == 0) {
if (ATy == BTy)
return false;
DEBUG(dbgs() << "LV: Zero dependence difference but different types\n");
return true;
}
assert(Val.isStrictlyPositive() && "Expect a positive value");
// Positive distance bigger than max vectorization factor.
if (ATy != BTy) {
DEBUG(dbgs() <<
"LV: ReadWrite-Write positive dependency with different types\n");
return false;
}
unsigned Distance = (unsigned) Val.getZExtValue();
// Bail out early if passed-in parameters make vectorization not feasible.
unsigned ForcedFactor = VectorizationFactor ? VectorizationFactor : 1;
unsigned ForcedUnroll = VectorizationUnroll ? VectorizationUnroll : 1;
// The distance must be bigger than the size needed for a vectorized version
// of the operation and the size of the vectorized operation must not be
// bigger than the currrent maximum size.
if (Distance < 2*TypeByteSize ||
2*TypeByteSize > MaxSafeDepDistBytes ||
Distance < TypeByteSize * ForcedUnroll * ForcedFactor) {
DEBUG(dbgs() << "LV: Failure because of Positive distance "
<< Val.getSExtValue() << '\n');
return true;
}
MaxSafeDepDistBytes = Distance < MaxSafeDepDistBytes ?
Distance : MaxSafeDepDistBytes;
bool IsTrueDataDependence = (!AIsWrite && BIsWrite);
if (IsTrueDataDependence &&
couldPreventStoreLoadForward(Distance, TypeByteSize))
return true;
DEBUG(dbgs() << "LV: Positive distance " << Val.getSExtValue() <<
" with max VF = " << MaxSafeDepDistBytes / TypeByteSize << '\n');
return false;
}
bool MemoryDepChecker::areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
MemAccessInfoSet &CheckDeps,
ValueToValueMap &Strides) {
MaxSafeDepDistBytes = -1U;
while (!CheckDeps.empty()) {
MemAccessInfo CurAccess = *CheckDeps.begin();
// Get the relevant memory access set.
EquivalenceClasses<MemAccessInfo>::iterator I =
AccessSets.findValue(AccessSets.getLeaderValue(CurAccess));
// Check accesses within this set.
EquivalenceClasses<MemAccessInfo>::member_iterator AI, AE;
AI = AccessSets.member_begin(I), AE = AccessSets.member_end();
// Check every access pair.
while (AI != AE) {
CheckDeps.erase(*AI);
EquivalenceClasses<MemAccessInfo>::member_iterator OI = llvm::next(AI);
while (OI != AE) {
// Check every accessing instruction pair in program order.
for (std::vector<unsigned>::iterator I1 = Accesses[*AI].begin(),
I1E = Accesses[*AI].end(); I1 != I1E; ++I1)
for (std::vector<unsigned>::iterator I2 = Accesses[*OI].begin(),
I2E = Accesses[*OI].end(); I2 != I2E; ++I2) {
if (*I1 < *I2 && isDependent(*AI, *I1, *OI, *I2, Strides))
return false;
if (*I2 < *I1 && isDependent(*OI, *I2, *AI, *I1, Strides))
return false;
}
++OI;
}
AI++;
}
}
return true;
}
bool LoopVectorizationLegality::canVectorizeMemory() {
typedef SmallVector<Value*, 16> ValueVector;
typedef SmallPtrSet<Value*, 16> ValueSet;
// Holds the Load and Store *instructions*.
ValueVector Loads;
ValueVector Stores;
// Holds all the different accesses in the loop.
unsigned NumReads = 0;
unsigned NumReadWrites = 0;
PtrRtCheck.Pointers.clear();
PtrRtCheck.Need = false;
const bool IsAnnotatedParallel = TheLoop->isAnnotatedParallel();
MemoryDepChecker DepChecker(SE, DL, TheLoop);
// For each block.
for (Loop::block_iterator bb = TheLoop->block_begin(),
be = TheLoop->block_end(); bb != be; ++bb) {
// Scan the BB and collect legal loads and stores.
for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
++it) {
// If this is a load, save it. If this instruction can read from memory
// but is not a load, then we quit. Notice that we don't handle function
// calls that read or write.
if (it->mayReadFromMemory()) {
// Many math library functions read the rounding mode. We will only
// vectorize a loop if it contains known function calls that don't set
// the flag. Therefore, it is safe to ignore this read from memory.
CallInst *Call = dyn_cast<CallInst>(it);
if (Call && getIntrinsicIDForCall(Call, TLI))
continue;
LoadInst *Ld = dyn_cast<LoadInst>(it);
if (!Ld) return false;
if (!Ld->isSimple() && !IsAnnotatedParallel) {
DEBUG(dbgs() << "LV: Found a non-simple load.\n");
return false;
}
Loads.push_back(Ld);
DepChecker.addAccess(Ld);
continue;
}
// Save 'store' instructions. Abort if other instructions write to memory.
if (it->mayWriteToMemory()) {
StoreInst *St = dyn_cast<StoreInst>(it);
if (!St) return false;
if (!St->isSimple() && !IsAnnotatedParallel) {
DEBUG(dbgs() << "LV: Found a non-simple store.\n");
return false;
}
Stores.push_back(St);
DepChecker.addAccess(St);
}
} // Next instr.
} // Next block.
// Now we have two lists that hold the loads and the stores.
// Next, we find the pointers that they use.
// Check if we see any stores. If there are no stores, then we don't
// care if the pointers are *restrict*.
if (!Stores.size()) {
DEBUG(dbgs() << "LV: Found a read-only loop!\n");
return true;
}
AccessAnalysis::DepCandidates DependentAccesses;
AccessAnalysis Accesses(DL, DependentAccesses);
// Holds the analyzed pointers. We don't want to call GetUnderlyingObjects
// multiple times on the same object. If the ptr is accessed twice, once
// for read and once for write, it will only appear once (on the write
// list). This is okay, since we are going to check for conflicts between
// writes and between reads and writes, but not between reads and reads.
ValueSet Seen;
ValueVector::iterator I, IE;
for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) {
StoreInst *ST = cast<StoreInst>(*I);
Value* Ptr = ST->getPointerOperand();
if (isUniform(Ptr)) {
DEBUG(dbgs() << "LV: We don't allow storing to uniform addresses\n");
return false;
}
// If we did *not* see this pointer before, insert it to the read-write
// list. At this phase it is only a 'write' list.
if (Seen.insert(Ptr)) {
++NumReadWrites;
Accesses.addStore(Ptr);
}
}
if (IsAnnotatedParallel) {
DEBUG(dbgs()
<< "LV: A loop annotated parallel, ignore memory dependency "
<< "checks.\n");
return true;
}
for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) {
LoadInst *LD = cast<LoadInst>(*I);
Value* Ptr = LD->getPointerOperand();
// If we did *not* see this pointer before, insert it to the
// read list. If we *did* see it before, then it is already in
// the read-write list. This allows us to vectorize expressions
// such as A[i] += x; Because the address of A[i] is a read-write
// pointer. This only works if the index of A[i] is consecutive.
// If the address of i is unknown (for example A[B[i]]) then we may
// read a few words, modify, and write a few words, and some of the
// words may be written to the same address.
bool IsReadOnlyPtr = false;
if (Seen.insert(Ptr) || !isStridedPtr(SE, DL, Ptr, TheLoop, Strides)) {
++NumReads;
IsReadOnlyPtr = true;
}
Accesses.addLoad(Ptr, IsReadOnlyPtr);
}
// If we write (or read-write) to a single destination and there are no
// other reads in this loop then is it safe to vectorize.
if (NumReadWrites == 1 && NumReads == 0) {
DEBUG(dbgs() << "LV: Found a write-only loop!\n");
return true;
}
// Build dependence sets and check whether we need a runtime pointer bounds
// check.
Accesses.buildDependenceSets();
bool NeedRTCheck = Accesses.isRTCheckNeeded();
// Find pointers with computable bounds. We are going to use this information
// to place a runtime bound check.
unsigned NumComparisons = 0;
bool CanDoRT = false;
if (NeedRTCheck)
CanDoRT = Accesses.canCheckPtrAtRT(PtrRtCheck, NumComparisons, SE, TheLoop,
Strides);
DEBUG(dbgs() << "LV: We need to do " << NumComparisons <<
" pointer comparisons.\n");
// If we only have one set of dependences to check pointers among we don't
// need a runtime check.
if (NumComparisons == 0 && NeedRTCheck)
NeedRTCheck = false;
// Check that we did not collect too many pointers or found an unsizeable
// pointer.
if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
PtrRtCheck.reset();
CanDoRT = false;
}
if (CanDoRT) {
DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n");
}
if (NeedRTCheck && !CanDoRT) {
DEBUG(dbgs() << "LV: We can't vectorize because we can't find " <<
"the array bounds.\n");
PtrRtCheck.reset();
return false;
}
PtrRtCheck.Need = NeedRTCheck;
bool CanVecMem = true;
if (Accesses.isDependencyCheckNeeded()) {
DEBUG(dbgs() << "LV: Checking memory dependencies\n");
CanVecMem = DepChecker.areDepsSafe(
DependentAccesses, Accesses.getDependenciesToCheck(), Strides);
MaxSafeDepDistBytes = DepChecker.getMaxSafeDepDistBytes();
if (!CanVecMem && DepChecker.shouldRetryWithRuntimeCheck()) {
DEBUG(dbgs() << "LV: Retrying with memory checks\n");
NeedRTCheck = true;
// Clear the dependency checks. We assume they are not needed.
Accesses.resetDepChecks();
PtrRtCheck.reset();
PtrRtCheck.Need = true;
CanDoRT = Accesses.canCheckPtrAtRT(PtrRtCheck, NumComparisons, SE,
TheLoop, Strides, true);
// Check that we did not collect too many pointers or found an unsizeable
// pointer.
if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
DEBUG(dbgs() << "LV: Can't vectorize with memory checks\n");
PtrRtCheck.reset();
return false;
}
CanVecMem = true;
}
}
DEBUG(dbgs() << "LV: We" << (NeedRTCheck ? "" : " don't") <<
" need a runtime memory check.\n");
return CanVecMem;
}
static bool hasMultipleUsesOf(Instruction *I,
SmallPtrSet<Instruction *, 8> &Insts) {
unsigned NumUses = 0;
for(User::op_iterator Use = I->op_begin(), E = I->op_end(); Use != E; ++Use) {
if (Insts.count(dyn_cast<Instruction>(*Use)))
++NumUses;
if (NumUses > 1)
return true;
}
return false;
}
static bool areAllUsesIn(Instruction *I, SmallPtrSet<Instruction *, 8> &Set) {
for(User::op_iterator Use = I->op_begin(), E = I->op_end(); Use != E; ++Use)
if (!Set.count(dyn_cast<Instruction>(*Use)))
return false;
return true;
}
bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
ReductionKind Kind) {
if (Phi->getNumIncomingValues() != 2)
return false;
// Reduction variables are only found in the loop header block.
if (Phi->getParent() != TheLoop->getHeader())
return false;
// Obtain the reduction start value from the value that comes from the loop
// preheader.
Value *RdxStart = Phi->getIncomingValueForBlock(TheLoop->getLoopPreheader());
// ExitInstruction is the single value which is used outside the loop.
// We only allow for a single reduction value to be used outside the loop.
// This includes users of the reduction, variables (which form a cycle
// which ends in the phi node).
Instruction *ExitInstruction = 0;
// Indicates that we found a reduction operation in our scan.
bool FoundReduxOp = false;
// We start with the PHI node and scan for all of the users of this
// instruction. All users must be instructions that can be used as reduction
// variables (such as ADD). We must have a single out-of-block user. The cycle
// must include the original PHI.
bool FoundStartPHI = false;
// To recognize min/max patterns formed by a icmp select sequence, we store
// the number of instruction we saw from the recognized min/max pattern,
// to make sure we only see exactly the two instructions.
unsigned NumCmpSelectPatternInst = 0;
ReductionInstDesc ReduxDesc(false, 0);
SmallPtrSet<Instruction *, 8> VisitedInsts;
SmallVector<Instruction *, 8> Worklist;
Worklist.push_back(Phi);
VisitedInsts.insert(Phi);
// A value in the reduction can be used:
// - By the reduction:
// - Reduction operation:
// - One use of reduction value (safe).
// - Multiple use of reduction value (not safe).
// - PHI:
// - All uses of the PHI must be the reduction (safe).
// - Otherwise, not safe.
// - By one instruction outside of the loop (safe).
// - By further instructions outside of the loop (not safe).
// - By an instruction that is not part of the reduction (not safe).
// This is either:
// * An instruction type other than PHI or the reduction operation.
// * A PHI in the header other than the initial PHI.
while (!Worklist.empty()) {
Instruction *Cur = Worklist.back();
Worklist.pop_back();
// No Users.
// If the instruction has no users then this is a broken chain and can't be
// a reduction variable.
if (Cur->use_empty())
return false;
bool IsAPhi = isa<PHINode>(Cur);
// A header PHI use other than the original PHI.
if (Cur != Phi && IsAPhi && Cur->getParent() == Phi->getParent())
return false;
// Reductions of instructions such as Div, and Sub is only possible if the
// LHS is the reduction variable.
if (!Cur->isCommutative() && !IsAPhi && !isa<SelectInst>(Cur) &&
!isa<ICmpInst>(Cur) && !isa<FCmpInst>(Cur) &&
!VisitedInsts.count(dyn_cast<Instruction>(Cur->getOperand(0))))
return false;
// Any reduction instruction must be of one of the allowed kinds.
ReduxDesc = isReductionInstr(Cur, Kind, ReduxDesc);
if (!ReduxDesc.IsReduction)
return false;
// A reduction operation must only have one use of the reduction value.
if (!IsAPhi && Kind != RK_IntegerMinMax && Kind != RK_FloatMinMax &&
hasMultipleUsesOf(Cur, VisitedInsts))
return false;
// All inputs to a PHI node must be a reduction value.
if(IsAPhi && Cur != Phi && !areAllUsesIn(Cur, VisitedInsts))
return false;
if (Kind == RK_IntegerMinMax && (isa<ICmpInst>(Cur) ||
isa<SelectInst>(Cur)))
++NumCmpSelectPatternInst;
if (Kind == RK_FloatMinMax && (isa<FCmpInst>(Cur) ||
isa<SelectInst>(Cur)))
++NumCmpSelectPatternInst;
// Check whether we found a reduction operator.
FoundReduxOp |= !IsAPhi;
// Process users of current instruction. Push non-PHI nodes after PHI nodes
// onto the stack. This way we are going to have seen all inputs to PHI
// nodes once we get to them.
SmallVector<Instruction *, 8> NonPHIs;
SmallVector<Instruction *, 8> PHIs;
for (Value::use_iterator UI = Cur->use_begin(), E = Cur->use_end(); UI != E;
++UI) {
Instruction *Usr = cast<Instruction>(*UI);
// Check if we found the exit user.
BasicBlock *Parent = Usr->getParent();
if (!TheLoop->contains(Parent)) {
// Exit if you find multiple outside users or if the header phi node is
// being used. In this case the user uses the value of the previous
// iteration, in which case we would loose "VF-1" iterations of the
// reduction operation if we vectorize.
if (ExitInstruction != 0 || Cur == Phi)
return false;
// The instruction used by an outside user must be the last instruction
// before we feed back to the reduction phi. Otherwise, we loose VF-1
// operations on the value.
if (std::find(Phi->op_begin(), Phi->op_end(), Cur) == Phi->op_end())
return false;
ExitInstruction = Cur;
continue;
}
// Process instructions only once (termination). Each reduction cycle
// value must only be used once, except by phi nodes and min/max
// reductions which are represented as a cmp followed by a select.
ReductionInstDesc IgnoredVal(false, 0);
if (VisitedInsts.insert(Usr)) {
if (isa<PHINode>(Usr))
PHIs.push_back(Usr);
else
NonPHIs.push_back(Usr);
} else if (!isa<PHINode>(Usr) &&
((!isa<FCmpInst>(Usr) &&
!isa<ICmpInst>(Usr) &&
!isa<SelectInst>(Usr)) ||
!isMinMaxSelectCmpPattern(Usr, IgnoredVal).IsReduction))
return false;
// Remember that we completed the cycle.
if (Usr == Phi)
FoundStartPHI = true;
}
Worklist.append(PHIs.begin(), PHIs.end());
Worklist.append(NonPHIs.begin(), NonPHIs.end());
}
// This means we have seen one but not the other instruction of the
// pattern or more than just a select and cmp.
if ((Kind == RK_IntegerMinMax || Kind == RK_FloatMinMax) &&
NumCmpSelectPatternInst != 2)
return false;
if (!FoundStartPHI || !FoundReduxOp || !ExitInstruction)
return false;
// We found a reduction var if we have reached the original phi node and we
// only have a single instruction with out-of-loop users.
// This instruction is allowed to have out-of-loop users.
AllowedExit.insert(ExitInstruction);
// Save the description of this reduction variable.
ReductionDescriptor RD(RdxStart, ExitInstruction, Kind,
ReduxDesc.MinMaxKind);
Reductions[Phi] = RD;
// We've ended the cycle. This is a reduction variable if we have an
// outside user and it has a binary op.
return true;
}
/// Returns true if the instruction is a Select(ICmp(X, Y), X, Y) instruction
/// pattern corresponding to a min(X, Y) or max(X, Y).
LoopVectorizationLegality::ReductionInstDesc
LoopVectorizationLegality::isMinMaxSelectCmpPattern(Instruction *I,
ReductionInstDesc &Prev) {
assert((isa<ICmpInst>(I) || isa<FCmpInst>(I) || isa<SelectInst>(I)) &&
"Expect a select instruction");
Instruction *Cmp = 0;
SelectInst *Select = 0;
// We must handle the select(cmp()) as a single instruction. Advance to the
// select.
if ((Cmp = dyn_cast<ICmpInst>(I)) || (Cmp = dyn_cast<FCmpInst>(I))) {
if (!Cmp->hasOneUse() || !(Select = dyn_cast<SelectInst>(*I->use_begin())))
return ReductionInstDesc(false, I);
return ReductionInstDesc(Select, Prev.MinMaxKind);
}
// Only handle single use cases for now.
if (!(Select = dyn_cast<SelectInst>(I)))
return ReductionInstDesc(false, I);
if (!(Cmp = dyn_cast<ICmpInst>(I->getOperand(0))) &&
!(Cmp = dyn_cast<FCmpInst>(I->getOperand(0))))
return ReductionInstDesc(false, I);
if (!Cmp->hasOneUse())
return ReductionInstDesc(false, I);
Value *CmpLeft;
Value *CmpRight;
// Look for a min/max pattern.
if (m_UMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_UIntMin);
else if (m_UMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_UIntMax);
else if (m_SMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_SIntMax);
else if (m_SMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_SIntMin);
else if (m_OrdFMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_FloatMin);
else if (m_OrdFMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_FloatMax);
else if (m_UnordFMin(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_FloatMin);
else if (m_UnordFMax(m_Value(CmpLeft), m_Value(CmpRight)).match(Select))
return ReductionInstDesc(Select, MRK_FloatMax);
return ReductionInstDesc(false, I);
}
LoopVectorizationLegality::ReductionInstDesc
LoopVectorizationLegality::isReductionInstr(Instruction *I,
ReductionKind Kind,
ReductionInstDesc &Prev) {
bool FP = I->getType()->isFloatingPointTy();
bool FastMath = (FP && I->isCommutative() && I->isAssociative());
switch (I->getOpcode()) {
default:
return ReductionInstDesc(false, I);
case Instruction::PHI:
if (FP && (Kind != RK_FloatMult && Kind != RK_FloatAdd &&
Kind != RK_FloatMinMax))
return ReductionInstDesc(false, I);
return ReductionInstDesc(I, Prev.MinMaxKind);
case Instruction::Sub:
case Instruction::Add:
return ReductionInstDesc(Kind == RK_IntegerAdd, I);
case Instruction::Mul:
return ReductionInstDesc(Kind == RK_IntegerMult, I);
case Instruction::And:
return ReductionInstDesc(Kind == RK_IntegerAnd, I);
case Instruction::Or:
return ReductionInstDesc(Kind == RK_IntegerOr, I);
case Instruction::Xor:
return ReductionInstDesc(Kind == RK_IntegerXor, I);
case Instruction::FMul:
return ReductionInstDesc(Kind == RK_FloatMult && FastMath, I);
case Instruction::FAdd:
return ReductionInstDesc(Kind == RK_FloatAdd && FastMath, I);
case Instruction::FCmp:
case Instruction::ICmp:
case Instruction::Select:
if (Kind != RK_IntegerMinMax &&
(!HasFunNoNaNAttr || Kind != RK_FloatMinMax))
return ReductionInstDesc(false, I);
return isMinMaxSelectCmpPattern(I, Prev);
}
}
LoopVectorizationLegality::InductionKind
LoopVectorizationLegality::isInductionVariable(PHINode *Phi) {
Type *PhiTy = Phi->getType();
// We only handle integer and pointer inductions variables.
if (!PhiTy->isIntegerTy() && !PhiTy->isPointerTy())
return IK_NoInduction;
// Check that the PHI is consecutive.
const SCEV *PhiScev = SE->getSCEV(Phi);
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(PhiScev);
if (!AR) {
DEBUG(dbgs() << "LV: PHI is not a poly recurrence.\n");
return IK_NoInduction;
}
const SCEV *Step = AR->getStepRecurrence(*SE);
// Integer inductions need to have a stride of one.
if (PhiTy->isIntegerTy()) {
if (Step->isOne())
return IK_IntInduction;
if (Step->isAllOnesValue())
return IK_ReverseIntInduction;
return IK_NoInduction;
}
// Calculate the pointer stride and check if it is consecutive.
const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
if (!C)
return IK_NoInduction;
assert(PhiTy->isPointerTy() && "The PHI must be a pointer");
uint64_t Size = DL->getTypeAllocSize(PhiTy->getPointerElementType());
if (C->getValue()->equalsInt(Size))
return IK_PtrInduction;
else if (C->getValue()->equalsInt(0 - Size))
return IK_ReversePtrInduction;
return IK_NoInduction;
}
bool LoopVectorizationLegality::isInductionVariable(const Value *V) {
Value *In0 = const_cast<Value*>(V);
PHINode *PN = dyn_cast_or_null<PHINode>(In0);
if (!PN)
return false;
return Inductions.count(PN);
}
bool LoopVectorizationLegality::blockNeedsPredication(BasicBlock *BB) {
assert(TheLoop->contains(BB) && "Unknown block used");
// Blocks that do not dominate the latch need predication.
BasicBlock* Latch = TheLoop->getLoopLatch();
return !DT->dominates(BB, Latch);
}
bool LoopVectorizationLegality::blockCanBePredicated(BasicBlock *BB,
SmallPtrSet<Value *, 8>& SafePtrs) {
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
// We might be able to hoist the load.
if (it->mayReadFromMemory()) {
LoadInst *LI = dyn_cast<LoadInst>(it);
if (!LI || !SafePtrs.count(LI->getPointerOperand()))
return false;
}
// We don't predicate stores at the moment.
if (it->mayWriteToMemory() || it->mayThrow())
return false;
// Check that we don't have a constant expression that can trap as operand.
for (Instruction::op_iterator OI = it->op_begin(), OE = it->op_end();
OI != OE; ++OI) {
if (Constant *C = dyn_cast<Constant>(*OI))
if (C->canTrap())
return false;
}
// The instructions below can trap.
switch (it->getOpcode()) {
default: continue;
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::URem:
case Instruction::SRem:
return false;
}
}
return true;
}
LoopVectorizationCostModel::VectorizationFactor
LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize,
unsigned UserVF) {
// Width 1 means no vectorize
VectorizationFactor Factor = { 1U, 0U };
if (OptForSize && Legal->getRuntimePointerCheck()->Need) {
DEBUG(dbgs() << "LV: Aborting. Runtime ptr check is required in Os.\n");
return Factor;
}
// Find the trip count.
unsigned TC = SE->getSmallConstantTripCount(TheLoop, TheLoop->getLoopLatch());
DEBUG(dbgs() << "LV: Found trip count: " << TC << '\n');
unsigned WidestType = getWidestType();
unsigned WidestRegister = TTI.getRegisterBitWidth(true);
unsigned MaxSafeDepDist = -1U;
if (Legal->getMaxSafeDepDistBytes() != -1U)
MaxSafeDepDist = Legal->getMaxSafeDepDistBytes() * 8;
WidestRegister = ((WidestRegister < MaxSafeDepDist) ?
WidestRegister : MaxSafeDepDist);
unsigned MaxVectorSize = WidestRegister / WidestType;
DEBUG(dbgs() << "LV: The Widest type: " << WidestType << " bits.\n");
DEBUG(dbgs() << "LV: The Widest register is: "
<< WidestRegister << " bits.\n");
if (MaxVectorSize == 0) {
DEBUG(dbgs() << "LV: The target has no vector registers.\n");
MaxVectorSize = 1;
}
assert(MaxVectorSize <= 32 && "Did not expect to pack so many elements"
" into one vector!");
unsigned VF = MaxVectorSize;
// If we optimize the program for size, avoid creating the tail loop.
if (OptForSize) {
// If we are unable to calculate the trip count then don't try to vectorize.
if (TC < 2) {
DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
return Factor;
}
// Find the maximum SIMD width that can fit within the trip count.
VF = TC % MaxVectorSize;
if (VF == 0)
VF = MaxVectorSize;
// If the trip count that we found modulo the vectorization factor is not
// zero then we require a tail.
if (VF < 2) {
DEBUG(dbgs() << "LV: Aborting. A tail loop is required in Os.\n");
return Factor;
}
}
if (UserVF != 0) {
assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
DEBUG(dbgs() << "LV: Using user VF " << UserVF << ".\n");
Factor.Width = UserVF;
return Factor;
}
float Cost = expectedCost(1);
unsigned Width = 1;
DEBUG(dbgs() << "LV: Scalar loop costs: " << (int)Cost << ".\n");
for (unsigned i=2; i <= VF; i*=2) {
// Notice that the vector loop needs to be executed less times, so
// we need to divide the cost of the vector loops by the width of
// the vector elements.
float VectorCost = expectedCost(i) / (float)i;
DEBUG(dbgs() << "LV: Vector loop of width " << i << " costs: " <<
(int)VectorCost << ".\n");
if (VectorCost < Cost) {
Cost = VectorCost;
Width = i;
}
}
DEBUG(dbgs() << "LV: Selecting VF = : "<< Width << ".\n");
Factor.Width = Width;
Factor.Cost = Width * Cost;
return Factor;
}
unsigned LoopVectorizationCostModel::getWidestType() {
unsigned MaxWidth = 8;
// For each block.
for (Loop::block_iterator bb = TheLoop->block_begin(),
be = TheLoop->block_end(); bb != be; ++bb) {
BasicBlock *BB = *bb;
// For each instruction in the loop.
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
Type *T = it->getType();
// Only examine Loads, Stores and PHINodes.
if (!isa<LoadInst>(it) && !isa<StoreInst>(it) && !isa<PHINode>(it))
continue;
// Examine PHI nodes that are reduction variables.
if (PHINode *PN = dyn_cast<PHINode>(it))
if (!Legal->getReductionVars()->count(PN))
continue;
// Examine the stored values.
if (StoreInst *ST = dyn_cast<StoreInst>(it))
T = ST->getValueOperand()->getType();
// Ignore loaded pointer types and stored pointer types that are not
// consecutive. However, we do want to take consecutive stores/loads of
// pointer vectors into account.
if (T->isPointerTy() && !isConsecutiveLoadOrStore(it))
continue;
MaxWidth = std::max(MaxWidth,
(unsigned)DL->getTypeSizeInBits(T->getScalarType()));
}
}
return MaxWidth;
}
unsigned
LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
unsigned UserUF,
unsigned VF,
unsigned LoopCost) {
// -- The unroll heuristics --
// We unroll the loop in order to expose ILP and reduce the loop overhead.
// There are many micro-architectural considerations that we can't predict
// at this level. For example frontend pressure (on decode or fetch) due to
// code size, or the number and capabilities of the execution ports.
//
// We use the following heuristics to select the unroll factor:
// 1. If the code has reductions the we unroll in order to break the cross
// iteration dependency.
// 2. If the loop is really small then we unroll in order to reduce the loop
// overhead.
// 3. We don't unroll if we think that we will spill registers to memory due
// to the increased register pressure.
// Use the user preference, unless 'auto' is selected.
if (UserUF != 0)
return UserUF;
// When we optimize for size we don't unroll.
if (OptForSize)
return 1;
// We used the distance for the unroll factor.
if (Legal->getMaxSafeDepDistBytes() != -1U)
return 1;
// Do not unroll loops with a relatively small trip count.
unsigned TC = SE->getSmallConstantTripCount(TheLoop,
TheLoop->getLoopLatch());
if (TC > 1 && TC < TinyTripCountUnrollThreshold)
return 1;
unsigned TargetVectorRegisters = TTI.getNumberOfRegisters(true);
DEBUG(dbgs() << "LV: The target has " << TargetVectorRegisters <<
" vector registers\n");
LoopVectorizationCostModel::RegisterUsage R = calculateRegisterUsage();
// We divide by these constants so assume that we have at least one
// instruction that uses at least one register.
R.MaxLocalUsers = std::max(R.MaxLocalUsers, 1U);
R.NumInstructions = std::max(R.NumInstructions, 1U);
// We calculate the unroll factor using the following formula.
// Subtract the number of loop invariants from the number of available
// registers. These registers are used by all of the unrolled instances.
// Next, divide the remaining registers by the number of registers that is
// required by the loop, in order to estimate how many parallel instances
// fit without causing spills.
unsigned UF = (TargetVectorRegisters - R.LoopInvariantRegs) / R.MaxLocalUsers;
// Clamp the unroll factor ranges to reasonable factors.
unsigned MaxUnrollSize = TTI.getMaximumUnrollFactor();
// If we did not calculate the cost for VF (because the user selected the VF)
// then we calculate the cost of VF here.
if (LoopCost == 0)
LoopCost = expectedCost(VF);
// Clamp the calculated UF to be between the 1 and the max unroll factor
// that the target allows.
if (UF > MaxUnrollSize)
UF = MaxUnrollSize;
else if (UF < 1)
UF = 1;
bool HasReductions = Legal->getReductionVars()->size();
// Decide if we want to unroll if we decided that it is legal to vectorize
// but not profitable.
if (VF == 1) {
if (TheLoop->getNumBlocks() > 1 || !HasReductions ||
LoopCost > SmallLoopCost)
return 1;
return UF;
}
if (HasReductions) {
DEBUG(dbgs() << "LV: Unrolling because of reductions.\n");
return UF;
}
// We want to unroll tiny loops in order to reduce the loop overhead.
// We assume that the cost overhead is 1 and we use the cost model
// to estimate the cost of the loop and unroll until the cost of the
// loop overhead is about 5% of the cost of the loop.
DEBUG(dbgs() << "LV: Loop cost is " << LoopCost << '\n');
if (LoopCost < SmallLoopCost) {
DEBUG(dbgs() << "LV: Unrolling to reduce branch cost.\n");
unsigned NewUF = SmallLoopCost / (LoopCost + 1);
return std::min(NewUF, UF);
}
DEBUG(dbgs() << "LV: Not Unrolling.\n");
return 1;
}
LoopVectorizationCostModel::RegisterUsage
LoopVectorizationCostModel::calculateRegisterUsage() {
// This function calculates the register usage by measuring the highest number
// of values that are alive at a single location. Obviously, this is a very
// rough estimation. We scan the loop in a topological order in order and
// assign a number to each instruction. We use RPO to ensure that defs are
// met before their users. We assume that each instruction that has in-loop
// users starts an interval. We record every time that an in-loop value is
// used, so we have a list of the first and last occurrences of each
// instruction. Next, we transpose this data structure into a multi map that
// holds the list of intervals that *end* at a specific location. This multi
// map allows us to perform a linear search. We scan the instructions linearly
// and record each time that a new interval starts, by placing it in a set.
// If we find this value in the multi-map then we remove it from the set.
// The max register usage is the maximum size of the set.
// We also search for instructions that are defined outside the loop, but are
// used inside the loop. We need this number separately from the max-interval
// usage number because when we unroll, loop-invariant values do not take
// more register.
LoopBlocksDFS DFS(TheLoop);
DFS.perform(LI);
RegisterUsage R;
R.NumInstructions = 0;
// Each 'key' in the map opens a new interval. The values
// of the map are the index of the 'last seen' usage of the
// instruction that is the key.
typedef DenseMap<Instruction*, unsigned> IntervalMap;
// Maps instruction to its index.
DenseMap<unsigned, Instruction*> IdxToInstr;
// Marks the end of each interval.
IntervalMap EndPoint;
// Saves the list of instruction indices that are used in the loop.
SmallSet<Instruction*, 8> Ends;
// Saves the list of values that are used in the loop but are
// defined outside the loop, such as arguments and constants.
SmallPtrSet<Value*, 8> LoopInvariants;
unsigned Index = 0;
for (LoopBlocksDFS::RPOIterator bb = DFS.beginRPO(),
be = DFS.endRPO(); bb != be; ++bb) {
R.NumInstructions += (*bb)->size();
for (BasicBlock::iterator it = (*bb)->begin(), e = (*bb)->end(); it != e;
++it) {
Instruction *I = it;
IdxToInstr[Index++] = I;
// Save the end location of each USE.
for (unsigned i = 0; i < I->getNumOperands(); ++i) {
Value *U = I->getOperand(i);
Instruction *Instr = dyn_cast<Instruction>(U);
// Ignore non-instruction values such as arguments, constants, etc.
if (!Instr) continue;
// If this instruction is outside the loop then record it and continue.
if (!TheLoop->contains(Instr)) {
LoopInvariants.insert(Instr);
continue;
}
// Overwrite previous end points.
EndPoint[Instr] = Index;
Ends.insert(Instr);
}
}
}
// Saves the list of intervals that end with the index in 'key'.
typedef SmallVector<Instruction*, 2> InstrList;
DenseMap<unsigned, InstrList> TransposeEnds;
// Transpose the EndPoints to a list of values that end at each index.
for (IntervalMap::iterator it = EndPoint.begin(), e = EndPoint.end();
it != e; ++it)
TransposeEnds[it->second].push_back(it->first);
SmallSet<Instruction*, 8> OpenIntervals;
unsigned MaxUsage = 0;
DEBUG(dbgs() << "LV(REG): Calculating max register usage:\n");
for (unsigned int i = 0; i < Index; ++i) {
Instruction *I = IdxToInstr[i];
// Ignore instructions that are never used within the loop.
if (!Ends.count(I)) continue;
// Remove all of the instructions that end at this location.
InstrList &List = TransposeEnds[i];
for (unsigned int j=0, e = List.size(); j < e; ++j)
OpenIntervals.erase(List[j]);
// Count the number of live interals.
MaxUsage = std::max(MaxUsage, OpenIntervals.size());
DEBUG(dbgs() << "LV(REG): At #" << i << " Interval # " <<
OpenIntervals.size() << '\n');
// Add the current instruction to the list of open intervals.
OpenIntervals.insert(I);
}
unsigned Invariant = LoopInvariants.size();
DEBUG(dbgs() << "LV(REG): Found max usage: " << MaxUsage << '\n');
DEBUG(dbgs() << "LV(REG): Found invariant usage: " << Invariant << '\n');
DEBUG(dbgs() << "LV(REG): LoopSize: " << R.NumInstructions << '\n');
R.LoopInvariantRegs = Invariant;
R.MaxLocalUsers = MaxUsage;
return R;
}
unsigned LoopVectorizationCostModel::expectedCost(unsigned VF) {
unsigned Cost = 0;
// For each block.
for (Loop::block_iterator bb = TheLoop->block_begin(),
be = TheLoop->block_end(); bb != be; ++bb) {
unsigned BlockCost = 0;
BasicBlock *BB = *bb;
// For each instruction in the old loop.
for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; ++it) {
// Skip dbg intrinsics.
if (isa<DbgInfoIntrinsic>(it))
continue;
unsigned C = getInstructionCost(it, VF);
BlockCost += C;
DEBUG(dbgs() << "LV: Found an estimated cost of " << C << " for VF " <<
VF << " For instruction: " << *it << '\n');
}
// We assume that if-converted blocks have a 50% chance of being executed.
// When the code is scalar then some of the blocks are avoided due to CF.
// When the code is vectorized we execute all code paths.
if (VF == 1 && Legal->blockNeedsPredication(*bb))
BlockCost /= 2;
Cost += BlockCost;
}
return Cost;
}
/// \brief Check whether the address computation for a non-consecutive memory
/// access looks like an unlikely candidate for being merged into the indexing
/// mode.
///
/// We look for a GEP which has one index that is an induction variable and all
/// other indices are loop invariant. If the stride of this access is also
/// within a small bound we decide that this address computation can likely be
/// merged into the addressing mode.
/// In all other cases, we identify the address computation as complex.
static bool isLikelyComplexAddressComputation(Value *Ptr,
LoopVectorizationLegality *Legal,
ScalarEvolution *SE,
const Loop *TheLoop) {
GetElementPtrInst *Gep = dyn_cast<GetElementPtrInst>(Ptr);
if (!Gep)
return true;
// We are looking for a gep with all loop invariant indices except for one
// which should be an induction variable.
unsigned NumOperands = Gep->getNumOperands();
for (unsigned i = 1; i < NumOperands; ++i) {
Value *Opd = Gep->getOperand(i);
if (!SE->isLoopInvariant(SE->getSCEV(Opd), TheLoop) &&
!Legal->isInductionVariable(Opd))
return true;
}
// Now we know we have a GEP ptr, %inv, %ind, %inv. Make sure that the step
// can likely be merged into the address computation.
unsigned MaxMergeDistance = 64;
const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Ptr));
if (!AddRec)
return true;
// Check the step is constant.
const SCEV *Step = AddRec->getStepRecurrence(*SE);
// Calculate the pointer stride and check if it is consecutive.
const SCEVConstant *C = dyn_cast<SCEVConstant>(Step);
if (!C)
return true;
const APInt &APStepVal = C->getValue()->getValue();
// Huge step value - give up.
if (APStepVal.getBitWidth() > 64)
return true;
int64_t StepVal = APStepVal.getSExtValue();
return StepVal > MaxMergeDistance;
}
static bool isStrideMul(Instruction *I, LoopVectorizationLegality *Legal) {
if (Legal->hasStride(I->getOperand(0)) || Legal->hasStride(I->getOperand(1)))
return true;
return false;
}
unsigned
LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
// If we know that this instruction will remain uniform, check the cost of
// the scalar version.
if (Legal->isUniformAfterVectorization(I))
VF = 1;
Type *RetTy = I->getType();
Type *VectorTy = ToVectorTy(RetTy, VF);
// TODO: We need to estimate the cost of intrinsic calls.
switch (I->getOpcode()) {
case Instruction::GetElementPtr:
// We mark this instruction as zero-cost because the cost of GEPs in
// vectorized code depends on whether the corresponding memory instruction
// is scalarized or not. Therefore, we handle GEPs with the memory
// instruction cost.
return 0;
case Instruction::Br: {
return TTI.getCFInstrCost(I->getOpcode());
}
case Instruction::PHI:
//TODO: IF-converted IFs become selects.
return 0;
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
case Instruction::FSub:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
// Since we will replace the stride by 1 the multiplication should go away.
if (I->getOpcode() == Instruction::Mul && isStrideMul(I, Legal))
return 0;
// Certain instructions can be cheaper to vectorize if they have a constant
// second vector operand. One example of this are shifts on x86.
TargetTransformInfo::OperandValueKind Op1VK =
TargetTransformInfo::OK_AnyValue;
TargetTransformInfo::OperandValueKind Op2VK =
TargetTransformInfo::OK_AnyValue;
if (isa<ConstantInt>(I->getOperand(1)))
Op2VK = TargetTransformInfo::OK_UniformConstantValue;
return TTI.getArithmeticInstrCost(I->getOpcode(), VectorTy, Op1VK, Op2VK);
}
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
const SCEV *CondSCEV = SE->getSCEV(SI->getCondition());
bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop));
Type *CondTy = SI->getCondition()->getType();
if (!ScalarCond)
CondTy = VectorType::get(CondTy, VF);
return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy);
}
case Instruction::ICmp:
case Instruction::FCmp: {
Type *ValTy = I->getOperand(0)->getType();
VectorTy = ToVectorTy(ValTy, VF);
return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy);
}
case Instruction::Store:
case Instruction::Load: {
StoreInst *SI = dyn_cast<StoreInst>(I);
LoadInst *LI = dyn_cast<LoadInst>(I);
Type *ValTy = (SI ? SI->getValueOperand()->getType() :
LI->getType());
VectorTy = ToVectorTy(ValTy, VF);
unsigned Alignment = SI ? SI->getAlignment() : LI->getAlignment();
unsigned AS = SI ? SI->getPointerAddressSpace() :
LI->getPointerAddressSpace();
Value *Ptr = SI ? SI->getPointerOperand() : LI->getPointerOperand();
// We add the cost of address computation here instead of with the gep
// instruction because only here we know whether the operation is
// scalarized.
if (VF == 1)
return TTI.getAddressComputationCost(VectorTy) +
TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
// Scalarized loads/stores.
int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
bool Reverse = ConsecutiveStride < 0;
unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ValTy);
unsigned VectorElementSize = DL->getTypeStoreSize(VectorTy)/VF;
if (!ConsecutiveStride || ScalarAllocatedSize != VectorElementSize) {
bool IsComplexComputation =
isLikelyComplexAddressComputation(Ptr, Legal, SE, TheLoop);
unsigned Cost = 0;
// The cost of extracting from the value vector and pointer vector.
Type *PtrTy = ToVectorTy(Ptr->getType(), VF);
for (unsigned i = 0; i < VF; ++i) {
// The cost of extracting the pointer operand.
Cost += TTI.getVectorInstrCost(Instruction::ExtractElement, PtrTy, i);
// In case of STORE, the cost of ExtractElement from the vector.
// In case of LOAD, the cost of InsertElement into the returned
// vector.
Cost += TTI.getVectorInstrCost(SI ? Instruction::ExtractElement :
Instruction::InsertElement,
VectorTy, i);
}
// The cost of the scalar loads/stores.
Cost += VF * TTI.getAddressComputationCost(PtrTy, IsComplexComputation);
Cost += VF * TTI.getMemoryOpCost(I->getOpcode(), ValTy->getScalarType(),
Alignment, AS);
return Cost;
}
// Wide load/stores.
unsigned Cost = TTI.getAddressComputationCost(VectorTy);
Cost += TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
if (Reverse)
Cost += TTI.getShuffleCost(TargetTransformInfo::SK_Reverse,
VectorTy, 0);
return Cost;
}
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::FPExt:
case Instruction::PtrToInt:
case Instruction::IntToPtr:
case Instruction::SIToFP:
case Instruction::UIToFP:
case Instruction::Trunc:
case Instruction::FPTrunc:
case Instruction::BitCast: {
// We optimize the truncation of induction variable.
// The cost of these is the same as the scalar operation.
if (I->getOpcode() == Instruction::Trunc &&
Legal->isInductionVariable(I->getOperand(0)))
return TTI.getCastInstrCost(I->getOpcode(), I->getType(),
I->getOperand(0)->getType());
Type *SrcVecTy = ToVectorTy(I->getOperand(0)->getType(), VF);
return TTI.getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy);
}
case Instruction::Call: {
CallInst *CI = cast<CallInst>(I);
Intrinsic::ID ID = getIntrinsicIDForCall(CI, TLI);
assert(ID && "Not an intrinsic call!");
Type *RetTy = ToVectorTy(CI->getType(), VF);
SmallVector<Type*, 4> Tys;
for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i)
Tys.push_back(ToVectorTy(CI->getArgOperand(i)->getType(), VF));
return TTI.getIntrinsicInstrCost(ID, RetTy, Tys);
}
default: {
// We are scalarizing the instruction. Return the cost of the scalar
// instruction, plus the cost of insert and extract into vector
// elements, times the vector width.
unsigned Cost = 0;
if (!RetTy->isVoidTy() && VF != 1) {
unsigned InsCost = TTI.getVectorInstrCost(Instruction::InsertElement,
VectorTy);
unsigned ExtCost = TTI.getVectorInstrCost(Instruction::ExtractElement,
VectorTy);
// The cost of inserting the results plus extracting each one of the
// operands.
Cost += VF * (InsCost + ExtCost * I->getNumOperands());
}
// The cost of executing VF copies of the scalar instruction. This opcode
// is unknown. Assume that it is the same as 'mul'.
Cost += VF * TTI.getArithmeticInstrCost(Instruction::Mul, VectorTy);
return Cost;
}
}// end of switch.
}
Type* LoopVectorizationCostModel::ToVectorTy(Type *Scalar, unsigned VF) {
if (Scalar->isVoidTy() || VF == 1)
return Scalar;
return VectorType::get(Scalar, VF);
}
char LoopVectorize::ID = 0;
static const char lv_name[] = "Loop Vectorization";
INITIALIZE_PASS_BEGIN(LoopVectorize, LV_NAME, lv_name, false, false)
INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false)
namespace llvm {
Pass *createLoopVectorizePass(bool NoUnrolling, bool AlwaysVectorize) {
return new LoopVectorize(NoUnrolling, AlwaysVectorize);
}
}
bool LoopVectorizationCostModel::isConsecutiveLoadOrStore(Instruction *Inst) {
// Check for a store.
if (StoreInst *ST = dyn_cast<StoreInst>(Inst))
return Legal->isConsecutivePtr(ST->getPointerOperand()) != 0;
// Check for a load.
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
return Legal->isConsecutivePtr(LI->getPointerOperand()) != 0;
return false;
}
void InnerLoopUnroller::scalarizeInstruction(Instruction *Instr) {
assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
// Holds vector parameters or scalars, in case of uniform vals.
SmallVector<VectorParts, 4> Params;
setDebugLocFromInst(Builder, Instr);
// Find all of the vectorized parameters.
for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
Value *SrcOp = Instr->getOperand(op);
// If we are accessing the old induction variable, use the new one.
if (SrcOp == OldInduction) {
Params.push_back(getVectorValue(SrcOp));
continue;
}
// Try using previously calculated values.
Instruction *SrcInst = dyn_cast<Instruction>(SrcOp);
// If the src is an instruction that appeared earlier in the basic block
// then it should already be vectorized.
if (SrcInst && OrigLoop->contains(SrcInst)) {
assert(WidenMap.has(SrcInst) && "Source operand is unavailable");
// The parameter is a vector value from earlier.
Params.push_back(WidenMap.get(SrcInst));
} else {
// The parameter is a scalar from outside the loop. Maybe even a constant.
VectorParts Scalars;
Scalars.append(UF, SrcOp);
Params.push_back(Scalars);
}
}
assert(Params.size() == Instr->getNumOperands() &&
"Invalid number of operands");
// Does this instruction return a value ?
bool IsVoidRetTy = Instr->getType()->isVoidTy();
Value *UndefVec = IsVoidRetTy ? 0 :
UndefValue::get(Instr->getType());
// Create a new entry in the WidenMap and initialize it to Undef or Null.
VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
// For each vector unroll 'part':
for (unsigned Part = 0; Part < UF; ++Part) {
// For each scalar that we create:
Instruction *Cloned = Instr->clone();
if (!IsVoidRetTy)
Cloned->setName(Instr->getName() + ".cloned");
// Replace the operands of the cloned instructions with extracted scalars.
for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
Value *Op = Params[op][Part];
Cloned->setOperand(op, Op);
}
// Place the cloned scalar in the new loop.
Builder.Insert(Cloned);
// If the original scalar returns a value we need to place it in a vector
// so that future users will be able to use it.
if (!IsVoidRetTy)
VecResults[Part] = Cloned;
}
}
void InnerLoopUnroller::vectorizeMemoryInstruction(Instruction *Instr) {
return scalarizeInstruction(Instr);
}
Value *InnerLoopUnroller::reverseVector(Value *Vec) {
return Vec;
}
Value *InnerLoopUnroller::getBroadcastInstrs(Value *V) {
return V;
}
Value *InnerLoopUnroller::getConsecutiveVector(Value* Val, int StartIdx,
bool Negate) {
// When unrolling and the VF is 1, we only need to add a simple scalar.
Type *ITy = Val->getType();
assert(!ITy->isVectorTy() && "Val must be a scalar");
Constant *C = ConstantInt::get(ITy, StartIdx, Negate);
return Builder.CreateAdd(Val, C, "induction");
}
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