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llvm/lib/Analysis/InlineCost.cpp
Dehao Chen 287fe25641 Do not inline hot callsites for samplepgo in thinlto compile phase. 
Summary: Because SamplePGO passes will be invoked twice in ThinLTO build: once at compile phase, the other at backend. We want to make sure the IR at the 2nd phase matches the hot part in profile, thus we do not want to inline hot callsites in the first phase.

Reviewers: tejohnson, eraman

Reviewed By: tejohnson

Subscribers: mehdi_amini, llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D31201

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298428 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-21 19:55:36 +00:00

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//===- InlineCost.cpp - Cost analysis for inliner -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements inline cost analysis.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/InlineCost.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "inline-cost"
STATISTIC(NumCallsAnalyzed, "Number of call sites analyzed");
static cl::opt<int> InlineThreshold(
"inline-threshold", cl::Hidden, cl::init(225), cl::ZeroOrMore,
cl::desc("Control the amount of inlining to perform (default = 225)"));
static cl::opt<int> HintThreshold(
"inlinehint-threshold", cl::Hidden, cl::init(325),
cl::desc("Threshold for inlining functions with inline hint"));
static cl::opt<int>
ColdCallSiteThreshold("inline-cold-callsite-threshold", cl::Hidden,
cl::init(45),
cl::desc("Threshold for inlining cold callsites"));
// We introduce this threshold to help performance of instrumentation based
// PGO before we actually hook up inliner with analysis passes such as BPI and
// BFI.
static cl::opt<int> ColdThreshold(
"inlinecold-threshold", cl::Hidden, cl::init(225),
cl::desc("Threshold for inlining functions with cold attribute"));
static cl::opt<int>
HotCallSiteThreshold("hot-callsite-threshold", cl::Hidden, cl::init(3000),
cl::ZeroOrMore,
cl::desc("Threshold for hot callsites "));
namespace {
class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
typedef InstVisitor<CallAnalyzer, bool> Base;
friend class InstVisitor<CallAnalyzer, bool>;
/// The TargetTransformInfo available for this compilation.
const TargetTransformInfo &TTI;
/// Getter for the cache of @llvm.assume intrinsics.
std::function<AssumptionCache &(Function &)> &GetAssumptionCache;
/// Getter for BlockFrequencyInfo
Optional<function_ref<BlockFrequencyInfo &(Function &)>> &GetBFI;
/// Profile summary information.
ProfileSummaryInfo *PSI;
/// The called function.
Function &F;
/// The candidate callsite being analyzed. Please do not use this to do
/// analysis in the caller function; we want the inline cost query to be
/// easily cacheable. Instead, use the cover function paramHasAttr.
CallSite CandidateCS;
/// Tunable parameters that control the analysis.
const InlineParams &Params;
int Threshold;
int Cost;
bool IsCallerRecursive;
bool IsRecursiveCall;
bool ExposesReturnsTwice;
bool HasDynamicAlloca;
bool ContainsNoDuplicateCall;
bool HasReturn;
bool HasIndirectBr;
bool HasFrameEscape;
/// Number of bytes allocated statically by the callee.
uint64_t AllocatedSize;
unsigned NumInstructions, NumVectorInstructions;
int FiftyPercentVectorBonus, TenPercentVectorBonus;
int VectorBonus;
/// While we walk the potentially-inlined instructions, we build up and
/// maintain a mapping of simplified values specific to this callsite. The
/// idea is to propagate any special information we have about arguments to
/// this call through the inlinable section of the function, and account for
/// likely simplifications post-inlining. The most important aspect we track
/// is CFG altering simplifications -- when we prove a basic block dead, that
/// can cause dramatic shifts in the cost of inlining a function.
DenseMap<Value *, Constant *> SimplifiedValues;
/// Keep track of the values which map back (through function arguments) to
/// allocas on the caller stack which could be simplified through SROA.
DenseMap<Value *, Value *> SROAArgValues;
/// The mapping of caller Alloca values to their accumulated cost savings. If
/// we have to disable SROA for one of the allocas, this tells us how much
/// cost must be added.
DenseMap<Value *, int> SROAArgCosts;
/// Keep track of values which map to a pointer base and constant offset.
DenseMap<Value *, std::pair<Value *, APInt>> ConstantOffsetPtrs;
// Custom simplification helper routines.
bool isAllocaDerivedArg(Value *V);
bool lookupSROAArgAndCost(Value *V, Value *&Arg,
DenseMap<Value *, int>::iterator &CostIt);
void disableSROA(DenseMap<Value *, int>::iterator CostIt);
void disableSROA(Value *V);
void accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
int InstructionCost);
bool isGEPFree(GetElementPtrInst &GEP);
bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset);
bool simplifyCallSite(Function *F, CallSite CS);
template <typename Callable>
bool simplifyInstruction(Instruction &I, Callable Evaluate);
ConstantInt *stripAndComputeInBoundsConstantOffsets(Value *&V);
/// Return true if the given argument to the function being considered for
/// inlining has the given attribute set either at the call site or the
/// function declaration. Primarily used to inspect call site specific
/// attributes since these can be more precise than the ones on the callee
/// itself.
bool paramHasAttr(Argument *A, Attribute::AttrKind Attr);
/// Return true if the given value is known non null within the callee if
/// inlined through this particular callsite.
bool isKnownNonNullInCallee(Value *V);
/// Update Threshold based on callsite properties such as callee
/// attributes and callee hotness for PGO builds. The Callee is explicitly
/// passed to support analyzing indirect calls whose target is inferred by
/// analysis.
void updateThreshold(CallSite CS, Function &Callee);
/// Return true if size growth is allowed when inlining the callee at CS.
bool allowSizeGrowth(CallSite CS);
// Custom analysis routines.
bool analyzeBlock(BasicBlock *BB, SmallPtrSetImpl<const Value *> &EphValues);
// Disable several entry points to the visitor so we don't accidentally use
// them by declaring but not defining them here.
void visit(Module *);
void visit(Module &);
void visit(Function *);
void visit(Function &);
void visit(BasicBlock *);
void visit(BasicBlock &);
// Provide base case for our instruction visit.
bool visitInstruction(Instruction &I);
// Our visit overrides.
bool visitAlloca(AllocaInst &I);
bool visitPHI(PHINode &I);
bool visitGetElementPtr(GetElementPtrInst &I);
bool visitBitCast(BitCastInst &I);
bool visitPtrToInt(PtrToIntInst &I);
bool visitIntToPtr(IntToPtrInst &I);
bool visitCastInst(CastInst &I);
bool visitUnaryInstruction(UnaryInstruction &I);
bool visitCmpInst(CmpInst &I);
bool visitSub(BinaryOperator &I);
bool visitBinaryOperator(BinaryOperator &I);
bool visitLoad(LoadInst &I);
bool visitStore(StoreInst &I);
bool visitExtractValue(ExtractValueInst &I);
bool visitInsertValue(InsertValueInst &I);
bool visitCallSite(CallSite CS);
bool visitReturnInst(ReturnInst &RI);
bool visitBranchInst(BranchInst &BI);
bool visitSwitchInst(SwitchInst &SI);
bool visitIndirectBrInst(IndirectBrInst &IBI);
bool visitResumeInst(ResumeInst &RI);
bool visitCleanupReturnInst(CleanupReturnInst &RI);
bool visitCatchReturnInst(CatchReturnInst &RI);
bool visitUnreachableInst(UnreachableInst &I);
public:
CallAnalyzer(const TargetTransformInfo &TTI,
std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
Optional<function_ref<BlockFrequencyInfo &(Function &)>> &GetBFI,
ProfileSummaryInfo *PSI, Function &Callee, CallSite CSArg,
const InlineParams &Params)
: TTI(TTI), GetAssumptionCache(GetAssumptionCache), GetBFI(GetBFI),
PSI(PSI), F(Callee), CandidateCS(CSArg), Params(Params),
Threshold(Params.DefaultThreshold), Cost(0), IsCallerRecursive(false),
IsRecursiveCall(false), ExposesReturnsTwice(false),
HasDynamicAlloca(false), ContainsNoDuplicateCall(false),
HasReturn(false), HasIndirectBr(false), HasFrameEscape(false),
AllocatedSize(0), NumInstructions(0), NumVectorInstructions(0),
FiftyPercentVectorBonus(0), TenPercentVectorBonus(0), VectorBonus(0),
NumConstantArgs(0), NumConstantOffsetPtrArgs(0), NumAllocaArgs(0),
NumConstantPtrCmps(0), NumConstantPtrDiffs(0),
NumInstructionsSimplified(0), SROACostSavings(0),
SROACostSavingsLost(0) {}
bool analyzeCall(CallSite CS);
int getThreshold() { return Threshold; }
int getCost() { return Cost; }
// Keep a bunch of stats about the cost savings found so we can print them
// out when debugging.
unsigned NumConstantArgs;
unsigned NumConstantOffsetPtrArgs;
unsigned NumAllocaArgs;
unsigned NumConstantPtrCmps;
unsigned NumConstantPtrDiffs;
unsigned NumInstructionsSimplified;
unsigned SROACostSavings;
unsigned SROACostSavingsLost;
void dump();
};
} // namespace
/// \brief Test whether the given value is an Alloca-derived function argument.
bool CallAnalyzer::isAllocaDerivedArg(Value *V) {
return SROAArgValues.count(V);
}
/// \brief Lookup the SROA-candidate argument and cost iterator which V maps to.
/// Returns false if V does not map to a SROA-candidate.
bool CallAnalyzer::lookupSROAArgAndCost(
Value *V, Value *&Arg, DenseMap<Value *, int>::iterator &CostIt) {
if (SROAArgValues.empty() || SROAArgCosts.empty())
return false;
DenseMap<Value *, Value *>::iterator ArgIt = SROAArgValues.find(V);
if (ArgIt == SROAArgValues.end())
return false;
Arg = ArgIt->second;
CostIt = SROAArgCosts.find(Arg);
return CostIt != SROAArgCosts.end();
}
/// \brief Disable SROA for the candidate marked by this cost iterator.
///
/// This marks the candidate as no longer viable for SROA, and adds the cost
/// savings associated with it back into the inline cost measurement.
void CallAnalyzer::disableSROA(DenseMap<Value *, int>::iterator CostIt) {
// If we're no longer able to perform SROA we need to undo its cost savings
// and prevent subsequent analysis.
Cost += CostIt->second;
SROACostSavings -= CostIt->second;
SROACostSavingsLost += CostIt->second;
SROAArgCosts.erase(CostIt);
}
/// \brief If 'V' maps to a SROA candidate, disable SROA for it.
void CallAnalyzer::disableSROA(Value *V) {
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(V, SROAArg, CostIt))
disableSROA(CostIt);
}
/// \brief Accumulate the given cost for a particular SROA candidate.
void CallAnalyzer::accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
int InstructionCost) {
CostIt->second += InstructionCost;
SROACostSavings += InstructionCost;
}
/// \brief Accumulate a constant GEP offset into an APInt if possible.
///
/// Returns false if unable to compute the offset for any reason. Respects any
/// simplified values known during the analysis of this callsite.
bool CallAnalyzer::accumulateGEPOffset(GEPOperator &GEP, APInt &Offset) {
const DataLayout &DL = F.getParent()->getDataLayout();
unsigned IntPtrWidth = DL.getPointerSizeInBits();
assert(IntPtrWidth == Offset.getBitWidth());
for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
GTI != GTE; ++GTI) {
ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
if (!OpC)
if (Constant *SimpleOp = SimplifiedValues.lookup(GTI.getOperand()))
OpC = dyn_cast<ConstantInt>(SimpleOp);
if (!OpC)
return false;
if (OpC->isZero())
continue;
// Handle a struct index, which adds its field offset to the pointer.
if (StructType *STy = GTI.getStructTypeOrNull()) {
unsigned ElementIdx = OpC->getZExtValue();
const StructLayout *SL = DL.getStructLayout(STy);
Offset += APInt(IntPtrWidth, SL->getElementOffset(ElementIdx));
continue;
}
APInt TypeSize(IntPtrWidth, DL.getTypeAllocSize(GTI.getIndexedType()));
Offset += OpC->getValue().sextOrTrunc(IntPtrWidth) * TypeSize;
}
return true;
}
/// \brief Use TTI to check whether a GEP is free.
///
/// Respects any simplified values known during the analysis of this callsite.
bool CallAnalyzer::isGEPFree(GetElementPtrInst &GEP) {
SmallVector<Value *, 4> Indices;
for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I)
if (Constant *SimpleOp = SimplifiedValues.lookup(*I))
Indices.push_back(SimpleOp);
else
Indices.push_back(*I);
return TargetTransformInfo::TCC_Free ==
TTI.getGEPCost(GEP.getSourceElementType(), GEP.getPointerOperand(),
Indices);
}
bool CallAnalyzer::visitAlloca(AllocaInst &I) {
// Check whether inlining will turn a dynamic alloca into a static
// alloca and handle that case.
if (I.isArrayAllocation()) {
Constant *Size = SimplifiedValues.lookup(I.getArraySize());
if (auto *AllocSize = dyn_cast_or_null<ConstantInt>(Size)) {
const DataLayout &DL = F.getParent()->getDataLayout();
Type *Ty = I.getAllocatedType();
AllocatedSize = SaturatingMultiplyAdd(
AllocSize->getLimitedValue(), DL.getTypeAllocSize(Ty), AllocatedSize);
return Base::visitAlloca(I);
}
}
// Accumulate the allocated size.
if (I.isStaticAlloca()) {
const DataLayout &DL = F.getParent()->getDataLayout();
Type *Ty = I.getAllocatedType();
AllocatedSize = SaturatingAdd(DL.getTypeAllocSize(Ty), AllocatedSize);
}
// We will happily inline static alloca instructions.
if (I.isStaticAlloca())
return Base::visitAlloca(I);
// FIXME: This is overly conservative. Dynamic allocas are inefficient for
// a variety of reasons, and so we would like to not inline them into
// functions which don't currently have a dynamic alloca. This simply
// disables inlining altogether in the presence of a dynamic alloca.
HasDynamicAlloca = true;
return false;
}
bool CallAnalyzer::visitPHI(PHINode &I) {
// FIXME: We should potentially be tracking values through phi nodes,
// especially when they collapse to a single value due to deleted CFG edges
// during inlining.
// FIXME: We need to propagate SROA *disabling* through phi nodes, even
// though we don't want to propagate it's bonuses. The idea is to disable
// SROA if it *might* be used in an inappropriate manner.
// Phi nodes are always zero-cost.
return true;
}
bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
bool SROACandidate =
lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt);
// Try to fold GEPs of constant-offset call site argument pointers. This
// requires target data and inbounds GEPs.
if (I.isInBounds()) {
// Check if we have a base + offset for the pointer.
Value *Ptr = I.getPointerOperand();
std::pair<Value *, APInt> BaseAndOffset = ConstantOffsetPtrs.lookup(Ptr);
if (BaseAndOffset.first) {
// Check if the offset of this GEP is constant, and if so accumulate it
// into Offset.
if (!accumulateGEPOffset(cast<GEPOperator>(I), BaseAndOffset.second)) {
// Non-constant GEPs aren't folded, and disable SROA.
if (SROACandidate)
disableSROA(CostIt);
return isGEPFree(I);
}
// Add the result as a new mapping to Base + Offset.
ConstantOffsetPtrs[&I] = BaseAndOffset;
// Also handle SROA candidates here, we already know that the GEP is
// all-constant indexed.
if (SROACandidate)
SROAArgValues[&I] = SROAArg;
return true;
}
}
// Lambda to check whether a GEP's indices are all constant.
auto IsGEPOffsetConstant = [&](GetElementPtrInst &GEP) {
for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I)
if (!isa<Constant>(*I) && !SimplifiedValues.lookup(*I))
return false;
return true;
};
if (IsGEPOffsetConstant(I)) {
if (SROACandidate)
SROAArgValues[&I] = SROAArg;
// Constant GEPs are modeled as free.
return true;
}
// Variable GEPs will require math and will disable SROA.
if (SROACandidate)
disableSROA(CostIt);
return isGEPFree(I);
}
/// Simplify \p I if its operands are constants and update SimplifiedValues.
/// \p Evaluate is a callable specific to instruction type that evaluates the
/// instruction when all the operands are constants.
template <typename Callable>
bool CallAnalyzer::simplifyInstruction(Instruction &I, Callable Evaluate) {
SmallVector<Constant *, 2> COps;
for (Value *Op : I.operands()) {
Constant *COp = dyn_cast<Constant>(Op);
if (!COp)
COp = SimplifiedValues.lookup(Op);
if (!COp)
return false;
COps.push_back(COp);
}
auto *C = Evaluate(COps);
if (!C)
return false;
SimplifiedValues[&I] = C;
return true;
}
bool CallAnalyzer::visitBitCast(BitCastInst &I) {
// Propagate constants through bitcasts.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getBitCast(COps[0], I.getType());
}))
return true;
// Track base/offsets through casts
std::pair<Value *, APInt> BaseAndOffset =
ConstantOffsetPtrs.lookup(I.getOperand(0));
// Casts don't change the offset, just wrap it up.
if (BaseAndOffset.first)
ConstantOffsetPtrs[&I] = BaseAndOffset;
// Also look for SROA candidates here.
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt))
SROAArgValues[&I] = SROAArg;
// Bitcasts are always zero cost.
return true;
}
bool CallAnalyzer::visitPtrToInt(PtrToIntInst &I) {
// Propagate constants through ptrtoint.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getPtrToInt(COps[0], I.getType());
}))
return true;
// Track base/offset pairs when converted to a plain integer provided the
// integer is large enough to represent the pointer.
unsigned IntegerSize = I.getType()->getScalarSizeInBits();
const DataLayout &DL = F.getParent()->getDataLayout();
if (IntegerSize >= DL.getPointerSizeInBits()) {
std::pair<Value *, APInt> BaseAndOffset =
ConstantOffsetPtrs.lookup(I.getOperand(0));
if (BaseAndOffset.first)
ConstantOffsetPtrs[&I] = BaseAndOffset;
}
// This is really weird. Technically, ptrtoint will disable SROA. However,
// unless that ptrtoint is *used* somewhere in the live basic blocks after
// inlining, it will be nuked, and SROA should proceed. All of the uses which
// would block SROA would also block SROA if applied directly to a pointer,
// and so we can just add the integer in here. The only places where SROA is
// preserved either cannot fire on an integer, or won't in-and-of themselves
// disable SROA (ext) w/o some later use that we would see and disable.
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt))
SROAArgValues[&I] = SROAArg;
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
}
bool CallAnalyzer::visitIntToPtr(IntToPtrInst &I) {
// Propagate constants through ptrtoint.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getIntToPtr(COps[0], I.getType());
}))
return true;
// Track base/offset pairs when round-tripped through a pointer without
// modifications provided the integer is not too large.
Value *Op = I.getOperand(0);
unsigned IntegerSize = Op->getType()->getScalarSizeInBits();
const DataLayout &DL = F.getParent()->getDataLayout();
if (IntegerSize <= DL.getPointerSizeInBits()) {
std::pair<Value *, APInt> BaseAndOffset = ConstantOffsetPtrs.lookup(Op);
if (BaseAndOffset.first)
ConstantOffsetPtrs[&I] = BaseAndOffset;
}
// "Propagate" SROA here in the same manner as we do for ptrtoint above.
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(Op, SROAArg, CostIt))
SROAArgValues[&I] = SROAArg;
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
}
bool CallAnalyzer::visitCastInst(CastInst &I) {
// Propagate constants through ptrtoint.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getCast(I.getOpcode(), COps[0], I.getType());
}))
return true;
// Disable SROA in the face of arbitrary casts we don't whitelist elsewhere.
disableSROA(I.getOperand(0));
return TargetTransformInfo::TCC_Free == TTI.getUserCost(&I);
}
bool CallAnalyzer::visitUnaryInstruction(UnaryInstruction &I) {
Value *Operand = I.getOperand(0);
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
const DataLayout &DL = F.getParent()->getDataLayout();
return ConstantFoldInstOperands(&I, COps[0], DL);
}))
return true;
// Disable any SROA on the argument to arbitrary unary operators.
disableSROA(Operand);
return false;
}
bool CallAnalyzer::paramHasAttr(Argument *A, Attribute::AttrKind Attr) {
unsigned ArgNo = A->getArgNo();
return CandidateCS.paramHasAttr(ArgNo + 1, Attr);
}
bool CallAnalyzer::isKnownNonNullInCallee(Value *V) {
// Does the *call site* have the NonNull attribute set on an argument? We
// use the attribute on the call site to memoize any analysis done in the
// caller. This will also trip if the callee function has a non-null
// parameter attribute, but that's a less interesting case because hopefully
// the callee would already have been simplified based on that.
if (Argument *A = dyn_cast<Argument>(V))
if (paramHasAttr(A, Attribute::NonNull))
return true;
// Is this an alloca in the caller? This is distinct from the attribute case
// above because attributes aren't updated within the inliner itself and we
// always want to catch the alloca derived case.
if (isAllocaDerivedArg(V))
// We can actually predict the result of comparisons between an
// alloca-derived value and null. Note that this fires regardless of
// SROA firing.
return true;
return false;
}
bool CallAnalyzer::allowSizeGrowth(CallSite CS) {
// If the normal destination of the invoke or the parent block of the call
// site is unreachable-terminated, there is little point in inlining this
// unless there is literally zero cost.
// FIXME: Note that it is possible that an unreachable-terminated block has a
// hot entry. For example, in below scenario inlining hot_call_X() may be
// beneficial :
// main() {
// hot_call_1();
// ...
// hot_call_N()
// exit(0);
// }
// For now, we are not handling this corner case here as it is rare in real
// code. In future, we should elaborate this based on BPI and BFI in more
// general threshold adjusting heuristics in updateThreshold().
Instruction *Instr = CS.getInstruction();
if (InvokeInst *II = dyn_cast<InvokeInst>(Instr)) {
if (isa<UnreachableInst>(II->getNormalDest()->getTerminator()))
return false;
} else if (isa<UnreachableInst>(Instr->getParent()->getTerminator()))
return false;
return true;
}
void CallAnalyzer::updateThreshold(CallSite CS, Function &Callee) {
// If no size growth is allowed for this inlining, set Threshold to 0.
if (!allowSizeGrowth(CS)) {
Threshold = 0;
return;
}
Function *Caller = CS.getCaller();
// return min(A, B) if B is valid.
auto MinIfValid = [](int A, Optional<int> B) {
return B ? std::min(A, B.getValue()) : A;
};
// return max(A, B) if B is valid.
auto MaxIfValid = [](int A, Optional<int> B) {
return B ? std::max(A, B.getValue()) : A;
};
// Use the OptMinSizeThreshold or OptSizeThreshold knob if they are available
// and reduce the threshold if the caller has the necessary attribute.
if (Caller->optForMinSize())
Threshold = MinIfValid(Threshold, Params.OptMinSizeThreshold);
else if (Caller->optForSize())
Threshold = MinIfValid(Threshold, Params.OptSizeThreshold);
// Adjust the threshold based on inlinehint attribute and profile based
// hotness information if the caller does not have MinSize attribute.
if (!Caller->optForMinSize()) {
if (Callee.hasFnAttribute(Attribute::InlineHint))
Threshold = MaxIfValid(Threshold, Params.HintThreshold);
if (PSI) {
BlockFrequencyInfo *CallerBFI = GetBFI ? &((*GetBFI)(*Caller)) : nullptr;
if (PSI->isHotCallSite(CS, CallerBFI)) {
DEBUG(dbgs() << "Hot callsite.\n");
Threshold = Params.HotCallSiteThreshold.getValue();
} else if (PSI->isFunctionEntryHot(&Callee)) {
DEBUG(dbgs() << "Hot callee.\n");
// If callsite hotness can not be determined, we may still know
// that the callee is hot and treat it as a weaker hint for threshold
// increase.
Threshold = MaxIfValid(Threshold, Params.HintThreshold);
} else if (PSI->isColdCallSite(CS, CallerBFI)) {
DEBUG(dbgs() << "Cold callsite.\n");
Threshold = MinIfValid(Threshold, Params.ColdCallSiteThreshold);
} else if (PSI->isFunctionEntryCold(&Callee)) {
DEBUG(dbgs() << "Cold callee.\n");
Threshold = MinIfValid(Threshold, Params.ColdThreshold);
}
}
}
// Finally, take the target-specific inlining threshold multiplier into
// account.
Threshold *= TTI.getInliningThresholdMultiplier();
}
bool CallAnalyzer::visitCmpInst(CmpInst &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// First try to handle simplified comparisons.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getCompare(I.getPredicate(), COps[0], COps[1]);
}))
return true;
if (I.getOpcode() == Instruction::FCmp)
return false;
// Otherwise look for a comparison between constant offset pointers with
// a common base.
Value *LHSBase, *RHSBase;
APInt LHSOffset, RHSOffset;
std::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS);
if (LHSBase) {
std::tie(RHSBase, RHSOffset) = ConstantOffsetPtrs.lookup(RHS);
if (RHSBase && LHSBase == RHSBase) {
// We have common bases, fold the icmp to a constant based on the
// offsets.
Constant *CLHS = ConstantInt::get(LHS->getContext(), LHSOffset);
Constant *CRHS = ConstantInt::get(RHS->getContext(), RHSOffset);
if (Constant *C = ConstantExpr::getICmp(I.getPredicate(), CLHS, CRHS)) {
SimplifiedValues[&I] = C;
++NumConstantPtrCmps;
return true;
}
}
}
// If the comparison is an equality comparison with null, we can simplify it
// if we know the value (argument) can't be null
if (I.isEquality() && isa<ConstantPointerNull>(I.getOperand(1)) &&
isKnownNonNullInCallee(I.getOperand(0))) {
bool IsNotEqual = I.getPredicate() == CmpInst::ICMP_NE;
SimplifiedValues[&I] = IsNotEqual ? ConstantInt::getTrue(I.getType())
: ConstantInt::getFalse(I.getType());
return true;
}
// Finally check for SROA candidates in comparisons.
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getOperand(0), SROAArg, CostIt)) {
if (isa<ConstantPointerNull>(I.getOperand(1))) {
accumulateSROACost(CostIt, InlineConstants::InstrCost);
return true;
}
disableSROA(CostIt);
}
return false;
}
bool CallAnalyzer::visitSub(BinaryOperator &I) {
// Try to handle a special case: we can fold computing the difference of two
// constant-related pointers.
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
Value *LHSBase, *RHSBase;
APInt LHSOffset, RHSOffset;
std::tie(LHSBase, LHSOffset) = ConstantOffsetPtrs.lookup(LHS);
if (LHSBase) {
std::tie(RHSBase, RHSOffset) = ConstantOffsetPtrs.lookup(RHS);
if (RHSBase && LHSBase == RHSBase) {
// We have common bases, fold the subtract to a constant based on the
// offsets.
Constant *CLHS = ConstantInt::get(LHS->getContext(), LHSOffset);
Constant *CRHS = ConstantInt::get(RHS->getContext(), RHSOffset);
if (Constant *C = ConstantExpr::getSub(CLHS, CRHS)) {
SimplifiedValues[&I] = C;
++NumConstantPtrDiffs;
return true;
}
}
}
// Otherwise, fall back to the generic logic for simplifying and handling
// instructions.
return Base::visitSub(I);
}
bool CallAnalyzer::visitBinaryOperator(BinaryOperator &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
auto Evaluate = [&](SmallVectorImpl<Constant *> &COps) {
Value *SimpleV = nullptr;
const DataLayout &DL = F.getParent()->getDataLayout();
if (auto FI = dyn_cast<FPMathOperator>(&I))
SimpleV = SimplifyFPBinOp(I.getOpcode(), COps[0], COps[1],
FI->getFastMathFlags(), DL);
else
SimpleV = SimplifyBinOp(I.getOpcode(), COps[0], COps[1], DL);
return dyn_cast_or_null<Constant>(SimpleV);
};
if (simplifyInstruction(I, Evaluate))
return true;
// Disable any SROA on arguments to arbitrary, unsimplified binary operators.
disableSROA(LHS);
disableSROA(RHS);
return false;
}
bool CallAnalyzer::visitLoad(LoadInst &I) {
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt)) {
if (I.isSimple()) {
accumulateSROACost(CostIt, InlineConstants::InstrCost);
return true;
}
disableSROA(CostIt);
}
return false;
}
bool CallAnalyzer::visitStore(StoreInst &I) {
Value *SROAArg;
DenseMap<Value *, int>::iterator CostIt;
if (lookupSROAArgAndCost(I.getPointerOperand(), SROAArg, CostIt)) {
if (I.isSimple()) {
accumulateSROACost(CostIt, InlineConstants::InstrCost);
return true;
}
disableSROA(CostIt);
}
return false;
}
bool CallAnalyzer::visitExtractValue(ExtractValueInst &I) {
// Constant folding for extract value is trivial.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getExtractValue(COps[0], I.getIndices());
}))
return true;
// SROA can look through these but give them a cost.
return false;
}
bool CallAnalyzer::visitInsertValue(InsertValueInst &I) {
// Constant folding for insert value is trivial.
if (simplifyInstruction(I, [&](SmallVectorImpl<Constant *> &COps) {
return ConstantExpr::getInsertValue(/*AggregateOperand*/ COps[0],
/*InsertedValueOperand*/ COps[1],
I.getIndices());
}))
return true;
// SROA can look through these but give them a cost.
return false;
}
/// \brief Try to simplify a call site.
///
/// Takes a concrete function and callsite and tries to actually simplify it by
/// analyzing the arguments and call itself with instsimplify. Returns true if
/// it has simplified the callsite to some other entity (a constant), making it
/// free.
bool CallAnalyzer::simplifyCallSite(Function *F, CallSite CS) {
// FIXME: Using the instsimplify logic directly for this is inefficient
// because we have to continually rebuild the argument list even when no
// simplifications can be performed. Until that is fixed with remapping
// inside of instsimplify, directly constant fold calls here.
if (!canConstantFoldCallTo(F))
return false;
// Try to re-map the arguments to constants.
SmallVector<Constant *, 4> ConstantArgs;
ConstantArgs.reserve(CS.arg_size());
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); I != E;
++I) {
Constant *C = dyn_cast<Constant>(*I);
if (!C)
C = dyn_cast_or_null<Constant>(SimplifiedValues.lookup(*I));
if (!C)
return false; // This argument doesn't map to a constant.
ConstantArgs.push_back(C);
}
if (Constant *C = ConstantFoldCall(F, ConstantArgs)) {
SimplifiedValues[CS.getInstruction()] = C;
return true;
}
return false;
}
bool CallAnalyzer::visitCallSite(CallSite CS) {
if (CS.hasFnAttr(Attribute::ReturnsTwice) &&
!F.hasFnAttribute(Attribute::ReturnsTwice)) {
// This aborts the entire analysis.
ExposesReturnsTwice = true;
return false;
}
if (CS.isCall() && cast<CallInst>(CS.getInstruction())->cannotDuplicate())
ContainsNoDuplicateCall = true;
if (Function *F = CS.getCalledFunction()) {
// When we have a concrete function, first try to simplify it directly.
if (simplifyCallSite(F, CS))
return true;
// Next check if it is an intrinsic we know about.
// FIXME: Lift this into part of the InstVisitor.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
switch (II->getIntrinsicID()) {
default:
return Base::visitCallSite(CS);
case Intrinsic::load_relative:
// This is normally lowered to 4 LLVM instructions.
Cost += 3 * InlineConstants::InstrCost;
return false;
case Intrinsic::memset:
case Intrinsic::memcpy:
case Intrinsic::memmove:
// SROA can usually chew through these intrinsics, but they aren't free.
return false;
case Intrinsic::localescape:
HasFrameEscape = true;
return false;
}
}
if (F == CS.getInstruction()->getParent()->getParent()) {
// This flag will fully abort the analysis, so don't bother with anything
// else.
IsRecursiveCall = true;
return false;
}
if (TTI.isLoweredToCall(F)) {
// We account for the average 1 instruction per call argument setup
// here.
Cost += CS.arg_size() * InlineConstants::InstrCost;
// Everything other than inline ASM will also have a significant cost
// merely from making the call.
if (!isa<InlineAsm>(CS.getCalledValue()))
Cost += InlineConstants::CallPenalty;
}
return Base::visitCallSite(CS);
}
// Otherwise we're in a very special case -- an indirect function call. See
// if we can be particularly clever about this.
Value *Callee = CS.getCalledValue();
// First, pay the price of the argument setup. We account for the average
// 1 instruction per call argument setup here.
Cost += CS.arg_size() * InlineConstants::InstrCost;
// Next, check if this happens to be an indirect function call to a known
// function in this inline context. If not, we've done all we can.
Function *F = dyn_cast_or_null<Function>(SimplifiedValues.lookup(Callee));
if (!F)
return Base::visitCallSite(CS);
// If we have a constant that we are calling as a function, we can peer
// through it and see the function target. This happens not infrequently
// during devirtualization and so we want to give it a hefty bonus for
// inlining, but cap that bonus in the event that inlining wouldn't pan
// out. Pretend to inline the function, with a custom threshold.
auto IndirectCallParams = Params;
IndirectCallParams.DefaultThreshold = InlineConstants::IndirectCallThreshold;
CallAnalyzer CA(TTI, GetAssumptionCache, GetBFI, PSI, *F, CS,
IndirectCallParams);
if (CA.analyzeCall(CS)) {
// We were able to inline the indirect call! Subtract the cost from the
// threshold to get the bonus we want to apply, but don't go below zero.
Cost -= std::max(0, CA.getThreshold() - CA.getCost());
}
return Base::visitCallSite(CS);
}
bool CallAnalyzer::visitReturnInst(ReturnInst &RI) {
// At least one return instruction will be free after inlining.
bool Free = !HasReturn;
HasReturn = true;
return Free;
}
bool CallAnalyzer::visitBranchInst(BranchInst &BI) {
// We model unconditional branches as essentially free -- they really
// shouldn't exist at all, but handling them makes the behavior of the
// inliner more regular and predictable. Interestingly, conditional branches
// which will fold away are also free.
return BI.isUnconditional() || isa<ConstantInt>(BI.getCondition()) ||
dyn_cast_or_null<ConstantInt>(
SimplifiedValues.lookup(BI.getCondition()));
}
bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
// We model unconditional switches as free, see the comments on handling
// branches.
if (isa<ConstantInt>(SI.getCondition()))
return true;
if (Value *V = SimplifiedValues.lookup(SI.getCondition()))
if (isa<ConstantInt>(V))
return true;
// Otherwise, we need to accumulate a cost proportional to the number of
// distinct successor blocks. This fan-out in the CFG cannot be represented
// for free even if we can represent the core switch as a jumptable that
// takes a single instruction.
//
// NB: We convert large switches which are just used to initialize large phi
// nodes to lookup tables instead in simplify-cfg, so this shouldn't prevent
// inlining those. It will prevent inlining in cases where the optimization
// does not (yet) fire.
SmallPtrSet<BasicBlock *, 8> SuccessorBlocks;
SuccessorBlocks.insert(SI.getDefaultDest());
for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I)
SuccessorBlocks.insert(I.getCaseSuccessor());
// Add cost corresponding to the number of distinct destinations. The first
// we model as free because of fallthrough.
Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost;
return false;
}
bool CallAnalyzer::visitIndirectBrInst(IndirectBrInst &IBI) {
// We never want to inline functions that contain an indirectbr. This is
// incorrect because all the blockaddress's (in static global initializers
// for example) would be referring to the original function, and this
// indirect jump would jump from the inlined copy of the function into the
// original function which is extremely undefined behavior.
// FIXME: This logic isn't really right; we can safely inline functions with
// indirectbr's as long as no other function or global references the
// blockaddress of a block within the current function.
HasIndirectBr = true;
return false;
}
bool CallAnalyzer::visitResumeInst(ResumeInst &RI) {
// FIXME: It's not clear that a single instruction is an accurate model for
// the inline cost of a resume instruction.
return false;
}
bool CallAnalyzer::visitCleanupReturnInst(CleanupReturnInst &CRI) {
// FIXME: It's not clear that a single instruction is an accurate model for
// the inline cost of a cleanupret instruction.
return false;
}
bool CallAnalyzer::visitCatchReturnInst(CatchReturnInst &CRI) {
// FIXME: It's not clear that a single instruction is an accurate model for
// the inline cost of a catchret instruction.
return false;
}
bool CallAnalyzer::visitUnreachableInst(UnreachableInst &I) {
// FIXME: It might be reasonably to discount the cost of instructions leading
// to unreachable as they have the lowest possible impact on both runtime and
// code size.
return true; // No actual code is needed for unreachable.
}
bool CallAnalyzer::visitInstruction(Instruction &I) {
// Some instructions are free. All of the free intrinsics can also be
// handled by SROA, etc.
if (TargetTransformInfo::TCC_Free == TTI.getUserCost(&I))
return true;
// We found something we don't understand or can't handle. Mark any SROA-able
// values in the operand list as no longer viable.
for (User::op_iterator OI = I.op_begin(), OE = I.op_end(); OI != OE; ++OI)
disableSROA(*OI);
return false;
}
/// \brief Analyze a basic block for its contribution to the inline cost.
///
/// This method walks the analyzer over every instruction in the given basic
/// block and accounts for their cost during inlining at this callsite. It
/// aborts early if the threshold has been exceeded or an impossible to inline
/// construct has been detected. It returns false if inlining is no longer
/// viable, and true if inlining remains viable.
bool CallAnalyzer::analyzeBlock(BasicBlock *BB,
SmallPtrSetImpl<const Value *> &EphValues) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
// FIXME: Currently, the number of instructions in a function regardless of
// our ability to simplify them during inline to constants or dead code,
// are actually used by the vector bonus heuristic. As long as that's true,
// we have to special case debug intrinsics here to prevent differences in
// inlining due to debug symbols. Eventually, the number of unsimplified
// instructions shouldn't factor into the cost computation, but until then,
// hack around it here.
if (isa<DbgInfoIntrinsic>(I))
continue;
// Skip ephemeral values.
if (EphValues.count(&*I))
continue;
++NumInstructions;
if (isa<ExtractElementInst>(I) || I->getType()->isVectorTy())
++NumVectorInstructions;
// If the instruction is floating point, and the target says this operation
// is expensive or the function has the "use-soft-float" attribute, this may
// eventually become a library call. Treat the cost as such.
if (I->getType()->isFloatingPointTy()) {
bool hasSoftFloatAttr = false;
// If the function has the "use-soft-float" attribute, mark it as
// expensive.
if (F.hasFnAttribute("use-soft-float")) {
Attribute Attr = F.getFnAttribute("use-soft-float");
StringRef Val = Attr.getValueAsString();
if (Val == "true")
hasSoftFloatAttr = true;
}
if (TTI.getFPOpCost(I->getType()) == TargetTransformInfo::TCC_Expensive ||
hasSoftFloatAttr)
Cost += InlineConstants::CallPenalty;
}
// If the instruction simplified to a constant, there is no cost to this
// instruction. Visit the instructions using our InstVisitor to account for
// all of the per-instruction logic. The visit tree returns true if we
// consumed the instruction in any way, and false if the instruction's base
// cost should count against inlining.
if (Base::visit(&*I))
++NumInstructionsSimplified;
else
Cost += InlineConstants::InstrCost;
// If the visit this instruction detected an uninlinable pattern, abort.
if (IsRecursiveCall || ExposesReturnsTwice || HasDynamicAlloca ||
HasIndirectBr || HasFrameEscape)
return false;
// If the caller is a recursive function then we don't want to inline
// functions which allocate a lot of stack space because it would increase
// the caller stack usage dramatically.
if (IsCallerRecursive &&
AllocatedSize > InlineConstants::TotalAllocaSizeRecursiveCaller)
return false;
// Check if we've past the maximum possible threshold so we don't spin in
// huge basic blocks that will never inline.
if (Cost > Threshold)
return false;
}
return true;
}
/// \brief Compute the base pointer and cumulative constant offsets for V.
///
/// This strips all constant offsets off of V, leaving it the base pointer, and
/// accumulates the total constant offset applied in the returned constant. It
/// returns 0 if V is not a pointer, and returns the constant '0' if there are
/// no constant offsets applied.
ConstantInt *CallAnalyzer::stripAndComputeInBoundsConstantOffsets(Value *&V) {
if (!V->getType()->isPointerTy())
return nullptr;
const DataLayout &DL = F.getParent()->getDataLayout();
unsigned IntPtrWidth = DL.getPointerSizeInBits();
APInt Offset = APInt::getNullValue(IntPtrWidth);
// Even though we don't look through PHI nodes, we could be called on an
// instruction in an unreachable block, which may be on a cycle.
SmallPtrSet<Value *, 4> Visited;
Visited.insert(V);
do {
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
if (!GEP->isInBounds() || !accumulateGEPOffset(*GEP, Offset))
return nullptr;
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast) {
V = cast<Operator>(V)->getOperand(0);
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (GA->isInterposable())
break;
V = GA->getAliasee();
} else {
break;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
} while (Visited.insert(V).second);
Type *IntPtrTy = DL.getIntPtrType(V->getContext());
return cast<ConstantInt>(ConstantInt::get(IntPtrTy, Offset));
}
/// \brief Analyze a call site for potential inlining.
///
/// Returns true if inlining this call is viable, and false if it is not
/// viable. It computes the cost and adjusts the threshold based on numerous
/// factors and heuristics. If this method returns false but the computed cost
/// is below the computed threshold, then inlining was forcibly disabled by
/// some artifact of the routine.
bool CallAnalyzer::analyzeCall(CallSite CS) {
++NumCallsAnalyzed;
// Perform some tweaks to the cost and threshold based on the direct
// callsite information.
// We want to more aggressively inline vector-dense kernels, so up the
// threshold, and we'll lower it if the % of vector instructions gets too
// low. Note that these bonuses are some what arbitrary and evolved over time
// by accident as much as because they are principled bonuses.
//
// FIXME: It would be nice to remove all such bonuses. At least it would be
// nice to base the bonus values on something more scientific.
assert(NumInstructions == 0);
assert(NumVectorInstructions == 0);
// Update the threshold based on callsite properties
updateThreshold(CS, F);
FiftyPercentVectorBonus = 3 * Threshold / 2;
TenPercentVectorBonus = 3 * Threshold / 4;
const DataLayout &DL = F.getParent()->getDataLayout();
// Track whether the post-inlining function would have more than one basic
// block. A single basic block is often intended for inlining. Balloon the
// threshold by 50% until we pass the single-BB phase.
bool SingleBB = true;
int SingleBBBonus = Threshold / 2;
// Speculatively apply all possible bonuses to Threshold. If cost exceeds
// this Threshold any time, and cost cannot decrease, we can stop processing
// the rest of the function body.
Threshold += (SingleBBBonus + FiftyPercentVectorBonus);
// Give out bonuses per argument, as the instructions setting them up will
// be gone after inlining.
for (unsigned I = 0, E = CS.arg_size(); I != E; ++I) {
if (CS.isByValArgument(I)) {
// We approximate the number of loads and stores needed by dividing the
// size of the byval type by the target's pointer size.
PointerType *PTy = cast<PointerType>(CS.getArgument(I)->getType());
unsigned TypeSize = DL.getTypeSizeInBits(PTy->getElementType());
unsigned PointerSize = DL.getPointerSizeInBits();
// Ceiling division.
unsigned NumStores = (TypeSize + PointerSize - 1) / PointerSize;
// If it generates more than 8 stores it is likely to be expanded as an
// inline memcpy so we take that as an upper bound. Otherwise we assume
// one load and one store per word copied.
// FIXME: The maxStoresPerMemcpy setting from the target should be used
// here instead of a magic number of 8, but it's not available via
// DataLayout.
NumStores = std::min(NumStores, 8U);
Cost -= 2 * NumStores * InlineConstants::InstrCost;
} else {
// For non-byval arguments subtract off one instruction per call
// argument.
Cost -= InlineConstants::InstrCost;
}
}
// The call instruction also disappears after inlining.
Cost -= InlineConstants::InstrCost + InlineConstants::CallPenalty;
// If there is only one call of the function, and it has internal linkage,
// the cost of inlining it drops dramatically.
bool OnlyOneCallAndLocalLinkage =
F.hasLocalLinkage() && F.hasOneUse() && &F == CS.getCalledFunction();
if (OnlyOneCallAndLocalLinkage)
Cost -= InlineConstants::LastCallToStaticBonus;
// If this function uses the coldcc calling convention, prefer not to inline
// it.
if (F.getCallingConv() == CallingConv::Cold)
Cost += InlineConstants::ColdccPenalty;
// Check if we're done. This can happen due to bonuses and penalties.
if (Cost > Threshold)
return false;
if (F.empty())
return true;
Function *Caller = CS.getInstruction()->getParent()->getParent();
// Check if the caller function is recursive itself.
for (User *U : Caller->users()) {
CallSite Site(U);
if (!Site)
continue;
Instruction *I = Site.getInstruction();
if (I->getParent()->getParent() == Caller) {
IsCallerRecursive = true;
break;
}
}
// Populate our simplified values by mapping from function arguments to call
// arguments with known important simplifications.
CallSite::arg_iterator CAI = CS.arg_begin();
for (Function::arg_iterator FAI = F.arg_begin(), FAE = F.arg_end();
FAI != FAE; ++FAI, ++CAI) {
assert(CAI != CS.arg_end());
if (Constant *C = dyn_cast<Constant>(CAI))
SimplifiedValues[&*FAI] = C;
Value *PtrArg = *CAI;
if (ConstantInt *C = stripAndComputeInBoundsConstantOffsets(PtrArg)) {
ConstantOffsetPtrs[&*FAI] = std::make_pair(PtrArg, C->getValue());
// We can SROA any pointer arguments derived from alloca instructions.
if (isa<AllocaInst>(PtrArg)) {
SROAArgValues[&*FAI] = PtrArg;
SROAArgCosts[PtrArg] = 0;
}
}
}
NumConstantArgs = SimplifiedValues.size();
NumConstantOffsetPtrArgs = ConstantOffsetPtrs.size();
NumAllocaArgs = SROAArgValues.size();
// FIXME: If a caller has multiple calls to a callee, we end up recomputing
// the ephemeral values multiple times (and they're completely determined by
// the callee, so this is purely duplicate work).
SmallPtrSet<const Value *, 32> EphValues;
CodeMetrics::collectEphemeralValues(&F, &GetAssumptionCache(F), EphValues);
// The worklist of live basic blocks in the callee *after* inlining. We avoid
// adding basic blocks of the callee which can be proven to be dead for this
// particular call site in order to get more accurate cost estimates. This
// requires a somewhat heavyweight iteration pattern: we need to walk the
// basic blocks in a breadth-first order as we insert live successors. To
// accomplish this, prioritizing for small iterations because we exit after
// crossing our threshold, we use a small-size optimized SetVector.
typedef SetVector<BasicBlock *, SmallVector<BasicBlock *, 16>,
SmallPtrSet<BasicBlock *, 16>>
BBSetVector;
BBSetVector BBWorklist;
BBWorklist.insert(&F.getEntryBlock());
// Note that we *must not* cache the size, this loop grows the worklist.
for (unsigned Idx = 0; Idx != BBWorklist.size(); ++Idx) {
// Bail out the moment we cross the threshold. This means we'll under-count
// the cost, but only when undercounting doesn't matter.
if (Cost > Threshold)
break;
BasicBlock *BB = BBWorklist[Idx];
if (BB->empty())
continue;
// Disallow inlining a blockaddress. A blockaddress only has defined
// behavior for an indirect branch in the same function, and we do not
// currently support inlining indirect branches. But, the inliner may not
// see an indirect branch that ends up being dead code at a particular call
// site. If the blockaddress escapes the function, e.g., via a global
// variable, inlining may lead to an invalid cross-function reference.
if (BB->hasAddressTaken())
return false;
// Analyze the cost of this block. If we blow through the threshold, this
// returns false, and we can bail on out.
if (!analyzeBlock(BB, EphValues))
return false;
TerminatorInst *TI = BB->getTerminator();
// Add in the live successors by first checking whether we have terminator
// that may be simplified based on the values simplified by this call.
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional()) {
Value *Cond = BI->getCondition();
if (ConstantInt *SimpleCond =
dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) {
BBWorklist.insert(BI->getSuccessor(SimpleCond->isZero() ? 1 : 0));
continue;
}
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
Value *Cond = SI->getCondition();
if (ConstantInt *SimpleCond =
dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) {
BBWorklist.insert(SI->findCaseValue(SimpleCond).getCaseSuccessor());
continue;
}
}
// If we're unable to select a particular successor, just count all of
// them.
for (unsigned TIdx = 0, TSize = TI->getNumSuccessors(); TIdx != TSize;
++TIdx)
BBWorklist.insert(TI->getSuccessor(TIdx));
// If we had any successors at this point, than post-inlining is likely to
// have them as well. Note that we assume any basic blocks which existed
// due to branches or switches which folded above will also fold after
// inlining.
if (SingleBB && TI->getNumSuccessors() > 1) {
// Take off the bonus we applied to the threshold.
Threshold -= SingleBBBonus;
SingleBB = false;
}
}
// If this is a noduplicate call, we can still inline as long as
// inlining this would cause the removal of the caller (so the instruction
// is not actually duplicated, just moved).
if (!OnlyOneCallAndLocalLinkage && ContainsNoDuplicateCall)
return false;
// We applied the maximum possible vector bonus at the beginning. Now,
// subtract the excess bonus, if any, from the Threshold before
// comparing against Cost.
if (NumVectorInstructions <= NumInstructions / 10)
Threshold -= FiftyPercentVectorBonus;
else if (NumVectorInstructions <= NumInstructions / 2)
Threshold -= (FiftyPercentVectorBonus - TenPercentVectorBonus);
return Cost < std::max(1, Threshold);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
/// \brief Dump stats about this call's analysis.
LLVM_DUMP_METHOD void CallAnalyzer::dump() {
#define DEBUG_PRINT_STAT(x) dbgs() << " " #x ": " << x << "\n"
DEBUG_PRINT_STAT(NumConstantArgs);
DEBUG_PRINT_STAT(NumConstantOffsetPtrArgs);
DEBUG_PRINT_STAT(NumAllocaArgs);
DEBUG_PRINT_STAT(NumConstantPtrCmps);
DEBUG_PRINT_STAT(NumConstantPtrDiffs);
DEBUG_PRINT_STAT(NumInstructionsSimplified);
DEBUG_PRINT_STAT(NumInstructions);
DEBUG_PRINT_STAT(SROACostSavings);
DEBUG_PRINT_STAT(SROACostSavingsLost);
DEBUG_PRINT_STAT(ContainsNoDuplicateCall);
DEBUG_PRINT_STAT(Cost);
DEBUG_PRINT_STAT(Threshold);
#undef DEBUG_PRINT_STAT
}
#endif
/// \brief Test that two functions either have or have not the given attribute
/// at the same time.
template <typename AttrKind>
static bool attributeMatches(Function *F1, Function *F2, AttrKind Attr) {
return F1->getFnAttribute(Attr) == F2->getFnAttribute(Attr);
}
/// \brief Test that there are no attribute conflicts between Caller and Callee
/// that prevent inlining.
static bool functionsHaveCompatibleAttributes(Function *Caller,
Function *Callee,
TargetTransformInfo &TTI) {
return TTI.areInlineCompatible(Caller, Callee) &&
AttributeFuncs::areInlineCompatible(*Caller, *Callee);
}
InlineCost llvm::getInlineCost(
CallSite CS, const InlineParams &Params, TargetTransformInfo &CalleeTTI,
std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
ProfileSummaryInfo *PSI) {
return getInlineCost(CS, CS.getCalledFunction(), Params, CalleeTTI,
GetAssumptionCache, GetBFI, PSI);
}
InlineCost llvm::getInlineCost(
CallSite CS, Function *Callee, const InlineParams &Params,
TargetTransformInfo &CalleeTTI,
std::function<AssumptionCache &(Function &)> &GetAssumptionCache,
Optional<function_ref<BlockFrequencyInfo &(Function &)>> GetBFI,
ProfileSummaryInfo *PSI) {
// Cannot inline indirect calls.
if (!Callee)
return llvm::InlineCost::getNever();
// Calls to functions with always-inline attributes should be inlined
// whenever possible.
if (CS.hasFnAttr(Attribute::AlwaysInline)) {
if (isInlineViable(*Callee))
return llvm::InlineCost::getAlways();
return llvm::InlineCost::getNever();
}
// Never inline functions with conflicting attributes (unless callee has
// always-inline attribute).
if (!functionsHaveCompatibleAttributes(CS.getCaller(), Callee, CalleeTTI))
return llvm::InlineCost::getNever();
// Don't inline this call if the caller has the optnone attribute.
if (CS.getCaller()->hasFnAttribute(Attribute::OptimizeNone))
return llvm::InlineCost::getNever();
// Don't inline functions which can be interposed at link-time. Don't inline
// functions marked noinline or call sites marked noinline.
// Note: inlining non-exact non-interposable functions is fine, since we know
// we have *a* correct implementation of the source level function.
if (Callee->isInterposable() || Callee->hasFnAttribute(Attribute::NoInline) ||
CS.isNoInline())
return llvm::InlineCost::getNever();
DEBUG(llvm::dbgs() << " Analyzing call of " << Callee->getName()
<< "...\n");
CallAnalyzer CA(CalleeTTI, GetAssumptionCache, GetBFI, PSI, *Callee, CS,
Params);
bool ShouldInline = CA.analyzeCall(CS);
DEBUG(CA.dump());
// Check if there was a reason to force inlining or no inlining.
if (!ShouldInline && CA.getCost() < CA.getThreshold())
return InlineCost::getNever();
if (ShouldInline && CA.getCost() >= CA.getThreshold())
return InlineCost::getAlways();
return llvm::InlineCost::get(CA.getCost(), CA.getThreshold());
}
bool llvm::isInlineViable(Function &F) {
bool ReturnsTwice = F.hasFnAttribute(Attribute::ReturnsTwice);
for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
// Disallow inlining of functions which contain indirect branches or
// blockaddresses.
if (isa<IndirectBrInst>(BI->getTerminator()) || BI->hasAddressTaken())
return false;
for (auto &II : *BI) {
CallSite CS(&II);
if (!CS)
continue;
// Disallow recursive calls.
if (&F == CS.getCalledFunction())
return false;
// Disallow calls which expose returns-twice to a function not previously
// attributed as such.
if (!ReturnsTwice && CS.isCall() &&
cast<CallInst>(CS.getInstruction())->canReturnTwice())
return false;
// Disallow inlining functions that call @llvm.localescape. Doing this
// correctly would require major changes to the inliner.
if (CS.getCalledFunction() &&
CS.getCalledFunction()->getIntrinsicID() ==
llvm::Intrinsic::localescape)
return false;
}
}
return true;
}
// APIs to create InlineParams based on command line flags and/or other
// parameters.
InlineParams llvm::getInlineParams(int Threshold) {
InlineParams Params;
// This field is the threshold to use for a callee by default. This is
// derived from one or more of:
// * optimization or size-optimization levels,
// * a value passed to createFunctionInliningPass function, or
// * the -inline-threshold flag.
// If the -inline-threshold flag is explicitly specified, that is used
// irrespective of anything else.
if (InlineThreshold.getNumOccurrences() > 0)
Params.DefaultThreshold = InlineThreshold;
else
Params.DefaultThreshold = Threshold;
// Set the HintThreshold knob from the -inlinehint-threshold.
Params.HintThreshold = HintThreshold;
// Set the HotCallSiteThreshold knob from the -hot-callsite-threshold.
Params.HotCallSiteThreshold = HotCallSiteThreshold;
// Set the ColdCallSiteThreshold knob from the -inline-cold-callsite-threshold.
Params.ColdCallSiteThreshold = ColdCallSiteThreshold;
// Set the OptMinSizeThreshold and OptSizeThreshold params only if the
// Set the OptMinSizeThreshold and OptSizeThreshold params only if the
// -inlinehint-threshold commandline option is not explicitly given. If that
// option is present, then its value applies even for callees with size and
// minsize attributes.
// If the -inline-threshold is not specified, set the ColdThreshold from the
// -inlinecold-threshold even if it is not explicitly passed. If
// -inline-threshold is specified, then -inlinecold-threshold needs to be
// explicitly specified to set the ColdThreshold knob
if (InlineThreshold.getNumOccurrences() == 0) {
Params.OptMinSizeThreshold = InlineConstants::OptMinSizeThreshold;
Params.OptSizeThreshold = InlineConstants::OptSizeThreshold;
Params.ColdThreshold = ColdThreshold;
} else if (ColdThreshold.getNumOccurrences() > 0) {
Params.ColdThreshold = ColdThreshold;
}
return Params;
}
InlineParams llvm::getInlineParams() {
return getInlineParams(InlineThreshold);
}
// Compute the default threshold for inlining based on the opt level and the
// size opt level.
static int computeThresholdFromOptLevels(unsigned OptLevel,
unsigned SizeOptLevel) {
if (OptLevel > 2)
return InlineConstants::OptAggressiveThreshold;
if (SizeOptLevel == 1) // -Os
return InlineConstants::OptSizeThreshold;
if (SizeOptLevel == 2) // -Oz
return InlineConstants::OptMinSizeThreshold;
return InlineThreshold;
}
InlineParams llvm::getInlineParams(unsigned OptLevel, unsigned SizeOptLevel) {
return getInlineParams(computeThresholdFromOptLevels(OptLevel, SizeOptLevel));
}
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