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Revert "[Constant Hoisting] Extend coverage of the constant hoisting pass."

Browse Source 
I will break this up into smaller pieces for review and recommit.

llvm-svn: 204393
This commit is contained in:
Juergen Ributzka 2014-03-20 20:17:13 +00:00
parent 7dae5f7baa
commit c55e0f3fc7
7 changed files with 307 additions and 451 deletions
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6
include/llvm/Analysis/TargetTransformInfo.h
View File

@ -297,10 +297,10 @@ public:
/// \brief Return the expected cost of materialization for the given integer
/// immediate of the specified type for a given instruction. The cost can be
/// zero if the immediate can be folded into the specified instruction.
virtual unsigned getIntImmCost(unsigned Opc, unsigned Idx, const APInt &Imm,
virtual unsigned getIntImmCost(unsigned Opcode, const APInt &Imm,
Type *Ty) const;
virtual unsigned getIntImmCost(Intrinsic::ID IID, const APInt &Imm,
Type *Ty) const;
virtual unsigned getIntImmCost(Intrinsic::ID IID, unsigned Idx,
const APInt &Imm, Type *Ty) const;
/// @}
/// \name Vector Target Information

16
lib/Analysis/TargetTransformInfo.cpp
View File

@ -148,14 +148,14 @@ unsigned TargetTransformInfo::getIntImmCost(const APInt &Imm, Type *Ty) const {
return PrevTTI->getIntImmCost(Imm, Ty);
}
unsigned TargetTransformInfo::getIntImmCost(unsigned Opc, unsigned Idx,
const APInt &Imm, Type *Ty) const {
return PrevTTI->getIntImmCost(Opc, Idx, Imm, Ty);
unsigned TargetTransformInfo::getIntImmCost(unsigned Opcode, const APInt &Imm,
Type *Ty) const {
return PrevTTI->getIntImmCost(Opcode, Imm, Ty);
}
unsigned TargetTransformInfo::getIntImmCost(Intrinsic::ID IID, unsigned Idx,
const APInt &Imm, Type *Ty) const {
return PrevTTI->getIntImmCost(IID, Idx, Imm, Ty);
unsigned TargetTransformInfo::getIntImmCost(Intrinsic::ID IID, const APInt &Imm,
Type *Ty) const {
return PrevTTI->getIntImmCost(IID, Imm, Ty);
}
unsigned TargetTransformInfo::getNumberOfRegisters(bool Vector) const {
@ -539,12 +539,12 @@ struct NoTTI final : ImmutablePass, TargetTransformInfo {
return TCC_Basic;
}
unsigned getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
unsigned getIntImmCost(unsigned Opcode, const APInt &Imm,
Type *Ty) const override {
return TCC_Free;
}
unsigned getIntImmCost(Intrinsic::ID IID, unsigned Idx, const APInt &Imm,
unsigned getIntImmCost(Intrinsic::ID IID, const APInt &Imm,
Type *Ty) const override {
return TCC_Free;
}

47
lib/Target/X86/X86TargetTransformInfo.cpp
View File

@ -103,9 +103,9 @@ public:
unsigned getIntImmCost(const APInt &Imm, Type *Ty) const override;
unsigned getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
unsigned getIntImmCost(unsigned Opcode, const APInt &Imm,
Type *Ty) const override;
unsigned getIntImmCost(Intrinsic::ID IID, unsigned Idx, const APInt &Imm,
unsigned getIntImmCost(Intrinsic::ID IID, const APInt &Imm,
Type *Ty) const override;
/// @}
@ -776,9 +776,6 @@ unsigned X86TTI::getIntImmCost(const APInt &Imm, Type *Ty) const {
if (BitSize == 0)
return ~0U;
if (Imm == 0)
return TCC_Free;
if (Imm.getBitWidth() <= 64 &&
(isInt<32>(Imm.getSExtValue()) || isUInt<32>(Imm.getZExtValue())))
return TCC_Basic;
@ -786,7 +783,7 @@ unsigned X86TTI::getIntImmCost(const APInt &Imm, Type *Ty) const {
return 2 * TCC_Basic;
}
unsigned X86TTI::getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
unsigned X86TTI::getIntImmCost(unsigned Opcode, const APInt &Imm,
Type *Ty) const {
assert(Ty->isIntegerTy());
@ -794,15 +791,7 @@ unsigned X86TTI::getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
if (BitSize == 0)
return ~0U;
unsigned ImmIdx = ~0U;
switch (Opcode) {
default: return TCC_Free;
case Instruction::GetElementPtr:
if (Idx != 0)
return TCC_Free;
case Instruction::Store:
ImmIdx = 0;
break;
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
@ -817,31 +806,28 @@ unsigned X86TTI::getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
case Instruction::Or:
case Instruction::Xor:
case Instruction::ICmp:
ImmIdx = 1;
break;
if (Imm.getBitWidth() <= 64 && isInt<32>(Imm.getSExtValue()))
return TCC_Free;
else
return X86TTI::getIntImmCost(Imm, Ty);
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::IntToPtr:
case Instruction::PtrToInt:
case Instruction::BitCast:
case Instruction::PHI:
case Instruction::Call:
case Instruction::Select:
case Instruction::Ret:
case Instruction::Load:
break;
case Instruction::Store:
return X86TTI::getIntImmCost(Imm, Ty);
}
if ((Idx == ImmIdx) &&
Imm.getBitWidth() <= 64 && isInt<32>(Imm.getSExtValue()))
return TCC_Free;
return X86TTI::getIntImmCost(Imm, Ty);
return TargetTransformInfo::getIntImmCost(Opcode, Imm, Ty);
}
unsigned X86TTI::getIntImmCost(Intrinsic::ID IID, unsigned Idx,
const APInt &Imm, Type *Ty) const {
unsigned X86TTI::getIntImmCost(Intrinsic::ID IID, const APInt &Imm,
Type *Ty) const {
assert(Ty->isIntegerTy());
unsigned BitSize = Ty->getPrimitiveSizeInBits();
@ -849,24 +835,21 @@ unsigned X86TTI::getIntImmCost(Intrinsic::ID IID, unsigned Idx,
return ~0U;
switch (IID) {
default: return TCC_Free;
default: return TargetTransformInfo::getIntImmCost(IID, Imm, Ty);
case Intrinsic::sadd_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::usub_with_overflow:
case Intrinsic::smul_with_overflow:
case Intrinsic::umul_with_overflow:
if ((Idx == 1) && Imm.getBitWidth() <= 64 && isInt<32>(Imm.getSExtValue()))
if (Imm.getBitWidth() <= 64 && isInt<32>(Imm.getSExtValue()))
return TCC_Free;
else
return X86TTI::getIntImmCost(Imm, Ty);
case Intrinsic::experimental_stackmap:
if (Idx < 2)
return TCC_Free;
case Intrinsic::experimental_patchpoint_void:
case Intrinsic::experimental_patchpoint_i64:
if ((Idx < 4 ) ||
(Imm.getBitWidth() <= 64 && isInt<64>(Imm.getSExtValue())))
if (Imm.getBitWidth() <= 64 && isInt<64>(Imm.getSExtValue()))
return TCC_Free;
else
return X86TTI::getIntImmCost(Imm, Ty);

648
lib/Transforms/Scalar/ConstantHoisting.cpp
View File

@ -35,14 +35,15 @@
#define DEBUG_TYPE "consthoist"
#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
@ -50,80 +51,42 @@ using namespace llvm;
STATISTIC(NumConstantsHoisted, "Number of constants hoisted");
STATISTIC(NumConstantsRebased, "Number of constants rebased");
namespace {
struct ConstantUser;
struct RebasedConstantInfo;
typedef SmallVector<ConstantUser, 8> ConstantUseListType;
typedef SmallVector<RebasedConstantInfo, 4> RebasedConstantListType;
/// \brief Keeps track of the user of a constant and the operand index where the
/// constant is used.
struct ConstantUser {
Instruction *Inst;
unsigned OpndIdx;
ConstantUser(Instruction *Inst, unsigned Idx) : Inst(Inst), OpndIdx(Idx) { }
};
/// \brief Keeps track of a constant candidate and its usees.
typedef SmallVector<User *, 4> ConstantUseListType;
struct ConstantCandidate {
ConstantUseListType Uses;
ConstantInt *ConstInt;
unsigned CumulativeCost;
ConstantCandidate(ConstantInt *ConstInt)
: ConstInt(ConstInt), CumulativeCost(0) { }
/// \brief Add the user to the use list and update the cost.
void addUser(Instruction *Inst, unsigned Idx, unsigned Cost) {
CumulativeCost += Cost;
Uses.push_back(ConstantUser(Inst, Idx));
}
};
/// \brief This represents a constant that has been rebased with respect to a
/// base constant. The difference to the base constant is recorded in Offset.
struct RebasedConstantInfo {
ConstantUseListType Uses;
Constant *Offset;
mutable BasicBlock *IDom;
RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset)
: Uses(Uses), Offset(Offset), IDom(nullptr) { }
};
/// \brief A base constant and all its rebased constants.
struct ConstantInfo {
ConstantInt *BaseConstant;
struct RebasedConstantInfo {
ConstantInt *OriginalConstant;
Constant *Offset;
ConstantUseListType Uses;
};
typedef SmallVector<RebasedConstantInfo, 4> RebasedConstantListType;
RebasedConstantListType RebasedConstants;
};
/// \brief The constant hoisting pass.
class ConstantHoisting : public FunctionPass {
typedef DenseMap<ConstantInt *, unsigned> ConstCandMapType;
typedef std::vector<ConstantCandidate> ConstCandVecType;
const TargetTransformInfo *TTI;
DominatorTree *DT;
BasicBlock *Entry;
/// Keeps track of constant candidates found in the function.
ConstCandMapType ConstCandMap;
ConstCandVecType ConstCandVec;
/// Keep track of cast instructions we already cloned.
SmallDenseMap<Instruction *, Instruction *> ClonedCastMap;
/// Keeps track of expensive constants found in the function.
typedef MapVector<ConstantInt *, ConstantCandidate> ConstantMapType;
ConstantMapType ConstantMap;
/// These are the final constants we decided to hoist.
SmallVector<ConstantInfo, 8> ConstantVec;
SmallVector<ConstantInfo, 4> Constants;
public:
static char ID; // Pass identification, replacement for typeid
ConstantHoisting() : FunctionPass(ID), TTI(0), DT(0), Entry(0) {
ConstantHoisting() : FunctionPass(ID), TTI(0) {
initializeConstantHoistingPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &Fn) override;
bool runOnFunction(Function &F) override;
const char *getPassName() const override { return "Constant Hoisting"; }
@ -134,49 +97,19 @@ public:
}
private:
/// \brief Initialize the pass.
void setup(Function &Fn) {
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
TTI = &getAnalysis<TargetTransformInfo>();
Entry = &Fn.getEntryBlock();
}
/// \brief Cleanup.
void cleanup() {
ConstantVec.clear();
ClonedCastMap.clear();
ConstCandVec.clear();
ConstCandMap.clear();
TTI = nullptr;
DT = nullptr;
Entry = nullptr;
}
/// \brief Find the common dominator of all uses and cache the result for
/// future lookup.
BasicBlock *getIDom(const RebasedConstantInfo &RCI) const {
if (RCI.IDom)
return RCI.IDom;
RCI.IDom = findIDomOfAllUses(RCI.Uses);
assert(RCI.IDom && "Invalid IDom.");
return RCI.IDom;
}
BasicBlock *findIDomOfAllUses(const ConstantUseListType &Uses) const;
Instruction *findMatInsertPt(Instruction *I, unsigned Idx = ~0U) const;
Instruction *findConstantInsertionPoint(const ConstantInfo &CI) const;
void collectConstantCandidates(Instruction *I, unsigned Idx, ConstantInt *C);
void collectConstantCandidates(Instruction *I);
void collectConstantCandidates(Function &Fn);
void findAndMakeBaseConstant(ConstCandVecType::iterator S,
ConstCandVecType::iterator E);
void findBaseConstants();
void emitBaseConstants(Instruction *Base, Constant *Offset,
const ConstantUser &CU);
bool emitBaseConstants();
void deleteDeadCastInst() const;
bool optimizeConstants(Function &F);
void CollectConstant(User *U, unsigned Opcode, Intrinsic::ID IID,
ConstantInt *C);
void CollectConstants(Instruction *I);
void CollectConstants(Function &F);
void FindAndMakeBaseConstant(ConstantMapType::iterator S,
ConstantMapType::iterator E);
void FindBaseConstants();
Instruction *FindConstantInsertionPoint(Function &F,
const ConstantInfo &CI) const;
void EmitBaseConstants(Function &F, User *U, Instruction *Base,
Constant *Offset, ConstantInt *OriginalConstant);
bool EmitBaseConstants(Function &F);
bool OptimizeConstants(Function &F);
};
}
@ -193,352 +126,297 @@ FunctionPass *llvm::createConstantHoistingPass() {
}
/// \brief Perform the constant hoisting optimization for the given function.
bool ConstantHoisting::runOnFunction(Function &Fn) {
DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n");
DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n');
bool ConstantHoisting::runOnFunction(Function &F) {
DEBUG(dbgs() << "********** Constant Hoisting **********\n");
DEBUG(dbgs() << "********** Function: " << F.getName() << '\n');
setup(Fn);
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
TTI = &getAnalysis<TargetTransformInfo>();
bool MadeChange = optimizeConstants(Fn);
if (MadeChange) {
DEBUG(dbgs() << "********** Function after Constant Hoisting: "
<< Fn.getName() << '\n');
DEBUG(dbgs() << Fn);
}
DEBUG(dbgs() << "********** End Constant Hoisting **********\n");
cleanup();
return MadeChange;
return OptimizeConstants(F);
}
/// \brief Find nearest common dominator of all uses.
/// FIXME: Replace this with NearestCommonDominator once it is in common code.
BasicBlock *
ConstantHoisting::findIDomOfAllUses(const ConstantUseListType &Uses) const {
// Collect all basic blocks.
SmallPtrSet<BasicBlock *, 8> BBs;
for (auto const &U : Uses)
BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());
if (BBs.count(Entry))
return Entry;
while (BBs.size() >= 2) {
BasicBlock *BB, *BB1, *BB2;
BB1 = *BBs.begin();
BB2 = *std::next(BBs.begin());
BB = DT->findNearestCommonDominator(BB1, BB2);
if (BB == Entry)
return Entry;
BBs.erase(BB1);
BBs.erase(BB2);
BBs.insert(BB);
}
assert((BBs.size() == 1) && "Expected only one element.");
return *BBs.begin();
}
/// \brief Find the constant materialization insertion point.
Instruction *ConstantHoisting::findMatInsertPt(Instruction *Inst,
unsigned Idx) const {
// The simple and common case.
if (!isa<PHINode>(Inst) && !isa<LandingPadInst>(Inst))
return Inst;
// We can't insert directly before a phi node or landing pad. Insert before
// the terminator of the incoming or dominating block.
assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!");
if (Idx != ~0U && isa<PHINode>(Inst))
return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
BasicBlock *IDom = DT->getNode(Inst->getParent())->getIDom()->getBlock();
return IDom->getTerminator();
}
/// \brief Find an insertion point that dominates all uses.
Instruction *ConstantHoisting::
findConstantInsertionPoint(const ConstantInfo &ConstInfo) const {
assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
// Collect all IDoms.
SmallPtrSet<BasicBlock *, 8> BBs;
for (auto const &RCI : ConstInfo.RebasedConstants)
BBs.insert(getIDom(RCI));
assert(!BBs.empty() && "No dominators!?");
if (BBs.count(Entry))
return &Entry->front();
while (BBs.size() >= 2) {
BasicBlock *BB, *BB1, *BB2;
BB1 = *BBs.begin();
BB2 = *std::next(BBs.begin());
BB = DT->findNearestCommonDominator(BB1, BB2);
if (BB == Entry)
return &Entry->front();
BBs.erase(BB1);
BBs.erase(BB2);
BBs.insert(BB);
}
assert((BBs.size() == 1) && "Expected only one element.");
Instruction &FirstInst = (*BBs.begin())->front();
return findMatInsertPt(&FirstInst);
}
/// \brief Record constant integer ConstInt for instruction Inst at operand
/// index Idx.
///
/// The operand at index Idx is not necessarily the constant inetger itself. It
/// could also be a cast instruction or a constant expression that uses the
// constant integer.
void ConstantHoisting::collectConstantCandidates(Instruction *Inst,
unsigned Idx,
ConstantInt *ConstInt) {
void ConstantHoisting::CollectConstant(User * U, unsigned Opcode,
Intrinsic::ID IID, ConstantInt *C) {
unsigned Cost;
// Ask the target about the cost of materializing the constant for the given
// instruction and operand index.
if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
ConstInt->getValue(), ConstInt->getType());
if (Opcode)
Cost = TTI->getIntImmCost(Opcode, C->getValue(), C->getType());
else
Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
ConstInt->getType());
Cost = TTI->getIntImmCost(IID, C->getValue(), C->getType());
// Ignore cheap integer constants.
if (Cost > TargetTransformInfo::TCC_Basic) {
ConstCandMapType::iterator Itr;
bool Inserted;
std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(ConstInt, 0));
if (Inserted) {
ConstCandVec.push_back(ConstantCandidate(ConstInt));
Itr->second = ConstCandVec.size() - 1;
}
ConstCandVec[Itr->second].addUser(Inst, Idx, Cost);
DEBUG(if (auto ConstInt = dyn_cast<ConstantInt>(Inst->getOperand(Idx)))
dbgs() << "Collect constant " << *ConstInt << " from " << *Inst
<< " with cost " << Cost << '\n';
else
dbgs() << "Collect constant " << *ConstInt << " indirectly from "
<< *Inst << " via " << *Inst->getOperand(Idx) << " with cost "
<< Cost << '\n';
);
ConstantCandidate &CC = ConstantMap[C];
CC.CumulativeCost += Cost;
CC.Uses.push_back(U);
DEBUG(dbgs() << "Collect constant " << *C << " with cost " << Cost
<< " from " << *U << '\n');
}
}
/// \brief Scan the instruction for expensive integer constants and record them
/// in the constant candidate vector.
void ConstantHoisting::collectConstantCandidates(Instruction *Inst) {
// Skip all cast instructions. They are visited indirectly later on.
if (Inst->isCast())
return;
// Can't handle inline asm. Skip it.
if (auto Call = dyn_cast<CallInst>(Inst))
if (isa<InlineAsm>(Call->getCalledValue()))
return;
/// \brief Scan the instruction or constant expression for expensive integer
/// constants and record them in the constant map.
void ConstantHoisting::CollectConstants(Instruction *I) {
unsigned Opcode = 0;
Intrinsic::ID IID = Intrinsic::not_intrinsic;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
IID = II->getIntrinsicID();
else
Opcode = I->getOpcode();
// Scan all operands.
for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
Value *Opnd = Inst->getOperand(Idx);
// Vist constant integers.
if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
collectConstantCandidates(Inst, Idx, ConstInt);
for (User::op_iterator O = I->op_begin(), E = I->op_end(); O != E; ++O) {
if (ConstantInt *C = dyn_cast<ConstantInt>(O)) {
CollectConstant(I, Opcode, IID, C);
continue;
}
// Visit cast instructions that have constant integers.
if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
// Only visit cast instructions, which have been skipped. All other
// instructions should have already been visited.
if (!CastInst->isCast())
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(O)) {
// We only handle constant cast expressions.
if (!CE->isCast())
continue;
if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
// Pretend the constant is directly used by the instruction and ignore
// the cast instruction.
collectConstantCandidates(Inst, Idx, ConstInt);
if (ConstantInt *C = dyn_cast<ConstantInt>(CE->getOperand(0))) {
// Ignore the cast expression and use the opcode of the instruction.
CollectConstant(CE, Opcode, IID, C);
continue;
}
}
// Visit constant expressions that have constant integers.
if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
// Only visit constant cast expressions.
if (!ConstExpr->isCast())
continue;
if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
// Pretend the constant is directly used by the instruction and ignore
// the constant expression.
collectConstantCandidates(Inst, Idx, ConstInt);
continue;
}
}
} // end of for all operands
}
}
/// \brief Collect all integer constants in the function that cannot be folded
/// into an instruction itself.
void ConstantHoisting::collectConstantCandidates(Function &Fn) {
for (Function::iterator BB : Fn)
for (BasicBlock::iterator I : *BB)
collectConstantCandidates(I);
void ConstantHoisting::CollectConstants(Function &F) {
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
CollectConstants(I);
}
/// \brief Find the base constant within the given range and rebase all other
/// constants with respect to the base constant.
void ConstantHoisting::findAndMakeBaseConstant(ConstCandVecType::iterator S,
ConstCandVecType::iterator E) {
auto MaxCostItr = S;
void ConstantHoisting::FindAndMakeBaseConstant(ConstantMapType::iterator S,
ConstantMapType::iterator E) {
ConstantMapType::iterator MaxCostItr = S;
unsigned NumUses = 0;
// Use the constant that has the maximum cost as base constant.
for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
NumUses += ConstCand->Uses.size();
if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
MaxCostItr = ConstCand;
for (ConstantMapType::iterator I = S; I != E; ++I) {
NumUses += I->second.Uses.size();
if (I->second.CumulativeCost > MaxCostItr->second.CumulativeCost)
MaxCostItr = I;
}
// Don't hoist constants that have only one use.
if (NumUses <= 1)
return;
ConstantInfo ConstInfo;
ConstInfo.BaseConstant = MaxCostItr->ConstInt;
Type *Ty = ConstInfo.BaseConstant->getType();
ConstantInfo CI;
CI.BaseConstant = MaxCostItr->first;
Type *Ty = CI.BaseConstant->getType();
// Rebase the constants with respect to the base constant.
for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
APInt Diff = ConstCand->ConstInt->getValue() -
ConstInfo.BaseConstant->getValue();
Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
ConstInfo.RebasedConstants.push_back(
RebasedConstantInfo(std::move(ConstCand->Uses), Offset));
for (ConstantMapType::iterator I = S; I != E; ++I) {
APInt Diff = I->first->getValue() - CI.BaseConstant->getValue();
ConstantInfo::RebasedConstantInfo RCI;
RCI.OriginalConstant = I->first;
RCI.Offset = ConstantInt::get(Ty, Diff);
RCI.Uses = std::move(I->second.Uses);
CI.RebasedConstants.push_back(RCI);
}
ConstantVec.push_back(ConstInfo);
Constants.push_back(CI);
}
/// \brief Finds and combines constant candidates that can be easily
/// rematerialized with an add from a common base constant.
void ConstantHoisting::findBaseConstants() {
// Sort the constants by value and type. This invalidates the mapping!
std::sort(ConstCandVec.begin(), ConstCandVec.end(),
[](const ConstantCandidate &LHS, const ConstantCandidate &RHS) {
if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
return LHS.ConstInt->getType()->getBitWidth() <
RHS.ConstInt->getType()->getBitWidth();
return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
});
/// \brief Finds and combines constants that can be easily rematerialized with
/// an add from a common base constant.
void ConstantHoisting::FindBaseConstants() {
// Sort the constants by value and type. This invalidates the mapping.
std::sort(ConstantMap.begin(), ConstantMap.end(),
[](const std::pair<ConstantInt *, ConstantCandidate> &LHS,
const std::pair<ConstantInt *, ConstantCandidate> &RHS) {
if (LHS.first->getType() != RHS.first->getType())
return LHS.first->getType()->getBitWidth() <
RHS.first->getType()->getBitWidth();
return LHS.first->getValue().ult(RHS.first->getValue());
});
// Simple linear scan through the sorted constant candidate vector for viable
// merge candidates.
auto MinValItr = ConstCandVec.begin();
for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
CC != E; ++CC) {
if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
// Simple linear scan through the sorted constant map for viable merge
// candidates.
ConstantMapType::iterator MinValItr = ConstantMap.begin();
for (ConstantMapType::iterator I = std::next(ConstantMap.begin()),
E = ConstantMap.end(); I != E; ++I) {
if (MinValItr->first->getType() == I->first->getType()) {
// Check if the constant is in range of an add with immediate.
APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
APInt Diff = I->first->getValue() - MinValItr->first->getValue();
if ((Diff.getBitWidth() <= 64) &&
TTI->isLegalAddImmediate(Diff.getSExtValue()))
continue;
}
// We either have now a different constant type or the constant is not in
// range of an add with immediate anymore.
findAndMakeBaseConstant(MinValItr, CC);
FindAndMakeBaseConstant(MinValItr, I);
// Start a new base constant search.
MinValItr = CC;
MinValItr = I;
}
// Finalize the last base constant search.
findAndMakeBaseConstant(MinValItr, ConstCandVec.end());
FindAndMakeBaseConstant(MinValItr, ConstantMap.end());
}
/// \brief Records the basic block of the instruction or all basic blocks of the
/// users of the constant expression.
static void CollectBasicBlocks(SmallPtrSet<BasicBlock *, 4> &BBs, Function &F,
User *U) {
if (Instruction *I = dyn_cast<Instruction>(U))
BBs.insert(I->getParent());
else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U))
// Find all users of this constant expression.
for (User *UU : CE->users())
// Only record users that are instructions. We don't want to go down a
// nested constant expression chain. Also check if the instruction is even
// in the current function.
if (Instruction *I = dyn_cast<Instruction>(UU))
if(I->getParent()->getParent() == &F)
BBs.insert(I->getParent());
}
/// \brief Find the instruction we should insert the constant materialization
/// before.
static Instruction *getMatInsertPt(Instruction *I, const DominatorTree *DT) {
if (!isa<PHINode>(I) && !isa<LandingPadInst>(I)) // Simple case.
return I;
// We can't insert directly before a phi node or landing pad. Insert before
// the terminator of the dominating block.
assert(&I->getParent()->getParent()->getEntryBlock() != I->getParent() &&
"PHI or landing pad in entry block!");
BasicBlock *IDom = DT->getNode(I->getParent())->getIDom()->getBlock();
return IDom->getTerminator();
}
/// \brief Find an insertion point that dominates all uses.
Instruction *ConstantHoisting::
FindConstantInsertionPoint(Function &F, const ConstantInfo &CI) const {
BasicBlock *Entry = &F.getEntryBlock();
// Collect all basic blocks.
SmallPtrSet<BasicBlock *, 4> BBs;
ConstantInfo::RebasedConstantListType::const_iterator RCI, RCE;
for (RCI = CI.RebasedConstants.begin(), RCE = CI.RebasedConstants.end();
RCI != RCE; ++RCI)
for (SmallVectorImpl<User *>::const_iterator U = RCI->Uses.begin(),
E = RCI->Uses.end(); U != E; ++U)
CollectBasicBlocks(BBs, F, *U);
if (BBs.count(Entry))
return getMatInsertPt(&Entry->front(), DT);
while (BBs.size() >= 2) {
BasicBlock *BB, *BB1, *BB2;
BB1 = *BBs.begin();
BB2 = *std::next(BBs.begin());
BB = DT->findNearestCommonDominator(BB1, BB2);
if (BB == Entry)
return getMatInsertPt(&Entry->front(), DT);
BBs.erase(BB1);
BBs.erase(BB2);
BBs.insert(BB);
}
assert((BBs.size() == 1) && "Expected only one element.");
Instruction &FirstInst = (*BBs.begin())->front();
return getMatInsertPt(&FirstInst, DT);
}
/// \brief Emit materialization code for all rebased constants and update their
/// users.
void ConstantHoisting::emitBaseConstants(Instruction *Base, Constant *Offset,
const ConstantUser &CU) {
Instruction *Mat = Base;
if (Offset) {
Instruction *InsertionPt = findMatInsertPt(CU.Inst, CU.OpndIdx);
Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
"const_mat", InsertionPt);
void ConstantHoisting::EmitBaseConstants(Function &F, User *U,
Instruction *Base, Constant *Offset,
ConstantInt *OriginalConstant) {
if (Instruction *I = dyn_cast<Instruction>(U)) {
Instruction *Mat = Base;
if (!Offset->isNullValue()) {
Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
"const_mat", getMatInsertPt(I, DT));
DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
<< " + " << *Offset << ") in BB "
<< Mat->getParent()->getName() << '\n' << *Mat << '\n');
Mat->setDebugLoc(CU.Inst->getDebugLoc());
}
Value *Opnd = CU.Inst->getOperand(CU.OpndIdx);
// Use the same debug location as the instruction we are about to update.
Mat->setDebugLoc(I->getDebugLoc());
// Visit constant integer.
if (isa<ConstantInt>(Opnd)) {
DEBUG(dbgs() << "Update: " << *CU.Inst << '\n');
CU.Inst->setOperand(CU.OpndIdx, Mat);
DEBUG(dbgs() << "To : " << *CU.Inst << '\n');
return;
}
// Visit cast instruction.
if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
assert(CastInst->isCast() && "Expected an cast instruction!");
// Check if we already have visited this cast instruction before to avoid
// unnecessary cloning.
Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
if (!ClonedCastInst) {
ClonedCastInst = CastInst->clone();
ClonedCastInst->setOperand(0, Mat);
ClonedCastInst->insertAfter(CastInst);
// Use the same debug location as the original cast instruction.
ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
DEBUG(dbgs() << "Clone instruction: " << *ClonedCastInst << '\n'
<< "To : " << *CastInst << '\n');
DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
<< " + " << *Offset << ") in BB "
<< I->getParent()->getName() << '\n' << *Mat << '\n');
}
DEBUG(dbgs() << "Update: " << *CU.Inst << '\n');
CU.Inst->setOperand(CU.OpndIdx, ClonedCastInst);
DEBUG(dbgs() << "To : " << *CU.Inst << '\n');
DEBUG(dbgs() << "Update: " << *I << '\n');
I->replaceUsesOfWith(OriginalConstant, Mat);
DEBUG(dbgs() << "To: " << *I << '\n');
return;
}
assert(isa<ConstantExpr>(U) && "Expected a ConstantExpr.");
ConstantExpr *CE = cast<ConstantExpr>(U);
SmallVector<std::pair<Instruction *, Instruction *>, 8> WorkList;
DEBUG(dbgs() << "Visit ConstantExpr " << *CE << '\n');
for (User *UU : CE->users()) {
DEBUG(dbgs() << "Check user "; UU->print(dbgs()); dbgs() << '\n');
// We only handel instructions here and won't walk down a ConstantExpr chain
// to replace all ConstExpr with instructions.
if (Instruction *I = dyn_cast<Instruction>(UU)) {
// Only update constant expressions in the current function.
if (I->getParent()->getParent() != &F) {
DEBUG(dbgs() << "Not in the same function - skip.\n");
continue;
}
// Visit constant expression.
if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
Instruction *ConstExprInst = ConstExpr->getAsInstruction();
ConstExprInst->setOperand(0, Mat);
ConstExprInst->insertBefore(findMatInsertPt(CU.Inst, CU.OpndIdx));
Instruction *Mat = Base;
Instruction *InsertBefore = getMatInsertPt(I, DT);
if (!Offset->isNullValue()) {
Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
"const_mat", InsertBefore);
// Use the same debug location as the instruction we are about to update.
ConstExprInst->setDebugLoc(CU.Inst->getDebugLoc());
// Use the same debug location as the instruction we are about to
// update.
Mat->setDebugLoc(I->getDebugLoc());
DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'
<< "From : " << *ConstExpr << '\n');
DEBUG(dbgs() << "Update: " << *CU.Inst << '\n');
CU.Inst->setOperand(CU.OpndIdx, ConstExprInst);
DEBUG(dbgs() << "To : " << *CU.Inst << '\n');
return;
DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)
<< " + " << *Offset << ") in BB "
<< I->getParent()->getName() << '\n' << *Mat << '\n');
}
Instruction *ICE = CE->getAsInstruction();
ICE->replaceUsesOfWith(OriginalConstant, Mat);
ICE->insertBefore(InsertBefore);
// Use the same debug location as the instruction we are about to update.
ICE->setDebugLoc(I->getDebugLoc());
WorkList.push_back(std::make_pair(I, ICE));
} else {
DEBUG(dbgs() << "Not an instruction - skip.\n");
}
}
SmallVectorImpl<std::pair<Instruction *, Instruction *> >::iterator I, E;
for (I = WorkList.begin(), E = WorkList.end(); I != E; ++I) {
DEBUG(dbgs() << "Create instruction: " << *I->second << '\n');
DEBUG(dbgs() << "Update: " << *I->first << '\n');
I->first->replaceUsesOfWith(CE, I->second);
DEBUG(dbgs() << "To: " << *I->first << '\n');
}
}
/// \brief Hoist and hide the base constant behind a bitcast and emit
/// materialization code for derived constants.
bool ConstantHoisting::emitBaseConstants() {
bool ConstantHoisting::EmitBaseConstants(Function &F) {
bool MadeChange = false;
for (auto const &ConstInfo : ConstantVec) {
SmallVectorImpl<ConstantInfo>::iterator CI, CE;
for (CI = Constants.begin(), CE = Constants.end(); CI != CE; ++CI) {
// Hoist and hide the base constant behind a bitcast.
Instruction *IP = findConstantInsertionPoint(ConstInfo);
IntegerType *Ty = ConstInfo.BaseConstant->getType();
Instruction *Base =
new BitCastInst(ConstInfo.BaseConstant, Ty, "const", IP);
DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseConstant << ") to BB "
<< IP->getParent()->getName() << '\n' << *Base << '\n');
Instruction *IP = FindConstantInsertionPoint(F, *CI);
IntegerType *Ty = CI->BaseConstant->getType();
Instruction *Base = new BitCastInst(CI->BaseConstant, Ty, "const", IP);
DEBUG(dbgs() << "Hoist constant (" << *CI->BaseConstant << ") to BB "
<< IP->getParent()->getName() << '\n');
NumConstantsHoisted++;
// Emit materialization code for all rebased constants.
for (auto const &RCI : ConstInfo.RebasedConstants) {
ConstantInfo::RebasedConstantListType::iterator RCI, RCE;
for (RCI = CI->RebasedConstants.begin(), RCE = CI->RebasedConstants.end();
RCI != RCE; ++RCI) {
NumConstantsRebased++;
for (auto const &U : RCI.Uses)
emitBaseConstants(Base, RCI.Offset, U);
for (SmallVectorImpl<User *>::iterator U = RCI->Uses.begin(),
E = RCI->Uses.end(); U != E; ++U)
EmitBaseConstants(F, *U, Base, RCI->Offset, RCI->OriginalConstant);
}
// Use the same debug location as the last user of the constant.
@ -554,37 +432,27 @@ bool ConstantHoisting::emitBaseConstants() {
return MadeChange;
}
/// \brief Check all cast instructions we made a copy of and remove them if they
/// have no more users.
void ConstantHoisting::deleteDeadCastInst() const {
for (auto const &I : ClonedCastMap)
if (I.first->use_empty())
I.first->removeFromParent();
}
/// \brief Optimize expensive integer constants in the given function.
bool ConstantHoisting::optimizeConstants(Function &Fn) {
// Collect all constant candidates.
collectConstantCandidates(Fn);
bool ConstantHoisting::OptimizeConstants(Function &F) {
bool MadeChange = false;
// There are no constant candidates to worry about.
if (ConstCandVec.empty())
return false;
// Collect all constant candidates.
CollectConstants(F);
// There are no constants to worry about.
if (ConstantMap.empty())
return MadeChange;
// Combine constants that can be easily materialized with an add from a common
// base constant.
findBaseConstants();
// There are no constants to emit.
if (ConstantVec.empty())
return false;
FindBaseConstants();
// Finally hoist the base constant and emit materializating code for dependent
// constants.
bool MadeChange = emitBaseConstants();
MadeChange |= EmitBaseConstants(F);
// Cleanup dead instructions.
deleteDeadCastInst();
ConstantMap.clear();
Constants.clear();
return MadeChange;
}

14
test/CodeGen/X86/lsr-interesting-step.ll
View File

@ -3,24 +3,26 @@
; The inner loop should require only one add (and no leas either).
; rdar://8100380
; CHECK: BB0_2:
; CHECK-NEXT: movb $0, flags(%rcx)
; CHECK-NEXT: addq %rax, %rcx
; CHECK-NEXT: cmpq $8192, %rcx
; CHECK: BB0_3:
; CHECK-NEXT: movb $0, flags(%rdx)
; CHECK-NEXT: addq %rax, %rdx
; CHECK-NEXT: cmpq $8192, %rdx
; CHECK-NEXT: jl
@flags = external global [8192 x i8], align 16 ; <[8192 x i8]*> [#uses=1]
define void @foo() nounwind {
entry:
br label %bb
%tmp = icmp slt i64 2, 8192 ; <i1> [#uses=1]
br i1 %tmp, label %bb, label %bb21
bb: ; preds = %entry
br label %bb7
bb7: ; preds = %bb, %bb17
%tmp8 = phi i64 [ %tmp18, %bb17 ], [ 2, %bb ] ; <i64> [#uses=2]
br label %bb10
%tmp9 = icmp slt i64 2, 8192 ; <i1> [#uses=1]
br i1 %tmp9, label %bb10, label %bb17
bb10: ; preds = %bb7
br label %bb11

17
test/CodeGen/X86/negate-add-zero.ll
View File

@ -827,7 +827,9 @@ declare void @_ZN11MatrixTools9transposeI11FixedMatrixIdLi6ELi6ELi0ELi0EEEENT_13
declare void @_ZN21HNodeTranslateRotate311toCartesianEv(%struct.HNodeTranslateRotate3*)
define linkonce void @_ZN21HNodeTranslateRotate36setVelERK9CDSVectorIdLi1EN3CDS12DefaultAllocEE(%struct.HNodeTranslateRotate3* %this, %"struct.CDSVector<double,0,CDS::DefaultAlloc>"* %velv) {
%1 = getelementptr double* null, i32 -1 ; <double*> [#uses=1]
entry:
%0 = add i32 0, -1 ; <i32> [#uses=1]
%1 = getelementptr double* null, i32 %0 ; <double*> [#uses=1]
%2 = load double* %1, align 8 ; <double> [#uses=1]
%3 = load double* null, align 8 ; <double> [#uses=2]
%4 = load double* null, align 8 ; <double> [#uses=2]
@ -888,12 +890,13 @@ define linkonce void @_ZN21HNodeTranslateRotate36setVelERK9CDSVectorIdLi1EN3CDS1
store double %52, double* %55, align 8
%56 = getelementptr %struct.HNodeTranslateRotate3* %this, i32 0, i32 0, i32 10, i32 0, i32 0, i32 2 ; <double*> [#uses=1]
store double %53, double* %56, align 8
%57 = getelementptr %"struct.SubVector<CDSVector<double, 1, CDS::DefaultAlloc> >"* null, i32 0, i32 0 ; <%"struct.CDSVector<double,0,CDS::DefaultAlloc>"**> [#uses=1]
store %"struct.CDSVector<double,0,CDS::DefaultAlloc>"* %velv, %"struct.CDSVector<double,0,CDS::DefaultAlloc>"** %57, align 8
%58 = getelementptr %"struct.SubVector<CDSVector<double, 1, CDS::DefaultAlloc> >"* null, i32 0, i32 1 ; <i32*> [#uses=1]
store i32 4, i32* %58, align 4
%59 = getelementptr %"struct.SubVector<CDSVector<double, 1, CDS::DefaultAlloc> >"* null, i32 0, i32 2 ; <i32*> [#uses=1]
store i32 3, i32* %59, align 8
%57 = add i32 0, 4 ; <i32> [#uses=1]
%58 = getelementptr %"struct.SubVector<CDSVector<double, 1, CDS::DefaultAlloc> >"* null, i32 0, i32 0 ; <%"struct.CDSVector<double,0,CDS::DefaultAlloc>"**> [#uses=1]
store %"struct.CDSVector<double,0,CDS::DefaultAlloc>"* %velv, %"struct.CDSVector<double,0,CDS::DefaultAlloc>"** %58, align 8
%59 = getelementptr %"struct.SubVector<CDSVector<double, 1, CDS::DefaultAlloc> >"* null, i32 0, i32 1 ; <i32*> [#uses=1]
store i32 %57, i32* %59, align 4
%60 = getelementptr %"struct.SubVector<CDSVector<double, 1, CDS::DefaultAlloc> >"* null, i32 0, i32 2 ; <i32*> [#uses=1]
store i32 3, i32* %60, align 8
unreachable
}

10
test/Transforms/ConstantHoisting/X86/phi.ll
View File

@ -19,11 +19,11 @@ return:
ret i8* %retval.0
; CHECK-LABEL: @test1
; CHECK: if.end:
; CHECK: %2 = inttoptr i64 %const to i8*
; CHECK-NEXT: br
; CHECK: return:
; CHECK-NEXT: %retval.0 = phi i8* [ null, %entry ], [ %2, %if.end ]
; CHECK: entry:
; CHECK: %const_mat = add i64 %const, 1
; CHECK-NEXT: %1 = inttoptr i64 %const_mat to i8*
; CHECK-NEXT: br i1 %cmp
; CHECK: %retval.0 = phi i8* [ null, %entry ], [ %1, %if.end ]
}
define void @test2(i1 %cmp, i64** %tmp) {