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llvm-project/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp

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//===----- LoadStoreVectorizer.cpp - GPU Load & Store Vectorizer ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Vectorize.h"
using namespace llvm;
#define DEBUG_TYPE "load-store-vectorizer"
STATISTIC(NumVectorInstructions, "Number of vector accesses generated");
STATISTIC(NumScalarsVectorized, "Number of scalar accesses vectorized");
namespace {
// TODO: Remove this
static const unsigned TargetBaseAlign = 4;
typedef SmallVector<Value *, 8> ValueList;
typedef MapVector<Value *, ValueList> ValueListMap;
class Vectorizer {
Function &F;
AliasAnalysis &AA;
DominatorTree &DT;
ScalarEvolution &SE;
TargetTransformInfo &TTI;
const DataLayout &DL;
IRBuilder<> Builder;
public:
Vectorizer(Function &F, AliasAnalysis &AA, DominatorTree &DT,
ScalarEvolution &SE, TargetTransformInfo &TTI)
: F(F), AA(AA), DT(DT), SE(SE), TTI(TTI),
DL(F.getParent()->getDataLayout()), Builder(SE.getContext()) {}
bool run();
private:
Value *getPointerOperand(Value *I);
unsigned getPointerAddressSpace(Value *I);
unsigned getAlignment(LoadInst *LI) const {
unsigned Align = LI->getAlignment();
if (Align != 0)
return Align;
return DL.getABITypeAlignment(LI->getType());
}
unsigned getAlignment(StoreInst *SI) const {
unsigned Align = SI->getAlignment();
if (Align != 0)
return Align;
return DL.getABITypeAlignment(SI->getValueOperand()->getType());
}
bool isConsecutiveAccess(Value *A, Value *B);
/// After vectorization, reorder the instructions that I depends on
/// (the instructions defining its operands), to ensure they dominate I.
void reorder(Instruction *I);
/// Returns the first and the last instructions in Chain.
std::pair<BasicBlock::iterator, BasicBlock::iterator>
getBoundaryInstrs(ArrayRef<Value *> Chain);
/// Erases the original instructions after vectorizing.
void eraseInstructions(ArrayRef<Value *> Chain);
/// "Legalize" the vector type that would be produced by combining \p
/// ElementSizeBits elements in \p Chain. Break into two pieces such that the
/// total size of each piece is 1, 2 or a multiple of 4 bytes. \p Chain is
/// expected to have more than 4 elements.
std::pair<ArrayRef<Value *>, ArrayRef<Value *>>
splitOddVectorElts(ArrayRef<Value *> Chain, unsigned ElementSizeBits);
/// Finds the largest prefix of Chain that's vectorizable, checking for
/// intervening instructions which may affect the memory accessed by the
/// instructions within Chain.
///
/// The elements of \p Chain must be all loads or all stores and must be in
/// address order.
ArrayRef<Value *> getVectorizablePrefix(ArrayRef<Value *> Chain);
/// Collects load and store instructions to vectorize.
std::pair<ValueListMap, ValueListMap> collectInstructions(BasicBlock *BB);
/// Processes the collected instructions, the \p Map. The elements of \p Map
/// should be all loads or all stores.
bool vectorizeChains(ValueListMap &Map);
/// Finds the load/stores to consecutive memory addresses and vectorizes them.
bool vectorizeInstructions(ArrayRef<Value *> Instrs);
/// Vectorizes the load instructions in Chain.
bool vectorizeLoadChain(ArrayRef<Value *> Chain,
SmallPtrSet<Value *, 16> *InstructionsProcessed);
/// Vectorizes the store instructions in Chain.
bool vectorizeStoreChain(ArrayRef<Value *> Chain,
SmallPtrSet<Value *, 16> *InstructionsProcessed);
/// Check if this load/store access is misaligned accesses
bool accessIsMisaligned(unsigned SzInBytes, unsigned AddressSpace,
unsigned Alignment);
};
class LoadStoreVectorizer : public FunctionPass {
public:
static char ID;
LoadStoreVectorizer() : FunctionPass(ID) {
initializeLoadStoreVectorizerPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
const char *getPassName() const override {
return "GPU Load and Store Vectorizer";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<ScalarEvolutionWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.setPreservesCFG();
}
};
}
INITIALIZE_PASS_BEGIN(LoadStoreVectorizer, DEBUG_TYPE,
"Vectorize load and Store instructions", false, false)
INITIALIZE_PASS_DEPENDENCY(SCEVAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_END(LoadStoreVectorizer, DEBUG_TYPE,
"Vectorize load and store instructions", false, false)
char LoadStoreVectorizer::ID = 0;
Pass *llvm::createLoadStoreVectorizerPass() {
return new LoadStoreVectorizer();
}
bool LoadStoreVectorizer::runOnFunction(Function &F) {
// Don't vectorize when the attribute NoImplicitFloat is used.
if (skipFunction(F) || F.hasFnAttribute(Attribute::NoImplicitFloat))
return false;
AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
TargetTransformInfo &TTI =
getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
Vectorizer V(F, AA, DT, SE, TTI);
return V.run();
}
// Vectorizer Implementation
bool Vectorizer::run() {
bool Changed = false;
// Scan the blocks in the function in post order.
for (BasicBlock *BB : post_order(&F)) {
ValueListMap LoadRefs, StoreRefs;
std::tie(LoadRefs, StoreRefs) = collectInstructions(BB);
Changed |= vectorizeChains(LoadRefs);
Changed |= vectorizeChains(StoreRefs);
}
return Changed;
}
Value *Vectorizer::getPointerOperand(Value *I) {
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return LI->getPointerOperand();
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->getPointerOperand();
return nullptr;
}
unsigned Vectorizer::getPointerAddressSpace(Value *I) {
if (LoadInst *L = dyn_cast<LoadInst>(I))
return L->getPointerAddressSpace();
if (StoreInst *S = dyn_cast<StoreInst>(I))
return S->getPointerAddressSpace();
return -1;
}
// FIXME: Merge with llvm::isConsecutiveAccess
bool Vectorizer::isConsecutiveAccess(Value *A, Value *B) {
Value *PtrA = getPointerOperand(A);
Value *PtrB = getPointerOperand(B);
unsigned ASA = getPointerAddressSpace(A);
unsigned ASB = getPointerAddressSpace(B);
// Check that the address spaces match and that the pointers are valid.
if (!PtrA || !PtrB || (ASA != ASB))
return false;
// Make sure that A and B are different pointers of the same size type.
unsigned PtrBitWidth = DL.getPointerSizeInBits(ASA);
Type *PtrATy = PtrA->getType()->getPointerElementType();
Type *PtrBTy = PtrB->getType()->getPointerElementType();
if (PtrA == PtrB ||
DL.getTypeStoreSize(PtrATy) != DL.getTypeStoreSize(PtrBTy) ||
DL.getTypeStoreSize(PtrATy->getScalarType()) !=
DL.getTypeStoreSize(PtrBTy->getScalarType()))
return false;
APInt Size(PtrBitWidth, DL.getTypeStoreSize(PtrATy));
APInt OffsetA(PtrBitWidth, 0), OffsetB(PtrBitWidth, 0);
PtrA = PtrA->stripAndAccumulateInBoundsConstantOffsets(DL, OffsetA);
PtrB = PtrB->stripAndAccumulateInBoundsConstantOffsets(DL, OffsetB);
APInt OffsetDelta = OffsetB - OffsetA;
// Check if they are based on the same pointer. That makes the offsets
// sufficient.
if (PtrA == PtrB)
return OffsetDelta == Size;
// Compute the necessary base pointer delta to have the necessary final delta
// equal to the size.
APInt BaseDelta = Size - OffsetDelta;
// Compute the distance with SCEV between the base pointers.
const SCEV *PtrSCEVA = SE.getSCEV(PtrA);
const SCEV *PtrSCEVB = SE.getSCEV(PtrB);
const SCEV *C = SE.getConstant(BaseDelta);
const SCEV *X = SE.getAddExpr(PtrSCEVA, C);
if (X == PtrSCEVB)
return true;
// Sometimes even this doesn't work, because SCEV can't always see through
// patterns that look like (gep (ext (add (shl X, C1), C2))). Try checking
// things the hard way.
// Look through GEPs after checking they're the same except for the last
// index.
GetElementPtrInst *GEPA = dyn_cast<GetElementPtrInst>(getPointerOperand(A));
GetElementPtrInst *GEPB = dyn_cast<GetElementPtrInst>(getPointerOperand(B));
if (!GEPA || !GEPB || GEPA->getNumOperands() != GEPB->getNumOperands())
return false;
unsigned FinalIndex = GEPA->getNumOperands() - 1;
for (unsigned i = 0; i < FinalIndex; i++)
if (GEPA->getOperand(i) != GEPB->getOperand(i))
return false;
Instruction *OpA = dyn_cast<Instruction>(GEPA->getOperand(FinalIndex));
Instruction *OpB = dyn_cast<Instruction>(GEPB->getOperand(FinalIndex));
if (!OpA || !OpB || OpA->getOpcode() != OpB->getOpcode() ||
OpA->getType() != OpB->getType())
return false;
// Only look through a ZExt/SExt.
if (!isa<SExtInst>(OpA) && !isa<ZExtInst>(OpA))
return false;
bool Signed = isa<SExtInst>(OpA);
OpA = dyn_cast<Instruction>(OpA->getOperand(0));
OpB = dyn_cast<Instruction>(OpB->getOperand(0));
if (!OpA || !OpB || OpA->getType() != OpB->getType())
return false;
// Now we need to prove that adding 1 to OpA won't overflow.
bool Safe = false;
// First attempt: if OpB is an add with NSW/NUW, and OpB is 1 added to OpA,
// we're okay.
if (OpB->getOpcode() == Instruction::Add &&
isa<ConstantInt>(OpB->getOperand(1)) &&
cast<ConstantInt>(OpB->getOperand(1))->getSExtValue() > 0) {
if (Signed)
Safe = cast<BinaryOperator>(OpB)->hasNoSignedWrap();
else
Safe = cast<BinaryOperator>(OpB)->hasNoUnsignedWrap();
}
unsigned BitWidth = OpA->getType()->getScalarSizeInBits();
// Second attempt:
// If any bits are known to be zero other than the sign bit in OpA, we can
// add 1 to it while guaranteeing no overflow of any sort.
if (!Safe) {
APInt KnownZero(BitWidth, 0);
APInt KnownOne(BitWidth, 0);
computeKnownBits(OpA, KnownZero, KnownOne, DL, 0, nullptr, OpA, &DT);
KnownZero &= ~APInt::getHighBitsSet(BitWidth, 1);
if (KnownZero != 0)
Safe = true;
}
if (!Safe)
return false;
const SCEV *OffsetSCEVA = SE.getSCEV(OpA);
const SCEV *OffsetSCEVB = SE.getSCEV(OpB);
const SCEV *One = SE.getConstant(APInt(BitWidth, 1));
const SCEV *X2 = SE.getAddExpr(OffsetSCEVA, One);
return X2 == OffsetSCEVB;
}
void Vectorizer::reorder(Instruction *I) {
SmallPtrSet<Instruction *, 16> InstructionsToMove;
SmallVector<Instruction *, 16> Worklist;
Worklist.push_back(I);
while (!Worklist.empty()) {
Instruction *IW = Worklist.pop_back_val();
int NumOperands = IW->getNumOperands();
for (int i = 0; i < NumOperands; i++) {
Instruction *IM = dyn_cast<Instruction>(IW->getOperand(i));
if (!IM || IM->getOpcode() == Instruction::PHI)
continue;
if (!DT.dominates(IM, I)) {
InstructionsToMove.insert(IM);
Worklist.push_back(IM);
assert(IM->getParent() == IW->getParent() &&
"Instructions to move should be in the same basic block");
}
}
}
// All instructions to move should follow I. Start from I, not from begin().
for (auto BBI = I->getIterator(), E = I->getParent()->end(); BBI != E;
++BBI) {
if (!is_contained(InstructionsToMove, &*BBI))
continue;
Instruction *IM = &*BBI;
--BBI;
IM->removeFromParent();
IM->insertBefore(I);
}
}
std::pair<BasicBlock::iterator, BasicBlock::iterator>
Vectorizer::getBoundaryInstrs(ArrayRef<Value *> Chain) {
Instruction *C0 = cast<Instruction>(Chain[0]);
BasicBlock::iterator FirstInstr = C0->getIterator();
BasicBlock::iterator LastInstr = C0->getIterator();
BasicBlock *BB = C0->getParent();
unsigned NumFound = 0;
for (Instruction &I : *BB) {
if (!is_contained(Chain, &I))
continue;
++NumFound;
if (NumFound == 1) {
FirstInstr = I.getIterator();
}
if (NumFound == Chain.size()) {
LastInstr = I.getIterator();
break;
}
}
// Range is [first, last).
return std::make_pair(FirstInstr, ++LastInstr);
}
void Vectorizer::eraseInstructions(ArrayRef<Value *> Chain) {
SmallVector<Instruction *, 16> Instrs;
for (Value *V : Chain) {
Value *PtrOperand = getPointerOperand(V);
assert(PtrOperand && "Instruction must have a pointer operand.");
Instrs.push_back(cast<Instruction>(V));
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(PtrOperand))
Instrs.push_back(GEP);
}
// Erase instructions.
for (Value *V : Instrs) {
Instruction *Instr = cast<Instruction>(V);
if (Instr->use_empty())
Instr->eraseFromParent();
}
}
std::pair<ArrayRef<Value *>, ArrayRef<Value *>>
Vectorizer::splitOddVectorElts(ArrayRef<Value *> Chain,
unsigned ElementSizeBits) {
unsigned ElemSizeInBytes = ElementSizeBits / 8;
unsigned SizeInBytes = ElemSizeInBytes * Chain.size();
unsigned NumRight = (SizeInBytes % 4) / ElemSizeInBytes;
unsigned NumLeft = Chain.size() - NumRight;
return std::make_pair(Chain.slice(0, NumLeft), Chain.slice(NumLeft));
}
ArrayRef<Value *> Vectorizer::getVectorizablePrefix(ArrayRef<Value *> Chain) {
// These are in BB order, unlike Chain, which is in address order.
SmallVector<std::pair<Value *, unsigned>, 16> MemoryInstrs;
SmallVector<std::pair<Value *, unsigned>, 16> ChainInstrs;
bool IsLoadChain = isa<LoadInst>(Chain[0]);
DEBUG({
for (Value *V : Chain) {
if (IsLoadChain)
assert(isa<LoadInst>(V) &&
"All elements of Chain must be loads, or all must be stores.");
else
assert(isa<StoreInst>(V) &&
"All elements of Chain must be loads, or all must be stores.");
}
});
unsigned InstrIdx = 0;
for (Instruction &I : make_range(getBoundaryInstrs(Chain))) {
++InstrIdx;
if (isa<LoadInst>(I) || isa<StoreInst>(I)) {
if (!is_contained(Chain, &I))
MemoryInstrs.push_back({&I, InstrIdx});
else
ChainInstrs.push_back({&I, InstrIdx});
} else if (IsLoadChain && (I.mayWriteToMemory() || I.mayThrow())) {
DEBUG(dbgs() << "LSV: Found may-write/throw operation: " << I << '\n');
break;
} else if (!IsLoadChain && (I.mayReadOrWriteMemory() || I.mayThrow())) {
DEBUG(dbgs() << "LSV: Found may-read/write/throw operation: " << I
<< '\n');
break;
}
}
// Loop until we find an instruction in ChainInstrs that we can't vectorize.
unsigned ChainInstrIdx, ChainInstrsLen;
for (ChainInstrIdx = 0, ChainInstrsLen = ChainInstrs.size();
ChainInstrIdx < ChainInstrsLen; ++ChainInstrIdx) {
Value *ChainInstr = ChainInstrs[ChainInstrIdx].first;
unsigned ChainInstrLoc = ChainInstrs[ChainInstrIdx].second;
bool AliasFound = false;
for (auto EntryMem : MemoryInstrs) {
Value *MemInstr = EntryMem.first;
unsigned MemInstrLoc = EntryMem.second;
if (isa<LoadInst>(MemInstr) && isa<LoadInst>(ChainInstr))
continue;
// We can ignore the alias as long as the load comes before the store,
// because that means we won't be moving the load past the store to
// vectorize it (the vectorized load is inserted at the location of the
// first load in the chain).
if (isa<StoreInst>(MemInstr) && isa<LoadInst>(ChainInstr) &&
ChainInstrLoc < MemInstrLoc)
continue;
// Same case, but in reverse.
if (isa<LoadInst>(MemInstr) && isa<StoreInst>(ChainInstr) &&
ChainInstrLoc > MemInstrLoc)
continue;
Instruction *M0 = cast<Instruction>(MemInstr);
Instruction *M1 = cast<Instruction>(ChainInstr);
if (!AA.isNoAlias(MemoryLocation::get(M0), MemoryLocation::get(M1))) {
DEBUG({
Value *Ptr0 = getPointerOperand(M0);
Value *Ptr1 = getPointerOperand(M1);
dbgs() << "LSV: Found alias:\n"
" Aliasing instruction and pointer:\n"
<< " " << *MemInstr << '\n'
<< " " << *Ptr0 << '\n'
<< " Aliased instruction and pointer:\n"
<< " " << *ChainInstr << '\n'
<< " " << *Ptr1 << '\n';
});
AliasFound = true;
break;
}
}
if (AliasFound)
break;
}
// Find the largest prefix of Chain whose elements are all in
// ChainInstrs[0, ChainInstrIdx). This is the largest vectorizable prefix of
// Chain. (Recall that Chain is in address order, but ChainInstrs is in BB
// order.)
auto VectorizableChainInstrs =
makeArrayRef(ChainInstrs.data(), ChainInstrIdx);
unsigned ChainIdx, ChainLen;
for (ChainIdx = 0, ChainLen = Chain.size(); ChainIdx < ChainLen; ++ChainIdx) {
Value *V = Chain[ChainIdx];
if (!any_of(VectorizableChainInstrs,
[V](std::pair<Value *, unsigned> CI) { return V == CI.first; }))
break;
}
return Chain.slice(0, ChainIdx);
}
std::pair<ValueListMap, ValueListMap>
Vectorizer::collectInstructions(BasicBlock *BB) {
ValueListMap LoadRefs;
ValueListMap StoreRefs;
for (Instruction &I : *BB) {
if (!I.mayReadOrWriteMemory())
continue;
if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
if (!LI->isSimple())
continue;
Type *Ty = LI->getType();
if (!VectorType::isValidElementType(Ty->getScalarType()))
continue;
// Skip weird non-byte sizes. They probably aren't worth the effort of
// handling correctly.
unsigned TySize = DL.getTypeSizeInBits(Ty);
if (TySize < 8)
continue;
Value *Ptr = LI->getPointerOperand();
unsigned AS = Ptr->getType()->getPointerAddressSpace();
unsigned VecRegSize = TTI.getLoadStoreVecRegBitWidth(AS);
// No point in looking at these if they're too big to vectorize.
if (TySize > VecRegSize / 2)
continue;
// Make sure all the users of a vector are constant-index extracts.
if (isa<VectorType>(Ty) && !all_of(LI->users(), [LI](const User *U) {
const Instruction *UI = cast<Instruction>(U);
return isa<ExtractElementInst>(UI) &&
isa<ConstantInt>(UI->getOperand(1));
}))
continue;
// TODO: Target hook to filter types.
// Save the load locations.
Value *ObjPtr = GetUnderlyingObject(Ptr, DL);
LoadRefs[ObjPtr].push_back(LI);
} else if (StoreInst *SI = dyn_cast<StoreInst>(&I)) {
if (!SI->isSimple())
continue;
Type *Ty = SI->getValueOperand()->getType();
if (!VectorType::isValidElementType(Ty->getScalarType()))
continue;
// Skip weird non-byte sizes. They probably aren't worth the effort of
// handling correctly.
unsigned TySize = DL.getTypeSizeInBits(Ty);
if (TySize < 8)
continue;
Value *Ptr = SI->getPointerOperand();
unsigned AS = Ptr->getType()->getPointerAddressSpace();
unsigned VecRegSize = TTI.getLoadStoreVecRegBitWidth(AS);
if (TySize > VecRegSize / 2)
continue;
if (isa<VectorType>(Ty) && !all_of(SI->users(), [SI](const User *U) {
const Instruction *UI = cast<Instruction>(U);
return isa<ExtractElementInst>(UI) &&
isa<ConstantInt>(UI->getOperand(1));
}))
continue;
// Save store location.
Value *ObjPtr = GetUnderlyingObject(Ptr, DL);
StoreRefs[ObjPtr].push_back(SI);
}
}
return {LoadRefs, StoreRefs};
}
bool Vectorizer::vectorizeChains(ValueListMap &Map) {
bool Changed = false;
for (const std::pair<Value *, ValueList> &Chain : Map) {
unsigned Size = Chain.second.size();
if (Size < 2)
continue;
DEBUG(dbgs() << "LSV: Analyzing a chain of length " << Size << ".\n");
// Process the stores in chunks of 64.
for (unsigned CI = 0, CE = Size; CI < CE; CI += 64) {
unsigned Len = std::min<unsigned>(CE - CI, 64);
ArrayRef<Value *> Chunk(&Chain.second[CI], Len);
Changed |= vectorizeInstructions(Chunk);
}
}
return Changed;
}
bool Vectorizer::vectorizeInstructions(ArrayRef<Value *> Instrs) {
DEBUG(dbgs() << "LSV: Vectorizing " << Instrs.size() << " instructions.\n");
SmallSetVector<int, 16> Heads, Tails;
int ConsecutiveChain[64];
// Do a quadratic search on all of the given stores and find all of the pairs
// of stores that follow each other.
for (int i = 0, e = Instrs.size(); i < e; ++i) {
ConsecutiveChain[i] = -1;
for (int j = e - 1; j >= 0; --j) {
if (i == j)
continue;
if (isConsecutiveAccess(Instrs[i], Instrs[j])) {
if (ConsecutiveChain[i] != -1) {
int CurDistance = std::abs(ConsecutiveChain[i] - i);
int NewDistance = std::abs(ConsecutiveChain[i] - j);
if (j < i || NewDistance > CurDistance)
continue; // Should not insert.
}
Tails.insert(j);
Heads.insert(i);
ConsecutiveChain[i] = j;
}
}
}
bool Changed = false;
SmallPtrSet<Value *, 16> InstructionsProcessed;
for (int Head : Heads) {
if (InstructionsProcessed.count(Instrs[Head]))
continue;
bool longerChainExists = false;
for (unsigned TIt = 0; TIt < Tails.size(); TIt++)
if (Head == Tails[TIt] &&
!InstructionsProcessed.count(Instrs[Heads[TIt]])) {
longerChainExists = true;
break;
}
if (longerChainExists)
continue;
// We found an instr that starts a chain. Now follow the chain and try to
// vectorize it.
SmallVector<Value *, 16> Operands;
int I = Head;
while (I != -1 && (Tails.count(I) || Heads.count(I))) {
if (InstructionsProcessed.count(Instrs[I]))
break;
Operands.push_back(Instrs[I]);
I = ConsecutiveChain[I];
}
bool Vectorized = false;
if (isa<LoadInst>(*Operands.begin()))
Vectorized = vectorizeLoadChain(Operands, &InstructionsProcessed);
else
Vectorized = vectorizeStoreChain(Operands, &InstructionsProcessed);
Changed |= Vectorized;
}
return Changed;
}
bool Vectorizer::vectorizeStoreChain(
ArrayRef<Value *> Chain, SmallPtrSet<Value *, 16> *InstructionsProcessed) {
StoreInst *S0 = cast<StoreInst>(Chain[0]);
// If the vector has an int element, default to int for the whole load.
Type *StoreTy;
for (const auto &V : Chain) {
StoreTy = cast<StoreInst>(V)->getValueOperand()->getType();
if (StoreTy->isIntOrIntVectorTy())
break;
if (StoreTy->isPtrOrPtrVectorTy()) {
StoreTy = Type::getIntNTy(F.getParent()->getContext(),
DL.getTypeSizeInBits(StoreTy));
break;
}
}
unsigned Sz = DL.getTypeSizeInBits(StoreTy);
unsigned AS = S0->getPointerAddressSpace();
unsigned VecRegSize = TTI.getLoadStoreVecRegBitWidth(AS);
unsigned VF = VecRegSize / Sz;
unsigned ChainSize = Chain.size();
if (!isPowerOf2_32(Sz) || VF < 2 || ChainSize < 2) {
InstructionsProcessed->insert(Chain.begin(), Chain.end());
return false;
}
ArrayRef<Value *> NewChain = getVectorizablePrefix(Chain);
if (NewChain.empty()) {
// No vectorization possible.
InstructionsProcessed->insert(Chain.begin(), Chain.end());
return false;
}
if (NewChain.size() == 1) {
// Failed after the first instruction. Discard it and try the smaller chain.
InstructionsProcessed->insert(NewChain.front());
return false;
}
// Update Chain to the valid vectorizable subchain.
Chain = NewChain;
ChainSize = Chain.size();
// Store size should be 1B, 2B or multiple of 4B.
// TODO: Target hook for size constraint?
unsigned SzInBytes = (Sz / 8) * ChainSize;
if (SzInBytes > 2 && SzInBytes % 4 != 0) {
DEBUG(dbgs() << "LSV: Size should be 1B, 2B "
"or multiple of 4B. Splitting.\n");
if (SzInBytes == 3)
return vectorizeStoreChain(Chain.slice(0, ChainSize - 1),
InstructionsProcessed);
auto Chains = splitOddVectorElts(Chain, Sz);
return vectorizeStoreChain(Chains.first, InstructionsProcessed) |
vectorizeStoreChain(Chains.second, InstructionsProcessed);
}
VectorType *VecTy;
VectorType *VecStoreTy = dyn_cast<VectorType>(StoreTy);
if (VecStoreTy)
VecTy = VectorType::get(StoreTy->getScalarType(),
Chain.size() * VecStoreTy->getNumElements());
else
VecTy = VectorType::get(StoreTy, Chain.size());
// If it's more than the max vector size, break it into two pieces.
// TODO: Target hook to control types to split to.
if (ChainSize > VF) {
DEBUG(dbgs() << "LSV: Vector factor is too big."
" Creating two separate arrays.\n");
return vectorizeStoreChain(Chain.slice(0, VF), InstructionsProcessed) |
vectorizeStoreChain(Chain.slice(VF), InstructionsProcessed);
}
DEBUG({
dbgs() << "LSV: Stores to vectorize:\n";
for (Value *V : Chain)
dbgs() << " " << *V << "\n";
});
// We won't try again to vectorize the elements of the chain, regardless of
// whether we succeed below.
InstructionsProcessed->insert(Chain.begin(), Chain.end());
// Check alignment restrictions.
unsigned Alignment = getAlignment(S0);
// If the store is going to be misaligned, don't vectorize it.
if (accessIsMisaligned(SzInBytes, AS, Alignment)) {
if (S0->getPointerAddressSpace() != 0)
return false;
// If we're storing to an object on the stack, we control its alignment,
// so we can cheat and change it!
Value *V = GetUnderlyingObject(S0->getPointerOperand(), DL);
if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(V)) {
AI->setAlignment(TargetBaseAlign);
Alignment = TargetBaseAlign;
} else {
return false;
}
}
BasicBlock::iterator First, Last;
std::tie(First, Last) = getBoundaryInstrs(Chain);
Builder.SetInsertPoint(&*Last);
Value *Vec = UndefValue::get(VecTy);
if (VecStoreTy) {
unsigned VecWidth = VecStoreTy->getNumElements();
for (unsigned I = 0, E = Chain.size(); I != E; ++I) {
StoreInst *Store = cast<StoreInst>(Chain[I]);
for (unsigned J = 0, NE = VecStoreTy->getNumElements(); J != NE; ++J) {
unsigned NewIdx = J + I * VecWidth;
Value *Extract = Builder.CreateExtractElement(Store->getValueOperand(),
Builder.getInt32(J));
if (Extract->getType() != StoreTy->getScalarType())
Extract = Builder.CreateBitCast(Extract, StoreTy->getScalarType());
Value *Insert =
Builder.CreateInsertElement(Vec, Extract, Builder.getInt32(NewIdx));
Vec = Insert;
}
}
} else {
for (unsigned I = 0, E = Chain.size(); I != E; ++I) {
StoreInst *Store = cast<StoreInst>(Chain[I]);
Value *Extract = Store->getValueOperand();
if (Extract->getType() != StoreTy->getScalarType())
Extract =
Builder.CreateBitOrPointerCast(Extract, StoreTy->getScalarType());
Value *Insert =
Builder.CreateInsertElement(Vec, Extract, Builder.getInt32(I));
Vec = Insert;
}
}
Value *Bitcast =
Builder.CreateBitCast(S0->getPointerOperand(), VecTy->getPointerTo(AS));
StoreInst *SI = cast<StoreInst>(Builder.CreateStore(Vec, Bitcast));
propagateMetadata(SI, Chain);
SI->setAlignment(Alignment);
eraseInstructions(Chain);
++NumVectorInstructions;
NumScalarsVectorized += Chain.size();
return true;
}
bool Vectorizer::vectorizeLoadChain(
ArrayRef<Value *> Chain, SmallPtrSet<Value *, 16> *InstructionsProcessed) {
LoadInst *L0 = cast<LoadInst>(Chain[0]);
// If the vector has an int element, default to int for the whole load.
Type *LoadTy;
for (const auto &V : Chain) {
LoadTy = cast<LoadInst>(V)->getType();
if (LoadTy->isIntOrIntVectorTy())
break;
if (LoadTy->isPtrOrPtrVectorTy()) {
LoadTy = Type::getIntNTy(F.getParent()->getContext(),
DL.getTypeSizeInBits(LoadTy));
break;
}
}
unsigned Sz = DL.getTypeSizeInBits(LoadTy);
unsigned AS = L0->getPointerAddressSpace();
unsigned VecRegSize = TTI.getLoadStoreVecRegBitWidth(AS);
unsigned VF = VecRegSize / Sz;
unsigned ChainSize = Chain.size();
if (!isPowerOf2_32(Sz) || VF < 2 || ChainSize < 2) {
InstructionsProcessed->insert(Chain.begin(), Chain.end());
return false;
}
ArrayRef<Value *> NewChain = getVectorizablePrefix(Chain);
if (NewChain.empty()) {
// No vectorization possible.
InstructionsProcessed->insert(Chain.begin(), Chain.end());
return false;
}
if (NewChain.size() == 1) {
// Failed after the first instruction. Discard it and try the smaller chain.
InstructionsProcessed->insert(NewChain.front());
return false;
}
// Update Chain to the valid vectorizable subchain.
Chain = NewChain;
ChainSize = Chain.size();
// Load size should be 1B, 2B or multiple of 4B.
// TODO: Should size constraint be a target hook?
unsigned SzInBytes = (Sz / 8) * ChainSize;
if (SzInBytes > 2 && SzInBytes % 4 != 0) {
DEBUG(dbgs() << "LSV: Size should be 1B, 2B "
"or multiple of 4B. Splitting.\n");
if (SzInBytes == 3)
return vectorizeLoadChain(Chain.slice(0, ChainSize - 1),
InstructionsProcessed);
auto Chains = splitOddVectorElts(Chain, Sz);
return vectorizeLoadChain(Chains.first, InstructionsProcessed) |
vectorizeLoadChain(Chains.second, InstructionsProcessed);
}
VectorType *VecTy;
VectorType *VecLoadTy = dyn_cast<VectorType>(LoadTy);
if (VecLoadTy)
VecTy = VectorType::get(LoadTy->getScalarType(),
Chain.size() * VecLoadTy->getNumElements());
else
VecTy = VectorType::get(LoadTy, Chain.size());
// If it's more than the max vector size, break it into two pieces.
// TODO: Target hook to control types to split to.
if (ChainSize > VF) {
DEBUG(dbgs() << "LSV: Vector factor is too big. "
"Creating two separate arrays.\n");
return vectorizeLoadChain(Chain.slice(0, VF), InstructionsProcessed) |
vectorizeLoadChain(Chain.slice(VF), InstructionsProcessed);
}
// We won't try again to vectorize the elements of the chain, regardless of
// whether we succeed below.
InstructionsProcessed->insert(Chain.begin(), Chain.end());
// Check alignment restrictions.
unsigned Alignment = getAlignment(L0);
// If the load is going to be misaligned, don't vectorize it.
if (accessIsMisaligned(SzInBytes, AS, Alignment)) {
if (L0->getPointerAddressSpace() != 0)
return false;
// If we're loading from an object on the stack, we control its alignment,
// so we can cheat and change it!
Value *V = GetUnderlyingObject(L0->getPointerOperand(), DL);
if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(V)) {
AI->setAlignment(TargetBaseAlign);
Alignment = TargetBaseAlign;
} else {
return false;
}
}
DEBUG({
dbgs() << "LSV: Loads to vectorize:\n";
for (Value *V : Chain)
V->dump();
});
// getVectorizablePrefix already computed getBoundaryInstrs. The value of
// Last may have changed since then, but the value of First won't have. If it
// matters, we could compute getBoundaryInstrs only once and reuse it here.
BasicBlock::iterator First, Last;
std::tie(First, Last) = getBoundaryInstrs(Chain);
Builder.SetInsertPoint(&*First);
Value *Bitcast =
Builder.CreateBitCast(L0->getPointerOperand(), VecTy->getPointerTo(AS));
LoadInst *LI = cast<LoadInst>(Builder.CreateLoad(Bitcast));
propagateMetadata(LI, Chain);
LI->setAlignment(Alignment);
if (VecLoadTy) {
SmallVector<Instruction *, 16> InstrsToErase;
unsigned VecWidth = VecLoadTy->getNumElements();
for (unsigned I = 0, E = Chain.size(); I != E; ++I) {
for (auto Use : Chain[I]->users()) {
Instruction *UI = cast<Instruction>(Use);
unsigned Idx = cast<ConstantInt>(UI->getOperand(1))->getZExtValue();
unsigned NewIdx = Idx + I * VecWidth;
Value *V = Builder.CreateExtractElement(LI, Builder.getInt32(NewIdx));
Instruction *Extracted = cast<Instruction>(V);
if (Extracted->getType() != UI->getType())
Extracted = cast<Instruction>(
Builder.CreateBitCast(Extracted, UI->getType()));
// Replace the old instruction.
UI->replaceAllUsesWith(Extracted);
InstrsToErase.push_back(UI);
}
}
// Bitcast might not be an Instruction, if the value being loaded is a
// constant. In that case, no need to reorder anything.
if (Instruction *BitcastInst = dyn_cast<Instruction>(Bitcast))
reorder(BitcastInst);
for (auto I : InstrsToErase)
I->eraseFromParent();
} else {
for (unsigned I = 0, E = Chain.size(); I != E; ++I) {
Value *V = Builder.CreateExtractElement(LI, Builder.getInt32(I));
Instruction *Extracted = cast<Instruction>(V);
Instruction *UI = cast<Instruction>(Chain[I]);
if (Extracted->getType() != UI->getType()) {
Extracted = cast<Instruction>(
Builder.CreateBitOrPointerCast(Extracted, UI->getType()));
}
// Replace the old instruction.
UI->replaceAllUsesWith(Extracted);
}
if (Instruction *BitcastInst = dyn_cast<Instruction>(Bitcast))
reorder(BitcastInst);
}
eraseInstructions(Chain);
++NumVectorInstructions;
NumScalarsVectorized += Chain.size();
return true;
}
bool Vectorizer::accessIsMisaligned(unsigned SzInBytes, unsigned AddressSpace,
unsigned Alignment) {
bool Fast = false;
bool Allows = TTI.allowsMisalignedMemoryAccesses(SzInBytes * 8, AddressSpace,
Alignment, &Fast);
// TODO: Remove TargetBaseAlign
return !(Allows && Fast) && (Alignment % SzInBytes) != 0 &&
(Alignment % TargetBaseAlign) != 0;
}
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