//===-- AMDGPUPromoteAlloca.cpp - Promote Allocas -------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Eliminates allocas by either converting them into vectors or by migrating
// them to local address space.
//
// Two passes are exposed by this file:
// - "promote-alloca-to-vector", which runs early in the pipeline and only
// promotes to vector. Promotion to vector is almost always profitable
// except when the alloca is too big and the promotion would result in
// very high register pressure.
// - "promote-alloca", which does both promotion to vector and LDS and runs
// much later in the pipeline. This runs after SROA because promoting to
// LDS is of course less profitable than getting rid of the alloca or
// vectorizing it, thus we only want to do it when the only alternative is
// lowering the alloca to stack.
//
// Note that both of them exist for the old and new PMs. The new PM passes are
// declared in AMDGPU.h and the legacy PM ones are declared here.s
//
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "Utils/AMDGPUBaseInfo.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/InstSimplifyFolder.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/IntrinsicsAMDGPU.h"
#include "llvm/IR/IntrinsicsR600.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#define DEBUG_TYPE "amdgpu-promote-alloca"
using namespace llvm;
namespace {
static cl::opt<bool>
DisablePromoteAllocaToVector("disable-promote-alloca-to-vector",
cl::desc("Disable promote alloca to vector"),
cl::init(false));
static cl::opt<bool>
DisablePromoteAllocaToLDS("disable-promote-alloca-to-lds",
cl::desc("Disable promote alloca to LDS"),
cl::init(false));
static cl::opt<unsigned> PromoteAllocaToVectorLimit(
"amdgpu-promote-alloca-to-vector-limit",
cl::desc("Maximum byte size to consider promote alloca to vector"),
cl::init(0));
static cl::opt<unsigned>
LoopUserWeight("promote-alloca-vector-loop-user-weight",
cl::desc("The bonus weight of users of allocas within loop "
"when sorting profitable allocas"),
cl::init(4));
// Shared implementation which can do both promotion to vector and to LDS.
class AMDGPUPromoteAllocaImpl {
private:
const TargetMachine &TM;
LoopInfo &LI;
Module *Mod = nullptr;
const DataLayout *DL = nullptr;
// FIXME: This should be per-kernel.
uint32_t LocalMemLimit = 0;
uint32_t CurrentLocalMemUsage = 0;
unsigned MaxVGPRs;
bool IsAMDGCN = false;
bool IsAMDHSA = false;
std::pair<Value *, Value *> getLocalSizeYZ(IRBuilder<> &Builder);
Value *getWorkitemID(IRBuilder<> &Builder, unsigned N);
/// BaseAlloca is the alloca root the search started from.
/// Val may be that alloca or a recursive user of it.
bool collectUsesWithPtrTypes(Value *BaseAlloca, Value *Val,
std::vector<Value *> &WorkList) const;
/// Val is a derived pointer from Alloca. OpIdx0/OpIdx1 are the operand
/// indices to an instruction with 2 pointer inputs (e.g. select, icmp).
/// Returns true if both operands are derived from the same alloca. Val should
/// be the same value as one of the input operands of UseInst.
bool binaryOpIsDerivedFromSameAlloca(Value *Alloca, Value *Val,
Instruction *UseInst, int OpIdx0,
int OpIdx1) const;
/// Check whether we have enough local memory for promotion.
bool hasSufficientLocalMem(const Function &F);
bool tryPromoteAllocaToVector(AllocaInst &I);
bool tryPromoteAllocaToLDS(AllocaInst &I, bool SufficientLDS);
void sortAllocasToPromote(SmallVectorImpl<AllocaInst *> &Allocas);
public:
AMDGPUPromoteAllocaImpl(TargetMachine &TM, LoopInfo &LI) : TM(TM), LI(LI) {
const Triple &TT = TM.getTargetTriple();
IsAMDGCN = TT.getArch() == Triple::amdgcn;
IsAMDHSA = TT.getOS() == Triple::AMDHSA;
}
bool run(Function &F, bool PromoteToLDS);
};
// FIXME: This can create globals so should be a module pass.
class AMDGPUPromoteAlloca : public FunctionPass {
public:
static char ID;
AMDGPUPromoteAlloca() : FunctionPass(ID) {}
bool runOnFunction(Function &F) override {
if (skipFunction(F))
return false;
if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>())
return AMDGPUPromoteAllocaImpl(
TPC->getTM<TargetMachine>(),
getAnalysis<LoopInfoWrapperPass>().getLoopInfo())
.run(F, /*PromoteToLDS*/ true);
return false;
}
StringRef getPassName() const override { return "AMDGPU Promote Alloca"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<LoopInfoWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
};
class AMDGPUPromoteAllocaToVector : public FunctionPass {
public:
static char ID;
AMDGPUPromoteAllocaToVector() : FunctionPass(ID) {}
bool runOnFunction(Function &F) override {
if (skipFunction(F))
return false;
if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>())
return AMDGPUPromoteAllocaImpl(
TPC->getTM<TargetMachine>(),
getAnalysis<LoopInfoWrapperPass>().getLoopInfo())
.run(F, /*PromoteToLDS*/ false);
return false;
}
StringRef getPassName() const override {
return "AMDGPU Promote Alloca to vector";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<LoopInfoWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
};
unsigned getMaxVGPRs(const TargetMachine &TM, const Function &F) {
if (!TM.getTargetTriple().isAMDGCN())
return 128;
const GCNSubtarget &ST = TM.getSubtarget<GCNSubtarget>(F);
unsigned MaxVGPRs = ST.getMaxNumVGPRs(ST.getWavesPerEU(F).first);
// A non-entry function has only 32 caller preserved registers.
// Do not promote alloca which will force spilling unless we know the function
// will be inlined.
if (!F.hasFnAttribute(Attribute::AlwaysInline) &&
!AMDGPU::isEntryFunctionCC(F.getCallingConv()))
MaxVGPRs = std::min(MaxVGPRs, 32u);
return MaxVGPRs;
}
} // end anonymous namespace
char AMDGPUPromoteAlloca::ID = 0;
char AMDGPUPromoteAllocaToVector::ID = 0;
INITIALIZE_PASS_BEGIN(AMDGPUPromoteAlloca, DEBUG_TYPE,
"AMDGPU promote alloca to vector or LDS", false, false)
// Move LDS uses from functions to kernels before promote alloca for accurate
// estimation of LDS available
INITIALIZE_PASS_DEPENDENCY(AMDGPULowerModuleLDSLegacy)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(AMDGPUPromoteAlloca, DEBUG_TYPE,
"AMDGPU promote alloca to vector or LDS", false, false)
INITIALIZE_PASS_BEGIN(AMDGPUPromoteAllocaToVector, DEBUG_TYPE "-to-vector",
"AMDGPU promote alloca to vector", false, false)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(AMDGPUPromoteAllocaToVector, DEBUG_TYPE "-to-vector",
"AMDGPU promote alloca to vector", false, false)
char &llvm::AMDGPUPromoteAllocaID = AMDGPUPromoteAlloca::ID;
char &llvm::AMDGPUPromoteAllocaToVectorID = AMDGPUPromoteAllocaToVector::ID;
PreservedAnalyses AMDGPUPromoteAllocaPass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &LI = AM.getResult<LoopAnalysis>(F);
bool Changed = AMDGPUPromoteAllocaImpl(TM, LI).run(F, /*PromoteToLDS=*/true);
if (Changed) {
PreservedAnalyses PA;
PA.preserveSet<CFGAnalyses>();
return PA;
}
return PreservedAnalyses::all();
}
PreservedAnalyses
AMDGPUPromoteAllocaToVectorPass::run(Function &F, FunctionAnalysisManager &AM) {
auto &LI = AM.getResult<LoopAnalysis>(F);
bool Changed = AMDGPUPromoteAllocaImpl(TM, LI).run(F, /*PromoteToLDS=*/false);
if (Changed) {
PreservedAnalyses PA;
PA.preserveSet<CFGAnalyses>();
return PA;
}
return PreservedAnalyses::all();
}
FunctionPass *llvm::createAMDGPUPromoteAlloca() {
return new AMDGPUPromoteAlloca();
}
FunctionPass *llvm::createAMDGPUPromoteAllocaToVector() {
return new AMDGPUPromoteAllocaToVector();
}
static void collectAllocaUses(AllocaInst &Alloca,
SmallVectorImpl<Use *> &Uses) {
SmallVector<Instruction *, 4> WorkList({&Alloca});
while (!WorkList.empty()) {
auto *Cur = WorkList.pop_back_val();
for (auto &U : Cur->uses()) {
Uses.push_back(&U);
if (isa<GetElementPtrInst>(U.getUser()))
WorkList.push_back(cast<Instruction>(U.getUser()));
}
}
}
void AMDGPUPromoteAllocaImpl::sortAllocasToPromote(
SmallVectorImpl<AllocaInst *> &Allocas) {
DenseMap<AllocaInst *, unsigned> Scores;
for (auto *Alloca : Allocas) {
LLVM_DEBUG(dbgs() << "Scoring: " << *Alloca << "\n");
unsigned &Score = Scores[Alloca];
// Increment score by one for each user + a bonus for users within loops.
SmallVector<Use *, 8> Uses;
collectAllocaUses(*Alloca, Uses);
for (auto *U : Uses) {
Instruction *Inst = cast<Instruction>(U->getUser());
if (isa<GetElementPtrInst>(Inst))
continue;
unsigned UserScore =
1 + (LoopUserWeight * LI.getLoopDepth(Inst->getParent()));
LLVM_DEBUG(dbgs() << " [+" << UserScore << "]:\t" << *Inst << "\n");
Score += UserScore;
}
LLVM_DEBUG(dbgs() << " => Final Score:" << Score << "\n");
}
stable_sort(Allocas, [&](AllocaInst *A, AllocaInst *B) {
return Scores.at(A) > Scores.at(B);
});
// clang-format off
LLVM_DEBUG(
dbgs() << "Sorted Worklist:\n";
for (auto *A: Allocas)
dbgs() << " " << *A << "\n";
);
// clang-format on
}
bool AMDGPUPromoteAllocaImpl::run(Function &F, bool PromoteToLDS) {
Mod = F.getParent();
DL = &Mod->getDataLayout();
const AMDGPUSubtarget &ST = AMDGPUSubtarget::get(TM, F);
if (!ST.isPromoteAllocaEnabled())
return false;
MaxVGPRs = getMaxVGPRs(TM, F);
bool SufficientLDS = PromoteToLDS ? hasSufficientLocalMem(F) : false;
// Use up to 1/4 of available register budget for vectorization.
// FIXME: Increase the limit for whole function budgets? Perhaps x2?
unsigned VectorizationBudget =
(PromoteAllocaToVectorLimit ? PromoteAllocaToVectorLimit * 8
: (MaxVGPRs * 32)) /
4;
SmallVector<AllocaInst *, 16> Allocas;
for (Instruction &I : F.getEntryBlock()) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
// Array allocations are probably not worth handling, since an allocation
// of the array type is the canonical form.
if (!AI->isStaticAlloca() || AI->isArrayAllocation())
continue;
Allocas.push_back(AI);
}
}
sortAllocasToPromote(Allocas);
bool Changed = false;
for (AllocaInst *AI : Allocas) {
const unsigned AllocaCost = DL->getTypeSizeInBits(AI->getAllocatedType());
// First, check if we have enough budget to vectorize this alloca.
if (AllocaCost <= VectorizationBudget) {
// If we do, attempt vectorization, otherwise, fall through and try
// promoting to LDS instead.
if (tryPromoteAllocaToVector(*AI)) {
Changed = true;
assert((VectorizationBudget - AllocaCost) < VectorizationBudget &&
"Underflow!");
VectorizationBudget -= AllocaCost;
LLVM_DEBUG(dbgs() << " Remaining vectorization budget:"
<< VectorizationBudget << "\n");
continue;
}
} else {
LLVM_DEBUG(dbgs() << "Alloca too big for vectorization (size:"
<< AllocaCost << ", budget:" << VectorizationBudget
<< "): " << *AI << "\n");
}
if (PromoteToLDS && tryPromoteAllocaToLDS(*AI, SufficientLDS))
Changed = true;
}
// NOTE: tryPromoteAllocaToVector removes the alloca, so Allocas contains
// dangling pointers. If we want to reuse it past this point, the loop above
// would need to be updated to remove successfully promoted allocas.
return Changed;
}
struct MemTransferInfo {
ConstantInt *SrcIndex = nullptr;
ConstantInt *DestIndex = nullptr;
};
// Checks if the instruction I is a memset user of the alloca AI that we can
// deal with. Currently, only non-volatile memsets that affect the whole alloca
// are handled.
static bool isSupportedMemset(MemSetInst *I, AllocaInst *AI,
const DataLayout &DL) {
using namespace PatternMatch;
// For now we only care about non-volatile memsets that affect the whole type
// (start at index 0 and fill the whole alloca).
//
// TODO: Now that we moved to PromoteAlloca we could handle any memsets
// (except maybe volatile ones?) - we just need to use shufflevector if it
// only affects a subset of the vector.
const unsigned Size = DL.getTypeStoreSize(AI->getAllocatedType());
return I->getOperand(0) == AI &&
match(I->getOperand(2), m_SpecificInt(Size)) && !I->isVolatile();
}
static Value *
calculateVectorIndex(Value *Ptr,
const std::map<GetElementPtrInst *, Value *> &GEPIdx) {
auto *GEP = dyn_cast<GetElementPtrInst>(Ptr->stripPointerCasts());
if (!GEP)
return ConstantInt::getNullValue(Type::getInt32Ty(Ptr->getContext()));
auto I = GEPIdx.find(GEP);
assert(I != GEPIdx.end() && "Must have entry for GEP!");
return I->second;
}
static Value *GEPToVectorIndex(GetElementPtrInst *GEP, AllocaInst *Alloca,
Type *VecElemTy, const DataLayout &DL) {
// TODO: Extracting a "multiple of X" from a GEP might be a useful generic
// helper.
unsigned BW = DL.getIndexTypeSizeInBits(GEP->getType());
MapVector<Value *, APInt> VarOffsets;
APInt ConstOffset(BW, 0);
if (GEP->getPointerOperand()->stripPointerCasts() != Alloca ||
!GEP->collectOffset(DL, BW, VarOffsets, ConstOffset))
return nullptr;
unsigned VecElemSize = DL.getTypeAllocSize(VecElemTy);
if (VarOffsets.size() > 1)
return nullptr;
if (VarOffsets.size() == 1) {
// Only handle cases where we don't need to insert extra arithmetic
// instructions.
const auto &VarOffset = VarOffsets.front();
if (!ConstOffset.isZero() || VarOffset.second != VecElemSize)
return nullptr;
return VarOffset.first;
}
APInt Quot;
uint64_t Rem;
APInt::udivrem(ConstOffset, VecElemSize, Quot, Rem);
if (Rem != 0)
return nullptr;
return ConstantInt::get(GEP->getContext(), Quot);
}
/// Promotes a single user of the alloca to a vector form.
///
/// \param Inst Instruction to be promoted.
/// \param DL Module Data Layout.
/// \param VectorTy Vectorized Type.
/// \param VecStoreSize Size of \p VectorTy in bytes.
/// \param ElementSize Size of \p VectorTy element type in bytes.
/// \param TransferInfo MemTransferInst info map.
/// \param GEPVectorIdx GEP -> VectorIdx cache.
/// \param CurVal Current value of the vector (e.g. last stored value)
/// \param[out] DeferredLoads \p Inst is added to this vector if it can't
/// be promoted now. This happens when promoting requires \p
/// CurVal, but \p CurVal is nullptr.
/// \return the stored value if \p Inst would have written to the alloca, or
/// nullptr otherwise.
static Value *promoteAllocaUserToVector(
Instruction *Inst, const DataLayout &DL, FixedVectorType *VectorTy,
unsigned VecStoreSize, unsigned ElementSize,
DenseMap<MemTransferInst *, MemTransferInfo> &TransferInfo,
std::map<GetElementPtrInst *, Value *> &GEPVectorIdx, Value *CurVal,
SmallVectorImpl<LoadInst *> &DeferredLoads) {
// Note: we use InstSimplifyFolder because it can leverage the DataLayout
// to do more folding, especially in the case of vector splats.
IRBuilder<InstSimplifyFolder> Builder(Inst->getContext(),
InstSimplifyFolder(DL));
Builder.SetInsertPoint(Inst);
const auto GetOrLoadCurrentVectorValue = [&]() -> Value * {
if (CurVal)
return CurVal;
// If the current value is not known, insert a dummy load and lower it on
// the second pass.
LoadInst *Dummy =
Builder.CreateLoad(VectorTy, PoisonValue::get(Builder.getPtrTy()),
"promotealloca.dummyload");
DeferredLoads.push_back(Dummy);
return Dummy;
};
const auto CreateTempPtrIntCast = [&Builder, DL](Value *Val,
Type *PtrTy) -> Value * {
assert(DL.getTypeStoreSize(Val->getType()) == DL.getTypeStoreSize(PtrTy));
const unsigned Size = DL.getTypeStoreSizeInBits(PtrTy);
if (!PtrTy->isVectorTy())
return Builder.CreateBitOrPointerCast(Val, Builder.getIntNTy(Size));
const unsigned NumPtrElts = cast<FixedVectorType>(PtrTy)->getNumElements();
// If we want to cast to cast, e.g. a <2 x ptr> into a <4 x i32>, we need to
// first cast the ptr vector to <2 x i64>.
assert((Size % NumPtrElts == 0) && "Vector size not divisble");
Type *EltTy = Builder.getIntNTy(Size / NumPtrElts);
return Builder.CreateBitOrPointerCast(
Val, FixedVectorType::get(EltTy, NumPtrElts));
};
Type *VecEltTy = VectorTy->getElementType();
switch (Inst->getOpcode()) {
case Instruction::Load: {
// Loads can only be lowered if the value is known.
if (!CurVal) {
DeferredLoads.push_back(cast<LoadInst>(Inst));
return nullptr;
}
Value *Index = calculateVectorIndex(
cast<LoadInst>(Inst)->getPointerOperand(), GEPVectorIdx);
// We're loading the full vector.
Type *AccessTy = Inst->getType();
TypeSize AccessSize = DL.getTypeStoreSize(AccessTy);
if (Constant *CI = dyn_cast<Constant>(Index)) {
if (CI->isZeroValue() && AccessSize == VecStoreSize) {
if (AccessTy->isPtrOrPtrVectorTy())
CurVal = CreateTempPtrIntCast(CurVal, AccessTy);
else if (CurVal->getType()->isPtrOrPtrVectorTy())
CurVal = CreateTempPtrIntCast(CurVal, CurVal->getType());
Value *NewVal = Builder.CreateBitOrPointerCast(CurVal, AccessTy);
Inst->replaceAllUsesWith(NewVal);
return nullptr;
}
}
// Loading a subvector.
if (isa<FixedVectorType>(AccessTy)) {
assert(AccessSize.isKnownMultipleOf(DL.getTypeStoreSize(VecEltTy)));
const unsigned NumLoadedElts = AccessSize / DL.getTypeStoreSize(VecEltTy);
auto *SubVecTy = FixedVectorType::get(VecEltTy, NumLoadedElts);
assert(DL.getTypeStoreSize(SubVecTy) == DL.getTypeStoreSize(AccessTy));
Value *SubVec = PoisonValue::get(SubVecTy);
for (unsigned K = 0; K < NumLoadedElts; ++K) {
Value *CurIdx =
Builder.CreateAdd(Index, ConstantInt::get(Index->getType(), K));
SubVec = Builder.CreateInsertElement(
SubVec, Builder.CreateExtractElement(CurVal, CurIdx), K);
}
if (AccessTy->isPtrOrPtrVectorTy())
SubVec = CreateTempPtrIntCast(SubVec, AccessTy);
else if (SubVecTy->isPtrOrPtrVectorTy())
SubVec = CreateTempPtrIntCast(SubVec, SubVecTy);
SubVec = Builder.CreateBitOrPointerCast(SubVec, AccessTy);
Inst->replaceAllUsesWith(SubVec);
return nullptr;
}
// We're loading one element.
Value *ExtractElement = Builder.CreateExtractElement(CurVal, Index);
if (AccessTy != VecEltTy)
ExtractElement = Builder.CreateBitOrPointerCast(ExtractElement, AccessTy);
Inst->replaceAllUsesWith(ExtractElement);
return nullptr;
}
case Instruction::Store: {
// For stores, it's a bit trickier and it depends on whether we're storing
// the full vector or not. If we're storing the full vector, we don't need
// to know the current value. If this is a store of a single element, we
// need to know the value.
StoreInst *SI = cast<StoreInst>(Inst);
Value *Index = calculateVectorIndex(SI->getPointerOperand(), GEPVectorIdx);
Value *Val = SI->getValueOperand();
// We're storing the full vector, we can handle this without knowing CurVal.
Type *AccessTy = Val->getType();
TypeSize AccessSize = DL.getTypeStoreSize(AccessTy);
if (Constant *CI = dyn_cast<Constant>(Index)) {
if (CI->isZeroValue() && AccessSize == VecStoreSize) {
if (AccessTy->isPtrOrPtrVectorTy())
Val = CreateTempPtrIntCast(Val, AccessTy);
else if (VectorTy->isPtrOrPtrVectorTy())
Val = CreateTempPtrIntCast(Val, VectorTy);
return Builder.CreateBitOrPointerCast(Val, VectorTy);
}
}
// Storing a subvector.
if (isa<FixedVectorType>(AccessTy)) {
assert(AccessSize.isKnownMultipleOf(DL.getTypeStoreSize(VecEltTy)));
const unsigned NumWrittenElts =
AccessSize / DL.getTypeStoreSize(VecEltTy);
const unsigned NumVecElts = VectorTy->getNumElements();
auto *SubVecTy = FixedVectorType::get(VecEltTy, NumWrittenElts);
assert(DL.getTypeStoreSize(SubVecTy) == DL.getTypeStoreSize(AccessTy));
if (SubVecTy->isPtrOrPtrVectorTy())
Val = CreateTempPtrIntCast(Val, SubVecTy);
else if (AccessTy->isPtrOrPtrVectorTy())
Val = CreateTempPtrIntCast(Val, AccessTy);
Val = Builder.CreateBitOrPointerCast(Val, SubVecTy);
Value *CurVec = GetOrLoadCurrentVectorValue();
for (unsigned K = 0, NumElts = std::min(NumWrittenElts, NumVecElts);
K < NumElts; ++K) {
Value *CurIdx =
Builder.CreateAdd(Index, ConstantInt::get(Index->getType(), K));
CurVec = Builder.CreateInsertElement(
CurVec, Builder.CreateExtractElement(Val, K), CurIdx);
}
return CurVec;
}
if (Val->getType() != VecEltTy)
Val = Builder.CreateBitOrPointerCast(Val, VecEltTy);
return Builder.CreateInsertElement(GetOrLoadCurrentVectorValue(), Val,
Index);
}
case Instruction::Call: {
if (auto *MTI = dyn_cast<MemTransferInst>(Inst)) {
// For memcpy, we need to know curval.
ConstantInt *Length = cast<ConstantInt>(MTI->getLength());
unsigned NumCopied = Length->getZExtValue() / ElementSize;
MemTransferInfo *TI = &TransferInfo[MTI];
unsigned SrcBegin = TI->SrcIndex->getZExtValue();
unsigned DestBegin = TI->DestIndex->getZExtValue();
SmallVector<int> Mask;
for (unsigned Idx = 0; Idx < VectorTy->getNumElements(); ++Idx) {
if (Idx >= DestBegin && Idx < DestBegin + NumCopied) {
Mask.push_back(SrcBegin++);
} else {
Mask.push_back(Idx);
}
}
return Builder.CreateShuffleVector(GetOrLoadCurrentVectorValue(), Mask);
}
if (auto *MSI = dyn_cast<MemSetInst>(Inst)) {
// For memset, we don't need to know the previous value because we
// currently only allow memsets that cover the whole alloca.
Value *Elt = MSI->getOperand(1);
const unsigned BytesPerElt = DL.getTypeStoreSize(VecEltTy);
if (BytesPerElt > 1) {
Value *EltBytes = Builder.CreateVectorSplat(BytesPerElt, Elt);
// If the element type of the vector is a pointer, we need to first cast
// to an integer, then use a PtrCast.
if (VecEltTy->isPointerTy()) {
Type *PtrInt = Builder.getIntNTy(BytesPerElt * 8);
Elt = Builder.CreateBitCast(EltBytes, PtrInt);
Elt = Builder.CreateIntToPtr(Elt, VecEltTy);
} else
Elt = Builder.CreateBitCast(EltBytes, VecEltTy);
}
return Builder.CreateVectorSplat(VectorTy->getElementCount(), Elt);
}
if (auto *Intr = dyn_cast<IntrinsicInst>(Inst)) {
if (Intr->getIntrinsicID() == Intrinsic::objectsize) {
Intr->replaceAllUsesWith(
Builder.getIntN(Intr->getType()->getIntegerBitWidth(),
DL.getTypeAllocSize(VectorTy)));
return nullptr;
}
}
llvm_unreachable("Unsupported call when promoting alloca to vector");
}
default:
llvm_unreachable("Inconsistency in instructions promotable to vector");
}
llvm_unreachable("Did not return after promoting instruction!");
}
static bool isSupportedAccessType(FixedVectorType *VecTy, Type *AccessTy,
const DataLayout &DL) {
// Access as a vector type can work if the size of the access vector is a
// multiple of the size of the alloca's vector element type.
//
// Examples:
// - VecTy = <8 x float>, AccessTy = <4 x float> -> OK
// - VecTy = <4 x double>, AccessTy = <2 x float> -> OK
// - VecTy = <4 x double>, AccessTy = <3 x float> -> NOT OK
// - 3*32 is not a multiple of 64
//
// We could handle more complicated cases, but it'd make things a lot more
// complicated.
if (isa<FixedVectorType>(AccessTy)) {
TypeSize AccTS = DL.getTypeStoreSize(AccessTy);
TypeSize VecTS = DL.getTypeStoreSize(VecTy->getElementType());
return AccTS.isKnownMultipleOf(VecTS);
}
return CastInst::isBitOrNoopPointerCastable(VecTy->getElementType(), AccessTy,
DL);
}
/// Iterates over an instruction worklist that may contain multiple instructions
/// from the same basic block, but in a different order.
template <typename InstContainer>
static void forEachWorkListItem(const InstContainer &WorkList,
std::function<void(Instruction *)> Fn) {
// Bucket up uses of the alloca by the block they occur in.
// This is important because we have to handle multiple defs/uses in a block
// ourselves: SSAUpdater is purely for cross-block references.
DenseMap<BasicBlock *, SmallDenseSet<Instruction *>> UsesByBlock;
for (Instruction *User : WorkList)
UsesByBlock[User->getParent()].insert(User);
for (Instruction *User : WorkList) {
BasicBlock *BB = User->getParent();
auto &BlockUses = UsesByBlock[BB];
// Already processed, skip.
if (BlockUses.empty())
continue;
// Only user in the block, directly process it.
if (BlockUses.size() == 1) {
Fn(User);
continue;
}
// Multiple users in the block, do a linear scan to see users in order.
for (Instruction &Inst : *BB) {
if (!BlockUses.contains(&Inst))
continue;
Fn(&Inst);
}
// Clear the block so we know it's been processed.
BlockUses.clear();
}
}
// FIXME: Should try to pick the most likely to be profitable allocas first.
bool AMDGPUPromoteAllocaImpl::tryPromoteAllocaToVector(AllocaInst &Alloca) {
LLVM_DEBUG(dbgs() << "Trying to promote to vector: " << Alloca << '\n');
if (DisablePromoteAllocaToVector) {
LLVM_DEBUG(dbgs() << " Promote alloca to vector is disabled\n");
return false;
}
Type *AllocaTy = Alloca.getAllocatedType();
auto *VectorTy = dyn_cast<FixedVectorType>(AllocaTy);
if (auto *ArrayTy = dyn_cast<ArrayType>(AllocaTy)) {
if (VectorType::isValidElementType(ArrayTy->getElementType()) &&
ArrayTy->getNumElements() > 0)
VectorTy = FixedVectorType::get(ArrayTy->getElementType(),
ArrayTy->getNumElements());
}
// FIXME: There is no reason why we can't support larger arrays, we
// are just being conservative for now.
// FIXME: We also reject alloca's of the form [ 2 x [ 2 x i32 ]] or
// equivalent. Potentially these could also be promoted but we don't currently
// handle this case
if (!VectorTy) {
LLVM_DEBUG(dbgs() << " Cannot convert type to vector\n");
return false;
}
if (VectorTy->getNumElements() > 16 || VectorTy->getNumElements() < 2) {
LLVM_DEBUG(dbgs() << " " << *VectorTy
<< " has an unsupported number of elements\n");
return false;
}
std::map<GetElementPtrInst *, Value *> GEPVectorIdx;
SmallVector<Instruction *> WorkList;
SmallVector<Instruction *> UsersToRemove;
SmallVector<Instruction *> DeferredInsts;
DenseMap<MemTransferInst *, MemTransferInfo> TransferInfo;
const auto RejectUser = [&](Instruction *Inst, Twine Msg) {
LLVM_DEBUG(dbgs() << " Cannot promote alloca to vector: " << Msg << "\n"
<< " " << *Inst << "\n");
return false;
};
SmallVector<Use *, 8> Uses;
collectAllocaUses(Alloca, Uses);
LLVM_DEBUG(dbgs() << " Attempting promotion to: " << *VectorTy << "\n");
Type *VecEltTy = VectorTy->getElementType();
unsigned ElementSize = DL->getTypeSizeInBits(VecEltTy) / 8;
for (auto *U : Uses) {
Instruction *Inst = cast<Instruction>(U->getUser());
if (Value *Ptr = getLoadStorePointerOperand(Inst)) {
// This is a store of the pointer, not to the pointer.
if (isa<StoreInst>(Inst) &&
U->getOperandNo() != StoreInst::getPointerOperandIndex())
return RejectUser(Inst, "pointer is being stored");
Type *AccessTy = getLoadStoreType(Inst);
if (AccessTy->isAggregateType())
return RejectUser(Inst, "unsupported load/store as aggregate");
assert(!AccessTy->isAggregateType() || AccessTy->isArrayTy());
// Check that this is a simple access of a vector element.
bool IsSimple = isa<LoadInst>(Inst) ? cast<LoadInst>(Inst)->isSimple()
: cast<StoreInst>(Inst)->isSimple();
if (!IsSimple)
return RejectUser(Inst, "not a simple load or store");
Ptr = Ptr->stripPointerCasts();
// Alloca already accessed as vector.
if (Ptr == &Alloca && DL->getTypeStoreSize(Alloca.getAllocatedType()) ==
DL->getTypeStoreSize(AccessTy)) {
WorkList.push_back(Inst);
continue;
}
if (!isSupportedAccessType(VectorTy, AccessTy, *DL))
return RejectUser(Inst, "not a supported access type");
WorkList.push_back(Inst);
continue;
}
if (auto *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
// If we can't compute a vector index from this GEP, then we can't
// promote this alloca to vector.
Value *Index = GEPToVectorIndex(GEP, &Alloca, VecEltTy, *DL);
if (!Index)
return RejectUser(Inst, "cannot compute vector index for GEP");
GEPVectorIdx[GEP] = Index;
UsersToRemove.push_back(Inst);
continue;
}
if (MemSetInst *MSI = dyn_cast<MemSetInst>(Inst);
MSI && isSupportedMemset(MSI, &Alloca, *DL)) {
WorkList.push_back(Inst);
continue;
}
if (MemTransferInst *TransferInst = dyn_cast<MemTransferInst>(Inst)) {
if (TransferInst->isVolatile())
return RejectUser(Inst, "mem transfer inst is volatile");
ConstantInt *Len = dyn_cast<ConstantInt>(TransferInst->getLength());
if (!Len || (Len->getZExtValue() % ElementSize))
return RejectUser(Inst, "mem transfer inst length is non-constant or "
"not a multiple of the vector element size");
if (!TransferInfo.count(TransferInst)) {
DeferredInsts.push_back(Inst);
WorkList.push_back(Inst);
TransferInfo[TransferInst] = MemTransferInfo();
}
auto getPointerIndexOfAlloca = [&](Value *Ptr) -> ConstantInt * {
GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr);
if (Ptr != &Alloca && !GEPVectorIdx.count(GEP))
return nullptr;
return dyn_cast<ConstantInt>(calculateVectorIndex(Ptr, GEPVectorIdx));
};
unsigned OpNum = U->getOperandNo();
MemTransferInfo *TI = &TransferInfo[TransferInst];
if (OpNum == 0) {
Value *Dest = TransferInst->getDest();
ConstantInt *Index = getPointerIndexOfAlloca(Dest);
if (!Index)
return RejectUser(Inst, "could not calculate constant dest index");
TI->DestIndex = Index;
} else {
assert(OpNum == 1);
Value *Src = TransferInst->getSource();
ConstantInt *Index = getPointerIndexOfAlloca(Src);
if (!Index)
return RejectUser(Inst, "could not calculate constant src index");
TI->SrcIndex = Index;
}
continue;
}
if (auto *Intr = dyn_cast<IntrinsicInst>(Inst)) {
if (Intr->getIntrinsicID() == Intrinsic::objectsize) {
WorkList.push_back(Inst);
continue;
}
}
// Ignore assume-like intrinsics and comparisons used in assumes.
if (isAssumeLikeIntrinsic(Inst)) {
if (!Inst->use_empty())
return RejectUser(Inst, "assume-like intrinsic cannot have any users");
UsersToRemove.push_back(Inst);
continue;
}
if (isa<ICmpInst>(Inst) && all_of(Inst->users(), [](User *U) {
return isAssumeLikeIntrinsic(cast<Instruction>(U));
})) {
UsersToRemove.push_back(Inst);
continue;
}
return RejectUser(Inst, "unhandled alloca user");
}
while (!DeferredInsts.empty()) {
Instruction *Inst = DeferredInsts.pop_back_val();
MemTransferInst *TransferInst = cast<MemTransferInst>(Inst);
// TODO: Support the case if the pointers are from different alloca or
// from different address spaces.
MemTransferInfo &Info = TransferInfo[TransferInst];
if (!Info.SrcIndex || !Info.DestIndex)
return RejectUser(
Inst, "mem transfer inst is missing constant src and/or dst index");
}
LLVM_DEBUG(dbgs() << " Converting alloca to vector " << *AllocaTy << " -> "
<< *VectorTy << '\n');
const unsigned VecStoreSize = DL->getTypeStoreSize(VectorTy);
// Alloca is uninitialized memory. Imitate that by making the first value
// undef.
SSAUpdater Updater;
Updater.Initialize(VectorTy, "promotealloca");
Updater.AddAvailableValue(Alloca.getParent(), UndefValue::get(VectorTy));
// First handle the initial worklist.
SmallVector<LoadInst *, 4> DeferredLoads;
forEachWorkListItem(WorkList, [&](Instruction *I) {
BasicBlock *BB = I->getParent();
// On the first pass, we only take values that are trivially known, i.e.
// where AddAvailableValue was already called in this block.
Value *Result = promoteAllocaUserToVector(
I, *DL, VectorTy, VecStoreSize, ElementSize, TransferInfo, GEPVectorIdx,
Updater.FindValueForBlock(BB), DeferredLoads);
if (Result)
Updater.AddAvailableValue(BB, Result);
});
// Then handle deferred loads.
forEachWorkListItem(DeferredLoads, [&](Instruction *I) {
SmallVector<LoadInst *, 0> NewDLs;
BasicBlock *BB = I->getParent();
// On the second pass, we use GetValueInMiddleOfBlock to guarantee we always
// get a value, inserting PHIs as needed.
Value *Result = promoteAllocaUserToVector(
I, *DL, VectorTy, VecStoreSize, ElementSize, TransferInfo, GEPVectorIdx,
Updater.GetValueInMiddleOfBlock(I->getParent()), NewDLs);
if (Result)
Updater.AddAvailableValue(BB, Result);
assert(NewDLs.empty() && "No more deferred loads should be queued!");
});
// Delete all instructions. On the first pass, new dummy loads may have been
// added so we need to collect them too.
DenseSet<Instruction *> InstsToDelete(WorkList.begin(), WorkList.end());
InstsToDelete.insert(DeferredLoads.begin(), DeferredLoads.end());
for (Instruction *I : InstsToDelete) {
assert(I->use_empty());
I->eraseFromParent();
}
// Delete all the users that are known to be removeable.
for (Instruction *I : reverse(UsersToRemove)) {
I->dropDroppableUses();
assert(I->use_empty());
I->eraseFromParent();
}
// Alloca should now be dead too.
assert(Alloca.use_empty());
Alloca.eraseFromParent();
return true;
}
std::pair<Value *, Value *>
AMDGPUPromoteAllocaImpl::getLocalSizeYZ(IRBuilder<> &Builder) {
Function &F = *Builder.GetInsertBlock()->getParent();
const AMDGPUSubtarget &ST = AMDGPUSubtarget::get(TM, F);
if (!IsAMDHSA) {
Function *LocalSizeYFn =
Intrinsic::getDeclaration(Mod, Intrinsic::r600_read_local_size_y);
Function *LocalSizeZFn =
Intrinsic::getDeclaration(Mod, Intrinsic::r600_read_local_size_z);
CallInst *LocalSizeY = Builder.CreateCall(LocalSizeYFn, {});
CallInst *LocalSizeZ = Builder.CreateCall(LocalSizeZFn, {});
ST.makeLIDRangeMetadata(LocalSizeY);
ST.makeLIDRangeMetadata(LocalSizeZ);
return std::pair(LocalSizeY, LocalSizeZ);
}
// We must read the size out of the dispatch pointer.
assert(IsAMDGCN);
// We are indexing into this struct, and want to extract the workgroup_size_*
// fields.
//
// typedef struct hsa_kernel_dispatch_packet_s {
// uint16_t header;
// uint16_t setup;
// uint16_t workgroup_size_x ;
// uint16_t workgroup_size_y;
// uint16_t workgroup_size_z;
// uint16_t reserved0;
// uint32_t grid_size_x ;
// uint32_t grid_size_y ;
// uint32_t grid_size_z;
//
// uint32_t private_segment_size;
// uint32_t group_segment_size;
// uint64_t kernel_object;
//
// #ifdef HSA_LARGE_MODEL
// void *kernarg_address;
// #elif defined HSA_LITTLE_ENDIAN
// void *kernarg_address;
// uint32_t reserved1;
// #else
// uint32_t reserved1;
// void *kernarg_address;
// #endif
// uint64_t reserved2;
// hsa_signal_t completion_signal; // uint64_t wrapper
// } hsa_kernel_dispatch_packet_t
//
Function *DispatchPtrFn =
Intrinsic::getDeclaration(Mod, Intrinsic::amdgcn_dispatch_ptr);
CallInst *DispatchPtr = Builder.CreateCall(DispatchPtrFn, {});
DispatchPtr->addRetAttr(Attribute::NoAlias);
DispatchPtr->addRetAttr(Attribute::NonNull);
F.removeFnAttr("amdgpu-no-dispatch-ptr");
// Size of the dispatch packet struct.
DispatchPtr->addDereferenceableRetAttr(64);
Type *I32Ty = Type::getInt32Ty(Mod->getContext());
Value *CastDispatchPtr = Builder.CreateBitCast(
DispatchPtr, PointerType::get(I32Ty, AMDGPUAS::CONSTANT_ADDRESS));
// We could do a single 64-bit load here, but it's likely that the basic
// 32-bit and extract sequence is already present, and it is probably easier
// to CSE this. The loads should be mergeable later anyway.
Value *GEPXY = Builder.CreateConstInBoundsGEP1_64(I32Ty, CastDispatchPtr, 1);
LoadInst *LoadXY = Builder.CreateAlignedLoad(I32Ty, GEPXY, Align(4));
Value *GEPZU = Builder.CreateConstInBoundsGEP1_64(I32Ty, CastDispatchPtr, 2);
LoadInst *LoadZU = Builder.CreateAlignedLoad(I32Ty, GEPZU, Align(4));
MDNode *MD = MDNode::get(Mod->getContext(), std::nullopt);
LoadXY->setMetadata(LLVMContext::MD_invariant_load, MD);
LoadZU->setMetadata(LLVMContext::MD_invariant_load, MD);
ST.makeLIDRangeMetadata(LoadZU);
// Extract y component. Upper half of LoadZU should be zero already.
Value *Y = Builder.CreateLShr(LoadXY, 16);
return std::pair(Y, LoadZU);
}
Value *AMDGPUPromoteAllocaImpl::getWorkitemID(IRBuilder<> &Builder,
unsigned N) {
Function *F = Builder.GetInsertBlock()->getParent();
const AMDGPUSubtarget &ST = AMDGPUSubtarget::get(TM, *F);
Intrinsic::ID IntrID = Intrinsic::not_intrinsic;
StringRef AttrName;
switch (N) {
case 0:
IntrID = IsAMDGCN ? (Intrinsic::ID)Intrinsic::amdgcn_workitem_id_x
: (Intrinsic::ID)Intrinsic::r600_read_tidig_x;
AttrName = "amdgpu-no-workitem-id-x";
break;
case 1:
IntrID = IsAMDGCN ? (Intrinsic::ID)Intrinsic::amdgcn_workitem_id_y
: (Intrinsic::ID)Intrinsic::r600_read_tidig_y;
AttrName = "amdgpu-no-workitem-id-y";
break;
case 2:
IntrID = IsAMDGCN ? (Intrinsic::ID)Intrinsic::amdgcn_workitem_id_z
: (Intrinsic::ID)Intrinsic::r600_read_tidig_z;
AttrName = "amdgpu-no-workitem-id-z";
break;
default:
llvm_unreachable("invalid dimension");
}
Function *WorkitemIdFn = Intrinsic::getDeclaration(Mod, IntrID);
CallInst *CI = Builder.CreateCall(WorkitemIdFn);
ST.makeLIDRangeMetadata(CI);
F->removeFnAttr(AttrName);
return CI;
}
static bool isCallPromotable(CallInst *CI) {
IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
if (!II)
return false;
switch (II->getIntrinsicID()) {
case Intrinsic::memcpy:
case Intrinsic::memmove:
case Intrinsic::memset:
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
case Intrinsic::invariant_start:
case Intrinsic::invariant_end:
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
case Intrinsic::objectsize:
return true;
default:
return false;
}
}
bool AMDGPUPromoteAllocaImpl::binaryOpIsDerivedFromSameAlloca(
Value *BaseAlloca, Value *Val, Instruction *Inst, int OpIdx0,
int OpIdx1) const {
// Figure out which operand is the one we might not be promoting.
Value *OtherOp = Inst->getOperand(OpIdx0);
if (Val == OtherOp)
OtherOp = Inst->getOperand(OpIdx1);
if (isa<ConstantPointerNull>(OtherOp))
return true;
Value *OtherObj = getUnderlyingObject(OtherOp);
if (!isa<AllocaInst>(OtherObj))
return false;
// TODO: We should be able to replace undefs with the right pointer type.
// TODO: If we know the other base object is another promotable
// alloca, not necessarily this alloca, we can do this. The
// important part is both must have the same address space at
// the end.
if (OtherObj != BaseAlloca) {
LLVM_DEBUG(
dbgs() << "Found a binary instruction with another alloca object\n");
return false;
}
return true;
}
bool AMDGPUPromoteAllocaImpl::collectUsesWithPtrTypes(
Value *BaseAlloca, Value *Val, std::vector<Value *> &WorkList) const {
for (User *User : Val->users()) {
if (is_contained(WorkList, User))
continue;
if (CallInst *CI = dyn_cast<CallInst>(User)) {
if (!isCallPromotable(CI))
return false;
WorkList.push_back(User);
continue;
}
Instruction *UseInst = cast<Instruction>(User);
if (UseInst->getOpcode() == Instruction::PtrToInt)
return false;
if (LoadInst *LI = dyn_cast<LoadInst>(UseInst)) {
if (LI->isVolatile())
return false;
continue;
}
if (StoreInst *SI = dyn_cast<StoreInst>(UseInst)) {
if (SI->isVolatile())
return false;
// Reject if the stored value is not the pointer operand.
if (SI->getPointerOperand() != Val)
return false;
} else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(UseInst)) {
if (RMW->isVolatile())
return false;
} else if (AtomicCmpXchgInst *CAS = dyn_cast<AtomicCmpXchgInst>(UseInst)) {
if (CAS->isVolatile())
return false;
}
// Only promote a select if we know that the other select operand
// is from another pointer that will also be promoted.
if (ICmpInst *ICmp = dyn_cast<ICmpInst>(UseInst)) {
if (!binaryOpIsDerivedFromSameAlloca(BaseAlloca, Val, ICmp, 0, 1))
return false;
// May need to rewrite constant operands.
WorkList.push_back(ICmp);
}
if (UseInst->getOpcode() == Instruction::AddrSpaceCast) {
// Give up if the pointer may be captured.
if (PointerMayBeCaptured(UseInst, true, true))
return false;
// Don't collect the users of this.
WorkList.push_back(User);
continue;
}
// Do not promote vector/aggregate type instructions. It is hard to track
// their users.
if (isa<InsertValueInst>(User) || isa<InsertElementInst>(User))
return false;
if (!User->getType()->isPointerTy())
continue;
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UseInst)) {
// Be conservative if an address could be computed outside the bounds of
// the alloca.
if (!GEP->isInBounds())
return false;
}
// Only promote a select if we know that the other select operand is from
// another pointer that will also be promoted.
if (SelectInst *SI = dyn_cast<SelectInst>(UseInst)) {
if (!binaryOpIsDerivedFromSameAlloca(BaseAlloca, Val, SI, 1, 2))
return false;
}
// Repeat for phis.
if (PHINode *Phi = dyn_cast<PHINode>(UseInst)) {
// TODO: Handle more complex cases. We should be able to replace loops
// over arrays.
switch (Phi->getNumIncomingValues()) {
case 1:
break;
case 2:
if (!binaryOpIsDerivedFromSameAlloca(BaseAlloca, Val, Phi, 0, 1))
return false;
break;
default:
return false;
}
}
WorkList.push_back(User);
if (!collectUsesWithPtrTypes(BaseAlloca, User, WorkList))
return false;
}
return true;
}
bool AMDGPUPromoteAllocaImpl::hasSufficientLocalMem(const Function &F) {
FunctionType *FTy = F.getFunctionType();
const AMDGPUSubtarget &ST = AMDGPUSubtarget::get(TM, F);
// If the function has any arguments in the local address space, then it's
// possible these arguments require the entire local memory space, so
// we cannot use local memory in the pass.
for (Type *ParamTy : FTy->params()) {
PointerType *PtrTy = dyn_cast<PointerType>(ParamTy);
if (PtrTy && PtrTy->getAddressSpace() == AMDGPUAS::LOCAL_ADDRESS) {
LocalMemLimit = 0;
LLVM_DEBUG(dbgs() << "Function has local memory argument. Promoting to "
"local memory disabled.\n");
return false;
}
}
LocalMemLimit = ST.getAddressableLocalMemorySize();
if (LocalMemLimit == 0)
return false;
SmallVector<const Constant *, 16> Stack;
SmallPtrSet<const Constant *, 8> VisitedConstants;
SmallPtrSet<const GlobalVariable *, 8> UsedLDS;
auto visitUsers = [&](const GlobalVariable *GV, const Constant *Val) -> bool {
for (const User *U : Val->users()) {
if (const Instruction *Use = dyn_cast<Instruction>(U)) {
if (Use->getParent()->getParent() == &F)
return true;
} else {
const Constant *C = cast<Constant>(U);
if (VisitedConstants.insert(C).second)
Stack.push_back(C);
}
}
return false;
};
for (GlobalVariable &GV : Mod->globals()) {
if (GV.getAddressSpace() != AMDGPUAS::LOCAL_ADDRESS)
continue;
if (visitUsers(&GV, &GV)) {
UsedLDS.insert(&GV);
Stack.clear();
continue;
}
// For any ConstantExpr uses, we need to recursively search the users until
// we see a function.
while (!Stack.empty()) {
const Constant *C = Stack.pop_back_val();
if (visitUsers(&GV, C)) {
UsedLDS.insert(&GV);
Stack.clear();
break;
}
}
}
const DataLayout &DL = Mod->getDataLayout();
SmallVector<std::pair<uint64_t, Align>, 16> AllocatedSizes;
AllocatedSizes.reserve(UsedLDS.size());
for (const GlobalVariable *GV : UsedLDS) {
Align Alignment =
DL.getValueOrABITypeAlignment(GV->getAlign(), GV->getValueType());
uint64_t AllocSize = DL.getTypeAllocSize(GV->getValueType());
// HIP uses an extern unsized array in local address space for dynamically
// allocated shared memory. In that case, we have to disable the promotion.
if (GV->hasExternalLinkage() && AllocSize == 0) {
LocalMemLimit = 0;
LLVM_DEBUG(dbgs() << "Function has a reference to externally allocated "
"local memory. Promoting to local memory "
"disabled.\n");
return false;
}
AllocatedSizes.emplace_back(AllocSize, Alignment);
}
// Sort to try to estimate the worst case alignment padding
//
// FIXME: We should really do something to fix the addresses to a more optimal
// value instead
llvm::sort(AllocatedSizes, llvm::less_second());
// Check how much local memory is being used by global objects
CurrentLocalMemUsage = 0;
// FIXME: Try to account for padding here. The real padding and address is
// currently determined from the inverse order of uses in the function when
// legalizing, which could also potentially change. We try to estimate the
// worst case here, but we probably should fix the addresses earlier.
for (auto Alloc : AllocatedSizes) {
CurrentLocalMemUsage = alignTo(CurrentLocalMemUsage, Alloc.second);
CurrentLocalMemUsage += Alloc.first;
}
unsigned MaxOccupancy =
ST.getOccupancyWithLocalMemSize(CurrentLocalMemUsage, F);
// Restrict local memory usage so that we don't drastically reduce occupancy,
// unless it is already significantly reduced.
// TODO: Have some sort of hint or other heuristics to guess occupancy based
// on other factors..
unsigned OccupancyHint = ST.getWavesPerEU(F).second;
if (OccupancyHint == 0)
OccupancyHint = 7;
// Clamp to max value.
OccupancyHint = std::min(OccupancyHint, ST.getMaxWavesPerEU());
// Check the hint but ignore it if it's obviously wrong from the existing LDS
// usage.
MaxOccupancy = std::min(OccupancyHint, MaxOccupancy);
// Round up to the next tier of usage.
unsigned MaxSizeWithWaveCount =
ST.getMaxLocalMemSizeWithWaveCount(MaxOccupancy, F);
// Program is possibly broken by using more local mem than available.
if (CurrentLocalMemUsage > MaxSizeWithWaveCount)
return false;
LocalMemLimit = MaxSizeWithWaveCount;
LLVM_DEBUG(dbgs() << F.getName() << " uses " << CurrentLocalMemUsage
<< " bytes of LDS\n"
<< " Rounding size to " << MaxSizeWithWaveCount
<< " with a maximum occupancy of " << MaxOccupancy << '\n'
<< " and " << (LocalMemLimit - CurrentLocalMemUsage)
<< " available for promotion\n");
return true;
}
// FIXME: Should try to pick the most likely to be profitable allocas first.
bool AMDGPUPromoteAllocaImpl::tryPromoteAllocaToLDS(AllocaInst &I,
bool SufficientLDS) {
LLVM_DEBUG(dbgs() << "Trying to promote to LDS: " << I << '\n');
if (DisablePromoteAllocaToLDS) {
LLVM_DEBUG(dbgs() << " Promote alloca to LDS is disabled\n");
return false;
}
const DataLayout &DL = Mod->getDataLayout();
IRBuilder<> Builder(&I);
const Function &ContainingFunction = *I.getParent()->getParent();
CallingConv::ID CC = ContainingFunction.getCallingConv();
// Don't promote the alloca to LDS for shader calling conventions as the work
// item ID intrinsics are not supported for these calling conventions.
// Furthermore not all LDS is available for some of the stages.
switch (CC) {
case CallingConv::AMDGPU_KERNEL:
case CallingConv::SPIR_KERNEL:
break;
default:
LLVM_DEBUG(
dbgs()
<< " promote alloca to LDS not supported with calling convention.\n");
return false;
}
// Not likely to have sufficient local memory for promotion.
if (!SufficientLDS)
return false;
const AMDGPUSubtarget &ST = AMDGPUSubtarget::get(TM, ContainingFunction);
unsigned WorkGroupSize = ST.getFlatWorkGroupSizes(ContainingFunction).second;
Align Alignment =
DL.getValueOrABITypeAlignment(I.getAlign(), I.getAllocatedType());
// FIXME: This computed padding is likely wrong since it depends on inverse
// usage order.
//
// FIXME: It is also possible that if we're allowed to use all of the memory
// could end up using more than the maximum due to alignment padding.
uint32_t NewSize = alignTo(CurrentLocalMemUsage, Alignment);
uint32_t AllocSize =
WorkGroupSize * DL.getTypeAllocSize(I.getAllocatedType());
NewSize += AllocSize;
if (NewSize > LocalMemLimit) {
LLVM_DEBUG(dbgs() << " " << AllocSize
<< " bytes of local memory not available to promote\n");
return false;
}
CurrentLocalMemUsage = NewSize;
std::vector<Value *> WorkList;
if (!collectUsesWithPtrTypes(&I, &I, WorkList)) {
LLVM_DEBUG(dbgs() << " Do not know how to convert all uses\n");
return false;
}
LLVM_DEBUG(dbgs() << "Promoting alloca to local memory\n");
Function *F = I.getParent()->getParent();
Type *GVTy = ArrayType::get(I.getAllocatedType(), WorkGroupSize);
GlobalVariable *GV = new GlobalVariable(
*Mod, GVTy, false, GlobalValue::InternalLinkage, PoisonValue::get(GVTy),
Twine(F->getName()) + Twine('.') + I.getName(), nullptr,
GlobalVariable::NotThreadLocal, AMDGPUAS::LOCAL_ADDRESS);
GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
GV->setAlignment(I.getAlign());
Value *TCntY, *TCntZ;
std::tie(TCntY, TCntZ) = getLocalSizeYZ(Builder);
Value *TIdX = getWorkitemID(Builder, 0);
Value *TIdY = getWorkitemID(Builder, 1);
Value *TIdZ = getWorkitemID(Builder, 2);
Value *Tmp0 = Builder.CreateMul(TCntY, TCntZ, "", true, true);
Tmp0 = Builder.CreateMul(Tmp0, TIdX);
Value *Tmp1 = Builder.CreateMul(TIdY, TCntZ, "", true, true);
Value *TID = Builder.CreateAdd(Tmp0, Tmp1);
TID = Builder.CreateAdd(TID, TIdZ);
LLVMContext &Context = Mod->getContext();
Value *Indices[] = {Constant::getNullValue(Type::getInt32Ty(Context)), TID};
Value *Offset = Builder.CreateInBoundsGEP(GVTy, GV, Indices);
I.mutateType(Offset->getType());
I.replaceAllUsesWith(Offset);
I.eraseFromParent();
SmallVector<IntrinsicInst *> DeferredIntrs;
for (Value *V : WorkList) {
CallInst *Call = dyn_cast<CallInst>(V);
if (!Call) {
if (ICmpInst *CI = dyn_cast<ICmpInst>(V)) {
PointerType *NewTy = PointerType::get(Context, AMDGPUAS::LOCAL_ADDRESS);
if (isa<ConstantPointerNull>(CI->getOperand(0)))
CI->setOperand(0, ConstantPointerNull::get(NewTy));
if (isa<ConstantPointerNull>(CI->getOperand(1)))
CI->setOperand(1, ConstantPointerNull::get(NewTy));
continue;
}
// The operand's value should be corrected on its own and we don't want to
// touch the users.
if (isa<AddrSpaceCastInst>(V))
continue;
PointerType *NewTy = PointerType::get(Context, AMDGPUAS::LOCAL_ADDRESS);
// FIXME: It doesn't really make sense to try to do this for all
// instructions.
V->mutateType(NewTy);
// Adjust the types of any constant operands.
if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
if (isa<ConstantPointerNull>(SI->getOperand(1)))
SI->setOperand(1, ConstantPointerNull::get(NewTy));
if (isa<ConstantPointerNull>(SI->getOperand(2)))
SI->setOperand(2, ConstantPointerNull::get(NewTy));
} else if (PHINode *Phi = dyn_cast<PHINode>(V)) {
for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
if (isa<ConstantPointerNull>(Phi->getIncomingValue(I)))
Phi->setIncomingValue(I, ConstantPointerNull::get(NewTy));
}
}
continue;
}
IntrinsicInst *Intr = cast<IntrinsicInst>(Call);
Builder.SetInsertPoint(Intr);
switch (Intr->getIntrinsicID()) {
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
// These intrinsics are for address space 0 only
Intr->eraseFromParent();
continue;
case Intrinsic::memcpy:
case Intrinsic::memmove:
// These have 2 pointer operands. In case if second pointer also needs
// to be replaced we defer processing of these intrinsics until all
// other values are processed.
DeferredIntrs.push_back(Intr);
continue;
case Intrinsic::memset: {
MemSetInst *MemSet = cast<MemSetInst>(Intr);
Builder.CreateMemSet(MemSet->getRawDest(), MemSet->getValue(),
MemSet->getLength(), MemSet->getDestAlign(),
MemSet->isVolatile());
Intr->eraseFromParent();
continue;
}
case Intrinsic::invariant_start:
case Intrinsic::invariant_end:
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
Intr->eraseFromParent();
// FIXME: I think the invariant marker should still theoretically apply,
// but the intrinsics need to be changed to accept pointers with any
// address space.
continue;
case Intrinsic::objectsize: {
Value *Src = Intr->getOperand(0);
Function *ObjectSize = Intrinsic::getDeclaration(
Mod, Intrinsic::objectsize,
{Intr->getType(),
PointerType::get(Context, AMDGPUAS::LOCAL_ADDRESS)});
CallInst *NewCall = Builder.CreateCall(
ObjectSize,
{Src, Intr->getOperand(1), Intr->getOperand(2), Intr->getOperand(3)});
Intr->replaceAllUsesWith(NewCall);
Intr->eraseFromParent();
continue;
}
default:
Intr->print(errs());
llvm_unreachable("Don't know how to promote alloca intrinsic use.");
}
}
for (IntrinsicInst *Intr : DeferredIntrs) {
Builder.SetInsertPoint(Intr);
Intrinsic::ID ID = Intr->getIntrinsicID();
assert(ID == Intrinsic::memcpy || ID == Intrinsic::memmove);
MemTransferInst *MI = cast<MemTransferInst>(Intr);
auto *B = Builder.CreateMemTransferInst(
ID, MI->getRawDest(), MI->getDestAlign(), MI->getRawSource(),
MI->getSourceAlign(), MI->getLength(), MI->isVolatile());
for (unsigned I = 0; I != 2; ++I) {
if (uint64_t Bytes = Intr->getParamDereferenceableBytes(I)) {
B->addDereferenceableParamAttr(I, Bytes);
}
}
Intr->eraseFromParent();
}
return true;
}