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//===- DXILResourceAccess.cpp - Resource access via load/store ------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "DXILResourceAccess.h"
#include "DirectX.h"
#include "llvm/Analysis/DXILResource.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsDirectX.h"
#include "llvm/InitializePasses.h"
#define DEBUG_TYPE "dxil-resource-access"
using namespace llvm;
static void replaceTypedBufferAccess(IntrinsicInst *II,
dxil::ResourceTypeInfo &RTI) {
const DataLayout &DL = II->getDataLayout();
auto *HandleType = cast<TargetExtType>(II->getOperand(0)->getType());
assert(HandleType->getName() == "dx.TypedBuffer" &&
"Unexpected typed buffer type");
Type *ContainedType = HandleType->getTypeParameter(0);
Type *LoadType =
StructType::get(ContainedType, Type::getInt1Ty(II->getContext()));
// We need the size of an element in bytes so that we can calculate the offset
// in elements given a total offset in bytes later.
Type *ScalarType = ContainedType->getScalarType();
uint64_t ScalarSize = DL.getTypeSizeInBits(ScalarType) / 8;
// Process users keeping track of indexing accumulated from GEPs.
struct AccessAndIndex {
User *Access;
Value *Index;
};
SmallVector<AccessAndIndex> Worklist;
for (User *U : II->users())
Worklist.push_back({U, nullptr});
SmallVector<Instruction *> DeadInsts;
while (!Worklist.empty()) {
AccessAndIndex Current = Worklist.back();
Worklist.pop_back();
if (auto *GEP = dyn_cast<GetElementPtrInst>(Current.Access)) {
IRBuilder<> Builder(GEP);
Value *Index;
APInt ConstantOffset(DL.getIndexTypeSizeInBits(GEP->getType()), 0);
if (GEP->accumulateConstantOffset(DL, ConstantOffset)) {
APInt Scaled = ConstantOffset.udiv(ScalarSize);
Index = ConstantInt::get(Builder.getInt32Ty(), Scaled);
} else {
auto IndexIt = GEP->idx_begin();
assert(cast<ConstantInt>(IndexIt)->getZExtValue() == 0 &&
"GEP is not indexing through pointer");
++IndexIt;
Index = *IndexIt;
assert(++IndexIt == GEP->idx_end() && "Too many indices in GEP");
}
for (User *U : GEP->users())
Worklist.push_back({U, Index});
DeadInsts.push_back(GEP);
} else if (auto *SI = dyn_cast<StoreInst>(Current.Access)) {
assert(SI->getValueOperand() != II && "Pointer escaped!");
IRBuilder<> Builder(SI);
Value *V = SI->getValueOperand();
if (V->getType() == ContainedType) {
// V is already the right type.
} else if (V->getType() == ScalarType) {
// We're storing a scalar, so we need to load the current value and only
// replace the relevant part.
auto *Load = Builder.CreateIntrinsic(
LoadType, Intrinsic::dx_resource_load_typedbuffer,
{II->getOperand(0), II->getOperand(1)});
auto *Struct = Builder.CreateExtractValue(Load, {0});
// If we have an offset from seeing a GEP earlier, use it.
Value *IndexOp = Current.Index
? Current.Index
: ConstantInt::get(Builder.getInt32Ty(), 0);
V = Builder.CreateInsertElement(Struct, V, IndexOp);
} else {
llvm_unreachable("Store to typed resource has invalid type");
}
auto *Inst = Builder.CreateIntrinsic(
Builder.getVoidTy(), Intrinsic::dx_resource_store_typedbuffer,
{II->getOperand(0), II->getOperand(1), V});
SI->replaceAllUsesWith(Inst);
DeadInsts.push_back(SI);
} else if (auto *LI = dyn_cast<LoadInst>(Current.Access)) {
IRBuilder<> Builder(LI);
Value *V = Builder.CreateIntrinsic(
LoadType, Intrinsic::dx_resource_load_typedbuffer,
{II->getOperand(0), II->getOperand(1)});
V = Builder.CreateExtractValue(V, {0});
if (Current.Index)
V = Builder.CreateExtractElement(V, Current.Index);
LI->replaceAllUsesWith(V);
DeadInsts.push_back(LI);
} else
llvm_unreachable("Unhandled instruction - pointer escaped?");
}
// Traverse the now-dead instructions in RPO and remove them.
for (Instruction *Dead : llvm::reverse(DeadInsts))
Dead->eraseFromParent();
II->eraseFromParent();
}
static bool transformResourcePointers(Function &F, DXILResourceTypeMap &DRTM) {
bool Changed = false;
SmallVector<std::pair<IntrinsicInst *, dxil::ResourceTypeInfo>> Resources;
for (BasicBlock &BB : F)
for (Instruction &I : BB)
if (auto *II = dyn_cast<IntrinsicInst>(&I))
if (II->getIntrinsicID() == Intrinsic::dx_resource_getpointer) {
auto *HandleTy = cast<TargetExtType>(II->getArgOperand(0)->getType());
Resources.emplace_back(II, DRTM[HandleTy]);
}
for (auto &[II, RI] : Resources) {
if (RI.isTyped()) {
Changed = true;
replaceTypedBufferAccess(II, RI);
}
// TODO: handle other resource types. We should probably have an
// `unreachable` here once we've added support for all of them.
}
return Changed;
}
PreservedAnalyses DXILResourceAccess::run(Function &F,
FunctionAnalysisManager &FAM) {
auto &MAMProxy = FAM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
DXILResourceTypeMap *DRTM =
MAMProxy.getCachedResult<DXILResourceTypeAnalysis>(*F.getParent());
assert(DRTM && "DXILResourceTypeAnalysis must be available");
bool MadeChanges = transformResourcePointers(F, *DRTM);
if (!MadeChanges)
return PreservedAnalyses::all();
PreservedAnalyses PA;
PA.preserve<DXILResourceTypeAnalysis>();
PA.preserve<DominatorTreeAnalysis>();
return PA;
}
namespace {
class DXILResourceAccessLegacy : public FunctionPass {
public:
bool runOnFunction(Function &F) override {
DXILResourceTypeMap &DRTM =
getAnalysis<DXILResourceTypeWrapperPass>().getResourceTypeMap();
return transformResourcePointers(F, DRTM);
}
StringRef getPassName() const override { return "DXIL Resource Access"; }
DXILResourceAccessLegacy() : FunctionPass(ID) {}
static char ID; // Pass identification.
void getAnalysisUsage(llvm::AnalysisUsage &AU) const override {
AU.addRequired<DXILResourceTypeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
}
};
char DXILResourceAccessLegacy::ID = 0;
} // end anonymous namespace
INITIALIZE_PASS_BEGIN(DXILResourceAccessLegacy, DEBUG_TYPE,
"DXIL Resource Access", false, false)
INITIALIZE_PASS_DEPENDENCY(DXILResourceTypeWrapperPass)
INITIALIZE_PASS_END(DXILResourceAccessLegacy, DEBUG_TYPE,
"DXIL Resource Access", false, false)
FunctionPass *llvm::createDXILResourceAccessLegacyPass() {
return new DXILResourceAccessLegacy();
}
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