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[DirectX] legalize memset
fixes #136243 This change converts memset into a series of geps and stores It is intentionally limited to memsets of fixed size It also converts the byte stores to type stores. DXIL does not support i8 plus this reduces the total number of gep and store instructions. This change also moves DXILFinalizeLinkage to run after Legalization to clean up any dead intrinsic definitions.
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4 files changed

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‎llvm/lib/Target/DirectX/DXILLegalizePass.cpp‎

Lines changed: 78 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include <functional>
@@ -151,6 +152,82 @@ downcastI64toI32InsertExtractElements(Instruction &I,
151152
}
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}
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void emitMemset(IRBuilder<> &Builder, Value *Dst, Value *Val,
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ConstantInt *SizeCI) {
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LLVMContext &Ctx = Builder.getContext();
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[[maybe_unused]] DataLayout DL =
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Builder.GetInsertBlock()->getModule()->getDataLayout();
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[[maybe_unused]] uint64_t OrigSize = SizeCI->getZExtValue();
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AllocaInst *Alloca = dyn_cast<AllocaInst>(Dst);
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assert(Alloca && "Expected memset on an Alloca");
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assert(OrigSize == Alloca->getAllocationSize(DL)->getFixedValue() &&
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"Expected for memset size to match DataLayout size");
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Type *AllocatedTy = Alloca->getAllocatedType();
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ArrayType *ArrTy = dyn_cast<ArrayType>(AllocatedTy);
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assert(ArrTy && "Expected Alloca for an Array Type");
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Type *ElemTy = ArrTy->getElementType();
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uint64_t Size = ArrTy->getArrayNumElements();
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[[maybe_unused]] uint64_t ElemSize = DL.getTypeStoreSize(ElemTy);
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assert(ElemSize > 0 && "Size must be set");
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assert(OrigSize == ElemSize * Size && "Size in bytes must match");
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Value *TypedVal = Val;
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if (Val->getType() != ElemTy)
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TypedVal = Builder.CreateIntCast(Val, ElemTy,
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false); // Or use CreateBitCast for float
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for (uint64_t I = 0; I < Size; ++I) {
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Value *Offset = ConstantInt::get(Type::getInt32Ty(Ctx), I);
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Value *Ptr = Builder.CreateGEP(ElemTy, Dst, Offset, "gep");
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Builder.CreateStore(TypedVal, Ptr);
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}
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}
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void removeLifetimesForMemset(CallInst *Memset,
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SmallVectorImpl<Instruction *> &ToRemove) {
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assert(Memset->getCalledFunction()->getIntrinsicID() == Intrinsic::memset &&
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"Expected a memset intrinsic");
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Value *DstPtr = Memset->getArgOperand(0);
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DstPtr = DstPtr->stripPointerCasts();
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for (User *U : DstPtr->users()) {
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if (auto *CI = dyn_cast<CallInst>(U)) {
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switch (CI->getIntrinsicID()) {
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case Intrinsic::lifetime_start:
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case Intrinsic::lifetime_end:
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ToRemove.push_back(CI);
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break;
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}
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}
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}
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}
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static void removeMemSet(Instruction &I,
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SmallVectorImpl<Instruction *> &ToRemove,
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DenseMap<Value *, Value *>) {
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if (CallInst *CI = dyn_cast<CallInst>(&I)) {
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Intrinsic::ID ID = CI->getIntrinsicID();
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if (ID == Intrinsic::memset) {
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IRBuilder<> Builder(&I);
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Value *Dst = CI->getArgOperand(0);
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Value *Val = CI->getArgOperand(1);
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[[maybe_unused]] ConstantInt *Size =
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dyn_cast<ConstantInt>(CI->getArgOperand(2));
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assert(Size && "Expected Size to be a ConstantInt");
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emitMemset(Builder, Dst, Val, Size);
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removeLifetimesForMemset(CI, ToRemove);
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ToRemove.push_back(CI);
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}
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}
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}
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namespace {
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class DXILLegalizationPipeline {
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@@ -181,6 +258,7 @@ class DXILLegalizationPipeline {
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LegalizationPipeline.push_back(fixI8TruncUseChain);
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LegalizationPipeline.push_back(downcastI64toI32InsertExtractElements);
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LegalizationPipeline.push_back(legalizeFreeze);
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LegalizationPipeline.push_back(removeMemSet);
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}
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};
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‎llvm/lib/Target/DirectX/DirectXTargetMachine.cpp‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -96,7 +96,6 @@ class DirectXPassConfig : public TargetPassConfig {
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FunctionPass *createTargetRegisterAllocator(bool) override { return nullptr; }
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void addCodeGenPrepare() override {
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addPass(createDXILFinalizeLinkageLegacyPass());
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addPass(createDXILIntrinsicExpansionLegacyPass());
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addPass(createDXILCBufferAccessLegacyPass());
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addPass(createDXILDataScalarizationLegacyPass());
@@ -106,6 +105,7 @@ class DirectXPassConfig : public TargetPassConfig {
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DxilScalarOptions.ScalarizeLoadStore = true;
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addPass(createScalarizerPass(DxilScalarOptions));
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addPass(createDXILLegalizeLegacyPass());
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addPass(createDXILFinalizeLinkageLegacyPass());
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addPass(createDXILTranslateMetadataLegacyPass());
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addPass(createDXILOpLoweringLegacyPass());
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addPass(createDXILPrepareModulePass());

‎llvm/test/CodeGen/DirectX/legalize-memset.ll‎

Lines changed: 81 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,81 @@
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt -S -passes='dxil-legalize' -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
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define void @replace_float_memset_test() {
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; CHECK-LABEL: define void @replace_float_memset_test() {
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; CHECK-NEXT: [[ACCUM_I_FLAT:%.*]] = alloca [2 x float], align 4
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; CHECK-NEXT: [[GEP:%.*]] = getelementptr float, ptr [[ACCUM_I_FLAT]], i32 0
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; CHECK-NEXT: store float 0.000000e+00, ptr [[GEP]], align 4
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; CHECK-NEXT: [[GEP1:%.*]] = getelementptr float, ptr [[ACCUM_I_FLAT]], i32 1
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; CHECK-NEXT: store float 0.000000e+00, ptr [[GEP1]], align 4
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; CHECK-NEXT: ret void
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;
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%accum.i.flat = alloca [2 x float], align 4
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call void @llvm.lifetime.start.p0(i64 8, ptr nonnull %accum.i.flat)
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call void @llvm.memset.p0.i32(ptr nonnull align 4 dereferenceable(8) %accum.i.flat, i8 0, i32 8, i1 false)
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call void @llvm.lifetime.end.p0(i64 8, ptr nonnull %accum.i.flat)
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ret void
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}
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define void @replace_half_memset_test() {
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; CHECK-LABEL: define void @replace_half_memset_test() {
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; CHECK-NEXT: [[ACCUM_I_FLAT:%.*]] = alloca [2 x half], align 4
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; CHECK-NEXT: [[GEP:%.*]] = getelementptr half, ptr [[ACCUM_I_FLAT]], i32 0
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; CHECK-NEXT: store half 0xH0000, ptr [[GEP]], align 2
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; CHECK-NEXT: [[GEP1:%.*]] = getelementptr half, ptr [[ACCUM_I_FLAT]], i32 1
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; CHECK-NEXT: store half 0xH0000, ptr [[GEP1]], align 2
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; CHECK-NEXT: ret void
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;
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%accum.i.flat = alloca [2 x half], align 4
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call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %accum.i.flat)
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call void @llvm.memset.p0.i32(ptr nonnull align 4 dereferenceable(8) %accum.i.flat, i8 0, i32 4, i1 false)
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call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %accum.i.flat)
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ret void
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}
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37+
define void @replace_double_memset_test() {
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; CHECK-LABEL: define void @replace_double_memset_test() {
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; CHECK-NEXT: [[ACCUM_I_FLAT:%.*]] = alloca [2 x double], align 4
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; CHECK-NEXT: [[GEP:%.*]] = getelementptr double, ptr [[ACCUM_I_FLAT]], i32 0
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; CHECK-NEXT: store double 0.000000e+00, ptr [[GEP]], align 8
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; CHECK-NEXT: [[GEP1:%.*]] = getelementptr double, ptr [[ACCUM_I_FLAT]], i32 1
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; CHECK-NEXT: store double 0.000000e+00, ptr [[GEP1]], align 8
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; CHECK-NEXT: ret void
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;
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%accum.i.flat = alloca [2 x double], align 4
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call void @llvm.lifetime.start.p0(i64 16, ptr nonnull %accum.i.flat)
48+
call void @llvm.memset.p0.i32(ptr nonnull align 4 dereferenceable(8) %accum.i.flat, i8 0, i32 16, i1 false)
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call void @llvm.lifetime.end.p0(i64 16, ptr nonnull %accum.i.flat)
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ret void
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}
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53+
define void @replace_int16_memset_test() {
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; CHECK-LABEL: define void @replace_int16_memset_test() {
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; CHECK-NEXT: [[CACHE_I:%.*]] = alloca [2 x i16], align 2
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; CHECK-NEXT: [[GEP:%.*]] = getelementptr i16, ptr [[CACHE_I]], i32 0
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; CHECK-NEXT: store i16 0, ptr [[GEP]], align 2
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; CHECK-NEXT: [[GEP1:%.*]] = getelementptr i16, ptr [[CACHE_I]], i32 1
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; CHECK-NEXT: store i16 0, ptr [[GEP1]], align 2
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; CHECK-NEXT: ret void
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;
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%cache.i = alloca [2 x i16], align 2
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call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %cache.i)
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call void @llvm.memset.p0.i32(ptr nonnull align 2 dereferenceable(4) %cache.i, i8 0, i32 4, i1 false)
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call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %cache.i)
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ret void
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}
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69+
define void @replace_int_memset_test() {
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; CHECK-LABEL: define void @replace_int_memset_test() {
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; CHECK-NEXT: [[ACCUM_I_FLAT:%.*]] = alloca [1 x i32], align 4
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; CHECK-NEXT: [[GEP:%.*]] = getelementptr i32, ptr [[ACCUM_I_FLAT]], i32 0
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; CHECK-NEXT: store i32 0, ptr [[GEP]], align 4
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; CHECK-NEXT: ret void
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;
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%accum.i.flat = alloca [1 x i32], align 4
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call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %accum.i.flat)
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call void @llvm.memset.p0.i32(ptr nonnull align 4 dereferenceable(8) %accum.i.flat, i8 0, i32 4, i1 false)
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call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %accum.i.flat)
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ret void
81+
}

‎llvm/test/CodeGen/DirectX/llc-pipeline.ll‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,6 @@
1313
; CHECK-OBJ-NEXT: Create Garbage Collector Module Metadata
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; CHECK-NEXT: ModulePass Manager
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; CHECK-NEXT: DXIL Finalize Linkage
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; CHECK-NEXT: DXIL Intrinsic Expansion
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; CHECK-NEXT: DXIL CBuffer Access
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; CHECK-NEXT: DXIL Data Scalarization
@@ -23,6 +22,7 @@
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; CHECK-NEXT: Dominator Tree Construction
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; CHECK-NEXT: Scalarize vector operations
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; CHECK-NEXT: DXIL Legalizer
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; CHECK-NEXT: DXIL Finalize Linkage
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; CHECK-NEXT: DXIL Resource Binding Analysis
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; CHECK-NEXT: DXIL Module Metadata analysis
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; CHECK-NEXT: DXIL Shader Flag Analysis

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