[llvm] [DirectX] Legalize memcpy (PR #139173)
via llvm-commits
llvm-commits at lists.llvm.org
Thu May 8 16:46:58 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-directx
Author: Deric C. (Icohedron)
<details>
<summary>Changes</summary>
Fixes #<!-- -->137188
This PR legalizes memcpy for DXIL in cases where:
- the src and dst arguments are from Alloca or a GlobalVariable,
- the types of the src and dst must be equivalent, and
- the len param is a ConstantInt
These assumption simplify the legalization and, with the addition of #<!-- -->138991, covers the currently-known cases of memcpy that appear when compiling DML shaders.
---
Full diff: https://github.com/llvm/llvm-project/pull/139173.diff
2 Files Affected:
- (modified) llvm/lib/Target/DirectX/DXILLegalizePass.cpp (+78)
- (added) llvm/test/CodeGen/DirectX/legalize-memcpy.ll (+174)
``````````diff
diff --git a/llvm/lib/Target/DirectX/DXILLegalizePass.cpp b/llvm/lib/Target/DirectX/DXILLegalizePass.cpp
index be77a70fa46ba..d9e560a9f8859 100644
--- a/llvm/lib/Target/DirectX/DXILLegalizePass.cpp
+++ b/llvm/lib/Target/DirectX/DXILLegalizePass.cpp
@@ -15,6 +15,7 @@
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
+#include "llvm/Support/ErrorHandling.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include <functional>
@@ -246,6 +247,58 @@ downcastI64toI32InsertExtractElements(Instruction &I,
}
}
+static void emitMemcpyExpansion(IRBuilder<> &Builder, Value *Dst, Value *Src,
+ ConstantInt *Length) {
+
+ uint64_t ByteLength = Length->getZExtValue();
+ if (ByteLength == 0)
+ return;
+
+ LLVMContext &Ctx = Builder.getContext();
+ const DataLayout &DL = Builder.GetInsertBlock()->getModule()->getDataLayout();
+
+ auto GetArrTyFromVal = [](Value *Val) {
+ if (auto *Alloca = dyn_cast<AllocaInst>(Val))
+ return dyn_cast<ArrayType>(Alloca->getAllocatedType());
+ if (auto *GlobalVar = dyn_cast<GlobalVariable>(Val))
+ return dyn_cast<ArrayType>(GlobalVar->getValueType());
+ llvm_unreachable(
+ "Expected an Alloca or GlobalVariable in memcpy Src and Dst");
+ };
+
+ ArrayType *ArrTy = GetArrTyFromVal(Dst);
+ assert(ArrTy && "Expected Dst of memcpy to be a Pointer to an Array Type");
+ if (auto *DstGlobalVar = dyn_cast<GlobalVariable>(Dst))
+ assert(!DstGlobalVar->isConstant() &&
+ "The Dst of memcpy must not be a constant Global Variable");
+
+ [[maybe_unused]] ArrayType *SrcArrTy = GetArrTyFromVal(Src);
+ assert(SrcArrTy && "Expected Src of memcpy to be a Pointer to an Array Type");
+
+ // This assumption simplifies implementation and covers currently-known
+ // use-cases for DXIL. It may be relaxed in the future if required.
+ assert(ArrTy == SrcArrTy && "Array Types of Src and Dst in memcpy must match");
+
+ Type *ElemTy = ArrTy->getElementType();
+ uint64_t ElemSize = DL.getTypeStoreSize(ElemTy);
+ assert(ElemSize > 0 && "Size must be set");
+
+ [[maybe_unused]] uint64_t Size = ArrTy->getArrayNumElements();
+ assert(ElemSize * Size >= ByteLength &&
+ "Array size must be at least as large as the memcpy length");
+
+ uint64_t NumElemsToCopy = ByteLength / ElemSize;
+ assert(ByteLength % ElemSize == 0 &&
+ "memcpy length must be divisible by array element type");
+ for (uint64_t I = 0; I < NumElemsToCopy; ++I) {
+ Value *Offset = ConstantInt::get(Type::getInt32Ty(Ctx), I);
+ Value *SrcPtr = Builder.CreateGEP(ElemTy, Src, Offset, "gep");
+ Value *SrcVal = Builder.CreateLoad(ElemTy, SrcPtr);
+ Value *DstPtr = Builder.CreateGEP(ElemTy, Dst, Offset, "gep");
+ Builder.CreateStore(SrcVal, DstPtr);
+ }
+}
+
static void emitMemsetExpansion(IRBuilder<> &Builder, Value *Dst, Value *Val,
ConstantInt *SizeCI,
DenseMap<Value *, Value *> &ReplacedValues) {
@@ -296,6 +349,30 @@ static void emitMemsetExpansion(IRBuilder<> &Builder, Value *Dst, Value *Val,
}
}
+static void removeMemCpy(Instruction &I,
+ SmallVectorImpl<Instruction *> &ToRemove,
+ DenseMap<Value *, Value *> &ReplacedValues) {
+
+ CallInst *CI = dyn_cast<CallInst>(&I);
+ if (!CI)
+ return;
+
+ Intrinsic::ID ID = CI->getIntrinsicID();
+ if (ID != Intrinsic::memcpy)
+ return;
+
+ IRBuilder<> Builder(&I);
+ Value *Dst = CI->getArgOperand(0);
+ Value *Src = CI->getArgOperand(1);
+ ConstantInt *Length = dyn_cast<ConstantInt>(CI->getArgOperand(2));
+ assert(Length && "Expected Length to be a ConstantInt");
+ ConstantInt *IsVolatile = dyn_cast<ConstantInt>(CI->getArgOperand(3));
+ assert(IsVolatile && "Expected IsVolatile to be a ConstantInt");
+ assert(IsVolatile->getZExtValue() == 0 && "Expected IsVolatile to be false");
+ emitMemcpyExpansion(Builder, Dst, Src, Length);
+ ToRemove.push_back(CI);
+}
+
static void removeMemSet(Instruction &I,
SmallVectorImpl<Instruction *> &ToRemove,
DenseMap<Value *, Value *> &ReplacedValues) {
@@ -348,6 +425,7 @@ class DXILLegalizationPipeline {
LegalizationPipeline.push_back(fixI8UseChain);
LegalizationPipeline.push_back(downcastI64toI32InsertExtractElements);
LegalizationPipeline.push_back(legalizeFreeze);
+ LegalizationPipeline.push_back(removeMemCpy);
LegalizationPipeline.push_back(removeMemSet);
}
};
diff --git a/llvm/test/CodeGen/DirectX/legalize-memcpy.ll b/llvm/test/CodeGen/DirectX/legalize-memcpy.ll
new file mode 100644
index 0000000000000..09a4d051a2822
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/legalize-memcpy.ll
@@ -0,0 +1,174 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -dxil-legalize -dxil-finalize-linkage -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+
+ at outputStrides = external local_unnamed_addr addrspace(2) global [2 x <4 x i32>], align 4
+
+define void @replace_2x4xint_global_memcpy_test() #0 {
+; CHECK-LABEL: define void @replace_2x4xint_global_memcpy_test(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: [[TMP1:%.*]] = alloca [2 x <4 x i32>], align 16
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 32, ptr nonnull [[TMP1]])
+; CHECK-NEXT: [[TMP2:%.*]] = load <4 x i32>, ptr addrspace(2) @outputStrides, align 16
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr <4 x i32>, ptr [[TMP1]], i32 0
+; CHECK-NEXT: store <4 x i32> [[TMP2]], ptr [[GEP]], align 16
+; CHECK-NEXT: [[TMP3:%.*]] = load <4 x i32>, ptr addrspace(2) getelementptr (<4 x i32>, ptr addrspace(2) @outputStrides, i32 1), align 16
+; CHECK-NEXT: [[GEP1:%.*]] = getelementptr <4 x i32>, ptr [[TMP1]], i32 1
+; CHECK-NEXT: store <4 x i32> [[TMP3]], ptr [[GEP1]], align 16
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 32, ptr nonnull [[TMP1]])
+; CHECK-NEXT: ret void
+;
+ %1 = alloca [2 x <4 x i32>], align 16
+ call void @llvm.lifetime.start.p0(i64 32, ptr nonnull %1)
+ call void @llvm.memcpy.p0.p2.i32(ptr nonnull align 16 dereferenceable(32) %1, ptr addrspace(2) align 16 dereferenceable(32) @outputStrides, i32 32, i1 false)
+ call void @llvm.lifetime.end.p0(i64 32, ptr nonnull %1)
+ ret void
+}
+
+define void @replace_int_memcpy_test() #0 {
+; CHECK-LABEL: define void @replace_int_memcpy_test(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = alloca [1 x i32], align 4
+; CHECK-NEXT: [[TMP2:%.*]] = alloca [1 x i32], align 4
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[TMP1]])
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[TMP2]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr i32, ptr [[TMP1]], i32 0
+; CHECK-NEXT: [[TMP3:%.*]] = load i32, ptr [[GEP]], align 4
+; CHECK-NEXT: [[GEP1:%.*]] = getelementptr i32, ptr [[TMP2]], i32 0
+; CHECK-NEXT: store i32 [[TMP3]], ptr [[GEP1]], align 4
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[TMP2]])
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[TMP1]])
+; CHECK-NEXT: ret void
+;
+ %1 = alloca [1 x i32], align 4
+ %2 = alloca [1 x i32], align 4
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %1)
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %2)
+ call void @llvm.memcpy.p0.p0.i32(ptr nonnull align 4 dereferenceable(4) %2, ptr align 4 dereferenceable(4) %1, i32 4, i1 false)
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %2)
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %1)
+ ret void
+}
+
+define void @replace_int16_memcpy_test() #0 {
+; CHECK-LABEL: define void @replace_int16_memcpy_test(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = alloca [2 x i16], align 2
+; CHECK-NEXT: [[TMP2:%.*]] = alloca [2 x i16], align 2
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[TMP1]])
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[TMP2]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr i16, ptr [[TMP1]], i32 0
+; CHECK-NEXT: [[TMP3:%.*]] = load i16, ptr [[GEP]], align 2
+; CHECK-NEXT: [[GEP1:%.*]] = getelementptr i16, ptr [[TMP2]], i32 0
+; CHECK-NEXT: store i16 [[TMP3]], ptr [[GEP1]], align 2
+; CHECK-NEXT: [[GEP2:%.*]] = getelementptr i16, ptr [[TMP1]], i32 1
+; CHECK-NEXT: [[TMP4:%.*]] = load i16, ptr [[GEP2]], align 2
+; CHECK-NEXT: [[GEP3:%.*]] = getelementptr i16, ptr [[TMP2]], i32 1
+; CHECK-NEXT: store i16 [[TMP4]], ptr [[GEP3]], align 2
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[TMP2]])
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[TMP1]])
+; CHECK-NEXT: ret void
+;
+ %1 = alloca [2 x i16], align 2
+ %2 = alloca [2 x i16], align 2
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %1)
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %2)
+ call void @llvm.memcpy.p0.p0.i32(ptr nonnull align 2 dereferenceable(4) %2, ptr align 2 dereferenceable(4) %1, i32 4, i1 false)
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %2)
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %1)
+ ret void
+}
+
+define void @replace_float_memcpy_test() #0 {
+; CHECK-LABEL: define void @replace_float_memcpy_test(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = alloca [2 x float], align 4
+; CHECK-NEXT: [[TMP2:%.*]] = alloca [2 x float], align 4
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 8, ptr nonnull [[TMP1]])
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 8, ptr nonnull [[TMP2]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr float, ptr [[TMP1]], i32 0
+; CHECK-NEXT: [[TMP3:%.*]] = load float, ptr [[GEP]], align 4
+; CHECK-NEXT: [[GEP1:%.*]] = getelementptr float, ptr [[TMP2]], i32 0
+; CHECK-NEXT: store float [[TMP3]], ptr [[GEP1]], align 4
+; CHECK-NEXT: [[GEP2:%.*]] = getelementptr float, ptr [[TMP1]], i32 1
+; CHECK-NEXT: [[TMP4:%.*]] = load float, ptr [[GEP2]], align 4
+; CHECK-NEXT: [[GEP3:%.*]] = getelementptr float, ptr [[TMP2]], i32 1
+; CHECK-NEXT: store float [[TMP4]], ptr [[GEP3]], align 4
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 8, ptr nonnull [[TMP2]])
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 8, ptr nonnull [[TMP1]])
+; CHECK-NEXT: ret void
+;
+ %1 = alloca [2 x float], align 4
+ %2 = alloca [2 x float], align 4
+ call void @llvm.lifetime.start.p0(i64 8, ptr nonnull %1)
+ call void @llvm.lifetime.start.p0(i64 8, ptr nonnull %2)
+ call void @llvm.memcpy.p0.p0.i32(ptr nonnull align 4 dereferenceable(8) %2, ptr align 4 dereferenceable(8) %1, i32 8, i1 false)
+ call void @llvm.lifetime.end.p0(i64 8, ptr nonnull %2)
+ call void @llvm.lifetime.end.p0(i64 8, ptr nonnull %1)
+ ret void
+}
+
+define void @replace_double_memcpy_test() #0 {
+; CHECK-LABEL: define void @replace_double_memcpy_test(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = alloca [2 x double], align 4
+; CHECK-NEXT: [[TMP2:%.*]] = alloca [2 x double], align 4
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 16, ptr nonnull [[TMP1]])
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 16, ptr nonnull [[TMP2]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr double, ptr [[TMP1]], i32 0
+; CHECK-NEXT: [[TMP3:%.*]] = load double, ptr [[GEP]], align 8
+; CHECK-NEXT: [[GEP1:%.*]] = getelementptr double, ptr [[TMP2]], i32 0
+; CHECK-NEXT: store double [[TMP3]], ptr [[GEP1]], align 8
+; CHECK-NEXT: [[GEP2:%.*]] = getelementptr double, ptr [[TMP1]], i32 1
+; CHECK-NEXT: [[TMP4:%.*]] = load double, ptr [[GEP2]], align 8
+; CHECK-NEXT: [[GEP3:%.*]] = getelementptr double, ptr [[TMP2]], i32 1
+; CHECK-NEXT: store double [[TMP4]], ptr [[GEP3]], align 8
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 16, ptr nonnull [[TMP2]])
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 16, ptr nonnull [[TMP1]])
+; CHECK-NEXT: ret void
+;
+ %1 = alloca [2 x double], align 4
+ %2 = alloca [2 x double], align 4
+ call void @llvm.lifetime.start.p0(i64 16, ptr nonnull %1)
+ call void @llvm.lifetime.start.p0(i64 16, ptr nonnull %2)
+ call void @llvm.memcpy.p0.p0.i32(ptr nonnull align 4 dereferenceable(8) %2, ptr align 4 dereferenceable(8) %1, i32 16, i1 false)
+ call void @llvm.lifetime.end.p0(i64 16, ptr nonnull %2)
+ call void @llvm.lifetime.end.p0(i64 16, ptr nonnull %1)
+ ret void
+}
+
+define void @replace_half_memcpy_test() #0 {
+; CHECK-LABEL: define void @replace_half_memcpy_test(
+; CHECK-SAME: ) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = alloca [2 x half], align 2
+; CHECK-NEXT: [[TMP2:%.*]] = alloca [2 x half], align 2
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[TMP1]])
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[TMP2]])
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr half, ptr [[TMP1]], i32 0
+; CHECK-NEXT: [[TMP3:%.*]] = load half, ptr [[GEP]], align 2
+; CHECK-NEXT: [[GEP1:%.*]] = getelementptr half, ptr [[TMP2]], i32 0
+; CHECK-NEXT: store half [[TMP3]], ptr [[GEP1]], align 2
+; CHECK-NEXT: [[GEP2:%.*]] = getelementptr half, ptr [[TMP1]], i32 1
+; CHECK-NEXT: [[TMP4:%.*]] = load half, ptr [[GEP2]], align 2
+; CHECK-NEXT: [[GEP3:%.*]] = getelementptr half, ptr [[TMP2]], i32 1
+; CHECK-NEXT: store half [[TMP4]], ptr [[GEP3]], align 2
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[TMP2]])
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[TMP1]])
+; CHECK-NEXT: ret void
+;
+ %1 = alloca [2 x half], align 2
+ %2 = alloca [2 x half], align 2
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %1)
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %2)
+ call void @llvm.memcpy.p0.p0.i32(ptr nonnull align 2 dereferenceable(4) %2, ptr align 2 dereferenceable(4) %1, i32 4, i1 false)
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %2)
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %1)
+ ret void
+}
+
+attributes #0 = {"hlsl.export"}
+
+
+declare void @llvm.lifetime.end.p0(i64 immarg, ptr captures(none))
+declare void @llvm.lifetime.start.p0(i64 immarg, ptr captures(none))
+declare void @llvm.memcpy.p0.p2.i32(ptr noalias, ptr addrspace(2) noalias readonly, i32, i1)
+declare void @llvm.memcpy.p0.p0.i32(ptr noalias, ptr noalias readonly, i32, i1)
``````````
</details>
https://github.com/llvm/llvm-project/pull/139173
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