[llvm] 771d152 - [SPIR-V] Preserve offset alignment in pointer cast legalization (#209251)
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llvm-commits at lists.llvm.org
Wed Jul 15 00:59:51 PDT 2026
Author: Arseniy Obolenskiy
Date: 2026-07-15T09:59:46+02:00
New Revision: 771d152cd10a05a10023beb0ff289ea1180b1751
URL: https://github.com/llvm/llvm-project/commit/771d152cd10a05a10023beb0ff289ea1180b1751
DIFF: https://github.com/llvm/llvm-project/commit/771d152cd10a05a10023beb0ff289ea1180b1751.diff
LOG: [SPIR-V] Preserve offset alignment in pointer cast legalization (#209251)
Splitting a load/store into per-element accesses reused the original
alignment for every element, which could wrongly strengthen or discard
alignment
Compute each split access alignment via commonAlignment with its
DataLayout derived byte offset matching SPIRVLegalizerInfo.cpp
Added:
Modified:
llvm/lib/Target/SPIRV/SPIRVLegalizePointerCast.cpp
llvm/test/CodeGen/SPIRV/passes/SPIRVLegalizePointerCast.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/SPIRV/SPIRVLegalizePointerCast.cpp b/llvm/lib/Target/SPIRV/SPIRVLegalizePointerCast.cpp
index 5832d88af750c..38960b23b26db 100644
--- a/llvm/lib/Target/SPIRV/SPIRVLegalizePointerCast.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVLegalizePointerCast.cpp
@@ -99,8 +99,10 @@ class SPIRVLegalizePointerCastImpl {
// type.
// Returns the loaded value.
Value *loadVectorFromVector(IRBuilder<> &B, FixedVectorType *SourceType,
- FixedVectorType *TargetType, Value *Source) {
+ FixedVectorType *TargetType, Value *Source,
+ Align OriginalAlign) {
LoadInst *NewLoad = B.CreateLoad(SourceType, Source);
+ NewLoad->setAlignment(OriginalAlign);
buildAssignType(B, SourceType, NewLoad);
Value *AssignValue = NewLoad;
if (TargetType->getElementType() != SourceType->getElementType()) {
@@ -226,11 +228,11 @@ class SPIRVLegalizePointerCastImpl {
return LI;
}
if (SVT && DVT)
- return loadVectorFromVector(B, SVT, DVT, GEP);
+ return loadVectorFromVector(B, SVT, DVT, GEP, BadLoad->getAlign());
if (SAT && DVT && SAT->getElementType() == DVT->getElementType())
- return loadVectorFromArray(B, DVT, GEP);
+ return loadVectorFromArray(B, DVT, GEP, BadLoad->getAlign());
if (MAT && DVT && MAT->getElementType() == DVT->getElementType())
- return loadVectorFromMatrixArray(B, DVT, GEP, MAT);
+ return loadVectorFromMatrixArray(B, DVT, GEP, MAT, BadLoad->getAlign());
llvm_unreachable("Failed to load from aggregate.");
}
@@ -266,10 +268,12 @@ class SPIRVLegalizePointerCastImpl {
// Loads elements from a matrix with an array of vector memory layout and
// constructs a vector.
Value *loadVectorFromMatrixArray(IRBuilder<> &B, FixedVectorType *TargetType,
- Value *Source,
- FixedVectorType *ArrElemVecTy) {
+ Value *Source, FixedVectorType *ArrElemVecTy,
+ Align OriginalAlign) {
Type *TargetElemTy = TargetType->getElementType();
unsigned ScalarsPerArrayElement = ArrElemVecTy->getNumElements();
+ const DataLayout &DL = B.GetInsertBlock()->getModule()->getDataLayout();
+ uint64_t ArrElemVecSize = DL.getTypeAllocSize(ArrElemVecTy);
// Load each element of the array.
SmallVector<Value *, 4> LoadedElements;
std::array<Type *, 2> Types = {Source->getType(), Source->getType()};
@@ -282,7 +286,9 @@ class SPIRVLegalizePointerCastImpl {
ConstantInt::get(B.getInt32Ty(), ArrayIndex)};
auto *ElementPtr = B.CreateIntrinsic(Intrinsic::spv_gep, {Types}, {Args});
GR->buildAssignPtr(B, ArrElemVecTy, ElementPtr);
- Value *LoadVec = B.CreateLoad(ArrElemVecTy, ElementPtr);
+ LoadInst *LoadVec = B.CreateLoad(ArrElemVecTy, ElementPtr);
+ LoadVec->setAlignment(
+ commonAlignment(OriginalAlign, ArrayIndex * ArrElemVecSize));
buildAssignType(B, ArrElemVecTy, LoadVec);
LoadedElements.push_back(makeExtractElement(B, TargetElemTy, LoadVec,
ElementIndexInArrayElem));
@@ -291,10 +297,12 @@ class SPIRVLegalizePointerCastImpl {
}
// Loads elements from an array and constructs a vector.
Value *loadVectorFromArray(IRBuilder<> &B, FixedVectorType *TargetType,
- Value *Source) {
+ Value *Source, Align OriginalAlign) {
// Load each element of the array.
SmallVector<Value *, 4> LoadedElements;
std::array<Type *, 2> Types = {Source->getType(), Source->getType()};
+ const DataLayout &DL = B.GetInsertBlock()->getModule()->getDataLayout();
+ uint64_t ElemSize = DL.getTypeAllocSize(TargetType->getElementType());
for (unsigned I = 0, E = TargetType->getNumElements(); I < E; ++I) {
// Create a GEP to access the i-th element of the array.
std::array<Value *, 4> Args = {B.getInt1(/*Inbounds=*/false), Source,
@@ -304,7 +312,8 @@ class SPIRVLegalizePointerCastImpl {
GR->buildAssignPtr(B, TargetType->getElementType(), ElementPtr);
// Load the value from the element pointer.
- Value *Load = B.CreateLoad(TargetType->getElementType(), ElementPtr);
+ LoadInst *Load = B.CreateLoad(TargetType->getElementType(), ElementPtr);
+ Load->setAlignment(commonAlignment(OriginalAlign, I * ElemSize));
buildAssignType(B, TargetType->getElementType(), Load);
LoadedElements.push_back(Load);
}
@@ -326,6 +335,8 @@ class SPIRVLegalizePointerCastImpl {
std::array<Type *, 2> Types = {DstArrayPtr->getType(),
DstArrayPtr->getType()};
+ const DataLayout &DL = B.GetInsertBlock()->getModule()->getDataLayout();
+ uint64_t ArrElemVecSize = DL.getTypeAllocSize(ArrElemVecTy);
for (unsigned I = 0; I < SrcNumElements; I += ScalarsPerArrayElement) {
unsigned ArrayIndex = I / ScalarsPerArrayElement;
@@ -344,7 +355,7 @@ class SPIRVLegalizePointerCastImpl {
// Build a vector from the extracted elements and store it.
Value *Vec = buildVectorFromLoadedElements(B, ArrElemVecTy, Elements);
StoreInst *SI = B.CreateStore(Vec, ElementPtr);
- SI->setAlignment(Alignment);
+ SI->setAlignment(commonAlignment(Alignment, ArrayIndex * ArrElemVecSize));
}
}
@@ -360,6 +371,8 @@ class SPIRVLegalizePointerCastImpl {
"Element types of array and vector must be the same.");
std::array<Type *, 2> Types = {DstArrayPtr->getType(),
DstArrayPtr->getType()};
+ const DataLayout &DL = B.GetInsertBlock()->getModule()->getDataLayout();
+ uint64_t ElemSize = DL.getTypeAllocSize(ElemTy);
for (unsigned I = 0, E = VecTy->getNumElements(); I < E; ++I) {
// Create a GEP to access the i-th element of the array.
@@ -373,7 +386,7 @@ class SPIRVLegalizePointerCastImpl {
Value *Element =
E == 1 ? SrcVector : makeExtractElement(B, ElemTy, SrcVector, I);
StoreInst *SI = B.CreateStore(Element, ElementPtr);
- SI->setAlignment(Alignment);
+ SI->setAlignment(commonAlignment(Alignment, I * ElemSize));
}
}
diff --git a/llvm/test/CodeGen/SPIRV/passes/SPIRVLegalizePointerCast.ll b/llvm/test/CodeGen/SPIRV/passes/SPIRVLegalizePointerCast.ll
index 7d2fb71275290..e4ad402c1ec95 100644
--- a/llvm/test/CodeGen/SPIRV/passes/SPIRVLegalizePointerCast.ll
+++ b/llvm/test/CodeGen/SPIRV/passes/SPIRVLegalizePointerCast.ll
@@ -6,6 +6,8 @@
@M = internal addrspace(10) global [4 x <2 x float>] zeroinitializer, align 4
@OUT = internal addrspace(10) global float zeroinitializer, align 4
+ at Arr = internal addrspace(10) global [8 x float] zeroinitializer, align 16
+ at OUTV = internal addrspace(10) global <4 x float> zeroinitializer, align 4
; Loading a <5 x float> through a [4 x <2 x float>] forces emit-intrinsics to
; insert spv.ptrcast; legalize-pointer-cast lowers it to typed <2 x float>
@@ -25,4 +27,36 @@ entry:
ret void
}
+; Loading a <4 x float> from an [8 x float] with a base alignment of 16 must
+; not strengthen or discard alignment on the split per-element loads: the
+; alignment of each load is the common alignment of the base align and its
+; byte offset (16, 4, 8, 4 for offsets 0, 4, 8, 12).
+
+define spir_func void @loadAlign() #0 {
+; CHECK-LABEL: define spir_func void @loadAlign(
+; CHECK: load float, ptr addrspace(10) %{{.*}}, align 16
+; CHECK: load float, ptr addrspace(10) %{{.*}}, align 4
+; CHECK: load float, ptr addrspace(10) %{{.*}}, align 8
+; CHECK: load float, ptr addrspace(10) %{{.*}}, align 4
+entry:
+ %v = load <4 x float>, ptr addrspace(10) @Arr, align 16
+ store <4 x float> %v, ptr addrspace(10) @OUTV, align 4
+ ret void
+}
+
+; Storing a <4 x float> into an [8 x float] with a base alignment of 16 must
+; apply the same commonAlignment rule to the split per-element stores.
+
+define spir_func void @storeAlign() #0 {
+; CHECK-LABEL: define spir_func void @storeAlign(
+; CHECK: store float %{{.*}}, ptr addrspace(10) %{{.*}}, align 16
+; CHECK: store float %{{.*}}, ptr addrspace(10) %{{.*}}, align 4
+; CHECK: store float %{{.*}}, ptr addrspace(10) %{{.*}}, align 8
+; CHECK: store float %{{.*}}, ptr addrspace(10) %{{.*}}, align 4
+entry:
+ %v = load <4 x float>, ptr addrspace(10) @OUTV, align 4
+ store <4 x float> %v, ptr addrspace(10) @Arr, align 16
+ ret void
+}
+
attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
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