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[DirectX] Fix bug where Flatten arrays was only using last index #144146

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merged 3 commits into from
Jun 16, 2025
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[DirectX] Fix bug where Flatten arrays was only using last index #144146

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d3ff099
[DirectX] Fix bug where Flatten arrays was only using last index
farzonl Jun 13, 2025
b1c6dab
address pr comment by making the comment more clear that index 0 is t…
farzonl Jun 13, 2025
97d9451
address pr comments, make loop in collectIndicesAndDimsFromGEP cleare…
farzonl Jun 16, 2025
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44 changes: 35 additions & 9 deletions llvm/lib/Target/DirectX/DXILFlattenArrays.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,13 @@ class DXILFlattenArraysVisitor
Value *genInstructionFlattenIndices(ArrayRef<Value *> Indices,
ArrayRef<uint64_t> Dims,
IRBuilder<> &Builder);

// Helper function to collect indices and dimensions from a GEP instruction
void collectIndicesAndDimsFromGEP(GetElementPtrInst &GEP,
SmallVectorImpl<Value *> &Indices,
SmallVectorImpl<uint64_t> &Dims,
bool &AllIndicesAreConstInt);

void
recursivelyCollectGEPs(GetElementPtrInst &CurrGEP,
ArrayType *FlattenedArrayType, Value *PtrOperand,
Expand Down Expand Up @@ -218,6 +225,26 @@ bool DXILFlattenArraysVisitor::visitAllocaInst(AllocaInst &AI) {
return true;
}

void DXILFlattenArraysVisitor::collectIndicesAndDimsFromGEP(
GetElementPtrInst &GEP, SmallVectorImpl<Value *> &Indices,
SmallVectorImpl<uint64_t> &Dims, bool &AllIndicesAreConstInt) {

Type *CurrentType = GEP.getSourceElementType();

// Note index 0 is the ptr index.
for (Value *Index : llvm::drop_begin(GEP.indices(), 1)) {
Indices.push_back(Index);
AllIndicesAreConstInt &= isa<ConstantInt>(Index);

if (auto *ArrayTy = dyn_cast<ArrayType>(CurrentType)) {
Dims.push_back(ArrayTy->getNumElements());
CurrentType = ArrayTy->getElementType();
} else {
assert(false && "Expected array type in GEP chain");
}
}
}

void DXILFlattenArraysVisitor::recursivelyCollectGEPs(
GetElementPtrInst &CurrGEP, ArrayType *FlattenedArrayType,
Value *PtrOperand, unsigned &GEPChainUseCount, SmallVector<Value *> Indices,
Expand All @@ -226,12 +253,8 @@ void DXILFlattenArraysVisitor::recursivelyCollectGEPs(
if (GEPChainMap.count(&CurrGEP) > 0)
return;

Value *LastIndex = CurrGEP.getOperand(CurrGEP.getNumOperands() - 1);
AllIndicesAreConstInt &= isa<ConstantInt>(LastIndex);
Indices.push_back(LastIndex);
assert(isa<ArrayType>(CurrGEP.getSourceElementType()));
Dims.push_back(
cast<ArrayType>(CurrGEP.getSourceElementType())->getNumElements());
// Collect indices and dimensions from the current GEP
collectIndicesAndDimsFromGEP(CurrGEP, Indices, Dims, AllIndicesAreConstInt);
bool IsMultiDimArr = isMultiDimensionalArray(CurrGEP.getSourceElementType());
if (!IsMultiDimArr) {
assert(GEPChainUseCount < FlattenedArrayType->getNumElements());
Expand Down Expand Up @@ -316,9 +339,12 @@ bool DXILFlattenArraysVisitor::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// Handle zero uses here because there won't be an update via
// a child in the chain later.
if (GEPChainUseCount == 0) {
SmallVector<Value *> Indices({GEP.getOperand(GEP.getNumOperands() - 1)});
SmallVector<uint64_t> Dims({ArrType->getNumElements()});
bool AllIndicesAreConstInt = isa<ConstantInt>(Indices[0]);
SmallVector<Value *> Indices;
SmallVector<uint64_t> Dims;
bool AllIndicesAreConstInt = true;

// Collect indices and dimensions from the GEP
collectIndicesAndDimsFromGEP(GEP, Indices, Dims, AllIndicesAreConstInt);
GEPData GEPInfo{std::move(FlattenedArrayType), PtrOperand,
std::move(Indices), std::move(Dims), AllIndicesAreConstInt};
return visitGetElementPtrInstInGEPChainBase(GEPInfo, GEP);
Expand Down
70 changes: 70 additions & 0 deletions llvm/test/CodeGen/DirectX/flatten-array.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -187,5 +187,75 @@ define void @global_gep_store() {
ret void
}

@g = local_unnamed_addr addrspace(3) global [2 x [2 x float]] zeroinitializer, align 4
define void @two_index_gep() {
; CHECK-LABEL: define void @two_index_gep(
; CHECK: [[THREAD_ID:%.*]] = tail call i32 @llvm.dx.thread.id(i32 0)
; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[THREAD_ID]], 2
; CHECK-NEXT: [[ADD:%.*]] = add i32 1, [[MUL]]
; CHECK-NEXT: [[GEP_PTR:%.*]] = getelementptr inbounds nuw [4 x float], ptr addrspace(3) @g.1dim, i32 0, i32 [[ADD]]
; CHECK-NEXT: load float, ptr addrspace(3) [[GEP_PTR]], align 4
; CHECK-NEXT: ret void
%1 = tail call i32 @llvm.dx.thread.id(i32 0)
%2 = getelementptr inbounds nuw [2 x [2 x float]], ptr addrspace(3) @g, i32 0, i32 %1, i32 1
%3 = load float, ptr addrspace(3) %2, align 4
ret void
}

define void @two_index_gep_const() {
; CHECK-LABEL: define void @two_index_gep_const(
; CHECK-NEXT: [[GEP_PTR:%.*]] = getelementptr inbounds nuw [4 x float], ptr addrspace(3) @g.1dim, i32 0, i32 3
; CHECK-NEXT: load float, ptr addrspace(3) [[GEP_PTR]], align 4
; CHECK-NEXT: ret void
%1 = getelementptr inbounds nuw [2 x [2 x float]], ptr addrspace(3) @g, i32 0, i32 1, i32 1
%3 = load float, ptr addrspace(3) %1, align 4
ret void
}

define void @gep_4d_index_test() {
; CHECK-LABEL: gep_4d_index_test
; CHECK: [[a:%.*]] = alloca [16 x i32], align 4
; CHECK-NEXT: getelementptr inbounds [16 x i32], ptr %.1dim, i32 0, i32 1
; CHECK-NEXT: getelementptr inbounds [16 x i32], ptr %.1dim, i32 0, i32 3
; CHECK-NEXT: getelementptr inbounds [16 x i32], ptr %.1dim, i32 0, i32 7
; CHECK-NEXT: getelementptr inbounds [16 x i32], ptr %.1dim, i32 0, i32 15
; CHECK-NEXT: ret void
%1 = alloca [2x[2 x[2 x [2 x i32]]]], align 4
%2 = getelementptr inbounds [2 x [2 x[2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 0, i32 0, i32 0, i32 1
%3 = getelementptr inbounds [2 x [2 x[2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 0, i32 0, i32 1, i32 1
%4 = getelementptr inbounds [2 x [2 x[2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 0, i32 1, i32 1, i32 1
%5 = getelementptr inbounds [2 x [2 x[2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 1, i32 1, i32 1, i32 1
ret void
}

define void @gep_4d_index_and_gep_chain_mixed() {
; CHECK-LABEL: gep_4d_index_and_gep_chain_mixed
; CHECK-NEXT: [[ALLOCA:%.*]] = alloca [16 x i32], align 4
; CHECK-COUNT-16: getelementptr inbounds [16 x i32], ptr [[ALLOCA]], i32 0, i32 {{[0-9]|1[0-5]}}
; CHECK-NEXT: ret void
%1 = alloca [2x[2 x[2 x [2 x i32]]]], align 4
%a4d0_0 = getelementptr inbounds [2 x [2 x [2 x [2 x i32]]]], [2 x [2 x[2 x [2 x i32]]]]* %1, i32 0, i32 0, i32 0
%a2d0_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %a4d0_0, i32 0, i32 0, i32 0
%a2d0_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %a4d0_0, i32 0, i32 0, i32 1
%a2d1_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %a4d0_0, i32 0, i32 1, i32 0
%a2d1_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %a4d0_0, i32 0, i32 1, i32 1
%b4d0_1 = getelementptr inbounds [2 x [2 x [2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 0, i32 1
%b2d0_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %b4d0_1, i32 0, i32 0, i32 0
%b2d0_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %b4d0_1, i32 0, i32 0, i32 1
%b2d1_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %b4d0_1, i32 0, i32 1, i32 0
%b2d1_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %b4d0_1, i32 0, i32 1, i32 1
%c4d1_0 = getelementptr inbounds [2 x [2 x [2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 1, i32 0
%c2d0_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %c4d1_0, i32 0, i32 0, i32 0
%c2d0_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %c4d1_0, i32 0, i32 0, i32 1
%c2d1_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %c4d1_0, i32 0, i32 1, i32 0
%c2d1_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %c4d1_0, i32 0, i32 1, i32 1
%g4d1_1 = getelementptr inbounds [2 x [2 x [2 x [2 x i32]]]], [2 x [2 x [2 x [2 x i32]]]]* %1, i32 0, i32 1, i32 1
%g2d0_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %g4d1_1, i32 0, i32 0, i32 0
%g2d0_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %g4d1_1, i32 0, i32 0, i32 1
%g2d1_0 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %g4d1_1, i32 0, i32 1, i32 0
%g2d1_1 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %g4d1_1, i32 0, i32 1, i32 1
ret void
}

; Make sure we don't try to walk the body of a function declaration.
declare void @opaque_function()
8 changes: 4 additions & 4 deletions llvm/test/CodeGen/DirectX/llc-vector-load-scalarize.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -111,13 +111,13 @@ define <4 x i32> @multid_load_test() #0 {
; CHECK-NEXT: [[TMP6:%.*]] = load i32, ptr addrspace(3) [[TMP5]], align 4
; CHECK-NEXT: [[TMP7:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 3) to ptr addrspace(3)
; CHECK-NEXT: [[TMP8:%.*]] = load i32, ptr addrspace(3) [[TMP7]], align 4
; CHECK-NEXT: [[TMP9:%.*]] = bitcast ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 1) to ptr addrspace(3)
; CHECK-NEXT: [[TMP9:%.*]] = bitcast ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 4) to ptr addrspace(3)
; CHECK-NEXT: [[TMP10:%.*]] = load i32, ptr addrspace(3) [[TMP9]], align 4
; CHECK-NEXT: [[TMP11:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 1), i32 1) to ptr addrspace(3)
; CHECK-NEXT: [[TMP11:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 4), i32 1) to ptr addrspace(3)
; CHECK-NEXT: [[TMP12:%.*]] = load i32, ptr addrspace(3) [[TMP11]], align 4
; CHECK-NEXT: [[TMP13:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 1), i32 2) to ptr addrspace(3)
; CHECK-NEXT: [[TMP13:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 4), i32 2) to ptr addrspace(3)
; CHECK-NEXT: [[TMP14:%.*]] = load i32, ptr addrspace(3) [[TMP13]], align 4
; CHECK-NEXT: [[TMP15:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 1), i32 3) to ptr addrspace(3)
; CHECK-NEXT: [[TMP15:%.*]] = bitcast ptr addrspace(3) getelementptr (i32, ptr addrspace(3) getelementptr inbounds ([36 x i32], ptr addrspace(3) @groushared2dArrayofVectors.scalarized.1dim, i32 0, i32 4), i32 3) to ptr addrspace(3)
; CHECK-NEXT: [[TMP16:%.*]] = load i32, ptr addrspace(3) [[TMP15]], align 4
; CHECK-NEXT: [[DOTI05:%.*]] = add i32 [[TMP2]], [[TMP10]]
; CHECK-NEXT: [[DOTI16:%.*]] = add i32 [[TMP4]], [[TMP12]]
Expand Down
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