[AMDGPU][LowerBufferFatPointers] Fix lack of rewrite when loading/storing null #154128
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…ring null Fixes llvm#154056. The fat buffer lowering pass was erroniously detecting that it did not need to run on functions that only load/store to the null constant (or other such constants). We thought this would be covered by specilaizing constants out to instructions, but that doesn't account foc trivial constants like null. Therefoe, we check the operands of instructions for buffer fat pointers in order to find such constants and ensure the pass runs.
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@llvm/pr-subscribers-backend-amdgpu Author: Krzysztof Drewniak (krzysz00) ChangesFixes #154056. The fat buffer lowering pass was erroniously detecting that it did not need to run on functions that only load/store to the null constant (or other such constants). We thought this would be covered by specilaizing constants out to instructions, but that doesn't account foc trivial constants like null. Therefoe, we check the operands of instructions for buffer fat pointers in order to find such constants and ensure the pass runs. Full diff: https://github.com/llvm/llvm-project/pull/154128.diff 1 Files Affected:
diff --git a/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp b/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp
index ed73dc8903908..7090bc8124f9c 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp
@@ -2366,8 +2366,12 @@ static bool containsBufferFatPointers(const Function &F,
BufferFatPtrToStructTypeMap *TypeMap) {
bool HasFatPointers = false;
for (const BasicBlock &BB : F)
- for (const Instruction &I : BB)
+ for (const Instruction &I : BB) {
HasFatPointers |= (I.getType() != TypeMap->remapType(I.getType()));
+ // Catch null pointer constasts in loads, stores, etc.
+ for (const Value *V : I.operand_values())
+ HasFatPointers |= (V->getType() != TypeMap->remapType(V->getType()));
+ }
return HasFatPointers;
}
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Forgot the test lol |
Co-authored-by: Nikita Popov <[email protected]>
arsenm
reviewed
Aug 18, 2025
| ; | ||
| store i32 0, ptr addrspace(7) null, align 4 | ||
| ret void | ||
| } |
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Can you also test the poison case
arsenm
approved these changes
Aug 18, 2025
nikic
approved these changes
Aug 18, 2025
…ect into store-to-null-crashes
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Fixes #154056.
The fat buffer lowering pass was erroniously detecting that it did not need to run on functions that only load/store to the null constant (or other such constants). We thought this would be covered by specializing constants out to instructions, but that doesn't account foc trivial constants like null. Therefore, we check the operands of instructions for buffer fat pointers in order to find such constants and ensure the pass runs.