[Mlir-commits] [mlir] [MLIR][OpenMP] Bail early in sortMapIndices if indices are the same (PR #169474)

[llvmlistbot at llvm.org]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mlir-openmp

Author: Aiden Grossman (boomanaiden154)

<details>
<summary>Changes</summary>

If we are given the same index in the comparator callback, simply return false. Otherwise we will end up adding invalid items to occludedChildren, causing extra items to get removed that should not be, resulting in failures that manifest in different forms (assertions, asan failures, ubsan failures, etc.).

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Full diff: https://github.com/llvm/llvm-project/pull/169474.diff


1 Files Affected:

- (modified) mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp (+6) 


``````````diff
diff --git a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
index 5511f4f1af1ad..98775c2d18bd4 100644
--- a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
@@ -4095,6 +4095,12 @@ static void sortMapIndices(llvm::SmallVectorImpl<size_t> &indices,
   llvm::SmallVector<size_t> occludedChildren;
   llvm::sort(
       indices.begin(), indices.end(), [&](const size_t a, const size_t b) {
+        // Bail early if we are asked to look at the same index. If we do not
+        // bail early, we can end up mistakenly adding indices to
+        // occludedChildren. This can occur with some types of libc++ hardening.
+        if (a == b)
+          return false;
+
         auto memberIndicesA = cast<ArrayAttr>(indexAttr[a]);
         auto memberIndicesB = cast<ArrayAttr>(indexAttr[b]);
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/169474