[flang-commits] [flang] [flang] fix hlfir stack merging issue on AIX (PR #78435)

[via flang-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-flang-fir-hlfir

Author: None (madanial0)

<details>
<summary>Changes</summary>

When running the `flang/test/HLFIR/simplify-hlfir-intrinsics.fir` test case on AIX we encounter issues building op as they are not found in the mlir context:
```
LLVM ERROR: Building op `arith.subi` but it isn't known in this MLIRContext: the dialect may not be loaded or this operation hasn't been added by the dialect. See also https://mlir.llvm.org/getting_started/Faq/#registered-loaded-dependent-whats-up-with-dialects-management
LLVM ERROR: Building op `hlfir.yield_element` but it isn't known in this MLIRContext: the dialect may not be loaded or this operation hasn't been added by the dialect. See also https://mlir.llvm.org/getting_started/Faq/#registered-loaded-dependent-whats-up-with-dialects-management
LLVM ERROR: Building op `hlfir.yield_element` but it isn't known in this MLIRContext: the dialect may not be loaded or this operation hasn't been added by the dialect. See also https://mlir.llvm.org/getting_started/Faq/#registered-loaded-dependent-whats-up-with-dialects-management
```
The issue is caused by the "Merge disjoint stack slots" pass and the error is not present if the source is built with `-mllvm --no-stack-coloring`  

Thanks to investigation by @<!-- -->stefanp-ibm we found that "the initializer_list {inputIndices[1], inputIndices[0]} has a lifetime that only exists for the range of the constructor for ValueRange. Once we get to stack coloring we merge the stack slot for that element with another stack slot and then it gets overwritten which corrupts transposedIndices"

The changes below prevents the corruption of transposedIndices and passes the test case.

---
Full diff: https://github.com/llvm/llvm-project/pull/78435.diff


2 Files Affected:

- (modified) flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp (+2-1) 
- (modified) flang/test/HLFIR/simplify-hlfir-intrinsics.fir (-3) 


``````````diff
diff --git a/flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp b/flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp
index 5f065056bac00c..c15ea737366c71 100644
--- a/flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp
+++ b/flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp
@@ -50,7 +50,8 @@ class TransposeAsElementalConversion
     auto genKernel = [&array](mlir::Location loc, fir::FirOpBuilder &builder,
                               mlir::ValueRange inputIndices) -> hlfir::Entity {
       assert(inputIndices.size() == 2 && "checked in TransposeOp::validate");
-      mlir::ValueRange transposedIndices{{inputIndices[1], inputIndices[0]}};
+      const std::initializer_list<mlir::Value> initList = {inputIndices[1], inputIndices[0]};
+      mlir::ValueRange transposedIndices(initList);
       hlfir::Entity element =
           hlfir::getElementAt(loc, builder, array, transposedIndices);
       hlfir::Entity val = hlfir::loadTrivialScalar(loc, builder, element);
diff --git a/flang/test/HLFIR/simplify-hlfir-intrinsics.fir b/flang/test/HLFIR/simplify-hlfir-intrinsics.fir
index b63ddf17515281..aeea8bfc973266 100644
--- a/flang/test/HLFIR/simplify-hlfir-intrinsics.fir
+++ b/flang/test/HLFIR/simplify-hlfir-intrinsics.fir
@@ -1,6 +1,3 @@
-// XFail the following test case on AIX due to potential miscompilation
-// TODO: Crash fir-opt on AIX
-// XFAIL: system-aix
 // RUN: fir-opt --simplify-hlfir-intrinsics %s | FileCheck %s
 
 // box with known extents

``````````

</details>


https://github.com/llvm/llvm-project/pull/78435