[llvm] [SeparateConstOffsetFromGEP] Fix offsets across trunc and ext (PR #225195)

[via llvm-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Alex MacLean (AlexMaclean)

<details>
<summary>Changes</summary>

Stop extracting offsets from arithmetic through a truncation followed by sign or zero extension.

[Compiler Explorer reproducer](https://godbolt.org/z/xK1WTT7nY) and [Alive2 counterexample](https://alive2.llvm.org/ce/z/KWcMNZ).


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Full diff: https://github.com/llvm/llvm-project/pull/225195.diff


3 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp (+2) 
- (modified) llvm/test/Transforms/SeparateConstOffsetFromGEP/NVPTX/split-gep.ll (+5-3) 
- (added) llvm/test/Transforms/SeparateConstOffsetFromGEP/NVPTX/trunc-ext.ll (+115) 


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</details>


https://github.com/llvm/llvm-project/pull/225195