[llvm] [SLP]Fix crash costing minbw-resized splat gather subtree roots (PR #225410)

[via llvm-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-vectorizers

Author: Alexey Bataev (alexey-bataev)

<details>
<summary>Changes</summary>

Splat gather subtree roots have no parent entry, but the min-bitwidth
resize-cost block assumed every non-root node has one and dereferenced
a null user. Charge the resize-back cast to the node's original scalar
type instead, matching the cast emitted when the reusing gather nodes
consume the resized vector.

Fixes https://github.com/llvm/llvm-project/pull/218250#issuecomment-5776455495


---
Full diff: https://github.com/llvm/llvm-project/pull/225410.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+7-4) 
- (added) llvm/test/Transforms/SLPVectorizer/AArch64/splat-gather-subtree-minbw.ll (+75) 


``````````diff
The server is unavailable at this time. Please wait a few minutes before you try again.
``````````

</details>


https://github.com/llvm/llvm-project/pull/225410