[llvm] [SLP]Look through truncation of shifted extracted sub-fields (PR #226803)

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llvmorg-github-actions[bot] wrote:


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

@llvm/pr-subscribers-llvm-transforms

Author: Alexey Bataev (alexey-bataev)

<details>
<summary>Changes</summary>

The masked sub-field of the shifted truncation of a wider scalar was
matched with the truncation as its source, while the other fields
matched the scalar itself, so the gather of the fields was rejected.
The field is within the truncated bits, look through the truncation.

Fixes #<!-- -->74380


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Full diff: https://github.com/llvm/llvm-project/pull/226803.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer/SLPUtils.cpp (+4-1) 
- (modified) llvm/test/Transforms/SLPVectorizer/X86/extracted-subfields-shifted-trunc.ll (+2-12) 


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</details>


https://github.com/llvm/llvm-project/pull/226803