[llvm] [InstCombine] Pull extract through broadcast (PR #143380)
Simon Pilgrim via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 25 01:56:36 PDT 2025
https://github.com/RKSimon approved this pull request.
LGTM @nikic any more comments? whether we're happy with out of bounds extraction from a known splat (possibly with undef shuffle indices) seems to be the only outstanding issue
```
define i4 @src(i4 %x) {
%v = insertelement <4 x i4> poison, i4 %x, i32 0
%s = shufflevector <4 x i4> %v, <4 x i4> poison, 0, 0, 4294967295, 0
%e = extractelement <4 x i4> %s, i32 4294967295
ret i4 %e
}
=>
define i4 @tgt(i4 %x) {
ret i4 %x
}
Transformation seems to be correct!
```
https://github.com/llvm/llvm-project/pull/143380
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