[all-commits] [llvm/llvm-project] 4b4699: [InstCombine] Don't cover up poison elements for s...
Luke Lau via All-commits
all-commits at lists.llvm.org
Sat May 24 05:47:39 PDT 2025
Branch: refs/heads/main
Home: https://github.com/llvm/llvm-project
Commit: 4b4699a13c9d05fa828b06bf398f1432ff3d9fb8
https://github.com/llvm/llvm-project/commit/4b4699a13c9d05fa828b06bf398f1432ff3d9fb8
Author: Luke Lau <luke at igalia.com>
Date: 2025-05-24 (Sat, 24 May 2025)
Changed paths:
M llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
M llvm/test/Transforms/InstCombine/vec_shuffle-inseltpoison.ll
M llvm/test/Transforms/InstCombine/vec_shuffle.ll
M llvm/test/Transforms/LoopVectorize/AArch64/deterministic-type-shrinkage.ll
Log Message:
-----------
[InstCombine] Don't cover up poison elements for shifts when folding shuffles thru binops (#141303)
As noted in the TODO, we don't need to cover up the poison elements
placed in the unused lanes for shifts, since it's not UB unlike div/rem.
New poison elements are only introduced in cases like
ShMask = <1,1,2,2> and C = <5,5,6,6> --> NewC = <poison,5,6,poison>
And the resulting shuffle won't use the poison lanes.
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