[llvm] [X86] combineTargetShuffle - fold VPERMV3(HI,MASK,LO) -> VPERMV(COMMUTE(MASK),CONCAT(LO,HI)) (PR #127199)

[Phoebe Wang via llvm-commits]

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@@ -42530,9 +42531,25 @@ static SDValue combineTargetShuffle(SDValue N, const SDLoc &DL,
     SmallVector<int, 32> Mask;
     if (getTargetShuffleMask(N, /*AllowSentinelZero=*/false, SrcOps, Mask)) {
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phoebewang wrote:

What happened under this condition? Why can't we unconditionally switch LO HI like above?

https://github.com/llvm/llvm-project/pull/127199