[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)) {
       assert(Mask.size() == NumElts && "Unexpected shuffle mask size");
+      // See if we can concatenate the commuted operands.
+      if (VT.is128BitVector() ||
+          (VT.is256BitVector() && Subtarget.useAVX512Regs())) {
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phoebewang wrote:

Hoist it with `bool CanConcatenate = ...`

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