[llvm] [RISCV] Make single source reverse legal in isShuffleMaskLegal (PR #125949)

[Craig Topper via llvm-commits]

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@@ -5811,6 +5811,11 @@ bool RISCVTargetLowering::isShuffleMaskLegal(ArrayRef<int> M, EVT VT) const {
   if (SVT.getScalarType() == MVT::i1)
     return false;
 
+  unsigned NumElts = M.size();
+  if (ShuffleVectorInst::isReverseMask(M, NumElts) &&
+      ShuffleVectorInst::isSingleSourceMask(M, NumElts))
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topperc wrote:

I think isReverseMask checks isSingleSourceMask.

https://github.com/llvm/llvm-project/pull/125949