[llvm] [WIP][VectorCombine] Fold "shuffle (binop (shuffle, shuffle)), undef" --> "binop (shuffle), (shuffle)" (PR #114101)

[Alexey Bataev via llvm-commits]

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@@ -1400,6 +1401,92 @@ bool VectorCombine::scalarizeLoadExtract(Instruction &I) {
   return true;
 }
 
+/// Try to fold "shuffle (binop (shuffle, shuffle)), undef" into "binop (shuffle), (shuffle)".
+bool VectorCombine::foldPermuteOfBinops(Instruction &I) {
+  BinaryOperator *BinOp;
+  ArrayRef<int> OuterMask;
+  if (!match(&I,
+             m_Shuffle(m_OneUse(m_BinOp(BinOp)), m_Undef(), m_Mask(OuterMask))))
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alexey-bataev wrote:

I think need to check that OuterMask operates on a `binop` only, does not permute with undef value

https://github.com/llvm/llvm-project/pull/114101