[llvm] [VectorCombine] Scalarize binop-like intrinsics (PR #138095)

[Luke Lau via llvm-commits]

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@@ -1135,9 +1167,16 @@ bool VectorCombine::scalarizeBinopOrCmp(Instruction &I) {
     ScalarInst->copyIRFlags(&I);
 
   // Fold the vector constants in the original vectors into a new base vector.
-  Value *NewVecC =
-      IsCmp ? Builder.CreateCmp(Pred, VecC0, VecC1)
-            : Builder.CreateBinOp((Instruction::BinaryOps)Opcode, VecC0, VecC1);
+  Value *NewVecC;
+  if (isa<CmpInst>(I))
+    NewVecC = Builder.CreateCmp(Pred, VecC0, VecC1);
+  else if (isa<BinaryOperator>(I))
+    NewVecC = Builder.CreateBinOp((Instruction::BinaryOps)Opcode, VecC0, VecC1);
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lukel97 wrote:

I presume the reason why this hasn't caused more issues in the wild is because InstCombine won't pull the shufflevector out if it's not safe to speculate, so VectorCombine won't match on it.

https://github.com/llvm/llvm-project/pull/138095