[llvm] InstCombine: Fold shufflevector(select) and shufflevector(phi) (PR #113746)

[Yingwei Zheng via llvm-commits]

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@@ -2900,6 +2900,17 @@ Instruction *InstCombinerImpl::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   if (Instruction *I = foldIdentityPaddedShuffles(SVI))
     return I;
 
+  if (Constant *C = dyn_cast<Constant>(RHS)) {
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dtcxzyw wrote:

```suggestion
  if (isa<Constant>(RHS)) {
```

https://github.com/llvm/llvm-project/pull/113746