[llvm] [VectorCombine] Add Cmp and Select for shuffleToIdentity (PR #92794)

[Ramkumar Ramachandra via llvm-commits]

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@@ -1832,12 +1842,17 @@ bool VectorCombine::foldShuffleToIdentity(Instruction &I) {
 
     // Check the operator is one that we support. We exclude div/rem in case
     // they hit UB from poison lanes.
-    if (isa<BinaryOperator>(FrontV) &&
-        !cast<BinaryOperator>(FrontV)->isIntDivRem()) {
+    if ((isa<BinaryOperator>(FrontV) &&
+         !cast<BinaryOperator>(FrontV)->isIntDivRem()) ||
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artagnon wrote:

Use `dyn_cast` in place of `isa` + `cast`.

https://github.com/llvm/llvm-project/pull/92794