[llvm] [SLP] Sort PHIs by ExtractElements when relevant (PR #131229)

[Matt Arsenault via llvm-commits]

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@@ -22690,8 +22690,41 @@ bool SLPVectorizerPass::vectorizeChainsInBlock(BasicBlock *BB, BoUpSLP &R) {
           if (NodeI1 != NodeI2)
             return NodeI1->getDFSNumIn() < NodeI2->getDFSNumIn();
           InstructionsState S = getSameOpcode({I1, I2}, *TLI);
-          if (S && !S.isAltShuffle())
+          if (S && !S.isAltShuffle()) {
+            if (!isa<ExtractElementInst>(I1) || !isa<ExtractElementInst>(I2))
+              continue;
+
+            auto E1 = cast<ExtractElementInst>(I1);
+            auto E2 = cast<ExtractElementInst>(I2);
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arsenm wrote:

dyn_cast instead of isa and cast. Also const auto *

https://github.com/llvm/llvm-project/pull/131229