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

[Alexey Bataev via llvm-commits]

================
@@ -22690,8 +22690,40 @@ 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()) {
+            const auto *E1 = dyn_cast<ExtractElementInst>(I1);
+            const auto *E2 = dyn_cast<ExtractElementInst>(I2);
+            if (!E1 || !E2)
+              continue;
+
+            // Sort on ExtractElementInsts primarily by vector operands. Prefer
+            // program order of the vector operands.
+            if (E1->getVectorOperand() != E2->getVectorOperand()) {
+              const Instruction *V1 =
+                  dyn_cast<Instruction>(E1->getVectorOperand());
+              const Instruction *V2 =
+                  dyn_cast<Instruction>(E2->getVectorOperand());
----------------
alexey-bataev wrote:

```suggestion
              const auto *V1 =
                  dyn_cast<Instruction>(E1->getVectorOperand());
              const auto *V2 =
                  dyn_cast<Instruction>(E2->getVectorOperand());
```

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