[llvm] [X86][APX] Convert store(cmov(load(x), y), x) to cstore(y, x) (PR #118946)

[Simon Pilgrim via llvm-commits]

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@@ -52786,6 +52804,42 @@ static SDValue combineStore(SDNode *N, SelectionDAG &DAG,
     }
   }
 
+  // Convert store(cmov(load(x), y), x) to cstore(y, x).
+  if ((VT == MVT::i16 || VT == MVT::i32 || VT == MVT::i64) &&
+      Subtarget.hasCF() && St->isSimple()) {
+    SDValue Cmov;
+    if (StoredVal.getOpcode() == X86ISD::CMOV)
+      Cmov = StoredVal;
+    else if (StoredVal.getOpcode() == ISD::TRUNCATE &&
+             StoredVal.getOperand(0).getOpcode() == X86ISD::CMOV)
+      Cmov = StoredVal.getOperand(0);
+    else
+      return SDValue();
+
+    auto *Ld = dyn_cast<LoadSDNode>(St->getChain());
+    if (!Ld || !Ld->isSimple() || Ld->getBasePtr() != St->getBasePtr())
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RKSimon wrote:

check for ext load?

https://github.com/llvm/llvm-project/pull/118946