[llvm] [X86] Optimized ADD + ADC to ADC (PR #173543)

[Phoebe Wang via llvm-commits]

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@@ -58164,6 +58164,16 @@ static SDValue combineX86AddSub(SDNode *N, SelectionDAG &DAG,
     }
   }
 
+  // Fold ADD(ADC(Y, C1, CF), C2) -> ADC(Y, C1 + C2, CF)
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phoebewang wrote:

As Craig mentioned, the combine has overflow difference. It happens even if C1 = 0. So C1 + C2 overflow doesn't matter.

https://github.com/llvm/llvm-project/pull/173543