[llvm] [TargetLowering] Change subtraction to do (LHS < RHS) XOR (RESULT < 0) (PR #150872)

[Craig Topper via llvm-commits]

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@@ -14497,6 +14497,35 @@ void RISCVTargetLowering::ReplaceNodeResults(SDNode *N,
     Results.push_back(customLegalizeToWOp(N, DAG, ExtOpc));
     break;
   }
+  case ISD::SSUBO: {
+    assert(N->getValueType(0) == MVT::i32 && Subtarget.is64Bit() &&
+           "Unexpected custom legalisation");
+
+    // If the RHS is a constant, we can simplify ConditionRHS below. Otherwise
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topperc wrote:

There is no variable named `ConditionRHS` below

https://github.com/llvm/llvm-project/pull/150872