[llvm] [SelectionDAG] Propagate poison in getNode with two operands if the second is poison. (PR #135387)

[Craig Topper via llvm-commits]

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@@ -7601,16 +7601,20 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
     case ISD::SDIV:
     case ISD::UREM:
     case ISD::SREM:
-      return getUNDEF(VT);       // fold op(arg1, undef) -> undef
+      // fold op(arg1, undef) -> undef, // fold op(arg1, poison) -> poison.
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topperc wrote:

Please also update the switch in the else block of the `N1.isUndef()` check on line 7573. We should be consistent about poison on both the left and right hand side for the same opcodes.

https://github.com/llvm/llvm-project/pull/135387