[llvm] [SelectionDAG] Treat CopyFromReg as freezing the value (PR #85932)

[Matt Arsenault via llvm-commits]

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@@ -5012,6 +5012,10 @@ bool SelectionDAG::isGuaranteedNotToBeUndefOrPoison(SDValue Op,
   case ISD::TargetFrameIndex:
     return true;
 
+  case ISD::CopyFromReg:
+    // Treat CopyFromReg as freezing the value.
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arsenm wrote:

Just add to the case above handling FrameIndex and co? Don't need the special comment?

https://github.com/llvm/llvm-project/pull/85932