[llvm] [TailDup][MachineSSAUpdater] Let RewriteUse insert a COPY when needed (PR #95553)

[Matt Arsenault via llvm-commits]

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@@ -236,6 +236,20 @@ void MachineSSAUpdater::RewriteUse(MachineOperand &U) {
     NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
   }
 
+  // Insert a COPY if needed to satisfy register class constraints for the using
+  // MO. Or, if possible, just constrain the class for NewVR to avoid the need
+  // for a COPY.
+  const TargetRegisterClass *UseRC =
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arsenm wrote:

Could ink the dyn_cast under the NewVR check, I guess s

https://github.com/llvm/llvm-project/pull/95553