[llvm] [AMDGPU] Insert spill codes for the SGPRs used for EXEC copy (PR #79428)

[Matt Arsenault via llvm-commits]

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@@ -137,5 +137,10 @@ bool SILowerWWMCopies::runOnMachineFunction(MachineFunction &MF) {
     }
   }
 
+  // SGPRs reserved for exec copy should be preserved as we encountered WWM_COPY
+  // instances.
+  if (Changed)
+    MFI->setPreserveExecCopyReservedReg();
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arsenm wrote:

Do you really need to track a separate field for this? Can't you just check if RegForExecCopy is used?

https://github.com/llvm/llvm-project/pull/79428