[llvm] [CodeGen][MRI] Introduce synthetic register classes (PR #86006)

[Yashwant Singh via llvm-commits]

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@@ -333,6 +333,7 @@ class CodeGenRegisterClass {
   uint8_t AllocationPriority;
   bool GlobalPriority;
   uint8_t TSFlags;
+  bool Synthetic;
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yashssh wrote:

Doc comment

https://github.com/llvm/llvm-project/pull/86006