[llvm] [X86][NFC] Reorder the registers to reduce unnecessary iterations (PR #70222)

[Phoebe Wang via llvm-commits]

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@@ -1182,11 +1182,27 @@ namespace X86II {
     }
   }
 
+  inline bool isXMMReg(unsigned RegNo) {
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phoebewang wrote:

Add doxygen for them.

https://github.com/llvm/llvm-project/pull/70222