[llvm] [X86][MC] Support encoding of EGPR for APX (PR #71909)

[Phoebe Wang via llvm-commits]

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@@ -1208,6 +1208,11 @@ namespace X86II {
     return RegNo >= X86::ZMM0 && RegNo <= X86::ZMM31;
   }
 
+  /// \returns true if \p RegNo is an apx extended register.
+  inline bool isApxExtendedReg(unsigned RegNo) {
+    return RegNo >= X86::R16 && RegNo <= X86::R31WH;
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phoebewang wrote:

Add an assert to make sure it won't be change in the future.

https://github.com/llvm/llvm-project/pull/71909