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

[Phoebe Wang via llvm-commits]

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@@ -46,6 +46,11 @@ class X86OpcodePrefixHelper {
   // | 40H | | WRXB |
   // +-----+ +------+
 
+  // REX2 (2 byte)
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phoebewang wrote:

2-byte or 2 bytes

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