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

[Shengchen Kan via llvm-commits]

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@@ -217,6 +271,12 @@ class X86OpcodePrefixHelper {
     case REX:
       emitByte(0x40 | W << 3 | R << 2 | X << 1 | B, CB);
       return;
+    case REX2:
+      emitByte(0xD5, CB);
+      emitByte(M << 7 | R2 << 6 | X2 << 5 | B2 << 4 | W << 3 | R << 2 | X << 1 |
+                   B,
+               CB);
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KanRobert wrote:

Done

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