[llvm] [X86][MC] Support encoding/decoding for APX variant ADD/SUB/ADC/SBB/OR/XOR instructions (PR #76319)

[Phoebe Wang via llvm-commits]

================
@@ -1576,6 +1603,8 @@ void X86MCCodeEmitter::encodeInstruction(const MCInst &MI,
 
     if (HasVEX_4V) // Skip 1st src (which is encoded in VEX_VVVV)
       ++SrcRegNum;
+    if (IsND) // Skip the NDD operand encoded in EVEX_VVVV
+      ++CurOp;
----------------
phoebewang wrote:

It's not clear from code, maybe `if (IsND || HasVEX_4V)`?

https://github.com/llvm/llvm-project/pull/76319