The x86 ISA has (at least) two encodings for PEXTRW:
1. in the SSE2 opcode (66 0f c5) the XMM operand uses r/m and the GPR operand uses reg
2. in the SSE4.1 opcode (66 0f 3a 15) the XMM operand uses reg and the GPR operand uses r/m
This changes the 16-bit x86_pextr encoding from 1 to 2 to match the other PEXTR* implementations (all #2 style).