ref: 7d0cb59987f5c5c70cf55e35e65aa6b7a5bc460e dir: /src/clz.386.s/
TEXT h264bsdCountLeadingZeros(SB),$0 BYTE $0x0F; BYTE $0xBD; BYTE $0xC5 /* BSRL RARG, AX */ XORL $31, AX RET