ref: 5a9f27d4e7ac352ec41113f804f13493a532b3f7 dir: /sys/src/libc/amd64/strlen.s/
TEXT strlen(SB),$0 MOVL $0, AX MOVQ $-1, CX CLD /* * look for end of string */ MOVQ RARG, DI REPN; SCASB MOVQ DI, AX SUBQ RARG, AX SUBQ $1, AX RET