ref: be15ce4a5cd95b86c8e4bd3fca6ce92624d8b01d dir: /sys/src/ape/lib/ap/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