ref: a6d852d0a63c3804fa651fdb8abbf6893f898afd dir: /sys/src/ape/lib/ap/amd64/cycles.s/
TEXT _cycles(SB),1,$0 /* time stamp counter; cycles since power up */ RDTSC MOVL AX, 0(RARG) /* lo */ MOVL DX, 4(RARG) /* hi */ RET