ref: c3ba64f6935322f09b6de5c2285544fd471c605d
dir: /sys/src/libc/power/cycles.s/
#define TBRL 268 #define TBRU 269 /* Time base Upper/Lower (Reading) */ /* * time stamp counter; _cycles since power up * Runs at fasthz/4 cycles per second (m->clkin>>3) */ TEXT cycles(SB),1,$0 loop: MOVW SPR(TBRU),R7 MOVW SPR(TBRL),R8 MOVW SPR(TBRU),R5 CMP R5,R7 BNE loop MOVW R7,0(R3) MOVW R8,4(R3) RETURN