ref: 1aa8352b43390f548da154b82b0b50e295d9c03f dir: /sys/src/libc/riscv64/cycles.s/
/* user-accessible CSRs */ #define CYCLO 0xc00 TEXT cycles(SB), 1, $-4 /* cycles since power up */ MOV CSR(CYCLO), RARG RET