ref: 511421003a44633d8907828aef280acc762cc56b dir: /sys/src/libc/riscv64/cycles.s/
#define RARG R8 /* user-accessible CSRs */ #define CYCLO 0xc00 TEXT cycles(SB), 1, $-4 /* cycles since power up */ MOV CSR(CYCLO), RARG RET