rdtsc_usage.md

#define USE_RDTSC 1

static inline unsigned long long rdtsc(void) {
    unsigned long long r;
    __asm__ __volatile__ ("rdtsc\n"
                          "shl $32,%%rdx\n"
                          "or %%rdx,%%rax\n"
                          "movq %%rax,%0" : "=r"(r) : : "edx", "eax", "rdx", "rax");
    return r;
}