Intel assembly timer routines for gcc inline asm

timers.h

#include <stdint.h>

// from http://download.intel.com/embedded/software/IA/324264.pdf
#define rdtscp_before() \
    ({ uint32_t cycles_high, cycles_low; \
    __asm__ volatile ("CPUID\n\t" \
                      "RDTSC\n\t" \
                      "mov %%edx, %0\n\t" \
                      "mov %%eax, %1\n\t": "=r" (cycles_high), "=r" (cycles_low)::  \
                      "%rax", "%rbx", "%rcx", "%rdx"); \
    (uint64_t)((uint64_t)cycles_high << 32) + cycles_low; })

#define rdtscp_after() \
    ({ uint32_t cycles_high, cycles_low; \
    __asm__ volatile ( "RDTSC\n\t" \
                      "mov %%edx, %0\n\t" \
                      "mov %%eax, %1\n\t" \
                      "CPUID\n\t" : "=r" (cycles_high), "=r" (cycles_low)::  \
                      "%rax", "%rbx", "%rcx", "%rdx"); \
    (uint64_t)((uint64_t)cycles_high << 32) + cycles_low; })