测试指令集在不同优化等级下生成汇编代码对比

demo.c

#include <stdio.h>
#include <stdint.h>
#include <string.h>


#if defined(__AVX__)
  #include <immintrin.h>
#endif

#if defined(__SSE2__)
  #include <emmintrin.h>
#endif

static void* libc_memcpy(char *dst, const char* src, size_t len) {
  return memcpy(dst, src, len);
}

static void* simd_memcpy(char *dst, const char* src, size_t len) {
  void *ptr = dst;
#if defined(__AVX__)
  while(len >= 32)
  {
    _mm256_store_si256((__m256i*)dst, (__m256i)*(__m256i*)src);
    len -= 32; dst += 32; src += 32; 
  }
#endif
#if defined(__SSE2__)
  while(len >= 16)
  {
    _mm_storeu_si128((__m128i*)dst, (__m128i)*(__m128i*)src);
    len -= 16; dst += 16; src += 16;
  }
#endif
  while (len >= 8)
  {
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
  }
  while (len >= 4)
  {
    ((int32_t*)dst)[0] = ((const int32_t*)src)[0];
    len -= 4; dst += 4; src += 4;
  }
  while (len >= 2)
  {
    ((int16_t*)dst)[0] = ((const int16_t*)src)[0];
    len -= 2; dst += 2; src += 2;
  }
  if (len)
    ((char*)dst)[0] = ((const char*)src)[0];
  return ptr;
}

static void* normal_memcpy(char *dst, const char* src, size_t len) {
  void *ptr = dst;
  while (len >= 32)
  {
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
  }
  while (len >= 16)
  {
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
  }
  while (len >= 8)
  {
    ((int64_t*)dst)[0] = ((const int64_t*)src)[0];
    len -= 8; dst += 8; src += 8;
  }
  while (len >= 4)
  {
    ((int32_t*)dst)[0] = ((const int32_t*)src)[0];
    len -= 4; dst += 4; src += 4;
  }
  while (len >= 2)
  {
    ((int16_t*)dst)[0] = ((const int16_t*)src)[0];
    len -= 2; dst += 2; src += 2;
  }
  if (len)
    ((char*)dst)[0] = ((const char*)src)[0];
  return ptr;
}
  
int main(int argc, const char* argv[])
{  
    /* 测试avx */
    const int n1 = 33;
    char ymmx_out[] = { [0 ... 32] = 0x0 };
    const char ymmx[] = "administrator123administrator123";
    simd_memcpy(ymmx_out, ymmx, n1);
    printf("simd_memcpy = [%s]\n", ymmx_out);
    normal_memcpy(ymmx_out, ymmx, n1);
    printf("normal_memcpy = [%s]\n", ymmx_out);
    libc_memcpy(ymmx_out, ymmx, n1);
    printf("libc_memcpy = [%s]\n", ymmx_out);

    /* 测试sse2 */
    const int n2 = 16;
    char mmx_out[] = { [0 ... 15] = 0x0 };
    const char mmx[] = "administrator123";
    simd_memcpy(mmx_out, mmx, n2);
    printf("simd_memcpy = [%s]\n", mmx_out);
    normal_memcpy(mmx_out, mmx, n2);
    printf("normal_memcpy = [%s]\n", mmx_out);
    libc_memcpy(mmx_out, mmx, n2);
    printf("libc_memcpy = [%s]\n", mmx_out);
    return 0;  
}