4个32位整数的SSE乘法 [英] SSE multiplication of 4 32-bit integers

问题描述

如何将四个32位整数乘以另外4个整数? 我没有找到任何可以做得到的指令.

How to multiply four 32-bit integers by another 4 integers? I didn't find any instruction which can do it.

推荐答案

如果需要 signed 32x32位整数乘法，则以下示例位于

If you need signed 32x32 bit integer multiplication then the following example at software.intel.com looks like it should do what you want:

static inline __m128i muly(const __m128i &a, const __m128i &b)
{
    __m128i tmp1 = _mm_mul_epu32(a,b); /* mul 2,0*/
    __m128i tmp2 = _mm_mul_epu32( _mm_srli_si128(a,4), _mm_srli_si128(b,4)); /* mul 3,1 */
    return _mm_unpacklo_epi32(_mm_shuffle_epi32(tmp1, _MM_SHUFFLE (0,0,2,0)), _mm_shuffle_epi32(tmp2, _MM_SHUFFLE (0,0,2,0))); /* shuffle results to [63..0] and pack */
}

您可能希望拥有两个版本-一个用于旧CPU，一个用于最新CPU，在这种情况下，您可以执行以下操作:

You might want to have two builds - one for old CPUs and one for recent CPUs, in which case you could do the following:

static inline __m128i muly(const __m128i &a, const __m128i &b)
{
#ifdef __SSE4_1__  // modern CPU - use SSE 4.1
    return _mm_mullo_epi32(a, b);
#else               // old CPU - use SSE 2
    __m128i tmp1 = _mm_mul_epu32(a,b); /* mul 2,0*/
    __m128i tmp2 = _mm_mul_epu32( _mm_srli_si128(a,4), _mm_srli_si128(b,4)); /* mul 3,1 */
    return _mm_unpacklo_epi32(_mm_shuffle_epi32(tmp1, _MM_SHUFFLE (0,0,2,0)), _mm_shuffle_epi32(tmp2, _MM_SHUFFLE (0,0,2,0))); /* shuffle results to [63..0] and pack */
#endif
}

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