如何将__m128反转为整数

Question

float a[4] = {1,2,3,4}, b[4] = {4,3,2,1};
uint32_t c[4];

int main() {

    __m128 pa = _mm_loadu_ps(a);

    __m128 pb = _mm_loadu_ps(b);
    __m128 pc = _mm_cmpgt_ps(pa, pb);
    _mm_storeu_ps((float*)c, pc);
    for (int i = 0;i  < 4; ++i) printf("%u\n", c[i]);
    return 0;
}

什么是正确的指示_mm_storeu_ps((float*)c, pc)？在这里,c是一个整数数组......我不认为这种方式是好的,还是更好吗？

Answer 1

在SSE2中有两个指令将__m128(float向量)转换为__m128i(int32_t向量):( _mm_cvtps_epi32带有舍入)和_mm_cvttps_epi32(带截断).

__m128i vi = _mm_cvttps_epi32(pc);
_mm_storeu_si128((__m128i *)c, vi);

如果你不能用SSE2,你应该转换float阵列int存储阵列后pc进入float阵列.

float d[4];
_mm_storeu_ps(d, pc);
c[0] = (int)d[0]; c[1] = (int)d[1]; c[2] = (int)d[2]; c[3] = (int)d[3];