如何将浮点向量向上/向下舍入到最接近的整数,就像这些函数一样?
Round - __m128
Ceil - roundf()
或SSE4.1ceilf()
。
Floor - _mm_ceil_ps
或SSE4.1floorf()
。
我需要在没有SSE4.1_mm_floor_ps
(roundps
/_mm_floor_ps
/_mm_ceil_ps
的情况下执行此操作_mm_round_ps(x, _MM_FROUND_TO_NEAREST_INT |_MM_FROUND_NO_EXC)
也可以截断为零,但对于这个应用程序,我不需要这样做。
我可以用SSE3和更早的(无SSSE3或SSE4)
所以函数声明如下:roundps
、__m128 RoundSse( __m128 x )
和__m128 CeilSse( __m128 x )
。
最佳答案
我将从http://dss.stephanierct.com/DevBlog/?p=8发布代码:
它应该采用按值形式(我刚从代码中删除了&
,不确定它是否正常):
static inline __m128 FloorSse(const __m128 x) {
__m128i v0 = _mm_setzero_si128();
__m128i v1 = _mm_cmpeq_epi32(v0, v0);
__m128i ji = _mm_srli_epi32(v1, 25);
__m128i tmp = _mm_slli_epi32(ji, 23); // I edited this (Added tmp) not sure about it
__m128 j = _mm_castsi128_ps(tmp); //create vector 1.0f // I edited this not sure about it
__m128i i = _mm_cvttps_epi32(x);
__m128 fi = _mm_cvtepi32_ps(i);
__m128 igx = _mm_cmpgt_ps(fi, x);
j = _mm_and_ps(igx, j);
return _mm_sub_ps(fi, j);
}
static inline __m128 CeilSse(const __m128 x) {
__m128i v0 = _mm_setzero_si128();
__m128i v1 = _mm_cmpeq_epi32(v0, v0);
__m128i ji = _mm_srli_epi32(v1, 25);
__m128i tmp = _mm_slli_epi32(ji, 23); // I edited this (Added tmp) not sure about it
__m128 j = _mm_castsi128_ps(tmp); //create vector 1.0f // I edited this not sure about it
__m128i i = _mm_cvttps_epi32(x);
__m128 fi = _mm_cvtepi32_ps(i);
__m128 igx = _mm_cmplt_ps(fi, x);
j = _mm_and_ps(igx, j);
return _mm_add_ps(fi, j);
}
static inline __m128 RoundSse(const __m128 a) {
__m128 v0 = _mm_setzero_ps(); //generate the highest value < 2
__m128 v1 = _mm_cmpeq_ps(v0, v0);
__m128i tmp = _mm_castps_si128(v1); // I edited this (Added tmp) not sure about it
tmp = _mm_srli_epi32(tmp, 2); // I edited this (Added tmp) not sure about it
__m128 vNearest2 = _mm_castsi128_ps(tmp); // I edited this (Added tmp) not sure about it
__m128i i = _mm_cvttps_epi32(a);
__m128 aTrunc = _mm_cvtepi32_ps(i); // truncate a
__m128 rmd = _mm_sub_ps(a, aTrunc); // get remainder
__m128 rmd2 = _mm_mul_ps(rmd, vNearest2); // mul remainder by near 2 will yield the needed offset
__m128i rmd2i = _mm_cvttps_epi32(rmd2); // after being truncated of course
__m128 rmd2Trunc = _mm_cvtepi32_ps(rmd2i);
__m128 r = _mm_add_ps(aTrunc, rmd2Trunc);
return r;
}
inline __m128 ModSee(const __m128 a, const __m128 aDiv) {
__m128 c = _mm_div_ps(a, aDiv);
__m128i i = _mm_cvttps_epi32(c);
__m128 cTrunc = _mm_cvtepi32_ps(i);
__m128 base = _mm_mul_ps(cTrunc, aDiv);
__m128 r = _mm_sub_ps(a, base);
return r;
}