From 2ffb22d2ad014e7fa8ee4c24263eb03abb9e86e5 Mon Sep 17 00:00:00 2001
From: Zuxy Meng <zuxy.meng@gmail.com>
Date: Sun, 5 Mar 2006 20:25:18 +0000
Subject: [PATCH] use xorps instead of mulps to toggle the sign of a float, as
suggested by Software Optimization Guide for AMD64 Processors. Patch by Zuxy
Meng < zuxy POIS meng AH gmail POIS com > OKed by Michael Original thread:
Date: Mar 5, 2006 8:15 PM Subject: [Ffmpeg-devel] [PATCH] Little optimization
to fft_sse.c
Originally committed as revision 5112 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
libavcodec/i386/fft_sse.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/libavcodec/i386/fft_sse.c b/libavcodec/i386/fft_sse.c
index 54851fb94f4..631848265a2 100644
--- a/libavcodec/i386/fft_sse.c
+++ b/libavcodec/i386/fft_sse.c
@@ -23,14 +23,14 @@
#include <xmmintrin.h>
-static const float p1p1p1m1[4] __attribute__((aligned(16))) =
- { 1.0, 1.0, 1.0, -1.0 };
+static const int p1p1p1m1[4] __attribute__((aligned(16))) =
+ { 0, 0, 0, 1 << 31 };
-static const float p1p1m1p1[4] __attribute__((aligned(16))) =
- { 1.0, 1.0, -1.0, 1.0 };
+static const int p1p1m1p1[4] __attribute__((aligned(16))) =
+ { 0, 0, 1 << 31, 0 };
-static const float p1p1m1m1[4] __attribute__((aligned(16))) =
- { 1.0, 1.0, -1.0, -1.0 };
+static const int p1p1m1m1[4] __attribute__((aligned(16))) =
+ { 0, 0, 1 << 31, 1 << 31 };
#if 0
static void print_v4sf(const char *str, __m128 a)
@@ -58,7 +58,6 @@ void ff_fft_calc_sse(FFTContext *s, FFTComplex *z)
r = (__m128 *)&z[0];
c1 = *(__m128 *)p1p1m1m1;
- c2 = *(__m128 *)p1p1p1m1;
if (s->inverse)
c2 = *(__m128 *)p1p1m1p1;
else
@@ -68,19 +67,20 @@ void ff_fft_calc_sse(FFTContext *s, FFTComplex *z)
do {
a = r[0];
b = _mm_shuffle_ps(a, a, _MM_SHUFFLE(1, 0, 3, 2));
- a = _mm_mul_ps(a, c1);
+ a = _mm_xor_ps(a, c1);
/* do the pass 0 butterfly */
a = _mm_add_ps(a, b);
a1 = r[1];
b = _mm_shuffle_ps(a1, a1, _MM_SHUFFLE(1, 0, 3, 2));
- a1 = _mm_mul_ps(a1, c1);
+ a1 = _mm_xor_ps(a1, c1);
/* do the pass 0 butterfly */
b = _mm_add_ps(a1, b);
/* multiply third by -i */
+ /* by toggling the sign bit */
b = _mm_shuffle_ps(b, b, _MM_SHUFFLE(2, 3, 1, 0));
- b = _mm_mul_ps(b, c2);
+ b = _mm_xor_ps(b, c2);
/* do the pass 1 butterfly */
r[0] = _mm_add_ps(a, b);
--
GitLab