Adds SSE support (only xcorr_kernel() for now)

There's no CPU detection for it, it only gets enabled by __SSE__
which gcc (other compilers?) defines automatically when supported
by -march=, which means at least all x86-64. For ia32, the user needs to
enable it in the CFLAGS.

celt/pitch.h

@@ -36,6 +36,10 @@
 
 #include "modes.h"
 
+#ifdef __SSE__
+#include "x86/pitch_sse.h"
+#endif
+
 void pitch_downsample(celt_sig * OPUS_RESTRICT x[], opus_val16 * OPUS_RESTRICT x_lp,
       int len, int C);
 
@@ -47,6 +51,7 @@ opus_val16 remove_doubling(opus_val16 *x, int maxperiod, int minperiod,
 
 /* OPT: This is the kernel you really want to optimize. It gets used a lot
    by the prefilter and by the PLC. */
+#ifndef OVERRIDE_XCORR_KERNEL
 static inline void xcorr_kernel(const opus_val16 * x, const opus_val16 * y, opus_val32 sum[4], int len)
 {
    int j;
@@ -111,6 +116,7 @@ static inline void xcorr_kernel(const opus_val16 * x, const opus_val16 * y, opus
       sum[3] = MAC16_16(sum[3],tmp,y_1);
    }
 }
+#endif /* OVERRIDE_XCORR_KERNEL */
 
 #ifdef FIXED_POINT
 opus_val32

celt/x86/pitch_sse.h

+/* Copyright (c) 2013 Xiph.Org Foundation
+   Written by Jean-Marc Valin */
+/**
+   @file pitch_sse.h
+   @brief Pitch analysis
+ */
+
+/*
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+
+   - Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+
+   - Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#ifndef PITCH_SSE_H
+#define PITCH_SSE_H
+
+#include <xmmintrin.h>
+#include "arch.h"
+
+#define OVERRIDE_XCORR_KERNEL
+
+static inline void xcorr_kernel(const opus_val16 * _x, const opus_val16 * _y, opus_val32 _sum[4], int len)
+{
+   int j;
+   __m128 sum;
+   __m128 x;
+   __m128 y;
+   __m128 y2;
+   __m128 y1;
+   __m128 y3;
+   __m128 tmp;
+   sum = _mm_loadu_ps(_sum);
+
+   x = _mm_loadu_ps(_x);
+   y = _mm_loadu_ps(_y);
+   y1 = _mm_loadu_ps(_y+1);
+   for (j=0;j<len-3;j+=4)
+   {
+      _x+=4;
+      _y+=4;
+      y2 = _mm_loadu_ps(_y);
+      y3 = _mm_loadu_ps(_y+1);
+      tmp = _mm_shuffle_ps(x, x, 0x00);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y));
+      tmp = _mm_shuffle_ps(x, x, 0x55);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y1));
+      tmp = _mm_shuffle_ps(x, x, 0xaa);
+      y = _mm_shuffle_ps(y, y2, 0x4e);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y));
+      tmp = _mm_shuffle_ps(x, x, 0xff);
+      y = _mm_shuffle_ps(y1, y3, 0x4e);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y));
+      x = _mm_loadu_ps(_x);
+      y = y2;
+      y1 = y3;
+   }
+   _y++;
+   if (j++<len)
+   {
+      tmp = _mm_shuffle_ps(x, x, 0x00);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y));
+   }
+   if (j++<len)
+   {
+      tmp = _mm_shuffle_ps(x, x, 0x55);
+      y = _mm_loadu_ps(_y++);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y));
+   }
+   if (j++<len)
+   {
+      tmp = _mm_shuffle_ps(x, x, 0xaa);
+      y = _mm_loadu_ps(_y++);
+      sum = _mm_add_ps(sum, _mm_mul_ps(tmp, y));
+   }
+   _mm_storeu_ps(_sum, sum);
+}
+
+#endif