x86/opusdsp: implement FMA3 accelerated postfilter and deemphasis

58893 decicycles in deemphasis_c,  130548 runs,    524 skips
9475 decicycles in deemphasis_fma3,  130686 runs,    386 skips -> 6.21x speedup

24866 decicycles in postfilter_c,   65386 runs,    150 skips
5268 decicycles in postfilter_fma3,   65505 runs,     31 skips -> 4.72x speedup

Total decoder speedup: ~14%

Deemphasis SIMD based on the following unrolling:
const float c1 = CELT_EMPH_COEFF, c2 = c1*c1, c3 = c2*c1, c4 = c3*c1;
float state = coeff;

for (int i = 0; i < len; i += 4) {
    y[0] = x[0] + c1*state;
    y[1] = x[1] + c2*state + c1*x[0];
    y[2] = x[2] + c3*state + c1*x[1] + c2*x[0];
    y[3] = x[3] + c4*state + c1*x[2] + c2*x[1] + c3*x[0];

    state = y[3];
    y += 4;
    x += 4;
}

1 files changed, 35 insertions, 0 deletions

diff --git a/libavcodec/x86/opusdsp_init.c b/libavcodec/x86/opusdsp_init.c
new file mode 100644
index 0000000000..6834c4e6a4
--- /dev/null
+++ b/libavcodec/x86/opusdsp_init.c
@@ -0,0 +1,35 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#include "libavutil/x86/cpu.h"
+#include "libavcodec/opusdsp.h"
+
+void ff_opus_postfilter_fma3(float *data, int period, float *gains, int len);
+float ff_opus_deemphasis_fma3(float *out, float *in, float coeff, int len);
+
+av_cold void ff_opus_dsp_init_x86(OpusDSP *ctx)
+{
+    int cpu_flags = av_get_cpu_flags();
+
+    if (EXTERNAL_FMA3_FAST(cpu_flags)) {
+        ctx->postfilter = ff_opus_postfilter_fma3;
+        ctx->deemphasis = ff_opus_deemphasis_fma3;
+    }
+}