truehd: add hand-scheduled ARM asm version of mlp_filter_channel.

Profiling results for overall audio decode and the mlp_filter_channel(_arm)
function in particular are as follows:

              Before          After
              Mean   StdDev   Mean   StdDev  Confidence  Change
6:2 total     380.4  22.0     370.8  17.0    87.4%       +2.6%  (insignificant)
6:2 function  60.7   7.2      36.6   8.1     100.0%      +65.8%
8:2 total     357.0  17.5     343.2  19.0    97.8%       +4.0%  (insignificant)
8:2 function  60.3   8.8      37.3   3.8     100.0%      +61.8%
6:6 total     717.2  23.2     658.4  15.7    100.0%      +8.9%
6:6 function  140.4  12.9     81.5   9.2     100.0%      +72.4%
8:8 total     981.9  16.2     896.2  24.5    100.0%      +9.6%
8:8 function  193.4  15.0     103.3  11.5    100.0%      +87.2%

Experiments with adding preload instructions to this function yielded no
useful benefit, so these have not been included.

The assembly version has also been tested with a fuzz tester to ensure that
any combinations of inputs not exercised by my available test streams still
generate mathematically identical results to the C version.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/arm/Makefile

@@ -16,6 +16,8 @@ OBJS-$(CONFIG_H264PRED)                += arm/h264pred_init_arm.o
 OBJS-$(CONFIG_H264QPEL)                += arm/h264qpel_init_arm.o
 OBJS-$(CONFIG_HPELDSP)                 += arm/hpeldsp_init_arm.o        \
                                           arm/hpeldsp_arm.o
+OBJS-$(CONFIG_MLP_DECODER)             += arm/mlpdsp_init_arm.o         \
+                                          arm/mlpdsp_arm.o
 OBJS-$(CONFIG_MPEGAUDIODSP)            += arm/mpegaudiodsp_init_arm.o
 OBJS-$(CONFIG_MPEGVIDEO)               += arm/mpegvideo_arm.o
 OBJS-$(CONFIG_NEON_CLOBBER_TEST)       += arm/neontest.o

libavcodec/arm/mlpdsp_init_arm.c

+/*
+ * Copyright (c) 2014 RISC OS Open Ltd
+ * Author: Ben Avison <bavison@riscosopen.org>
+ *
+ * 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 <stdint.h>
+
+#include "libavutil/arm/cpu.h"
+#include "libavutil/attributes.h"
+#include "libavcodec/mlpdsp.h"
+
+void ff_mlp_filter_channel_arm(int32_t *state, const int32_t *coeff,
+                               int firorder, int iirorder,
+                               unsigned int filter_shift, int32_t mask,
+                               int blocksize, int32_t *sample_buffer);
+
+av_cold void ff_mlpdsp_init_arm(MLPDSPContext *c)
+{
+    c->mlp_filter_channel = ff_mlp_filter_channel_arm;
+}

libavcodec/mlpdsp.c

@@ -60,6 +60,8 @@ static void mlp_filter_channel(int32_t *state, const int32_t *coeff,
 av_cold void ff_mlpdsp_init(MLPDSPContext *c)
 {
     c->mlp_filter_channel = mlp_filter_channel;
+    if (ARCH_ARM)
+        ff_mlpdsp_init_arm(c);
     if (ARCH_X86)
         ff_mlpdsp_init_x86(c);
 }

libavcodec/mlpdsp.h

@@ -32,6 +32,7 @@ typedef struct MLPDSPContext {
 } MLPDSPContext;
 
 void ff_mlpdsp_init(MLPDSPContext *c);
+void ff_mlpdsp_init_arm(MLPDSPContext *c);
 void ff_mlpdsp_init_x86(MLPDSPContext *c);
 
 #endif /* AVCODEC_MLPDSP_H */