arm: Add an option for making sure NEON registers aren't clobbered

This is pretty much based on the same test for XMM registers.
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -287,6 +287,8 @@ Developer options (useful when working on Libav itself):
   --enable-extra-warnings  enable more compiler warnings
   --samples=PATH           location of test samples for FATE, if not set use
                            \$LIBAV_SAMPLES at make invocation time.
+  --enable-neon-clobber-test check NEON registers for clobbering (should be
+                           used only for debugging purposes)
   --enable-xmm-clobber-test check XMM registers for clobbering (Win64-only;
                            should be used only for debugging purposes)
   --enable-random          randomly enable/disable components
@@ -1174,6 +1176,7 @@ CONFIG_LIST="
     lzo
     mdct
     memalign_hack
+    neon_clobber_test
     network
     nonfree
     pod2man
@@ -4059,6 +4062,16 @@ test_ldflags -Wl,-Bsymbolic && append SHFLAGS -Wl,-Bsymbolic
 # -wN '..@*' is more selective than -x, but not available everywhere.
 check_stripflags -wN \'..@*\' || check_stripflags -x || strip='true'
 
+enabled neon_clobber_test &&
+    check_ldflags -Wl,--wrap,avcodec_open2              \
+                  -Wl,--wrap,avcodec_decode_audio4      \
+                  -Wl,--wrap,avcodec_decode_video2      \
+                  -Wl,--wrap,avcodec_decode_subtitle2   \
+                  -Wl,--wrap,avcodec_encode_audio2      \
+                  -Wl,--wrap,avcodec_encode_video2      \
+                  -Wl,--wrap,avcodec_encode_subtitle ||
+    disable neon_clobber_test
+
 enabled xmm_clobber_test &&
     check_ldflags -Wl,--wrap,avcodec_open2              \
                   -Wl,--wrap,avcodec_decode_audio4      \

libavcodec/arm/Makefile

@@ -23,6 +23,7 @@ OBJS-$(CONFIG_HPELDSP)                 += arm/hpeldsp_init_arm.o        \
                                           arm/hpeldsp_arm.o
 OBJS-$(CONFIG_MPEGAUDIODSP)            += arm/mpegaudiodsp_init_arm.o
 OBJS-$(CONFIG_MPEGVIDEO)               += arm/mpegvideo_arm.o
+OBJS-$(CONFIG_NEON_CLOBBER_TEST)       += arm/neontest.o
 OBJS-$(CONFIG_VC1_DECODER)             += arm/vc1dsp_init_arm.o
 OBJS-$(CONFIG_VORBIS_DECODER)          += arm/vorbisdsp_init_arm.o
 OBJS-$(CONFIG_VP3DSP)                  += arm/vp3dsp_init_arm.o

libavcodec/arm/neontest.c

+/*
+ * check NEON registers for clobbers
+ * Copyright (c) 2013 Martin Storsjo
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavcodec/avcodec.h"
+#include "libavutil/arm/neontest.h"
+
+wrap(avcodec_open2(AVCodecContext *avctx,
+                   AVCodec *codec,
+                   AVDictionary **options))
+{
+    testneonclobbers(avcodec_open2, avctx, codec, options);
+}
+
+wrap(avcodec_decode_audio4(AVCodecContext *avctx,
+                           AVFrame *frame,
+                           int *got_frame_ptr,
+                           AVPacket *avpkt))
+{
+    testneonclobbers(avcodec_decode_audio4, avctx, frame,
+                     got_frame_ptr, avpkt);
+}
+
+wrap(avcodec_decode_video2(AVCodecContext *avctx,
+                           AVFrame *picture,
+                           int *got_picture_ptr,
+                           AVPacket *avpkt))
+{
+    testneonclobbers(avcodec_decode_video2, avctx, picture,
+                     got_picture_ptr, avpkt);
+}
+
+wrap(avcodec_decode_subtitle2(AVCodecContext *avctx,
+                              AVSubtitle *sub,
+                              int *got_sub_ptr,
+                              AVPacket *avpkt))
+{
+    testneonclobbers(avcodec_decode_subtitle2, avctx, sub,
+                     got_sub_ptr, avpkt);
+}
+
+wrap(avcodec_encode_audio2(AVCodecContext *avctx,
+                           AVPacket *avpkt,
+                           const AVFrame *frame,
+                           int *got_packet_ptr))
+{
+    testneonclobbers(avcodec_encode_audio2, avctx, avpkt, frame,
+                     got_packet_ptr);
+}
+
+wrap(avcodec_encode_subtitle(AVCodecContext *avctx,
+                             uint8_t *buf, int buf_size,
+                             const AVSubtitle *sub))
+{
+    testneonclobbers(avcodec_encode_subtitle, avctx, buf, buf_size, sub);
+}
+
+wrap(avcodec_encode_video2(AVCodecContext *avctx, AVPacket *avpkt,
+                           const AVFrame *frame, int *got_packet_ptr))
+{
+    testneonclobbers(avcodec_encode_video2, avctx, avpkt, frame, got_packet_ptr);
+}

libavutil/arm/neontest.h

+/*
+ * check NEON registers for clobbering
+ * Copyright (c) 2008 Ramiro Polla <ramiro.polla@gmail.com>
+ * Copyright (c) 2013 Martin Storsjo
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+
+#include "libavutil/bswap.h"
+
+#define storeneonregs(mem)                \
+    __asm__ volatile(                     \
+        "vstm %0, {d8-d15}\n\t"           \
+        :: "r"(mem) : "memory")
+
+#define testneonclobbers(func, ctx, ...)                        \
+    uint64_t neon[2][8];                                        \
+    int ret;                                                    \
+    storeneonregs(neon[0]);                                     \
+    ret = __real_ ## func(ctx, __VA_ARGS__);                    \
+    storeneonregs(neon[1]);                                     \
+    if (memcmp(neon[0], neon[1], sizeof(neon[0]))) {            \
+        int i;                                                  \
+        av_log(ctx, AV_LOG_ERROR,                               \
+               "NEON REGS CLOBBERED IN %s!\n", #func);          \
+        for (i = 0; i < 8; i ++)                                \
+            if (neon[0][i] != neon[1][i]) {                     \
+                av_log(ctx, AV_LOG_ERROR,                       \
+                       "d%-2d = %016"PRIx64"\n",                \
+                       8 + i, av_bswap64(neon[0][i]));          \
+                av_log(ctx, AV_LOG_ERROR,                       \
+                       "   -> %016"PRIx64"\n",                  \
+                       av_bswap64(neon[1][i]));                 \
+            }                                                   \
+        abort();                                                \
+    }                                                           \
+    return ret
+
+#define wrap(func)      \
+int __real_ ## func;    \
+int __wrap_ ## func;    \
+int __wrap_ ## func