http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59824
Bug ID: 59824
Summary: [4.9 Regression] r206418 miscompiles ffmpeg
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: trippels at gcc dot gnu.org
Starting with r206418 ffmpeg gets miscompiled:
% mplayer movie.avi
...
Program received signal SIGSEGV, Segmentation fault.
ff_mpeg4_set_one_direct_mv (i=0, my=0, mx=0, s=0x55555588e180) at
libavcodec/mpeg4video.c:111
111 s->mv[0][i][1] = s->direct_scale_mv[0][p_my + tab_bias] + my;
(gdb) bt
#0 ff_mpeg4_set_one_direct_mv (i=0, my=0, mx=0, s=0x55555588e180) at
libavcodec/mpeg4video.c:111
#1 ff_mpeg4_set_direct_mv (s=s@entry=0x55555588e180, mx=mx@entry=0, my=0) at
libavcodec/mpeg4video.c:172
#2 0x00007ffff67e5f33 in mpeg4_decode_mb (s=0x55555588e180,
block=0x555555aa65c0) at libavcodec/mpeg4videodec.c:1580
#3 0x00007ffff6655a44 in decode_slice (s=s@entry=0x55555588e180) at
libavcodec/h263dec.c:238
#4 0x00007ffff6656666 in ff_h263_decode_frame (avctx=0x555555887c80,
data=0x5555558879e0, got_frame=0x7fffffffcfd4, avpkt=<optimized out>) at
libavcodec/h263dec.c:587
#5 0x00007ffff68ff5be in avcodec_decode_video2 (avctx=0x555555887c80,
picture=0x5555558879e0, got_picture_ptr=0x7fffffffcfd4, avpkt=0x7fffffffd000)
at libavcodec/utils.c:2123
#6 0x00005555556b061a in decode ()
#7 0x00005555556012e4 in decode_video ()
#8 0x00005555555a8a3d in update_video ()
#9 0x000055555559c494 in main ()
(gdb)
It looks like the following function (from libavcodec/mpeg4video.c) gets
miscompiled:
90 static inline void ff_mpeg4_set_one_direct_mv(MpegEncContext *s, int mx,
91 int my, int i)
92 {
93 int xy = s->block_index[i];
94 uint16_t time_pp = s->pp_time;
95 uint16_t time_pb = s->pb_time;
96 int p_mx, p_my;
97
98 p_mx = s->next_picture.motion_val[0][xy][0];
99 if ((unsigned)(p_mx + tab_bias) < tab_size) {
100 s->mv[0][i][0] = s->direct_scale_mv[0][p_mx + tab_bias] + mx;
101 s->mv[1][i][0] = mx ? s->mv[0][i][0] - p_mx
102 : s->direct_scale_mv[1][p_mx + tab_bias];
103 } else {
104 s->mv[0][i][0] = p_mx * time_pb / time_pp + mx;
105 s->mv[1][i][0] = mx ? s->mv[0][i][0] - p_mx
106 : p_mx * (time_pb - time_pp) / time_pp;
107 }
108 p_my = s->next_picture.motion_val[0][xy][1];
109 if ((unsigned)(p_my + tab_bias) < tab_size) {
110 s->mv[0][i][1] = s->direct_scale_mv[0][p_my + tab_bias] + my;
111 s->mv[1][i][1] = my ? s->mv[0][i][1] - p_my
112 : s->direct_scale_mv[1][p_my + tab_bias];
113 } else {
114 s->mv[0][i][1] = p_my * time_pb / time_pp + my;
115 s->mv[1][i][1] = my ? s->mv[0][i][1] - p_my
116 : p_my * (time_pb - time_pp) / time_pp;
117 }
118 }
When I put an "__attribute__ ((optimize(0)))" above it, ffmpeg no longer
crashes.
I will attach the proprocessed file.
