[Bug c/60902] New: ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[Bug c/60902] New: ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[arthur.marsh at internode dot on.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

            Bug ID: 60902
           Summary: ffmpeg built with gcc 4.9 RC produces incorrect flac
                    playback code
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arthur.marsh at internode dot on.net

Using the gcc-4.9 version 4.9-20140411-2 on Debian GNU/Linux amd64, I'm getting
incorrect code for ffmpeg flac format decoding (same source code compiled with
gcc-4.8 version 4.8.2-19 works fine).

The problem only affects some flac files that have nonetheless been passed as
valid by flac version 1.3.0.

The error returned is similar to:

[flac @ 0x7f3b540092e0] invalid subframe paddingB sq=    0B f=0/0
[flac @ 0x7f3b540092e0] decode_frame() failed

The bug report against ffmpeg is at:

https://trac.ffmpeg.org/ticket/3559

I am *NOT* a C programmer and am not familiar with the flac format decoding
process but am posting this in case anyone who is might be prepared to
investigate further.

Thanks for any help or suggestions.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |X86_64-*-Linux-gnu
          Component|c                           |target

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
What options are you compiling ffmpeg with?

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[arthur.marsh at internode dot on.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #2 from Arthur Marsh <arthur.marsh at internode dot on.net> ---
Created attachment 32637
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32637&action=edit
config.mak produced by ./configure --cc=gcc-4.9 --host-cc=gcc-4.9
--dep-cc=gcc-4.9

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[arthur.marsh at internode dot on.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #3 from Arthur Marsh <arthur.marsh at internode dot on.net> ---
I've attached the config.mak produced by ./configure --cc=gcc-4.9
--host-cc=gcc-4.9 --dep-cc=gcc-4.9

The CFLAGS from config.mak:

CFLAGS=   -std=c99 -fomit-frame-pointer -pthread -D_GNU_SOURCE=1 -D_REENTRANT
-I
/usr/include/SDL -g -Wdeclaration-after-statement -Wall -Wdisabled-optimization
-Wpointer-arith -Wredundant-decls -Wwrite-strings -Wtype-limits -Wundef
-missing-prototypes -Wno-pointer-to-int-cast -Wstrict-prototypes -Wempty-body
-Wno-parentheses -Wno-switch -Wno-format-zero-length -Wno-pointer-sign -O3
-fno-math-errno -fno-signed-zeros -fno-tree-vectorize
-Werror=implicit-function-declaration -Werror=missing-prototypes
-Werror=return-type -Werror=vla -Wno-maybe-uninitialized

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[arthur.marsh at internode dot on.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #4 from Arthur Marsh <arthur.marsh at internode dot on.net> ---
I've attached the config.mak produced by ./configure --cc=gcc-4.9
--host-cc=gcc-4.9 --dep-cc=gcc-4.9

The CFLAGS from config.mak:

CFLAGS=   -std=c99 -fomit-frame-pointer -pthread -D_GNU_SOURCE=1 -D_REENTRANT
-I
/usr/include/SDL -g -Wdeclaration-after-statement -Wall -Wdisabled-optimization
-Wpointer-arith -Wredundant-decls -Wwrite-strings -Wtype-limits -Wundef
-missing-prototypes -Wno-pointer-to-int-cast -Wstrict-prototypes -Wempty-body
-Wno-parentheses -Wno-switch -Wno-format-zero-length -Wno-pointer-sign -O3
-fno-math-errno -fno-signed-zeros -fno-tree-vectorize
-Werror=implicit-function-declaration -Werror=missing-prototypes
-Werror=return-type -Werror=vla -Wno-maybe-uninitialized

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Can you try adding -fno-strict-aliasing -fwrapv ?

Next is does ffmpeg have inline-asm for the flac codec?  This requires some C
code knowledge though.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> Can you try adding -fno-strict-aliasing -fwrapv ?

And -fno-aggressive-loop-optimizations.  I see the vectorizer is already turned
off.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[arthur.marsh at internode dot on.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #7 from Arthur Marsh <arthur.marsh at internode dot on.net> ---
OK, I modified the CFLAGS statement in config.mak to what is below, re-ran make
clean and make, and still experienced the same problems.

CFLAGS=   -std=c99 -fomit-frame-pointer -pthread -D_GNU_SOURCE=1 -D_REENTRANT
-I/usr/include/SDL -g -Wdeclaration-after-statement -Wall
-Wdisabled-optimization -Wpointer-arith -Wredundant-decls -Wwrite-strings
-Wtype-limits -Wundef -Wmissing-prototypes -Wno-pointer-to-int-cast
-Wstrict-prototypes -Wempty-body -Wno-parentheses -Wno-switch
-Wno-format-zero-length -Wno-pointer-sign -O3 -fno-math-errno -fno-signed-zeros
-fno-tree-vectorize -Werror=implicit-function-declaration
-Werror=missing-prototypes -Werror=return-type -Werror=vla
-Wno-maybe-uninitialized -fno-strict-aliasing -fwrapv
-fno-aggressive-loop-optimizations

Thanks for your interest.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[arthur.marsh at internode dot on.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #8 from Arthur Marsh <arthur.marsh at internode dot on.net> ---
PS, no assembly language in the flac decoding process as far as I could see.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |trippels at gcc dot gnu.org

--- Comment #9 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Compiling ffmpeg with -fsanitize=undefined shows:

 % ffplay -v 9 -loglevel 99 -i 10.innocent_starter.tiny.flac
...
Input #0, flac, from '10.innocent_starter.tiny.flac':
  Metadata:
    ARTIST          : 水樹奈々
    ALBUM           : THE MUSEUM
    TITLE           : innocent starter
    DATE            : 2007
    GENRE           : JPop
    track           : 10
    CDDB            : e111e110
  Duration: 00:04:40.64, bitrate: 59 kb/s
    Stream #0:0, 56, 1/44100: Audio: flac, 44100 Hz, stereo, s16
detected 4 logical cores
[ffplay_abuffer @ 0x7fc9940066a0] Setting 'sample_rate' to value '44100'
[ffplay_abuffer @ 0x7fc9940066a0] Setting 'sample_fmt' to value 's16'
[ffplay_abuffer @ 0x7fc9940066a0] Setting 'channels' to value '2'
[ffplay_abuffer @ 0x7fc9940066a0] Setting 'time_base' to value '1/44100'
[ffplay_abuffer @ 0x7fc9940066a0] Setting 'channel_layout' to value '0x3'
[ffplay_abuffer @ 0x7fc9940066a0] tb:1/44100 samplefmt:s16 samplerate:44100
chlayout:0x3
[AVFilterGraph @ 0x7fc994001790] query_formats: 2 queried, 3 merged, 0 already
done, 0 delayed
Audio frame changed from rate:44100 ch:2 fmt:s16 layout:stereo serial:-1 to
rate:44100 ch:2 fmt:s16 layout:stereo serial:1
[ffplay_abuffer @ 0x7fc988000f00] Setting 'sample_rate' to value '44100'
[ffplay_abuffer @ 0x7fc988000f00] Setting 'sample_fmt' to value 's16'
[ffplay_abuffer @ 0x7fc988000f00] Setting 'channels' to value '2'
[ffplay_abuffer @ 0x7fc988000f00] Setting 'time_base' to value '1/44100'
[ffplay_abuffer @ 0x7fc988000f00] Setting 'channel_layout' to value '0x3'
[ffplay_abuffer @ 0x7fc988000f00] tb:1/44100 samplefmt:s16 samplerate:44100
chlayout:0x3
[AVFilterGraph @ 0x7fc988000be0] query_formats: 2 queried, 3 merged, 0 already
done, 0 delayed
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/golomb.h:332:28:
runtime error: left shift of negative value -1
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp_template.c:85:36:
runtime error: left shift of negative value -4
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp_template.c:86:36:
runtime error: left shift of negative value -4
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp_template.c:100:36:
runtime error: left shift of negative value -5
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp_template.c:101:36:
runtime error: left shift of negative value -2
[flac @ 0x7fc994003a20] invalid subframe paddingB sq=    0B f=0/0   
[flac @ 0x7fc994003a20] decode_frame() failed
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:63:16:
runtime error: signed integer overflow: 1246 * -2064943 cannot be represented
in type 
'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:63:12:
runtime error: signed integer overflow: 1722048318 + 1035287866 cannot be
represented 
in type 'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:58:20:
runtime error: signed integer overflow: 1777 * -2064943 cannot be represented
in type 
'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:56:20:
runtime error: signed integer overflow: -1668 * -2064943 cannot be represented
in type
 'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:58:16:
runtime error: signed integer overflow: 1024856828 + 1571300099 cannot be
represented 
in type 'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:61:16:
runtime error: signed integer overflow: 1246 * -3189343 cannot be represented
in type 
'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:56:16:
runtime error: signed integer overflow: -1372495215 + -1772004530 cannot be
represente
d in type 'int'
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp.c:61:12:
runtime error: signed integer overflow: -1496662804 + -1546546990 cannot be
represente
d in type 'int'
[flac @ 0x7fc994003a20] invalid subframe padding
[flac @ 0x7fc994003a20] decode_frame() failed
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp_template.c:71:36:
runtime error: left shift of negative value -2349
/var/tmp/portage/media-video/ffmpeg-2.2.1/work/ffmpeg-2.2.1/libavcodec/flacdsp_template.c:72:36:
runtime error: left shift of negative value -5961
[flac @ 0x7fc994004c20] invalid subframe paddingB sq=    0B f=0/0   
[flac @ 0x7fc994004c20] decode_frame() failed
[flac @ 0x7fc994004c20] invalid subframe paddingB sq=    0B f=0/0   
[flac @ 0x7fc994004c20] decode_frame() failed
[flac @ 0x7fc994003480] underread: 6275 orig size: 9378  0B f=0/0   
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
[flac @ 0x7fc9940012b0] sample/frame number mismatch in adjacent frames
    Last message repeated 1 times
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Subject: [Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`902

--- Comment #10 from Arthur Marsh <arthur.marsh at internode dot on.net> ---
I haven't been able to reproduce what was shown in comment 9, but appreciate
the effort taken to reproduce the problem.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #11 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
OK I'm down to one function from ./libavcodec/flacdec.c:

208 __attribute__ ((optimize(0)))
209 static int decode_residuals(FLACContext *s, int32_t *decoded, int
pred_order)
210 {
211     int i, tmp, partition, method_type, rice_order;
212     int rice_bits, rice_esc;
213     int samples;
214
215     method_type = get_bits(&s->gb, 2);
216     if (method_type > 1) {
217         av_log(s->avctx, AV_LOG_ERROR, "illegal residual coding method
%d\n",
218                method_type);
219         return AVERROR_INVALIDDATA;
220     }
221
222     rice_order = get_bits(&s->gb, 4);
223
224     samples= s->blocksize >> rice_order;
225     if (samples << rice_order != s->blocksize) {
226         av_log(s->avctx, AV_LOG_ERROR, "invalid rice order: %i blocksize
%i\n",
227                rice_order, s->blocksize);
228         return AVERROR_INVALIDDATA;
229     }
230
231     if (pred_order > samples) {
232         av_log(s->avctx, AV_LOG_ERROR, "invalid predictor order: %i >
%i\n",
233                pred_order, samples);
234         return AVERROR_INVALIDDATA;
235     }
236
237     rice_bits = 4 + method_type;
238     rice_esc  = (1 << rice_bits) - 1;
239
240     decoded += pred_order;
241     i= pred_order;
242     for (partition = 0; partition < (1 << rice_order); partition++) {
243         tmp = get_bits(&s->gb, rice_bits);
244         if (tmp == rice_esc) {
245             tmp = get_bits(&s->gb, 5);
246             for (; i < samples; i++)
247                 *decoded++ = get_sbits_long(&s->gb, tmp);
248         } else {
249             for (; i < samples; i++) {
250                 *decoded++ = get_sr_golomb_flac(&s->gb, tmp, INT_MAX, 0);
251             }
252         }
253         i= 0;
254     }
255
256     return 0;
257 }
258

Without __attribute__ ((optimize(0))) it gets miscompiled.

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #12 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Created attachment 32638
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32638&action=edit
Unreduced testcase

[Bug target/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1
             Status|UNCONFIRMED                 |NEW
      Known to work|                            |4.7.3, 4.8.3
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2014-04-20
                 CC|                            |law at gcc dot gnu.org
     Ever confirmed|0                           |1
   Target Milestone|---                         |4.9.0
      Known to fail|                            |4.9.0

--- Comment #13 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Started with r205279.

[Bug tree-optimization/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #15 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Created attachment 32640
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32640&action=edit
bad assembler output r205279

[Bug tree-optimization/60902] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #14 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Created attachment 32639
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32639&action=edit
good assembler output r205278

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #16 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
*** Bug 60904 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #17 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Created attachment 32641
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32641&action=edit
Testcase from PR60904

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #18 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
*** Bug 60905 has been marked as a duplicate of this bug. ***

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #19 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Created attachment 32642
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32642&action=edit
Testcase from PR60905

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #20 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
All three testcases use the same inline function libavcodec/golomb.h:

314 /**
315  * read unsigned golomb rice code (jpegls).
316  */
317 static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit,
318                                        int esc_len)
319 {
320     unsigned int buf;
321     int log;
322
323     OPEN_READER(re, gb);
324     UPDATE_CACHE(re, gb);
325     buf = GET_CACHE(re, gb);
326
327     log = av_log2(buf);
328
329     if (log - k >= 32 - MIN_CACHE_BITS + (MIN_CACHE_BITS == 32) &&
330         32 - log < limit) {
331         buf >>= log - k;
332         buf  += (30 - log) << k;
333         LAST_SKIP_BITS(re, gb, 32 + k - log);
334         CLOSE_READER(re, gb);
335
336         return buf;
337     } else {
338         int i;
339         for (i = 0; i < limit && SHOW_UBITS(re, gb, 1) == 0; i++) {
340             if (gb->size_in_bits <= re_index)
341                 return -1;
342             LAST_SKIP_BITS(re, gb, 1);
343             UPDATE_CACHE(re, gb);
344         }
345         SKIP_BITS(re, gb, 1);
346
347         if (i < limit - 1) {
348             if (k) {
349                 buf = SHOW_UBITS(re, gb, k);
350                 LAST_SKIP_BITS(re, gb, k);
351             } else {
352                 buf = 0;
353             }
354
355             CLOSE_READER(re, gb);
356             return buf + (i << k);
357         } else if (i == limit - 1) {
358             buf = SHOW_UBITS(re, gb, esc_len);
359             LAST_SKIP_BITS(re, gb, esc_len);
360             CLOSE_READER(re, gb);
361
362             return buf + 1;
363         } else
364             return -1;
365     }
366 }

And indeed adding __attribute__ ((optimize(0))) to it "fixes" all three
testcases. 
The function looks suspicious and I'm not sure if the code is valid.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #22 from Jeffrey A. Law <law at redhat dot com> ---
I'm still working my way through the code, but it looks like we're mucking up
the value for "buf" and "k".  Not really sure if that's the root cause is just
a downstream effect.  Anyway, once the buf computation goes awry bad the
callers start to see unexpected results and the bogus errors.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #23 from Jeffrey A. Law <law at redhat dot com> ---
I think I see what's going on...  Definitely mine.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #24 from Jeffrey A. Law <law at redhat dot com> ---
So the issue here is we have an ASM which feeds an eq/neq condition found
inside a loop. The eq/neq condition creates an equivalency that is (mis) used
when we thread through the loop backedge.

The code which records temporary equivalences for jump threading ignores
GIMPLE_ASMs, so as we reprocess the block, the old equivalence isn't replaced
with anything new.  ie, the old equivalence doesn't get invalidated. 

As a result we re-use the implied value from the conditional in a previous
iteration of the loop to incorrectly simplify a test and all hell breaks loose.

In the past we were so conservative when traversing loop backedges that it was
safe to totally ignore GIMPLE_ASMs in this code.  That's no longer the safe
thing to do.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #25 from Jeffrey A. Law <law at redhat dot com> ---
Patch in testing.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P1                          |P2
   Target Milestone|4.9.0                       |4.9.1

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #26 from Jeffrey A. Law <law at redhat dot com> ---
Testing is good.  Just trying to build a nice little testcase for the
regression suite.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #27 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Jeffrey A. Law from comment #26)
> Testing is good.  Just trying to build a nice little testcase for the
> regression suite.

Thanks. Another thing I've noticed is that ac3 audio doesn't work
(no sound at all) when ffmpeg is compiled by gcc-4.9. I haven't figured
it out yet, but it appears to be a different issue, because it also
happens with r205279 reverted.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #28 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Markus Trippelsdorf from comment #27)
> (In reply to Jeffrey A. Law from comment #26)
> > Testing is good.  Just trying to build a nice little testcase for the
> > regression suite.
> 
> Another thing I've noticed is that ac3 audio doesn't work
> (no sound at all) when ffmpeg is compiled by gcc-4.9. I haven't figured
> it out yet, but it appears to be a different issue, because it also
> happens with r205279 reverted.

Luckily this issue is already fixed on the gcc-4.9 branch.

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #29 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Markus Trippelsdorf from comment #28)
> (In reply to Markus Trippelsdorf from comment #27)
> > (In reply to Jeffrey A. Law from comment #26)
> > > Testing is good.  Just trying to build a nice little testcase for the
> > > regression suite.
> > 
> > Another thing I've noticed is that ac3 audio doesn't work
> > (no sound at all) when ffmpeg is compiled by gcc-4.9. I haven't figured
> > it out yet, but it appears to be a different issue, because it also
> > happens with r205279 reverted.
> 
> Luckily this issue is already fixed on the gcc-4.9 branch.

Ah, it only happens with r205279 reverted. It could be a latent issue.
Would be good to check if it happens with your fix, too.
Could you attach your patch?

[Bug tree-optimization/60902] [4.9/4.10 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #31 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Author: law
Date: Wed Apr 23 18:04:46 2014
New Revision: 209716

URL: http://gcc.gnu.org/viewcvs?rev=209716&root=gcc&view=rev
Log:
    PR tree-optimization/60902
    * tree-ssa-threadedge.c
    (record_temporary_equivalences_from_stmts_at_dest): Make sure to
    invalidate outputs from statements that do not produce useful
    outputs for threading.

    PR tree-optimization/60902
    * gcc.target/i386/pr60902.c: New test.

Added:
    trunk/gcc/testsuite/gcc.target/i386/pr60902.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-threadedge.c

[Bug tree-optimization/60902] [4.9 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[jamrial at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

James Almer <jamrial at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jamrial at gmail dot com

--- Comment #32 from James Almer <jamrial at gmail dot com> ---
Please, don't forget to backport the fix to the 4.9 branch.
gcc 4.9.0 is almost unusable for ffmpeg because this didn't make it on time.

Thanks.

[Bug tree-optimization/60902] [4.9 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #33 from Jeffrey A. Law <law at redhat dot com> ---
James,

The whole point behind leaving the 4.9 regression marker is to ensure this BZ
gets reviewed as part of the 4.9.1 process.  I'd consider this high priority
for 4.9.1 and fully expect the fix will be included in 4.9.1.

[Bug tree-optimization/60902] [4.9 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #34 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Author: law
Date: Mon Apr 28 13:38:19 2014
New Revision: 209860

URL: http://gcc.gnu.org/viewcvs?rev=209860&root=gcc&view=rev
Log:
    PR tree-optimization/60902
    * tree-ssa-threadedge.c
    (record_temporary_equivalences_from_stmts_at_dest): Only iterate
    over real defs when invalidating outputs from statements that do not
    produce useful outputs for threading.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-ssa-threadedge.c

[Bug tree-optimization/60902] [4.9 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

--- Comment #35 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Author: law
Date: Tue May 13 20:26:30 2014
New Revision: 210398

URL: http://gcc.gnu.org/viewcvs?rev=210398&root=gcc&view=rev
Log:
    PR tree-optimization/60902
    * tree-ssa-threadedge.c
    (record_temporary_equivalences_from_stmts_at_dest): Make sure to
    invalidate outputs from statements that do not produce useful
    outputs for threading.

    PR tree-optimization/60902
    * gcc.target/i386/pr60902.c: New test.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr60902.c
Modified:
    branches/gcc-4_9-branch/gcc/ChangeLog
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_9-branch/gcc/tree-ssa-threadedge.c

[Bug tree-optimization/60902] [4.9 Regression] ffmpeg built with gcc 4.9 RC produces incorrect flac playback code

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60902

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #37 from Jeffrey A. Law <law at redhat dot com> ---
Fix backported to branch