[Bug inline-asm/45160] New: [GCC 4.4.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[Bug inline-asm/45160] New: [GCC 4.4.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

A testcase for x86 architecture (Intel Core i5 CPU here):

1) Download
http://sourceforge.net/projects/faac/files/faad2-src/faad2-2.6/faad2-2.6.1.tar.gz/download

2) Build it using these commands

perl -pi -e 's|dnl AC_PROG_CXX|AC_PROG_CXX|' configure.in
autoreconf -vif
configure --disable-static

using GCC 4.2.4 and GCC 4.4.x

3) faad binary compiled with GCC 4.4.x will fail to properly decode some AAC
files (a sample file can be downloaded here
http://bugzilla.mplayerhq.hu/attachment.cgi?id=651 )

faad -o outfile.wav out.aac
...

Decoding out.aac took:  0.21 sec. 285.83x real-time. (GCC 4.2.x)
Decoding out.aac took:  1.55 sec.  38.72x real-time. (GCC 4.4.x)

So, we have two bugs here:

1) faad2's AAC decode algorithm fails to work correctly under GCC 4.4.x (even
with gcc -O2 -march=i686).
3) faad2's AAC decode algorithm compiled with GCC 4.4.x works an order of
magnitude slower than the same code code compiled using GCC 4.2.x.


-- 
           Summary: [GCC 4.4.x regression] Invalid assembly code is
                    generated for x86 architecture for faad2 library (AAC
                    decode algorithm)
           Product: gcc
           Version: 4.4.5
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: inline-asm
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: t dot artem at mailcity dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [GCC 4.4.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #1 from t dot artem at mailcity dot com  2010-08-02 00:09 -------
faad2 2.7.0 exhibits the same misbehavior, you can download it here:

http://downloads.sourceforge.net/faac/faad2-2.7.tar.bz2

No extra commands are required for compilation, just ./configure && make

---

P.S. You may want to use 

./configure --enable-static --disable-shared

in order to get a single binary which doesn't use any external libraries (thus
it will be easier to verify the bug).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [GCC 4.4.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #2 from t dot artem at mailcity dot com  2010-08-02 00:31 -------
Created an attachment (id=21368)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21368&action=view)
faad2 2.7.0 complete sources with -save-temps

Complete sources with -save-temps for GCC 4.2.4 and GCC 4.4.4.

The same compilation flags:

-march=i686 -O2 -pipe -save-temps


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #3 from t dot artem at mailcity dot com  2010-08-02 13:09 -------
I've just tested GCC 4.5.1 and it also miscompiles the source code.


-- 

t dot artem at mailcity dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[GCC 4.4.x regression]      |[4.4.x/4.5.x regression]
                   |Invalid assembly code is    |Invalid assembly code is
                   |generated for x86           |generated for x86
                   |architecture for faad2      |architecture for faad2
                   |library (AAC decode         |library (AAC decode
                   |algorithm)                  |algorithm)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #4 from t dot artem at mailcity dot com  2010-08-02 13:10 -------
Created an attachment (id=21369)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21369&action=view)
faad2 2.7.0 complete sources with -save-temps for GCC 4.5.1


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #5 from t dot artem at mailcity dot com  2010-08-02 13:15 -------
I've found the culprit (or better say mplayer developer hinted), it is
-fstrict-aliasing optimization.

With -fno-strict-aliasing GCC 4.4.x and 4.5.x produce proper code.

Please, advise.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2010-08-02 14:12 -------
Why CC me?  I have no clue about faad2, the strict-aliasing thing hints
at errors in faad2, not gcc.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|rguenth at gcc dot gnu dot  |
                   |org                         |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #7 from t dot artem at mailcity dot com  2010-08-02 15:49 -------
(In reply to comment #6)
> Why CC me?  I have no clue about faad2, the strict-aliasing thing hints
> at errors in faad2, not gcc.
> 

Richard, I don't know who is who amongst GCC developers, but you are a
prominent person, so I thought you know someone who can help shed light on this
issue.

Like I said GCC 4.2.x has no problems compiling this library, so I have no idea
who to blame and who else I should get in touch with.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[pinskia at gcc dot gnu dot org]

------- Comment #8 from pinskia at gcc dot gnu dot org  2010-08-02 16:21 -------
> Like I said GCC 4.2.x has no problems compiling this library, so I have no idea
> who to blame and who else I should get in touch with.

I would get into contact with the developers of the library first.  Yes GCC has
some bugs but the library could have a bug still.  Since the problem disappreas
with -fno-strict-aliasing that normally points at a bug in the library.  In
that it does not follow the C/C++ alisaing rules.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #9 from t dot artem at mailcity dot com  2010-08-02 20:27 -------
The culprit is the ic_predict.c file. When I compile it with
-fno-strict-aliasing (while everything else is being compiled with
-fstrict-aliasing) libfaad works correctly.

These are the warnings which I get from GCC:

ic_predict.c: In function 'flt_round':
ic_predict.c:58: warning: dereferencing type-punned pointer will break
strict-aliasing rules
ic_predict.c:58: warning: dereferencing type-punned pointer will break
strict-aliasing rules
ic_predict.c:58: warning: dereferencing type-punned pointer will break
strict-aliasing rules
ic_predict.c:60: warning: dereferencing type-punned pointer will break
strict-aliasing rules
ic_predict.c: In function 'ic_prediction':
ic_predict.c:78: warning: dereferencing pointer 'tmp' does break
strict-aliasing rules
ic_predict.c:77: note: initialized from here
ic_predict.c:78: warning: dereferencing pointer 'tmp' does break
strict-aliasing rules
ic_predict.c:77: note: initialized from here
ic_predict.c:78: warning: dereferencing pointer 'tmp' does break
strict-aliasing rules
ic_predict.c:77: note: initialized from here
ic_predict.c:78: warning: dereferencing pointer 'tmp' does break
strict-aliasing rules
ic_predict.c:77: note: initialized from here
ic_predict.c:78: warning: dereferencing pointer 'tmp' does break
strict-aliasing rules
ic_predict.c:77: note: initialized from here
ic_predict.c:78: warning: dereferencing pointer 'tmp' does break
strict-aliasing rules
ic_predict.c:77: note: initialized from here

Maybe GCC developers could devise a patch for this file because
http://www.audiocoding.com/faad2.html site seems to be dead.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[rguenth at gcc dot gnu dot org]

------- Comment #10 from rguenth at gcc dot gnu dot org  2010-08-30 15:47 -------
Not a gcc bug.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160

[Bug inline-asm/45160] [4.4.x/4.5.x regression] Invalid assembly code is generated for x86 architecture for faad2 library (AAC decode algorithm)

[t dot artem at mailcity dot com]

------- Comment #11 from t dot artem at mailcity dot com  2010-09-06 20:19 -------
(In reply to comment #9)
> Maybe GCC developers could devise a patch for this file because
> http://www.audiocoding.com/faad2.html site seems to be dead.
> 

(In reply to comment #10)
> Not a gcc bug.
> 

FAAD developers don't answer my e-mails, so what I can do? Resort to compile
FAAD library using a specially compiled GCC? What about other less experienced
users? There just a few warnings which I suppose can be easily resolved ...


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45160