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* [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail
@ 2013-02-20 11:53 quintin at lix dot polytechnique.fr
2013-02-20 13:11 ` [Bug c/56407] [4.7 Regression] " jakub at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: quintin at lix dot polytechnique.fr @ 2013-02-20 11:53 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
Bug #: 56407
Summary: Optimizations (-O2 -O3) make comparison of arrays of
ints to fail
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: quintin@lix.polytechnique.fr
Created attachment 29509
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29509
The .c .i .s .o files
This is my first bug report, so I hope this is really a bug and that I file it
correctly.
Versions of my stuff:
- gcc (Debian 4.7.2-5) 4.7.2
- Linux 3.2.0-4-amd64 #1 SMP Debian 3.2.35-2 x86_64 GNU/Linux
- Intel(R) Core(TM)2 Duo CPU T9600 @ 2.80GHz
gcc compile stuff:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.7.2-5'
--with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object
--enable-plugin --enable-objc-gc --with-arch-32=i586 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.2 (Debian 4.7.2-5)
The bug appears when I compile the program with -O2 or -O3:
$ gcc -O3 gcc_bug.c -o gcc_bug
$ ./gcc_bug && echo ok || echo fail
fail
But it works fine with -O1:
$ gcc -O1 gcc_bug.c -o gcc_bug
$ ./gcc_bug && echo ok || echo fail
ok
It works fine with an older version of gcc:
$ gcc --version
gcc (GCC) 4.4.6 20120305 (Red Hat 4.4.6-4)
$ gcc -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla
--enable-bootstrap --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk
--disable-dssi --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre
--enable-libgcj-multifile --enable-java-maintainer-mode
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libjava-multilib
--with-ppl --with-cloog --with-tune=generic --with-arch_32=i686
--build=x86_64-redhat-linux
Thread model: posix
gcc version 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC)
$ gcc -O3 gcc_bug.c -o gcc_bug
$ ./gcc_bug && echo ok || echo fail
ok
When the program fails with gcc 4.7.2 valgrind tells me:
$ gcc -O3 -g gcc_bug.c -o gcc_bug
$ valgrind ./gcc_bug
==3383== Memcheck, a memory error detector
==3383== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==3383== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==3383== Command: ./gcc_bug
==3383==
==3383== Conditional jump or move depends on uninitialised value(s)
==3383== at 0x40079E: test (gcc_bug.c:21)
==3383== by 0x400482: main (gcc_bug.c:41)
==3383==
==3383==
==3383== HEAP SUMMARY:
==3383== in use at exit: 0 bytes in 0 blocks
==3383== total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3383==
==3383== All heap blocks were freed -- no leaks are possible
==3383==
==3383== For counts of detected and suppressed errors, rerun with: -v
==3383== Use --track-origins=yes to see where uninitialised values come from
==3383== ERROR SUMMARY: 2 errors from 1 contexts (suppressed: 4 from 4)
Whereas all is fine for valgrind with -O1. Also all is fine with -fwrapv:
$ gcc -O3 -fwrapv gcc_bug.c -o gcc_bug
$ ./gcc_bug && echo ok || echo fail
ok
I suppose the bug appears when gcc is doing some optimizations but I do not
know which. Any small modifications to the program make it work. For example if
I remove the ``if ( comm ) {" line or if I replace ``for( j = 1 ; j <= sz" by
``for( j = 1 ; j < sz".
======================================
extern void exit(int);
extern int rand(void);
void copy(int *r,int *a,int na) {
int i;
for( i = 0 ; i < na ; i++ ) {
r[i] = a[i];
}
}
void random(int *a,int na) {
int i;
for( i = 0 ; i < na ; i++ ) {
a[i] = rand();
}
}
int cmp(int *a,int *b,int n) {
int i;
for( i = 0 ; i < n ; i++ ) {
if ( a[i] != b[i] ) return -1;
}
return 0;
}
void test(int sz,int comm) {
int j,n;
int v[64],w[64];
for( j = 1 ; j <= sz ; j++ ) {
n = (2 * j - 1) * (2 * j - 1);
random(w,n);
copy(v,w,n);
if ( comm ) {
if ( cmp(v,w,n) ) exit(-1);
}
}
exit(0);
}
int main(void) {
test(2,1);
return 0;
}
======================================
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c/56407] [4.7 Regression] Optimizations (-O2 -O3) make comparison of arrays of ints to fail
2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
@ 2013-02-20 13:11 ` jakub at gcc dot gnu.org
2013-04-03 9:53 ` [Bug tree-optimization/56407] " rguenth at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-02-20 13:11 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-02-20
CC| |jakub at gcc dot gnu.org
Target Milestone|--- |4.7.3
Summary|Optimizations (-O2 -O3) |[4.7 Regression]
|make comparison of arrays |Optimizations (-O2 -O3)
|of ints to fail |make comparison of arrays
| |of ints to fail
Ever Confirmed|0 |1
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-20 13:10:50 UTC ---
Started around http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=173853
and got fixed (or made latent) with
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186566
Seems -fno-ivopts fixes this.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/56407] [4.7 Regression] Optimizations (-O2 -O3) make comparison of arrays of ints to fail
2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
2013-02-20 13:11 ` [Bug c/56407] [4.7 Regression] " jakub at gcc dot gnu.org
@ 2013-04-03 9:53 ` rguenth at gcc dot gnu.org
2013-04-03 10:23 ` rguenth at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-04-03 9:53 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
Component|c |tree-optimization
Known to work| |4.8.0
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/56407] [4.7 Regression] Optimizations (-O2 -O3) make comparison of arrays of ints to fail
2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
2013-02-20 13:11 ` [Bug c/56407] [4.7 Regression] " jakub at gcc dot gnu.org
2013-04-03 9:53 ` [Bug tree-optimization/56407] " rguenth at gcc dot gnu.org
@ 2013-04-03 10:23 ` rguenth at gcc dot gnu.org
2013-04-03 10:26 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-04-03 10:23 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-03 10:22:53 UTC ---
Testcase, also fails at -O2:
/* { dg-do run } */
extern void abort(void);
extern int rand(void);
static void copy(int *r,int *a,int na)
{
int i;
for( i = 0 ; i < na ; i++ )
r[i] = a[i];
}
static void foo(int *a,int na)
{
int i;
for( i = 0 ; i < na ; i++ )
a[i] = rand();
}
static int cmp(int *a,int *b,int n)
{
int i;
for( i = 0 ; i < n ; i++ )
if ( a[i] != b[i] )
return -1;
return 0;
}
void __attribute__((noinline,noclone))
test(int sz,int comm)
{
int j,n;
int v[64],w[64];
for( j = 1 ; j <= sz ; j++ )
{
n = (2 * j - 1) * (2 * j - 1);
foo(w,n);
copy(v,w,n);
if ( comm )
if ( cmp(v,w,n) ) abort ();
}
}
int main()
{
test(2,1);
return 0;
}
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/56407] [4.7 Regression] Optimizations (-O2 -O3) make comparison of arrays of ints to fail
2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
` (2 preceding siblings ...)
2013-04-03 10:23 ` rguenth at gcc dot gnu.org
@ 2013-04-03 10:26 ` rguenth at gcc dot gnu.org
2013-04-11 7:59 ` rguenth at gcc dot gnu.org
2014-06-12 13:24 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-04-03 10:26 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-03 10:26:53 UTC ---
Author: rguenth
Date: Wed Apr 3 10:25:23 2013
New Revision: 197399
URL: http://gcc.gnu.org/viewcvs?rev=197399&root=gcc&view=rev
Log:
2013-04-03 Richard Biener <rguenther@suse.de>
PR tree-optimization/56407
* gcc.dg/torture/pr56407.c: New testcase.
Added:
trunk/gcc/testsuite/gcc.dg/torture/pr56407.c
Modified:
trunk/gcc/testsuite/ChangeLog
Author: rguenth
Date: Wed Apr 3 10:26:13 2013
New Revision: 197400
URL: http://gcc.gnu.org/viewcvs?rev=197400&root=gcc&view=rev
Log:
2013-04-03 Richard Biener <rguenther@suse.de>
PR tree-optimization/56407
* gcc.dg/torture/pr56407.c: New testcase.
Added:
branches/gcc-4_8-branch/gcc/testsuite/gcc.dg/torture/pr56407.c
Modified:
branches/gcc-4_8-branch/gcc/testsuite/ChangeLog
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/56407] [4.7 Regression] Optimizations (-O2 -O3) make comparison of arrays of ints to fail
2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
` (3 preceding siblings ...)
2013-04-03 10:26 ` rguenth at gcc dot gnu.org
@ 2013-04-11 7:59 ` rguenth at gcc dot gnu.org
2014-06-12 13:24 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-04-11 7:59 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.7.3 |4.7.4
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-11 07:59:32 UTC ---
GCC 4.7.3 is being released, adjusting target milestone.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/56407] [4.7 Regression] Optimizations (-O2 -O3) make comparison of arrays of ints to fail
2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
` (4 preceding siblings ...)
2013-04-11 7:59 ` rguenth at gcc dot gnu.org
@ 2014-06-12 13:24 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-06-12 13:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56407
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
Target Milestone|4.7.4 |4.8.0
Known to fail| |4.7.4
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed in 4.8.0.
^ permalink raw reply [flat|nested] 7+ messages in thread
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2013-02-20 11:53 [Bug c/56407] New: Optimizations (-O2 -O3) make comparison of arrays of ints to fail quintin at lix dot polytechnique.fr
2013-02-20 13:11 ` [Bug c/56407] [4.7 Regression] " jakub at gcc dot gnu.org
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