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* [Bug c/52943] New: likely wrong code bug
@ 2012-04-12 3:28 regehr at cs dot utah.edu
2012-04-12 9:24 ` [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: regehr at cs dot utah.edu @ 2012-04-12 3:28 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52943
Bug #: 52943
Summary: likely wrong code bug
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: regehr@cs.utah.edu
CC: chenyang@cs.utah.edu
[regehr@dyson r23]$ current-gcc -O2 small.c ; ./a.out
0
[regehr@dyson r23]$ current-gcc -O3 small.c ; ./a.out
1
[regehr@dyson r23]$ cat small.c
int printf (const char *, ...);
int a[] = { 0, 0, 0, 6 };
int b;
int
main ()
{
for (;;)
{
b = 3;
for (; b; b -= 1)
a[b] = a[3] > 1;
break;
}
printf ("%d\n", a[1]);
return 0;
}
[regehr@dyson r23]$ current-gcc -v
Using built-in specs.
COLLECT_GCC=current-gcc
COLLECT_LTO_WRAPPER=/uusoc/exports/scratch/regehr/z/compiler-install/gcc-r186359-install/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.8.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --with-libelf=/usr/local --enable-lto
--prefix=/home/regehr/z/compiler-install/gcc-r186359-install
--program-prefix=r186359- --enable-languages=c,c++
Thread model: posix
gcc version 4.8.0 20120411 (experimental) (GCC)
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning
2012-04-12 3:28 [Bug c/52943] New: likely wrong code bug regehr at cs dot utah.edu
@ 2012-04-12 9:24 ` rguenth at gcc dot gnu.org
2012-04-12 9:25 ` rguenth at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-04-12 9:24 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52943
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2012-04-12
Component|c |tree-optimization
Known to work| |4.6.3
AssignedTo|unassigned at gcc dot |rguenth at gcc dot gnu.org
|gnu.org |
Target Milestone|--- |4.7.1
Summary|likely wrong code bug |[4.7/4.8 Regression] likely
| |wrong code bug caused by
| |predictive commoning
Ever Confirmed|0 |1
Known to fail| |4.7.0
--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-12 09:23:11 UTC ---
Confirmed. Predictive commoning again.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning
2012-04-12 3:28 [Bug c/52943] New: likely wrong code bug regehr at cs dot utah.edu
2012-04-12 9:24 ` [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning rguenth at gcc dot gnu.org
@ 2012-04-12 9:25 ` rguenth at gcc dot gnu.org
2012-04-12 11:41 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-04-12 9:25 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52943
--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-12 09:24:48 UTC ---
(compute_affine_dependence
stmt_a: D.1717_2 = a[3];
stmt_b: a[b.0_15] = D.1719_4;
(subscript_dependence_tester
(analyze_overlapping_iterations
(chrec_a = 3)
(chrec_b = {3, +, -1}_1)
(analyze_siv_subscript
)
(overlap_iterations_a = no dependence
)
(overlap_iterations_b = no dependence
)
)
(dependence classified: scev_known)
)
) -> no dependence
Obviously wrong.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning
2012-04-12 3:28 [Bug c/52943] New: likely wrong code bug regehr at cs dot utah.edu
2012-04-12 9:24 ` [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning rguenth at gcc dot gnu.org
2012-04-12 9:25 ` rguenth at gcc dot gnu.org
@ 2012-04-12 11:41 ` rguenth at gcc dot gnu.org
2012-04-12 12:52 ` rguenth at gcc dot gnu.org
2012-04-12 12:52 ` rguenth at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-04-12 11:41 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52943
--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-12 11:39:12 UTC ---
Author: rguenth
Date: Thu Apr 12 11:38:47 2012
New Revision: 186374
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186374
Log:
2012-04-12 Richard Guenther <rguenther@suse.de>
PR tree-optimization/52943
* tree-chrec.h (chrec_is_positive): Remove.
* tree-scalar-evolution.c (chrec_is_positive): Move ...
* tree-data-ref.c (chrec_is_positive): ... here. Make static.
Return false for a constant zero instead of negative.
(analyze_siv_subscript_cst_affine): Handle zero difference
in the initial condition explicitely.
* gcc.dg/torture/pr52943.c: New testcase.
Added:
trunk/gcc/testsuite/gcc.dg/torture/pr52943.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-chrec.h
trunk/gcc/tree-data-ref.c
trunk/gcc/tree-scalar-evolution.c
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning
2012-04-12 3:28 [Bug c/52943] New: likely wrong code bug regehr at cs dot utah.edu
` (3 preceding siblings ...)
2012-04-12 12:52 ` rguenth at gcc dot gnu.org
@ 2012-04-12 12:52 ` rguenth at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-04-12 12:52 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52943
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-12 12:50:54 UTC ---
Fixed.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning
2012-04-12 3:28 [Bug c/52943] New: likely wrong code bug regehr at cs dot utah.edu
` (2 preceding siblings ...)
2012-04-12 11:41 ` rguenth at gcc dot gnu.org
@ 2012-04-12 12:52 ` rguenth at gcc dot gnu.org
2012-04-12 12:52 ` rguenth at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-04-12 12:52 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52943
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-04-12 12:50:30 UTC ---
Author: rguenth
Date: Thu Apr 12 12:50:22 2012
New Revision: 186377
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186377
Log:
2012-04-12 Richard Guenther <rguenther@suse.de>
PR tree-optimization/52943
* tree-chrec.h (chrec_is_positive): Remove.
* tree-scalar-evolution.c (chrec_is_positive): Move ...
* tree-data-ref.c (chrec_is_positive): ... here. Make static.
Return false for a constant zero instead of negative.
(analyze_siv_subscript_cst_affine): Handle zero difference
in the initial condition explicitely.
* gcc.dg/torture/pr52943.c: New testcase.
Added:
branches/gcc-4_7-branch/gcc/testsuite/gcc.dg/torture/pr52943.c
Modified:
branches/gcc-4_7-branch/gcc/ChangeLog
branches/gcc-4_7-branch/gcc/testsuite/ChangeLog
branches/gcc-4_7-branch/gcc/tree-chrec.h
branches/gcc-4_7-branch/gcc/tree-data-ref.c
branches/gcc-4_7-branch/gcc/tree-scalar-evolution.c
^ permalink raw reply [flat|nested] 6+ messages in thread
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2012-04-12 3:28 [Bug c/52943] New: likely wrong code bug regehr at cs dot utah.edu
2012-04-12 9:24 ` [Bug tree-optimization/52943] [4.7/4.8 Regression] likely wrong code bug caused by predictive commoning rguenth at gcc dot gnu.org
2012-04-12 9:25 ` rguenth at gcc dot gnu.org
2012-04-12 11:41 ` rguenth at gcc dot gnu.org
2012-04-12 12:52 ` rguenth at gcc dot gnu.org
2012-04-12 12:52 ` rguenth at gcc dot gnu.org
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