https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #31 from Andrew Pinski ---
For the testcase in comment #0 we do warn:
: In function 'void foo()':
:7:47: warning: iteration 3 invokes undefined behavior
[-Waggressive-loop-optimizations]
7 | for (i=0, accum=a[0]; i < N; i++,
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Jackie Rosen jackie.rosen at hushmail dot com changed:
What|Removed |Added
CC|
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #28 from Jakub Jelinek jakub at gcc dot gnu.org 2013-04-30
06:07:23 UTC ---
The warning is only printed if the loop has a single exit and known constant
iteration count without the undefined behavior analysis, and when the
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #29 from Jakub Jelinek jakub at gcc dot gnu.org 2013-04-30
06:45:54 UTC ---
If you want another testcase which doesn't warn and is optimized based on the
assumption that undefined behavior doesn't occur, then say:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #27 from Paul Pluzhnikov ppluzhnikov at google dot com 2013-04-29
23:18:29 UTC ---
Here is a reduced test case in which g++ (GCC) 4.9.0 20130426 (experimental)
produces infinite loop with -O2 due to aggressive loop optimization,
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #25 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-14
09:13:45 UTC ---
Author: jakub
Date: Thu Mar 14 09:13:36 2013
New Revision: 196650
URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=196650
Log:
PR
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #26 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-14
10:54:45 UTC ---
Author: jakub
Date: Thu Mar 14 10:54:38 2013
New Revision: 196655
URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=196655
Log:
PR
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Jakub Jelinek jakub at gcc dot gnu.org changed:
What|Removed |Added
Attachment #29657|0 |1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #24 from Richard Biener rguenth at gcc dot gnu.org 2013-03-13
11:00:11 UTC ---
(In reply to comment #23)
Created attachment 29661 [details]
gcc48-pr53265.patch
Updated patch as per IRC discussions. Still need to look at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Jakub Jelinek jakub at gcc dot gnu.org changed:
What|Removed |Added
Attachment #29639|0 |1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #15 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
11:26:15 UTC ---
Created attachment 29651
-- http://gcc.gnu.org/bugzilla/attachment.cgi?id=29651
X2
Incremental debugging hack.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #16 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
11:30:02 UTC ---
First issue is (with -Werror -O2) error on attribs.c. Reduced testcase:
const void *a, *b, *c, *d, *e;
const void *f[4];
void
foo (void)
{
unsigned long
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #17 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
11:48:09 UTC ---
Second issue is from caller-save.c (setup_save_areas), again -Werror -O2:
int a, b[53][5], c[53][5];
int bar (void);
void
foo (void)
{
int i,
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #18 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
12:35:59 UTC ---
There is also a problem in unwind-dw2.c, but that looks like something we
should probably fix:
../../../libgcc/unwind-dw2.c: In function
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #19 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
12:40:54 UTC ---
On:
int a[18];
void
foo (void)
{
int i;
for (i = 16; i 32; i++)
a[i] = 26;
}
distilled from unwind-dw2.c, I'm just surprised that at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #20 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
14:13:56 UTC ---
Ok, based on reading what exactly record_estimate does, I've tried:
--- tree-ssa-loop-niter.c.xx2013-03-12 13:47:08.0 +0100
+++
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Jakub Jelinek jakub at gcc dot gnu.org changed:
What|Removed |Added
Attachment #29650|0 |1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #22 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-12
21:47:38 UTC ---
Short C testcase reproducing the exp_ch7.adb issue (for -O2):
void bar (int);
__attribute__((noinline)) static int
foo (int x)
{
int i = 1;
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Richard Biener rguenth at gcc dot gnu.org changed:
What|Removed |Added
CC|
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #5 from Richard Biener rguenth at gcc dot gnu.org 2013-03-11
14:14:06 UTC ---
The following avoids the miscompile in these obvious cases:
Index: gcc/tree-ssa-loop-niter.c
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #6 from Richard Biener rguenth at gcc dot gnu.org 2013-03-11
14:16:20 UTC ---
To warn,
1) add a flag to struct loop whether we warned for the loop already
2) in both discover_iteration_bound_by_body_walk and
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #7 from Richard Biener rguenth at gcc dot gnu.org 2013-03-11
14:17:28 UTC ---
When warnings are disabled the whole function can be skipped and
both estimate and bound be initialized by the result from
number_of_latch_executions
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #8 from Jakub Jelinek jakub at gcc dot gnu.org 2013-03-11
15:49:00 UTC ---
Created attachment 29637
-- http://gcc.gnu.org/bugzilla/attachment.cgi?id=29637
gcc48-pr53265.patch
Untested patch. Not sure about the warning
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #9 from Richard Biener rguenth at gcc dot gnu.org 2013-03-11
15:58:41 UTC ---
(In reply to comment #8)
Created attachment 29637 [details]
gcc48-pr53265.patch
Untested patch. Not sure about the warning wording, plus no
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #10 from Alexander Monakov amonakov at gcc dot gnu.org 2013-03-11
16:15:36 UTC ---
(In reply to comment #8)
Not sure about the warning wording
What about (... iteration %E invokes undefined behavior, max)?
plus no idea
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Manuel López-Ibáñez manu at gcc dot gnu.org changed:
What|Removed |Added
CC||manu at gcc
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #12 from Manuel López-Ibáñez manu at gcc dot gnu.org 2013-03-11
16:49:25 UTC ---
(In reply to comment #10)
(In reply to comment #8)
Not sure about the warning wording
What about (... iteration %E invokes undefined behavior,
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Jakub Jelinek jakub at gcc dot gnu.org changed:
What|Removed |Added
Attachment #29637|0 |1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
--- Comment #3 from Jakub Jelinek jakub at gcc dot gnu.org 2013-01-31
12:13:24 UTC ---
Another testcase, this time from PR56161 :
void bar (void *);
void
fn6 (void)
{
double a[4][3], b[12];
int i;
bar (b);
for (i = 0; i
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Jakub Jelinek jakub at gcc dot gnu.org changed:
What|Removed |Added
CC||jakub at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53265
Richard Guenther rguenth at gcc dot gnu.org changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
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