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* [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop
@ 2006-08-07 16:34 schwab at suse dot de
2006-08-07 16:34 ` [Bug middle-end/28636] " schwab at suse dot de
` (9 more replies)
0 siblings, 10 replies; 11+ messages in thread
From: schwab at suse dot de @ 2006-08-07 16:34 UTC (permalink / raw)
To: gcc-bugs
$ gcc -O2 input.c -o input
$ ./input
input: input.c:36: main: Assertion `s.buffer_position == s.buffer_end' failed.
The loop loses the increment of s.buffer_position.
--
Summary: [4.0/4.1 regression] Miscompiled loop
Product: gcc
Version: 4.1.2
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: schwab at suse dot de
GCC target triplet: ia64-*-*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
@ 2006-08-07 16:34 ` schwab at suse dot de
2006-08-07 17:34 ` pinskia at gcc dot gnu dot org
` (8 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: schwab at suse dot de @ 2006-08-07 16:34 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from schwab at suse dot de 2006-08-07 16:34 -------
Created an attachment (id=12039)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12039&action=view)
Testcase
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
2006-08-07 16:34 ` [Bug middle-end/28636] " schwab at suse dot de
@ 2006-08-07 17:34 ` pinskia at gcc dot gnu dot org
2006-08-07 17:51 ` schwab at suse dot de
` (7 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-08-07 17:34 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2006-08-07 17:34 -------
I bet this is a loop.c bug.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |pinskia at gcc dot gnu dot
| |org
Target Milestone|--- |4.0.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
2006-08-07 16:34 ` [Bug middle-end/28636] " schwab at suse dot de
2006-08-07 17:34 ` pinskia at gcc dot gnu dot org
@ 2006-08-07 17:51 ` schwab at suse dot de
2006-08-08 0:04 ` schwab at suse dot de
` (6 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: schwab at suse dot de @ 2006-08-07 17:51 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from schwab at suse dot de 2006-08-07 17:51 -------
-floop-optimize2 doesn't help.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug middle-end/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (2 preceding siblings ...)
2006-08-07 17:51 ` schwab at suse dot de
@ 2006-08-08 0:04 ` schwab at suse dot de
2006-08-08 9:09 ` [Bug rtl-optimization/28636] " rguenth at gcc dot gnu dot org
` (5 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: schwab at suse dot de @ 2006-08-08 0:04 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from schwab at suse dot de 2006-08-08 00:04 -------
Looks like introduced during the tree-ssa merge.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (3 preceding siblings ...)
2006-08-08 0:04 ` schwab at suse dot de
@ 2006-08-08 9:09 ` rguenth at gcc dot gnu dot org
2006-09-09 22:10 ` ebotcazou at gcc dot gnu dot org
` (4 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-08-08 9:09 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2006-08-08 09:09 -------
Confirmed. The problem is probably latent on mainline. check_header is being
miscompiled, -O -fno-loop-optimize2 -fno-loop-optimize -fno-branch-count-reg
is enough to trigger the bug (i.e. no loop bug).
extern void abort(void);
struct input_ty
{
unsigned char *buffer_position;
unsigned char *buffer_end;
};
int input_getc_complicated (struct input_ty *x) { return 0; }
int
check_header (struct input_ty *deeper)
{
unsigned len;
for (len = 0; len < 6; len++)
if (((deeper)->buffer_position < (deeper)->buffer_end
? *((deeper)->buffer_position)++
: input_getc_complicated((deeper))) < 0)
return 0;
return 1;
}
struct input_ty s;
unsigned char b[6];
int
main (void)
{
s.buffer_position = b;
s.buffer_end = b + sizeof b;
if (!check_header(&s))
return 1;
if (s.buffer_position != s.buffer_end)
abort();
return 0;
}
it looks like ifcvt messes up in pass 3 and puts the post-inc in the cond-exec
block.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Component|middle-end |rtl-optimization
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2006-08-08 09:09:48
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (4 preceding siblings ...)
2006-08-08 9:09 ` [Bug rtl-optimization/28636] " rguenth at gcc dot gnu dot org
@ 2006-09-09 22:10 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:27 ` ebotcazou at gcc dot gnu dot org
` (3 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2006-09-09 22:10 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from ebotcazou at gcc dot gnu dot org 2006-09-09 22:09 -------
> it looks like ifcvt messes up in pass 3 and puts the post-inc in the
> cond-exec block.
It's actually the combiner that wrongly ditches the post-inc, at least with
the last set of options you posted. Amazingly enough, on the 4.1 branch, the
combiner is the first pass which deduces that
*((deeper)->buffer_position)++ < 0
is always false. In particular, we have this little gem in t97.final_cleanup
unsigned char * D.1386;
_Bool iftmp.0;
iftmp.0 = (int) *D.1386 < 0;
even at -O2! This is optimized on mainline, which hides the problem there.
Fixing...
--
ebotcazou at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |ebotcazou at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
Last reconfirmed|2006-08-08 09:09:48 |2006-09-09 22:09:59
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (5 preceding siblings ...)
2006-09-09 22:10 ` ebotcazou at gcc dot gnu dot org
@ 2006-09-10 21:27 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:28 ` ebotcazou at gcc dot gnu dot org
` (2 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2006-09-10 21:27 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from ebotcazou at gcc dot gnu dot org 2006-09-10 21:27 -------
Subject: Bug 28636
Author: ebotcazou
Date: Sun Sep 10 21:27:36 2006
New Revision: 116827
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=116827
Log:
PR rtl-optimization/28636
* combine.c (force_to_mode): Test for side-effects before
substituting by zero.
(simplify_shift_const): Likewise for zero or other constants.
Added:
trunk/gcc/testsuite/gcc.c-torture/execute/20060910-1.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/combine.c
trunk/gcc/testsuite/ChangeLog
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (6 preceding siblings ...)
2006-09-10 21:27 ` ebotcazou at gcc dot gnu dot org
@ 2006-09-10 21:28 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:29 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:34 ` ebotcazou at gcc dot gnu dot org
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2006-09-10 21:28 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from ebotcazou at gcc dot gnu dot org 2006-09-10 21:28 -------
Subject: Bug 28636
Author: ebotcazou
Date: Sun Sep 10 21:28:03 2006
New Revision: 116828
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=116828
Log:
PR rtl-optimization/28636
* combine.c (force_to_mode): Test for side-effects before
substituting by zero.
(simplify_shift_const): Likewise for zero or other constants.
Added:
branches/gcc-4_1-branch/gcc/testsuite/gcc.c-torture/execute/20060910-1.c
Modified:
branches/gcc-4_1-branch/gcc/ChangeLog
branches/gcc-4_1-branch/gcc/combine.c
branches/gcc-4_1-branch/gcc/testsuite/ChangeLog
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (7 preceding siblings ...)
2006-09-10 21:28 ` ebotcazou at gcc dot gnu dot org
@ 2006-09-10 21:29 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:34 ` ebotcazou at gcc dot gnu dot org
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2006-09-10 21:29 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from ebotcazou at gcc dot gnu dot org 2006-09-10 21:28 -------
Subject: Bug 28636
Author: ebotcazou
Date: Sun Sep 10 21:28:39 2006
New Revision: 116829
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=116829
Log:
PR rtl-optimization/28636
* combine.c (force_to_mode): Test for side-effects before
substituting by zero.
(simplify_shift_const): Likewise for zero or other constants.
Added:
branches/gcc-4_0-branch/gcc/testsuite/gcc.c-torture/execute/20060910-1.c
Modified:
branches/gcc-4_0-branch/gcc/ChangeLog
branches/gcc-4_0-branch/gcc/combine.c
branches/gcc-4_0-branch/gcc/testsuite/ChangeLog
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/28636] [4.0/4.1 regression] Miscompiled loop
2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
` (8 preceding siblings ...)
2006-09-10 21:29 ` ebotcazou at gcc dot gnu dot org
@ 2006-09-10 21:34 ` ebotcazou at gcc dot gnu dot org
9 siblings, 0 replies; 11+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2006-09-10 21:34 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from ebotcazou at gcc dot gnu dot org 2006-09-10 21:34 -------
Fixed everywhere.
--
ebotcazou at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
URL| |http://gcc.gnu.org/ml/gcc-
| |patches/2006-
| |09/msg00383.html
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28636
^ permalink raw reply [flat|nested] 11+ messages in thread
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2006-08-07 16:34 [Bug middle-end/28636] New: [4.0/4.1 regression] Miscompiled loop schwab at suse dot de
2006-08-07 16:34 ` [Bug middle-end/28636] " schwab at suse dot de
2006-08-07 17:34 ` pinskia at gcc dot gnu dot org
2006-08-07 17:51 ` schwab at suse dot de
2006-08-08 0:04 ` schwab at suse dot de
2006-08-08 9:09 ` [Bug rtl-optimization/28636] " rguenth at gcc dot gnu dot org
2006-09-09 22:10 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:27 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:28 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:29 ` ebotcazou at gcc dot gnu dot org
2006-09-10 21:34 ` ebotcazou at gcc dot gnu dot org
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