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* [Bug tree-optimization/41898] New: GCC ignores restrict on array
@ 2009-11-01 20:25 jason at gcc dot gnu dot org
2009-11-01 20:59 ` [Bug tree-optimization/41898] " rguenth at gcc dot gnu dot org
2009-11-01 21:01 ` rguenth at gcc dot gnu dot org
0 siblings, 2 replies; 3+ messages in thread
From: jason at gcc dot gnu dot org @ 2009-11-01 20:25 UTC (permalink / raw)
To: gcc-bugs
Adding a pointless array qualifier to the restrict-1.c test makes it not work
with gcc -O2; we fail to optimize away the call to link_error.
int * __restrict__ a[1];
int * __restrict__ b[1];
extern void link_error (void);
int main()
{
a[0][0] = 1;
b[0][0] = 1;
if (a[0][0] != 1)
link_error ();
return 0;
}
--
Summary: GCC ignores restrict on array
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jason at gcc dot gnu dot org
BugsThisDependsOn: 6392
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41898
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/41898] GCC ignores restrict on array
2009-11-01 20:25 [Bug tree-optimization/41898] New: GCC ignores restrict on array jason at gcc dot gnu dot org
@ 2009-11-01 20:59 ` rguenth at gcc dot gnu dot org
2009-11-01 21:01 ` rguenth at gcc dot gnu dot org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-11-01 20:59 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rguenth at gcc dot gnu dot org 2009-11-01 20:59 -------
Without __restrict__ we don't optimize the call to link_error either. Because
the stores may alias - they are only redundant because of the identical
RHS. See PR23094 for that missed optimization.
But restrict indeed doesn't help here. Testcase that can be optimized
only because of restrict:
int * __restrict__ a[1];
int * __restrict__ b[1];
extern void link_error (void);
int main()
{
a[0][0] = 0;
b[0][0] = 1;
if (a[0][0] != 0)
link_error ();
return 0;
}
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2009-11-01 20:59:25
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41898
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/41898] GCC ignores restrict on array
2009-11-01 20:25 [Bug tree-optimization/41898] New: GCC ignores restrict on array jason at gcc dot gnu dot org
2009-11-01 20:59 ` [Bug tree-optimization/41898] " rguenth at gcc dot gnu dot org
@ 2009-11-01 21:01 ` rguenth at gcc dot gnu dot org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-11-01 21:01 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from rguenth at gcc dot gnu dot org 2009-11-01 21:00 -------
It works with
int * __restrict__ a;
int * __restrict__ b;
extern void link_error (void);
int main()
{
a[0] = 0;
b[0] = 1;
if (a[0] != 0)
link_error ();
return 0;
}
--
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=41898
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-11-01 21:01 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2009-11-01 20:25 [Bug tree-optimization/41898] New: GCC ignores restrict on array jason at gcc dot gnu dot org
2009-11-01 20:59 ` [Bug tree-optimization/41898] " rguenth at gcc dot gnu dot org
2009-11-01 21:01 ` rguenth at gcc dot gnu dot org
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