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* [Bug tree-optimization/46281] New: Inefficient unswitching (too many copies)
@ 2010-11-02 22:23 davidxl at gcc dot gnu.org
2010-11-03 11:00 ` [Bug tree-optimization/46281] " rguenth at gcc dot gnu.org
2021-07-26 9:34 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: davidxl at gcc dot gnu.org @ 2010-11-02 22:23 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46281
Summary: Inefficient unswitching (too many copies)
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: davidxl@gcc.gnu.org
Compiling the following program with -O3:
extern int gen_int(int);
extern void ref_int_p(int*);
void kernel3 ()
{
int i;
int j;
int k;
int l;
int m;
int a[200];
j = gen_int (0);
k = gen_int (0);
l = gen_int (0);
m = gen_int (0);
for (i = 0; i < 200; i++)
{
if (j < k || j < l || j < m ) // || j << 3 || k << 4)
a[i] = 1;
else
a[i] -= j;
}
ref_int_p (&a[0]);
return;
}
Gcc unswitches the loop, but generate three copies of the loop -- it should
only generate 2 copies.
LLVM correctly generates two copies.
David
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/46281] Inefficient unswitching (too many copies)
2010-11-02 22:23 [Bug tree-optimization/46281] New: Inefficient unswitching (too many copies) davidxl at gcc dot gnu.org
@ 2010-11-03 11:00 ` rguenth at gcc dot gnu.org
2021-07-26 9:34 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2010-11-03 11:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46281
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/46281] Inefficient unswitching (too many copies)
2010-11-02 22:23 [Bug tree-optimization/46281] New: Inefficient unswitching (too many copies) davidxl at gcc dot gnu.org
2010-11-03 11:00 ` [Bug tree-optimization/46281] " rguenth at gcc dot gnu.org
@ 2021-07-26 9:34 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-07-26 9:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46281
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2021-07-26
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note you need the uncommented part to hit the issue on the trunk
So:
if (j < k || j < l || j < m || j << 3 || k << 4)
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-07-26 9:34 UTC | newest]
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2010-11-02 22:23 [Bug tree-optimization/46281] New: Inefficient unswitching (too many copies) davidxl at gcc dot gnu.org
2010-11-03 11:00 ` [Bug tree-optimization/46281] " rguenth at gcc dot gnu.org
2021-07-26 9:34 ` pinskia at gcc dot gnu.org
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