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* [Bug tree-optimization/28794] New: missed optimization with non COND_EXPR and vrp and comparisions
@ 2006-08-21 23:24 pinskia at gcc dot gnu dot org
2006-08-21 23:31 ` [Bug tree-optimization/28794] " pinskia at gcc dot gnu dot org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-08-21 23:24 UTC (permalink / raw)
To: gcc-bugs
int f(int x, int y)
{
int t;
for (t = 0; t < 50; t++)
g(t>0);
}
void f1(int x, int y)
{
int t;
for (t = 0; t < 50; t++)
g(t!=0);
}
--------------
The above two functions should produce the same code with f1 being better than
f.
If we change it to:
void f2(int x, int y)
{
int t;
for (t = 0; t < 50; t++)
{
int tt;
if (t>0)
tt = 1;
else
tt = 0;
g(tt);
}
}
-----
We get f1 so we are only folding comparisions in a COND_EXPR which is wrong, we
should also be doing them in MODIFY_EXPRs too.
--
Summary: missed optimization with non COND_EXPR and vrp and
comparisions
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pinskia at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28794
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/28794] missed optimization with non COND_EXPR and vrp and comparisions
2006-08-21 23:24 [Bug tree-optimization/28794] New: missed optimization with non COND_EXPR and vrp and comparisions pinskia at gcc dot gnu dot org
@ 2006-08-21 23:31 ` pinskia at gcc dot gnu dot org
2006-08-21 23:53 ` [Bug tree-optimization/28794] missed optimization with non-COND_EXPR " pinskia at gcc dot gnu dot org
2006-08-22 8:10 ` rguenth at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-08-21 23:31 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-08-21 23:31 -------
I found this while trying to figure out how to get VRP to optimize:
a_1 != 0 into a_1 if the range of a_1 is [0,1] (well with a NOP_EXPR).
If I do it inside simplify_cond_using_ranges, I miss all the MODIFY_EXPRs.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28794
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/28794] missed optimization with non-COND_EXPR and vrp and comparisions
2006-08-21 23:24 [Bug tree-optimization/28794] New: missed optimization with non COND_EXPR and vrp and comparisions pinskia at gcc dot gnu dot org
2006-08-21 23:31 ` [Bug tree-optimization/28794] " pinskia at gcc dot gnu dot org
@ 2006-08-21 23:53 ` pinskia at gcc dot gnu dot org
2006-08-22 8:10 ` rguenth at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-08-21 23:53 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2006-08-21 23:52 -------
For x86, there is no difference in the code gen for f and f1/f2, but for PPC32,
there is:
for f1/f2:
addic %r0,%r31,-1
subfe %r3,%r0,%r31
For f:
srawi %r3,%r31,31
subf %r3,%r31,%r3
srwi %r3,%r3,31
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|missed optimization with non|missed optimization with
|COND_EXPR and vrp and |non-COND_EXPR and vrp and
|comparisions |comparisions
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28794
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/28794] missed optimization with non-COND_EXPR and vrp and comparisions
2006-08-21 23:24 [Bug tree-optimization/28794] New: missed optimization with non COND_EXPR and vrp and comparisions pinskia at gcc dot gnu dot org
2006-08-21 23:31 ` [Bug tree-optimization/28794] " pinskia at gcc dot gnu dot org
2006-08-21 23:53 ` [Bug tree-optimization/28794] missed optimization with non-COND_EXPR " pinskia at gcc dot gnu dot org
@ 2006-08-22 8:10 ` rguenth at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-08-22 8:10 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2006-08-22 08:10 -------
Confirmed.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu dot
| |org
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2006-08-22 08:10:03
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28794
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2006-08-22 8:10 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2006-08-21 23:24 [Bug tree-optimization/28794] New: missed optimization with non COND_EXPR and vrp and comparisions pinskia at gcc dot gnu dot org
2006-08-21 23:31 ` [Bug tree-optimization/28794] " pinskia at gcc dot gnu dot org
2006-08-21 23:53 ` [Bug tree-optimization/28794] missed optimization with non-COND_EXPR " pinskia at gcc dot gnu dot org
2006-08-22 8:10 ` rguenth at gcc dot gnu dot org
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