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* [Bug tree-optimization/19788] New: Inconsistent handling of -1.
@ 2005-02-06 10:20 kazu@cs.umass.edu
2005-02-06 15:29 ` [Bug tree-optimization/19788] " kazu@cs.umass.edu
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: kazu@cs.umass.edu @ 2005-02-06 10:20 UTC (permalink / raw)
To: gcc-bugs
Consider:
int
foo (void)
{
return -1;
}
int
bar (void)
{
unsigned int a = 0xffffffff;
return a;
}
int
baz (void)
{
int a = -1;
unsigned int b = 0xffffffff;
return a == (int) b;
}
Here is what I get:
;; Function foo (foo)
foo ()
{
<bb 0>:
return -1;
}
;; Function bar (bar)
bar ()
{
int D.1124;
<bb 0>:
D.1124 = -000000001;
return D.1124;
}
;; Function baz (baz)
baz ()
{
int b.0;
<bb 0>:
b.0 = -000000001;
return b.0 == -1;
}
Note that -1 is represented in two different ways in foo and bar.
Worse yet, the tree optimizers do not know that they are equal in baz.
baz is optimized as expected at RTL level.
--
Summary: Inconsistent handling of -1.
Product: gcc
Version: unknown
Status: UNCONFIRMED
Keywords: missed-optimization, TREE
Severity: enhancement
Priority: P2
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: kazu at cs dot umass dot edu
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
@ 2005-02-06 15:29 ` kazu@cs.umass.edu
2005-02-06 16:05 ` pinskia@gcc.gnu.org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: kazu@cs.umass.edu @ 2005-02-06 15:29 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
OtherBugsDependingO| |19721
nThis| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
2005-02-06 15:29 ` [Bug tree-optimization/19788] " kazu@cs.umass.edu
@ 2005-02-06 16:05 ` pinskia@gcc.gnu.org
2005-02-06 16:54 ` schlie@comcast.net
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia@gcc.gnu.org @ 2005-02-06 16:05 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-02-06 16:04 -------
Confirmed. The problem is from TREE_OVERFLOW/TREE_CONSTANT_OVERFLOW.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2005-02-06 16:04:44
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
2005-02-06 15:29 ` [Bug tree-optimization/19788] " kazu@cs.umass.edu
2005-02-06 16:05 ` pinskia@gcc.gnu.org
@ 2005-02-06 16:54 ` schlie@comcast.net
2005-02-06 16:54 ` pinskia@gcc.gnu.org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: schlie@comcast.net @ 2005-02-06 16:54 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From schlie at comcast dot net 2005-02-06 17:14 -------
(In reply to comment #1)
- as I'm curious as to what the "proper" interpretation/handling of
target dependant constant value casts should be; it seems that in
the provided example, the optimized transformations of 0xffffffff
to an (int)-1 intermediate value in bar & baz are consistent, assuming:
(((0xffffffff) >> ((sizeof(int) * BITS_PER_UNIT)) & 1)
however would have expected the comparison between a & b in baz
to have been optimized away; is this a reasonable expectation?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
` (2 preceding siblings ...)
2005-02-06 16:54 ` schlie@comcast.net
@ 2005-02-06 16:54 ` pinskia@gcc.gnu.org
2005-02-08 5:46 ` pinskia at gcc dot gnu dot org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia@gcc.gnu.org @ 2005-02-06 16:54 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-02-06 17:17 -------
(In reply to comment #2)
> (In reply to comment #1)
Really TREE_OVERFLOW/TREE_CONSTANT_OVERFLOW should go away, there has been some talk about
removing them. on the tree level, having that flag set we really say the constant is no longer be able to
prograte which causes the real problem.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
` (3 preceding siblings ...)
2005-02-06 16:54 ` pinskia@gcc.gnu.org
@ 2005-02-08 5:46 ` pinskia at gcc dot gnu dot org
2005-03-16 12:31 ` steven at gcc dot gnu dot org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-02-08 5:46 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-02-07 20:17 -------
(In reply to comment #3)
> (In reply to comment #2)
> > (In reply to comment #1)
> Really TREE_OVERFLOW/TREE_CONSTANT_OVERFLOW should go away, there has been some talk
about
> removing them. on the tree level, having that flag set we really say the constant is no longer be able
to
> prograte which causes the real problem.
Note I am talking about:
http://www.srcf.ucam.org/~jsm28/gcc/
"Similarly, it should also be possible to get rid of at least one of TREE_OVERFLOW and
TREE_CONSTANT_OVERFLOW, which also describe what are essentially front-end properties."
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
` (4 preceding siblings ...)
2005-02-08 5:46 ` pinskia at gcc dot gnu dot org
@ 2005-03-16 12:31 ` steven at gcc dot gnu dot org
2005-03-16 14:53 ` kazu at cs dot umass dot edu
2005-03-16 14:54 ` pinskia at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: steven at gcc dot gnu dot org @ 2005-03-16 12:31 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From steven at gcc dot gnu dot org 2005-03-16 12:30 -------
Someone should check if this is fixed now, by this patch:
http://gcc.gnu.org/ml/gcc-patches/2005-03/msg01122.html
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |stevenb at suse dot de
Status|NEW |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
` (5 preceding siblings ...)
2005-03-16 12:31 ` steven at gcc dot gnu dot org
@ 2005-03-16 14:53 ` kazu at cs dot umass dot edu
2005-03-16 14:54 ` pinskia at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: kazu at cs dot umass dot edu @ 2005-03-16 14:53 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From kazu at cs dot umass dot edu 2005-03-16 14:53 -------
Here is what I get from the current mainline.
;; Function foo (foo)
foo ()
{
int D.1132;
<bb 0>:
return -1;
}
;; Function bar (bar)
bar ()
{
unsigned int a;
int D.1137;
<bb 0>:
return -000000001;
}
;; Function baz (baz)
baz ()
{
unsigned int b;
int a;
int b.0;
int D.1143;
<bb 0>:
return 1;
}
So the problem seems to be fixed.
It would still be nice to see -1 instead of -000000001 though.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/19788] Inconsistent handling of -1.
2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
` (6 preceding siblings ...)
2005-03-16 14:53 ` kazu at cs dot umass dot edu
@ 2005-03-16 14:54 ` pinskia at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-03-16 14:54 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |4.1.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19788
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2005-03-16 14:54 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
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2005-02-06 10:20 [Bug tree-optimization/19788] New: Inconsistent handling of -1 kazu@cs.umass.edu
2005-02-06 15:29 ` [Bug tree-optimization/19788] " kazu@cs.umass.edu
2005-02-06 16:05 ` pinskia@gcc.gnu.org
2005-02-06 16:54 ` schlie@comcast.net
2005-02-06 16:54 ` pinskia@gcc.gnu.org
2005-02-08 5:46 ` pinskia at gcc dot gnu dot org
2005-03-16 12:31 ` steven at gcc dot gnu dot org
2005-03-16 14:53 ` kazu at cs dot umass dot edu
2005-03-16 14:54 ` pinskia at gcc dot gnu dot org
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