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* [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading
@ 2003-12-04 10:21 rth at gcc dot gnu dot org
2003-12-04 10:22 ` [Bug optimization/13301] " rth at gcc dot gnu dot org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: rth at gcc dot gnu dot org @ 2003-12-04 10:21 UTC (permalink / raw)
To: gcc-bugs
$ ./cc1 -quiet -Wall -O z.c
z.c: In function `test':
z.c:22: warning: 'idx' might be used uninitialized in this function
The test case is representative of (reportedly many) similar warnings
generated from the Linux source code. The warning is suppressed at -O2
by rtl's jump bypassing pass. IMO this case should be handled by the
tree-level jump threading routines.
--
Summary: [tree-ssa] deficiency in jump threading
Product: gcc
Version: tree-ssa
Status: UNCONFIRMED
Severity: enhancement
Priority: P2
Component: optimization
AssignedTo: law at gcc dot gnu dot org
ReportedBy: rth at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug optimization/13301] [tree-ssa] deficiency in jump threading
2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
@ 2003-12-04 10:22 ` rth at gcc dot gnu dot org
2003-12-04 10:45 ` pinskia at gcc dot gnu dot org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rth at gcc dot gnu dot org @ 2003-12-04 10:22 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rth at gcc dot gnu dot org 2003-12-04 10:22 -------
Created an attachment (id=5274)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=5274&action=view)
Test case.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug optimization/13301] [tree-ssa] deficiency in jump threading
2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
2003-12-04 10:22 ` [Bug optimization/13301] " rth at gcc dot gnu dot org
@ 2003-12-04 10:45 ` pinskia at gcc dot gnu dot org
2003-12-04 11:12 ` rth at redhat dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2003-12-04 10:45 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2003-12-04 10:45 -------
I do not know if the tree jump threading supports switch tables at all (or the GNU extensions for
multiple cases) but it would be good to know the real case of this bug.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2003-12-04 10:45:19
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug optimization/13301] [tree-ssa] deficiency in jump threading
2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
2003-12-04 10:22 ` [Bug optimization/13301] " rth at gcc dot gnu dot org
2003-12-04 10:45 ` pinskia at gcc dot gnu dot org
@ 2003-12-04 11:12 ` rth at redhat dot com
2003-12-04 22:19 ` law at redhat dot com
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rth at redhat dot com @ 2003-12-04 11:12 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From rth at redhat dot com 2003-12-04 11:12 -------
Subject: Re: [tree-ssa] deficiency in jump threading
On Thu, Dec 04, 2003 at 10:45:19AM -0000, pinskia at gcc dot gnu dot org wrote:
> I do not know if the tree jump threading supports switch tables at all...
It does, but that's not the problem. Past the switch, the
"return NULL" gets compiled to "retval = NULL; goto retloc;"
and we must thread *that* goto with the if condition that
immediately follows.
> but it would be good to know the real case of this bug.
I have no doubt that there is a PHI node in the block that
contains the if condition, and that it is causing the
existing jump threading pass to give up.
I also happen to know that Jeff said that he is working on
this type of problem, so I assigned the PR to him.
r~
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug optimization/13301] [tree-ssa] deficiency in jump threading
2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
` (2 preceding siblings ...)
2003-12-04 11:12 ` rth at redhat dot com
@ 2003-12-04 22:19 ` law at redhat dot com
2004-01-11 17:22 ` pinskia at gcc dot gnu dot org
2004-01-15 19:01 ` law at gcc dot gnu dot org
5 siblings, 0 replies; 7+ messages in thread
From: law at redhat dot com @ 2003-12-04 22:19 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From law at redhat dot com 2003-12-04 22:19 -------
Subject: Re: [tree-ssa] deficiency in jump threading
In message <20031204111206.14420.qmail@sources.redhat.com>, "rth at redhat dot
com" writes:
>
>------- Additional Comments From rth at redhat dot com 2003-12-04 11:12 ----
>---
>Subject: Re: [tree-ssa] deficiency in jump threading
>
>On Thu, Dec 04, 2003 at 10:45:19AM -0000, pinskia at gcc dot gnu dot org wrot
>e:
>> I do not know if the tree jump threading supports switch tables at all...
>
>It does, but that's not the problem. Past the switch, the
>"return NULL" gets compiled to "retval = NULL; goto retloc;"
>and we must thread *that* goto with the if condition that
>immediately follows.
>
>> but it would be good to know the real case of this bug.
>
>I have no doubt that there is a PHI node in the block that
>contains the if condition, and that it is causing the
>existing jump threading pass to give up.
>
>I also happen to know that Jeff said that he is working on
>this type of problem, so I assigned the PR to him.
Yup. I've gone back to jump threading from the not-so-brief poking at
memory consumption issues.
jeff
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug optimization/13301] [tree-ssa] deficiency in jump threading
2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
` (3 preceding siblings ...)
2003-12-04 22:19 ` law at redhat dot com
@ 2004-01-11 17:22 ` pinskia at gcc dot gnu dot org
2004-01-15 19:01 ` law at gcc dot gnu dot org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-01-11 17:22 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |tree-ssa
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug optimization/13301] [tree-ssa] deficiency in jump threading
2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
` (4 preceding siblings ...)
2004-01-11 17:22 ` pinskia at gcc dot gnu dot org
@ 2004-01-15 19:01 ` law at gcc dot gnu dot org
5 siblings, 0 replies; 7+ messages in thread
From: law at gcc dot gnu dot org @ 2004-01-15 19:01 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From law at gcc dot gnu dot org 2004-01-15 19:01 -------
Fixed by my Jan 15, 2004 improvement to tree-ssa-dom.c
--
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13301
^ permalink raw reply [flat|nested] 7+ messages in thread
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2003-12-04 10:21 [Bug optimization/13301] New: [tree-ssa] deficiency in jump threading rth at gcc dot gnu dot org
2003-12-04 10:22 ` [Bug optimization/13301] " rth at gcc dot gnu dot org
2003-12-04 10:45 ` pinskia at gcc dot gnu dot org
2003-12-04 11:12 ` rth at redhat dot com
2003-12-04 22:19 ` law at redhat dot com
2004-01-11 17:22 ` pinskia at gcc dot gnu dot org
2004-01-15 19:01 ` law at gcc dot gnu dot org
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