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* [Bug tree-optimization/23659] New: Should able to add dereferencing (statements with VUSE) without rerunning may_alias
@ 2005-08-31 17:00 pinskia at gcc dot gnu dot org
2005-08-31 17:02 ` [Bug tree-optimization/23659] " 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 @ 2005-08-31 17:00 UTC (permalink / raw)
To: gcc-bugs
An example of this comes from PR 18298:
extern "C" int strcmp (const char*, const char*);
char s[2048] = "a";
inline bool foo(const char *str) {
return !strcmp(s,str);
}
int main() {
while(!(foo(""))) {
s[0] = '\0';
}
return 0;
}
In fab, we replace:
# VUSE <s_1>;
D.1754_4 = strcmp (&s[0], &""[0]);
With
D.1777_6 = (const unsigned char *) &s[0];
D.1778_9 = *D.1777_6;
D.1779_3 = (int) D.1778_9;
D.1754_4 = D.1779_3;
And the " D.1778_9 = *D.1777_6;" statement does not have a VUSE which causes wrong code if we
have a V_MAY_DEF/V_MUST_DEF above (which happens in the testcase).
The main reason why I am asking this question so that in the tree combiner, I don't want to rerun
may_alias after each time I run the tree combiner which just becomes too expensive.
An example for the tree combiner would be:
int f(char *a)
{
int b = strlen(a);
return b == 0;
}
--
Summary: Should able to add dereferencing (statements with VUSE)
without rerunning may_alias
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P2
Component: tree-optimization
AssignedTo: dnovillo at gcc dot gnu dot org
ReportedBy: pinskia at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23659
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/23659] Should able to add dereferencing (statements with VUSE) without rerunning may_alias
2005-08-31 17:00 [Bug tree-optimization/23659] New: Should able to add dereferencing (statements with VUSE) without rerunning may_alias pinskia at gcc dot gnu dot org
@ 2005-08-31 17:02 ` pinskia at gcc dot gnu dot org
2005-08-31 21:41 ` steven at gcc dot gnu dot org
2005-08-31 21:57 ` dnovillo at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-08-31 17:02 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2005-08-31 17:00:14
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23659
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/23659] Should able to add dereferencing (statements with VUSE) without rerunning may_alias
2005-08-31 17:00 [Bug tree-optimization/23659] New: Should able to add dereferencing (statements with VUSE) without rerunning may_alias pinskia at gcc dot gnu dot org
2005-08-31 17:02 ` [Bug tree-optimization/23659] " pinskia at gcc dot gnu dot org
@ 2005-08-31 21:41 ` steven at gcc dot gnu dot org
2005-08-31 21:57 ` dnovillo at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: steven at gcc dot gnu dot org @ 2005-08-31 21:41 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From steven at gcc dot gnu dot org 2005-08-31 21:38 -------
Can the alias gurus please give their view on this one?
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |dberlin at gcc dot gnu dot
| |org, dnovillo at gcc dot gnu
| |dot org
Keywords| |alias
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23659
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/23659] Should able to add dereferencing (statements with VUSE) without rerunning may_alias
2005-08-31 17:00 [Bug tree-optimization/23659] New: Should able to add dereferencing (statements with VUSE) without rerunning may_alias pinskia at gcc dot gnu dot org
2005-08-31 17:02 ` [Bug tree-optimization/23659] " pinskia at gcc dot gnu dot org
2005-08-31 21:41 ` steven at gcc dot gnu dot org
@ 2005-08-31 21:57 ` dnovillo at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: dnovillo at gcc dot gnu dot org @ 2005-08-31 21:57 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From dnovillo at gcc dot gnu dot org 2005-08-31 21:41 -------
Working on it.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23659
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2005-08-31 21:41 UTC | newest]
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2005-08-31 17:00 [Bug tree-optimization/23659] New: Should able to add dereferencing (statements with VUSE) without rerunning may_alias pinskia at gcc dot gnu dot org
2005-08-31 17:02 ` [Bug tree-optimization/23659] " pinskia at gcc dot gnu dot org
2005-08-31 21:41 ` steven at gcc dot gnu dot org
2005-08-31 21:57 ` dnovillo at gcc dot gnu dot org
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