https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67955
Bug ID: 67955
Summary: tree-dse does not use pointer info
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
Consider this testcase, with dead store '*p = 1':
...
int
f ()
{
int a;
int *p = &a;
*p = 1;
a = 2;
return a;
}
...
We compile with -O2 -fno-tree-ccp -fno-tree-forwprop -fno-tree-fre.
At dse1 we have
...
f ()
{
int * p;
int a;
int _5;
<bb 2>:
p_1 = &a;
*p_1 = 1;
a = 2;
_5 = a;
a ={v} {CLOBBER};
return _5;
}
...
So, the dead store '*p_1 = 1' has not been eliminated.
However, at ealias we already know:
...
Alias information for f
Aliased symbols
a, UID D.1757, int, is addressable
Call clobber information
ESCAPED, points-to non-local, points-to vars: { }
Flow-insensitive points-to information
p_1, points-to vars: { D.1757 }
...
So, we could use points-to info in dce.
