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[Bug tree-optimization/42635] New: no-op conversions hinder if-conversion
- From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 6 Jan 2010 15:16:26 -0000
- Subject: [Bug tree-optimization/42635] New: no-op conversions hinder if-conversion
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
The following two functions are not if-converted at the tree level (the 2nd
example happens a lot from VEC code via VEC_BASE):
int *bar (char *p)
{
int *q;
if (p)
q = (int *)p;
else
q = (int *)0;
return q;
}
struct X { int q; };
int *foo (struct X *p)
{
int *q;
if (p)
q = &p->q;
else
q = (int *)0;
return q;
}
before phiopt1 we have
bar (char * p)
{
int * q;
<bb 2>:
if (p_2(D) != 0B)
goto <bb 3>;
else
goto <bb 4>;
<bb 3>:
q_3 = (int *) p_2(D);
<bb 4>:
# q_1 = PHI <q_3(3), 0B(2)>
return q_1;
which can be optimized to just
<bb 2>:
return (int *) p_2(D);
well - with a separate stmt for the conversion.
--
Summary: no-op conversions hinder if-conversion
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: rguenth at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42635