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* [Bug tree-optimization/45218] New: Mathematical simplification missed at tree-level
@ 2010-08-06 22:39 bernds at gcc dot gnu dot org
2010-08-06 22:51 ` [Bug tree-optimization/45218] " steven at gcc dot gnu dot org
0 siblings, 1 reply; 2+ messages in thread
From: bernds at gcc dot gnu dot org @ 2010-08-06 22:39 UTC (permalink / raw)
To: gcc-bugs
Consider
a = (x / 39) * 32 + (x % 39)
If we have no instruction to produce both the quotient and the remaineder, this
can be computed as
y = x / 39
z = x - y * 39
a = y * 32 + z
The last line can be simplified by substituting:
a = y * 32 + x - y * 39
a = y * (32 - 39) + x
a = x - y * 7
Testcase:
int i_size;
extern void foo (void);
int udf_check_anchor_block(int block)
{
i_size = ( ( ( (block) / 39 ) << 5 ) + ( block % 39 ));
return 1;
}
The tree optimization phase misses this, and this PR should stay open until
that is resolved. The combiner can handle it if it is able to look at 4
instructions.
--
Summary: Mathematical simplification missed at tree-level
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bernds at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45218
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/45218] Mathematical simplification missed at tree-level
2010-08-06 22:39 [Bug tree-optimization/45218] New: Mathematical simplification missed at tree-level bernds at gcc dot gnu dot org
@ 2010-08-06 22:51 ` steven at gcc dot gnu dot org
0 siblings, 0 replies; 2+ messages in thread
From: steven at gcc dot gnu dot org @ 2010-08-06 22:51 UTC (permalink / raw)
To: gcc-bugs
--
steven at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2010-08-06 22:51:00
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45218
^ permalink raw reply [flat|nested] 2+ messages in thread
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2010-08-06 22:39 [Bug tree-optimization/45218] New: Mathematical simplification missed at tree-level bernds at gcc dot gnu dot org
2010-08-06 22:51 ` [Bug tree-optimization/45218] " steven at gcc dot gnu dot org
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