[Bug rtl-optimization/30747] New: gcc should optimize x / (cond ? const1 : const2)
ak at muc dot de
gcc-bugzilla@gcc.gnu.org
Fri Feb 9 15:41:00 GMT 2007
(seen on other targets too)
For
x / (cond ? const1 : const2)
gcc currently always generates a slow general purpose div. But it would
be much faster to rewrite it to
cond ? (x / const1 : x / const2)
and then use the optimized sequences for division by constant
In the Linux kernel there are a few cases where this would help.
e.g. it is common in device drivers which manage a ring buffer and the ring
size depends on the hardware revision.
It would be also useful for some other cases where it is not easy
to rewrite the code by hand to the better form.
I made it rtl-optimization, although I presume it could be as well
done on tree level?
--
Summary: gcc should optimize x / (cond ? const1 : const2)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ak at muc dot de
GCC target triplet: x86_64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30747
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