public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug middle-end/23664] New: fold does not change (a&C1)+(b&C2) to (a&C1)|(b&C2) iff (C1 & C2) == 0
@ 2005-09-01 0:40 pinskia at gcc dot gnu dot org
2005-09-01 0:42 ` [Bug middle-end/23664] " pinskia at gcc dot gnu dot org
2005-09-17 2:12 ` pinskia at gcc dot gnu dot org
0 siblings, 2 replies; 3+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-09-01 0:40 UTC (permalink / raw)
To: gcc-bugs
These two functions should produce the same asm:
int f(int a, int b)
{
return (a&0xF)+(b&0xF0);
}
int f1(int a, int b)
{
return (a&0xF)|(b&0xF0);
}
For PPC, we get:
_f:
rlwinm r4,r4,0,24,27
rlwinm r3,r3,0,28,31
add r3,r3,r4
blr
_f1:
rlwinm r4,r4,0,24,27
rlwimi r3,r4,0,0,27
blr
Which shows the | is more efficient than the + one.
--
Summary: fold does not change (a&C1)+(b&C2) to (a&C1)|(b&C2) iff
(C1 & C2) == 0
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P2
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pinskia at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc-*-*
OtherBugsDependingO 19987
nThis:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23664
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2005-09-17 2:12 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-09-01 0:40 [Bug middle-end/23664] New: fold does not change (a&C1)+(b&C2) to (a&C1)|(b&C2) iff (C1 & C2) == 0 pinskia at gcc dot gnu dot org
2005-09-01 0:42 ` [Bug middle-end/23664] " pinskia at gcc dot gnu dot org
2005-09-17 2:12 ` pinskia at gcc dot gnu dot org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).