public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [Bug c/14473] New: Failure to use count register
@ 2004-03-08 2:13 anton at samba dot org
2004-03-08 2:21 ` [Bug optimization/14473] " pinskia at gcc dot gnu dot org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: anton at samba dot org @ 2004-03-08 2:13 UTC (permalink / raw)
To: gcc-bugs
I found this in ppc32 3.3.3 (Debian), it also appears in 3.4.0 20040215.
If the loop count is large enough, it wont use the count register in the second
loop. eg:
#if 1
#define LOOPS 100000
#else
#define LOOPS 10
#endif
int main()
{
unsigned long i;
i = LOOPS;
while (i--) {
asm volatile("":::"memory");
}
i = LOOPS;
while (i--) {
asm volatile("":::"memory");
}
}
produces the following code:
lis 0,0x1
ori 0,0,34464
mtctr 0
.L13:
bdnz .L13
lis 0,0x1
ori 0,0,34464
.L12:
addic. 0,0,-1
bne+ 0,.L12
blr
If you reduce COUNT it will use the count register for both loops as expected
--
Summary: Failure to use count register
Product: gcc
Version: 3.4.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: anton at samba dot org
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14473
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug optimization/14473] Failure to use count register 2004-03-08 2:13 [Bug c/14473] New: Failure to use count register anton at samba dot org @ 2004-03-08 2:21 ` pinskia at gcc dot gnu dot org 2004-03-08 5:52 ` amodra at bigpond dot net dot au 2004-06-04 5:52 ` [Bug rtl-optimization/14473] " pinskia at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu dot org @ 2004-03-08 2:21 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-03-08 02:21 ------- I can confirm this on the mainline and the tree-ssa, I have not looked to see if the doloop rewrite fixes it as I do not have the lno branch on the computer which I have access to right now. -- What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Component|c |optimization Ever Confirmed| |1 Keywords| |pessimizes-code Known to fail| |3.4.0 3.3.3 3.5.0 tree-ssa Last reconfirmed|0000-00-00 00:00:00 |2004-03-08 02:21:31 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14473 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug optimization/14473] Failure to use count register 2004-03-08 2:13 [Bug c/14473] New: Failure to use count register anton at samba dot org 2004-03-08 2:21 ` [Bug optimization/14473] " pinskia at gcc dot gnu dot org @ 2004-03-08 5:52 ` amodra at bigpond dot net dot au 2004-06-04 5:52 ` [Bug rtl-optimization/14473] " pinskia at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: amodra at bigpond dot net dot au @ 2004-03-08 5:52 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From amodra at bigpond dot net dot au 2004-03-08 05:52 ------- I thought this looked familiar. There's an old patch of mine at http://gcc.gnu.org/ml/gcc-patches/2002-09/msg01194.html -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14473 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug rtl-optimization/14473] Failure to use count register 2004-03-08 2:13 [Bug c/14473] New: Failure to use count register anton at samba dot org 2004-03-08 2:21 ` [Bug optimization/14473] " pinskia at gcc dot gnu dot org 2004-03-08 5:52 ` amodra at bigpond dot net dot au @ 2004-06-04 5:52 ` pinskia at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu dot org @ 2004-06-04 5:52 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-06-04 05:52 ------- Fixed on the mainline, most likely by the rewrite of doloop optimization. -- What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED Target Milestone|--- |3.5.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14473 ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2004-06-04 5:52 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2004-03-08 2:13 [Bug c/14473] New: Failure to use count register anton at samba dot org 2004-03-08 2:21 ` [Bug optimization/14473] " pinskia at gcc dot gnu dot org 2004-03-08 5:52 ` amodra at bigpond dot net dot au 2004-06-04 5:52 ` [Bug rtl-optimization/14473] " 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).