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* [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10.
@ 2005-09-01 2:04 pinskia at gcc dot gnu dot org
2005-09-01 2:38 ` [Bug middle-end/23669] " pinskia at gcc dot gnu dot org
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-09-01 2:04 UTC (permalink / raw)
To: gcc-bugs
Another idea from LLVM.
The following two functions should be the same asm:
int f(int a)
{
return (-a)/10;
}
int f1(int a)
{
return a/-10;
}
----
We currently get on PPC:
_f:
lis r0,0x6666
neg r3,r3
ori r0,r0,26215
mulhw r0,r3,r0
srawi r3,r3,31
srawi r0,r0,2
subf r3,r3,r0
blr
_f1:
lis r0,0x6666
ori r0,r0,26215
mulhw r0,r3,r0
srawi r3,r3,31
srawi r0,r0,2
subf r3,r0,r3
blr
As you can see f1 has one less instruction which should be better.
--
Summary: fold does convert (-a)/10 into a/-10.
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
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
OtherBugsDependingO 19987
nThis:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669
^ permalink raw reply [flat|nested] 10+ messages in thread* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10. 2005-09-01 2:04 [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10 pinskia at gcc dot gnu dot org @ 2005-09-01 2:38 ` pinskia at gcc dot gnu dot org 2005-09-17 2:12 ` pinskia at gcc dot gnu dot org ` (2 subsequent siblings) 3 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-09-01 2:38 UTC (permalink / raw) To: gcc-bugs -- What |Removed |Added ---------------------------------------------------------------------------- Severity|normal |enhancement http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10. 2005-09-01 2:04 [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10 pinskia at gcc dot gnu dot org 2005-09-01 2:38 ` [Bug middle-end/23669] " pinskia at gcc dot gnu dot org @ 2005-09-17 2:12 ` pinskia at gcc dot gnu dot org 2005-10-01 17:25 ` mrnobo1024 at yahoo dot com 2005-10-01 17:34 ` [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-09-17 2:12 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2005-09-17 02:12 ------- Confirmed. -- What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever Confirmed| |1 Last reconfirmed|0000-00-00 00:00:00 |2005-09-17 02:12:00 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10. 2005-09-01 2:04 [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10 pinskia at gcc dot gnu dot org 2005-09-01 2:38 ` [Bug middle-end/23669] " pinskia at gcc dot gnu dot org 2005-09-17 2:12 ` pinskia at gcc dot gnu dot org @ 2005-10-01 17:25 ` mrnobo1024 at yahoo dot com 2005-10-01 17:34 ` [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 10+ messages in thread From: mrnobo1024 at yahoo dot com @ 2005-10-01 17:25 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From mrnobo1024 at yahoo dot com 2005-10-01 17:25 ------- Those expressions are only the same for floating point types. f(-2147483648) == -214748364 f1(-2147483648) == 214748364 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv 2005-09-01 2:04 [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10 pinskia at gcc dot gnu dot org ` (2 preceding siblings ...) 2005-10-01 17:25 ` mrnobo1024 at yahoo dot com @ 2005-10-01 17:34 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-10-01 17:34 UTC (permalink / raw) To: gcc-bugs ------- Additional Comments From pinskia at gcc dot gnu dot org 2005-10-01 17:34 ------- (In reply to comment #2) > Those expressions are only the same for floating point types. But -a for INT_MIN is undefined for signed type since it is an overflow. So the conversion is only valid for -fno-wrapv which is default for C, C++, Ada, and fortran. -- What |Removed |Added ---------------------------------------------------------------------------- Summary|fold does convert (-a)/10 |fold does convert (-a)/10 |into a/-10. |into a/-10 with -fno-wrapv http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <bug-23669-6528@http.gcc.gnu.org/bugzilla/>]
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv [not found] <bug-23669-6528@http.gcc.gnu.org/bugzilla/> @ 2005-11-25 6:17 ` pinskia at gcc dot gnu dot org 2005-11-26 18:08 ` pinskia at gcc dot gnu dot org ` (3 subsequent siblings) 4 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-11-25 6:17 UTC (permalink / raw) To: gcc-bugs ------- Comment #4 from pinskia at gcc dot gnu dot org 2005-11-25 06:17 ------- Ok, I have a patch which copies the code for Real divides into the int divides, though it adds !flag_wrapv. Though I am worry about the non truncate divide, I think it should be the same for them but for some reason I am worried. -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|unassigned at gcc dot gnu |pinskia at gcc dot gnu dot |dot org |org Status|NEW |ASSIGNED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv [not found] <bug-23669-6528@http.gcc.gnu.org/bugzilla/> 2005-11-25 6:17 ` pinskia at gcc dot gnu dot org @ 2005-11-26 18:08 ` pinskia at gcc dot gnu dot org 2005-11-26 22:18 ` pinskia at gcc dot gnu dot org ` (2 subsequent siblings) 4 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-11-26 18:08 UTC (permalink / raw) To: gcc-bugs ------- Comment #5 from pinskia at gcc dot gnu dot org 2005-11-26 18:08 ------- Patch posted: http://gcc.gnu.org/ml/gcc-patches/2005-11/msg01850.html -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- URL| |http://gcc.gnu.org/ml/gcc- | |patches/2005- | |11/msg01850.html Keywords| |patch http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv [not found] <bug-23669-6528@http.gcc.gnu.org/bugzilla/> 2005-11-25 6:17 ` pinskia at gcc dot gnu dot org 2005-11-26 18:08 ` pinskia at gcc dot gnu dot org @ 2005-11-26 22:18 ` pinskia at gcc dot gnu dot org 2005-11-26 22:18 ` pinskia at gcc dot gnu dot org 2005-12-12 20:09 ` pinskia at gcc dot gnu dot org 4 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-11-26 22:18 UTC (permalink / raw) To: gcc-bugs ------- Comment #7 from pinskia at gcc dot gnu dot org 2005-11-26 22:18 ------- Fixed. -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |RESOLVED Resolution| |FIXED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv [not found] <bug-23669-6528@http.gcc.gnu.org/bugzilla/> ` (2 preceding siblings ...) 2005-11-26 22:18 ` pinskia at gcc dot gnu dot org @ 2005-11-26 22:18 ` pinskia at gcc dot gnu dot org 2005-12-12 20:09 ` pinskia at gcc dot gnu dot org 4 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-11-26 22:18 UTC (permalink / raw) To: gcc-bugs ------- Comment #6 from pinskia at gcc dot gnu dot org 2005-11-26 22:18 ------- Subject: Bug 23669 Author: pinskia Date: Sat Nov 26 22:18:04 2005 New Revision: 107543 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=107543 Log: 2005-11-26 Andrew Pinski <pinskia@physics.uc.edu> PR middle-end/23669 * fold-const.c (fold_binary): Convert -A/-B to A/B for signed types when overflow is undefined. 2005-11-26 Andrew Pinski <pinskia@physics.uc.edu> PR middle-end/23669 * gcc.dg/tree-ssa/divide-1.c: New test. * gcc.dg/tree-ssa/divide-2.c: New test. Added: trunk/gcc/testsuite/gcc.dg/tree-ssa/divide-1.c trunk/gcc/testsuite/gcc.dg/tree-ssa/divide-2.c Modified: trunk/gcc/ChangeLog trunk/gcc/fold-const.c trunk/gcc/testsuite/ChangeLog -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv [not found] <bug-23669-6528@http.gcc.gnu.org/bugzilla/> ` (3 preceding siblings ...) 2005-11-26 22:18 ` pinskia at gcc dot gnu dot org @ 2005-12-12 20:09 ` pinskia at gcc dot gnu dot org 4 siblings, 0 replies; 10+ messages in thread From: pinskia at gcc dot gnu dot org @ 2005-12-12 20:09 UTC (permalink / raw) To: gcc-bugs -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |4.2.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669 ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2005-12-12 20:09 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-09-01 2:04 [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10 pinskia at gcc dot gnu dot org
2005-09-01 2:38 ` [Bug middle-end/23669] " pinskia at gcc dot gnu dot org
2005-09-17 2:12 ` pinskia at gcc dot gnu dot org
2005-10-01 17:25 ` mrnobo1024 at yahoo dot com
2005-10-01 17:34 ` [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv pinskia at gcc dot gnu dot org
[not found] <bug-23669-6528@http.gcc.gnu.org/bugzilla/>
2005-11-25 6:17 ` pinskia at gcc dot gnu dot org
2005-11-26 18:08 ` pinskia at gcc dot gnu dot org
2005-11-26 22:18 ` pinskia at gcc dot gnu dot org
2005-11-26 22:18 ` pinskia at gcc dot gnu dot org
2005-12-12 20:09 ` pinskia at gcc dot gnu dot org
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