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* [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels
@ 2011-01-12 15:48 d.g.gorbachev at gmail dot com
2011-01-13 10:56 ` [Bug rtl-optimization/47270] " rguenth at gcc dot gnu.org
` (9 more replies)
0 siblings, 10 replies; 11+ messages in thread
From: d.g.gorbachev at gmail dot com @ 2011-01-12 15:48 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Summary: [4.4/4.5/4.6 Regression] GCC produces
unnecessary/wrong code on -O2 and -O3 levels
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: d.g.gorbachev@gmail.com
Host: i686-pc-linux-gnu
Target: i686-pc-linux-gnu
Build: i686-pc-linux-gnu
$ cat > testcase.c
register int r asm("esi");
void foo(void)
{
if (r)
__asm__("sar\t%0" : "+r" (r));
__asm__("sar\t%0" : "+r" (r));
}
^D
$ gcc -O2 -S testcase.c
$ cat testcase.s
[...]
foo:
.LFB0:
xorl %eax, %eax
testl %esi, %esi
je .L2
#APP
# 6 "testcase.c" 1
sar %esi
# 0 "" 2
#NO_APP
movl %esi, %eax
.L2:
movl %eax, %esi
#APP
# 8 "testcase.c" 1
sar %esi
# 0 "" 2
#NO_APP
ret
[...]
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
@ 2011-01-13 10:56 ` rguenth at gcc dot gnu.org
2011-01-17 12:37 ` jakub at gcc dot gnu.org
` (8 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2011-01-13 10:56 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |4.4.6
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
2011-01-13 10:56 ` [Bug rtl-optimization/47270] " rguenth at gcc dot gnu.org
@ 2011-01-17 12:37 ` jakub at gcc dot gnu.org
2011-01-26 18:21 ` [Bug rtl-optimization/47270] [4.4/4.5/4.6 Regression] GCC produces unnecessary " d.g.gorbachev at gmail dot com
` (7 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: jakub at gcc dot gnu.org @ 2011-01-17 12:37 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P4
CC| |jakub at gcc dot gnu.org
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-01-17 12:06:11 UTC ---
Why do you think it is wrong? If %esi is non-zero upon entry, then it is just
moved to %eax and back, so it isn't changed, if it was zero upon entry, then 0
is loaded into it.
The reason for the extra code is that pre attempts to optimize it (register
vars are not SSA vars), so we get at *.optimized:
int prephitmp.4;
int r.0;
<bb 2>:
r.0_1 = r;
if (r.0_1 != 0)
goto <bb 3>;
else
goto <bb 4>;
<bb 3>:
__asm__("sar %0" : "=r" r : "0" r.0_1);
prephitmp.4_2 = r;
<bb 4>:
# prephitmp.4_8 = PHI <0(2), prephitmp.4_2(3)>
__asm__("sar %0" : "=r" r : "0" prephitmp.4_8);
and RTL optimizations aren't able to undo that. I doubt anything can be done
about this easily, with -fno-tree-pre you get your expected output.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.4/4.5/4.6 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
2011-01-13 10:56 ` [Bug rtl-optimization/47270] " rguenth at gcc dot gnu.org
2011-01-17 12:37 ` jakub at gcc dot gnu.org
@ 2011-01-26 18:21 ` d.g.gorbachev at gmail dot com
2011-04-16 10:30 ` [Bug rtl-optimization/47270] [4.4/4.5/4.6/4.7 " jakub at gcc dot gnu.org
` (6 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: d.g.gorbachev at gmail dot com @ 2011-01-26 18:21 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Dmitry Gorbachev <d.g.gorbachev at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Summary|[4.4/4.5/4.6 Regression] |[4.4/4.5/4.6 Regression]
|GCC produces |GCC produces unnecessary
|unnecessary/wrong code on |code on -O2 and -O3 levels
|-O2 and -O3 levels |
--- Comment #2 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> 2011-01-26 18:03:33 UTC ---
Ah, yes; changed the summary.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.4/4.5/4.6/4.7 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (2 preceding siblings ...)
2011-01-26 18:21 ` [Bug rtl-optimization/47270] [4.4/4.5/4.6 Regression] GCC produces unnecessary " d.g.gorbachev at gmail dot com
@ 2011-04-16 10:30 ` jakub at gcc dot gnu.org
2012-03-13 14:54 ` [Bug rtl-optimization/47270] [4.5/4.6/4.7/4.8 " jakub at gcc dot gnu.org
` (5 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: jakub at gcc dot gnu.org @ 2011-04-16 10:30 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.4.6 |4.4.7
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.5/4.6/4.7/4.8 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (3 preceding siblings ...)
2011-04-16 10:30 ` [Bug rtl-optimization/47270] [4.4/4.5/4.6/4.7 " jakub at gcc dot gnu.org
@ 2012-03-13 14:54 ` jakub at gcc dot gnu.org
2012-07-02 13:13 ` [Bug rtl-optimization/47270] [4.6/4.7/4.8 " rguenth at gcc dot gnu.org
` (4 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: jakub at gcc dot gnu.org @ 2012-03-13 14:54 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.4.7 |4.5.4
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-13 12:47:27 UTC ---
4.4 branch is being closed, moving to 4.5.4 target.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.6/4.7/4.8 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (4 preceding siblings ...)
2012-03-13 14:54 ` [Bug rtl-optimization/47270] [4.5/4.6/4.7/4.8 " jakub at gcc dot gnu.org
@ 2012-07-02 13:13 ` rguenth at gcc dot gnu.org
2013-03-05 23:29 ` steven at gcc dot gnu.org
` (3 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-07-02 13:13 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.5.4 |4.6.4
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.6/4.7/4.8 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (5 preceding siblings ...)
2012-07-02 13:13 ` [Bug rtl-optimization/47270] [4.6/4.7/4.8 " rguenth at gcc dot gnu.org
@ 2013-03-05 23:29 ` steven at gcc dot gnu.org
2013-04-12 15:18 ` [Bug rtl-optimization/47270] [4.7/4.8/4.9 " jakub at gcc dot gnu.org
` (2 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: steven at gcc dot gnu.org @ 2013-03-05 23:29 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-03-05
Ever Confirmed|0 |1
--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> 2013-03-05 23:28:58 UTC ---
(In reply to comment #1)
> and RTL optimizations aren't able to undo that. I doubt anything can
> be done about this easily.
Perhaps tree-ssa-uncprop should handle this.
FWIW, I've always thought that constant propagation into PHI arguments
was a mistake...
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.7/4.8/4.9 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (6 preceding siblings ...)
2013-03-05 23:29 ` steven at gcc dot gnu.org
@ 2013-04-12 15:18 ` jakub at gcc dot gnu.org
2013-04-12 20:34 ` d.g.gorbachev at gmail dot com
2013-12-25 0:00 ` steven at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-04-12 15:18 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.6.4 |4.7.4
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-12 15:16:51 UTC ---
GCC 4.6.4 has been released and the branch has been closed.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.7/4.8/4.9 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (7 preceding siblings ...)
2013-04-12 15:18 ` [Bug rtl-optimization/47270] [4.7/4.8/4.9 " jakub at gcc dot gnu.org
@ 2013-04-12 20:34 ` d.g.gorbachev at gmail dot com
2013-12-25 0:00 ` steven at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: d.g.gorbachev at gmail dot com @ 2013-04-12 20:34 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
--- Comment #6 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> 2013-04-12 20:34:31 UTC ---
I can't reproduce the bug with GCC 4.7.3 and 4.8.1.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/47270] [4.7/4.8/4.9 Regression] GCC produces unnecessary code on -O2 and -O3 levels
2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
` (8 preceding siblings ...)
2013-04-12 20:34 ` d.g.gorbachev at gmail dot com
@ 2013-12-25 0:00 ` steven at gcc dot gnu.org
9 siblings, 0 replies; 11+ messages in thread
From: steven at gcc dot gnu.org @ 2013-12-25 0:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47270
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #7 from Steven Bosscher <steven at gcc dot gnu.org> ---
Apparently fixed (probably by IRA).
^ permalink raw reply [flat|nested] 11+ messages in thread
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2011-01-12 15:48 [Bug rtl-optimization/47270] New: [4.4/4.5/4.6 Regression] GCC produces unnecessary/wrong code on -O2 and -O3 levels d.g.gorbachev at gmail dot com
2011-01-13 10:56 ` [Bug rtl-optimization/47270] " rguenth at gcc dot gnu.org
2011-01-17 12:37 ` jakub at gcc dot gnu.org
2011-01-26 18:21 ` [Bug rtl-optimization/47270] [4.4/4.5/4.6 Regression] GCC produces unnecessary " d.g.gorbachev at gmail dot com
2011-04-16 10:30 ` [Bug rtl-optimization/47270] [4.4/4.5/4.6/4.7 " jakub at gcc dot gnu.org
2012-03-13 14:54 ` [Bug rtl-optimization/47270] [4.5/4.6/4.7/4.8 " jakub at gcc dot gnu.org
2012-07-02 13:13 ` [Bug rtl-optimization/47270] [4.6/4.7/4.8 " rguenth at gcc dot gnu.org
2013-03-05 23:29 ` steven at gcc dot gnu.org
2013-04-12 15:18 ` [Bug rtl-optimization/47270] [4.7/4.8/4.9 " jakub at gcc dot gnu.org
2013-04-12 20:34 ` d.g.gorbachev at gmail dot com
2013-12-25 0:00 ` steven at gcc dot gnu.org
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