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* [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu
@ 2014-06-20 23:07 su at cs dot ucdavis.edu
2014-06-23 7:59 ` [Bug tree-optimization/61576] [4.10 Regression] " jakub at gcc dot gnu.org
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: su at cs dot ucdavis.edu @ 2014-06-20 23:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
Bug ID: 61576
Summary: wrong code at -O3 on x86_64-linux-gnu
Product: gcc
Version: 4.10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: su at cs dot ucdavis.edu
The current gcc trunk miscompiles the following testcase on x86_64-linux at -O3
in both 32-bit and 64-bit modes.
This is a regression from 4.9.x.
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 4.10.0 20140620 (experimental) [trunk revision 211848] (GCC)
$
$ gcc-trunk -O2 small.c; a.out
0
$ gcc-4.9.0 -O3 small.c; a.out
0
$
$ gcc-trunk -O3 small.c; a.out
1
$
--------------------------------
int printf (const char *, ...);
volatile int a, b;
int c, d, e, f;
static int
fn1 ()
{
if (b)
{
d++;
e = c || f;
}
return 0;
}
int
main ()
{
for (; a < 1; a++)
{
fn1 ();
continue;
}
printf ("%d\n", d);
return 0;
}
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
@ 2014-06-23 7:59 ` jakub at gcc dot gnu.org
2014-06-23 10:41 ` rguenth at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakub at gcc dot gnu.org @ 2014-06-23 7:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-06-23
CC| |chrbr at gcc dot gnu.org,
| |jakub at gcc dot gnu.org
Target Milestone|--- |4.10.0
Summary|wrong code at -O3 on |[4.10 Regression] wrong
|x86_64-linux-gnu |code at -O3 on
| |x86_64-linux-gnu
Ever confirmed|0 |1
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Worked up to and including r209971, started to ICE with r209972, that got fixed
in r211263. The wrong-code started in r211302. Given that was a cost change,
supposedly this has been latent before?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
2014-06-23 7:59 ` [Bug tree-optimization/61576] [4.10 Regression] " jakub at gcc dot gnu.org
@ 2014-06-23 10:41 ` rguenth at gcc dot gnu.org
2014-06-23 10:44 ` rguenth at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-06-23 10:41 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, but it doesn't do any PHI hoisting. -fno-tree-loop-if-convert fixes it,
-O2 -ftree-loop-if-convert breaks it.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
2014-06-23 7:59 ` [Bug tree-optimization/61576] [4.10 Regression] " jakub at gcc dot gnu.org
2014-06-23 10:41 ` rguenth at gcc dot gnu.org
@ 2014-06-23 10:44 ` rguenth at gcc dot gnu.org
2014-06-23 14:13 ` ysrumyan at gmail dot com
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-06-23 10:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ysrumyan at gmail dot com
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
+Found cond scalar reduction.
+d.6_12 = d_lsm.14_16 + 1;
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
` (2 preceding siblings ...)
2014-06-23 10:44 ` rguenth at gcc dot gnu.org
@ 2014-06-23 14:13 ` ysrumyan at gmail dot com
2014-06-26 8:00 ` izamyatin at gmail dot com
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: ysrumyan at gmail dot com @ 2014-06-23 14:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
--- Comment #4 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
There is an issue with phi-node and reduction stmt - after r211302 new hammock
was inserted between reduction stmt and bb containing phi:
<bb 6>:
d.6_12 = d_lsm.14_17 + 1;
if (c.8_13 != 0)
goto <bb 7>;
else
goto <bb 8>;
<bb 7>:
<bb 8>:
# iftmp.7_15 = PHI <1(7), _19(6)>
<bb 9>:
# d_lsm.14_16 = PHI <d_lsm.14_17(5), d.6_12(8)>
but algorithm for converting conditional scalar reduction assumes that basic
block containing reduction is one of predecessors of phi-block. I added check
on it and test is passed.
BTW I wonder why such code motion has been done - in fact, redundant
computations were introduced in loop, before this fix all computations related
to hammock were hoisted out off loop:
<bb 4>:
d_lsm.14_25 = d;
c.8_13 = c;
f.9_14 = f;
_18 = f.9_14 != 0;
_19 = (int) _18;
iftmp.7_15 = c.8_13 != 0 ? 1 : _19;
e_lsm.15_26 = e;
<bb 5>:
# d_lsm.14_17 = PHI <d_lsm.14_25(4), d_lsm.14_16(9)>
# e_lsm.15_1 = PHI <e_lsm.15_26(4), e_lsm.15_24(9)>
b.4_10 ={v} b;
if (b.4_10 != 0)
goto <bb 6>;
else
goto <bb 7>;
<bb 6>:
d.6_12 = d_lsm.14_17 + 1;
<bb 7>:
# d_lsm.14_16 = PHI <d_lsm.14_17(5), d.6_12(6)>
# e_lsm.15_24 = PHI <e_lsm.15_1(5), iftmp.7_15(6)>
I will send for review patch after required testing completion.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
` (3 preceding siblings ...)
2014-06-23 14:13 ` ysrumyan at gmail dot com
@ 2014-06-26 8:00 ` izamyatin at gmail dot com
2014-07-08 7:52 ` kyukhin at gcc dot gnu.org
2014-11-19 13:50 ` [Bug tree-optimization/61576] [5 " rguenth at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: izamyatin at gmail dot com @ 2014-06-26 8:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
Igor Zamyatin <izamyatin at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |izamyatin at gmail dot com
--- Comment #5 from Igor Zamyatin <izamyatin at gmail dot com> ---
Patch is posted at http://gcc.gnu.org/ml/gcc-patches/2014-06/msg01866.html
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
` (4 preceding siblings ...)
2014-06-26 8:00 ` izamyatin at gmail dot com
@ 2014-07-08 7:52 ` kyukhin at gcc dot gnu.org
2014-11-19 13:50 ` [Bug tree-optimization/61576] [5 " rguenth at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: kyukhin at gcc dot gnu.org @ 2014-07-08 7:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
--- Comment #6 from Kirill Yukhin <kyukhin at gcc dot gnu.org> ---
Author: kyukhin
Date: Tue Jul 8 07:52:12 2014
New Revision: 212347
URL: https://gcc.gnu.org/viewcvs?rev=212347&root=gcc&view=rev
Log:
PR tree-optimization/61576
gcc/
* tree-if-conv.c (is_cond_scalar_reduction): Add check that
basic block containing reduction statement is predecessor
of phi basi block.
gcc/testsuite/
* gcc.dg/torture/pr61576.c: New test.
Added:
trunk/gcc/testsuite/gcc.dg/torture/pr61576.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-if-conv.c
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/61576] [5 Regression] wrong code at -O3 on x86_64-linux-gnu
2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
` (5 preceding siblings ...)
2014-07-08 7:52 ` kyukhin at gcc dot gnu.org
@ 2014-11-19 13:50 ` rguenth at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-11-19 13:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2014-06-20 23:07 [Bug tree-optimization/61576] New: wrong code at -O3 on x86_64-linux-gnu su at cs dot ucdavis.edu
2014-06-23 7:59 ` [Bug tree-optimization/61576] [4.10 Regression] " jakub at gcc dot gnu.org
2014-06-23 10:41 ` rguenth at gcc dot gnu.org
2014-06-23 10:44 ` rguenth at gcc dot gnu.org
2014-06-23 14:13 ` ysrumyan at gmail dot com
2014-06-26 8:00 ` izamyatin at gmail dot com
2014-07-08 7:52 ` kyukhin at gcc dot gnu.org
2014-11-19 13:50 ` [Bug tree-optimization/61576] [5 " rguenth at gcc dot gnu.org
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