* [Bug target/19672] [3.4/4.0/4.1 Regression] Performance regression in simple loop code
[not found] <bug-19672-8689@http.gcc.gnu.org/bugzilla/>
@ 2005-10-18 9:48 ` bonzini at gcc dot gnu dot org
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From: bonzini at gcc dot gnu dot org @ 2005-10-18 9:48 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from bonzini at gcc dot gnu dot org 2005-10-18 09:48 -------
Can anybody try killloop-branch? Just a wild guess.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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2005-10-18 9:48 ` [Bug target/19672] [3.4/4.0/4.1 Regression] Performance regression in simple loop code bonzini at gcc dot gnu dot org
@ 2005-10-18 9:55 ` bonzini at gcc dot gnu dot org
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From: bonzini at gcc dot gnu dot org @ 2005-10-18 9:55 UTC (permalink / raw)
To: gcc-bugs
------- Comment #10 from bonzini at gcc dot gnu dot org 2005-10-18 09:55 -------
There is also a (minor) register allocation problem in both outputs:
8048392: 0f be 01 movsbl (%ecx),%eax ! |
8048395: 0f be 13 movsbl (%ebx),%edx ! |
8048398: 29 c2 sub %eax,%edx ! |
804839a: 89 d0 mov %edx,%eax ! |
804839c: 74 e2 je 8048380 ! --+
This could obviously become
8048392: 0f be 11 movsbl (%ecx),%edx
8048395: 0f be 03 movsbl (%ebx),%eax
8048398: 2b c2 sub %edx,%eax
804839c: 74 e2 je 8048380
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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2005-10-18 9:48 ` [Bug target/19672] [3.4/4.0/4.1 Regression] Performance regression in simple loop code bonzini at gcc dot gnu dot org
2005-10-18 9:55 ` bonzini at gcc dot gnu dot org
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From: bonzini at gcc dot gnu dot org @ 2005-10-18 10:07 UTC (permalink / raw)
To: gcc-bugs
------- Comment #11 from bonzini at gcc dot gnu dot org 2005-10-18 10:07 -------
The code I get from -mbranch-cost=1 is extremely similar to what 3.2.2
produced:
.L7:
cmpl %ebx, %edi
jae .L2
cmpl %ecx, %esi
jae .L2
decl %ebx
movsbl -1(%ecx),%eax
decl %ecx
movsbl (%ebx),%edx
subl %eax, %edx
movl %edx, %eax
je .L7
.L2:
The front-end is correctly producing a TRUTH_AND_EXPR, i.e. the
short-circuiting is not required. RTL expansion will use jae (short-circuited
evaluation) or seta, depending on the branch cost.
However, the tuning here is wrong because on a pentium4 I do get a 40% speedup
from -mbranch-cost=1.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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From: bonzini at gcc dot gnu dot org @ 2005-10-18 11:41 UTC (permalink / raw)
To: gcc-bugs
------- Comment #12 from bonzini at gcc dot gnu dot org 2005-10-18 11:41 -------
Created an attachment (id=10016)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10016&action=view)
patch to fix the bug
Indeed, RTL expansion will use jae (short-circuited evaluation) or seta,
depending on the branch cost, but in a very involuted way which screws up the
tuning.
This patch makes it more direct.
--
bonzini at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|unassigned at gcc dot gnu |bonzini at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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From: bonzini at gcc dot gnu dot org @ 2005-10-18 16:04 UTC (permalink / raw)
To: gcc-bugs
------- Comment #13 from bonzini at gcc dot gnu dot org 2005-10-18 16:04 -------
The patch is not good because I forgot to check fallthrough edges. The code I
added goes above, just before "case CALL_EXPR:".
Restarting a bootstrap with a correct patch.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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From: cvs-commit at gcc dot gnu dot org @ 2005-10-19 10:37 UTC (permalink / raw)
To: gcc-bugs
------- Comment #14 from cvs-commit at gcc dot gnu dot org 2005-10-19 10:37 -------
Subject: Bug 19672
CVSROOT: /cvs/gcc
Module name: gcc
Changes by: bonzini@gcc.gnu.org 2005-10-19 10:37:31
Modified files:
gcc : ChangeLog dojump.c
Log message:
2005-10-18 Paolo Bonzini <bonzini@gnu.org>
PR #19672
* dojump.c (do_jump): Handle TRUTH_AND_EXPR and TRUTH_OR_EXPR here.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.10182&r2=2.10183
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/dojump.c.diff?cvsroot=gcc&r1=1.42&r2=1.43
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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From: cvs-commit at gcc dot gnu dot org @ 2005-10-19 10:41 UTC (permalink / raw)
To: gcc-bugs
------- Comment #15 from cvs-commit at gcc dot gnu dot org 2005-10-19 10:41 -------
Subject: Bug 19672
CVSROOT: /cvs/gcc
Module name: gcc
Branch: gcc-4_0-branch
Changes by: bonzini@gcc.gnu.org 2005-10-19 10:41:09
Modified files:
gcc : dojump.c ChangeLog
Log message:
2005-10-18 Paolo Bonzini <bonzini@gnu.org>
PR #19672
* dojump.c (do_jump): Handle TRUTH_AND_EXPR and TRUTH_OR_EXPR here.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/dojump.c.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=1.37.8.1&r2=1.37.8.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-4_0-branch&r1=2.7592.2.470&r2=2.7592.2.471
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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From: cvs-commit at gcc dot gnu dot org @ 2005-10-19 10:50 UTC (permalink / raw)
To: gcc-bugs
------- Comment #16 from cvs-commit at gcc dot gnu dot org 2005-10-19 10:50 -------
Subject: Bug 19672
CVSROOT: /cvs/gcc
Module name: gcc
Branch: gcc-3_4-branch
Changes by: bonzini@gcc.gnu.org 2005-10-19 10:49:57
Modified files:
gcc : ChangeLog dojump.c
Log message:
2005-10-19 Paolo Bonzini <bonzini@gnu.org>
PR #19672
* dojump.c (do_jump): Handle TRUTH_AND_EXPR and TRUTH_OR_EXPR
like TRUTH_ANDIF_EXPR and TRUTH_ORIF_EXPR, if the branch cost
is low enough.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.923&r2=2.2326.2.924
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/dojump.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.9.4.2&r2=1.9.4.3
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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From: bonzini at gcc dot gnu dot org @ 2005-10-19 10:57 UTC (permalink / raw)
To: gcc-bugs
------- Comment #17 from bonzini at gcc dot gnu dot org 2005-10-19 10:57 -------
Patches committed to all active branches.
--
bonzini at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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2005-10-19 10:57 ` bonzini at gcc dot gnu dot org
@ 2005-10-19 11:40 ` pinskia at gcc dot gnu dot org
2005-11-05 12:15 ` [Bug target/19672] [3.4] " bonzini at gcc dot gnu dot org
2005-11-21 2:26 ` [Bug target/19672] [3.4 Regression] " gdr at gcc dot gnu dot org
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From: pinskia at gcc dot gnu dot org @ 2005-10-19 11:40 UTC (permalink / raw)
To: gcc-bugs
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.0.3 |3.4.5
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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2005-11-21 2:26 ` [Bug target/19672] [3.4 Regression] " gdr at gcc dot gnu dot org
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From: bonzini at gcc dot gnu dot org @ 2005-11-05 12:15 UTC (permalink / raw)
To: gcc-bugs
------- Comment #18 from bonzini at gcc dot gnu dot org 2005-11-05 12:15 -------
Patch had to be reverted on 3.4
--
bonzini at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Known to fail|3.3.3 3.4.0 4.0.0 4.1.0 |3.3.3 3.4.5 4.0.2
Known to work|2.95.3 3.2.3 |2.95.3 3.2.3 4.0.3 4.1.0
Resolution|FIXED |
Summary|[3.4/4.0/4.1 Regression] |[3.4] Performance regression
|Performance regression in |in simple loop code
|simple loop code |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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2005-11-05 12:15 ` [Bug target/19672] [3.4] " bonzini at gcc dot gnu dot org
@ 2005-11-21 2:26 ` gdr at gcc dot gnu dot org
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From: gdr at gcc dot gnu dot org @ 2005-11-21 2:26 UTC (permalink / raw)
To: gcc-bugs
------- Comment #19 from gdr at gcc dot gnu dot org 2005-11-21 02:26 -------
Fixed for 4.0.x and higher.
Won't fix in 3.4.x
--
gdr at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |FIXED
Target Milestone|3.4.5 |4.0.3
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19672
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