public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2
@ 2013-04-23 16:25 tony.howard-co84udjx at yopmail dot com
2013-04-24 8:10 ` [Bug tree-optimization/57051] " mpolacek at gcc dot gnu.org
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: tony.howard-co84udjx at yopmail dot com @ 2013-04-23 16:25 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
Bug #: 57051
Summary: Optimization regression in 4.8.0 from 4.7.2
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: tony.howard-co84udjx@yopmail.com
The problem can be exhibited using the following snippet of code:
/* begin */
int total = 0;
inline void foo(int bar)
{
total += bar*10;
}
void hello()
{
for(int i = 0; i < 10; ++i)
{
foo(i);
}
}
/* end */
With the option -O3,
gcc 4.7.2 and previous versions produce the following assembly code:
hello():
addl $450, total(%rip)
ret
gcc 4.8.0 fails to optimize the code:
hello():
movdqa .LC0(%rip), %xmm0
movdqa %xmm0, %xmm2
psrldq $8, %xmm2
paddd %xmm2, %xmm0
movdqa %xmm0, %xmm3
psrldq $4, %xmm3
paddd %xmm3, %xmm0
movdqa %xmm0, %xmm4
movd %xmm4, -12(%rsp)
movl -12(%rsp), %eax
addl total(%rip), %eax
addl $170, %eax
movl %eax, total(%rip)
ret
The results can be easily reproduced using http://gcc.godbolt.org/
The 4.7.2's configure options are:
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.7.2-11precise2' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object
--enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
The 4.8.0's configure options are:
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.8.0-3ubuntu3~12.04' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin
--with-system-zlib --enable-objc-gc --enable-multiarch --disable-werror
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64
--with-tune=generic --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
The problem is not linked to Linaro or Ubuntu patches as it can be reproduced
as well on a stock version of gcc 4.8.0
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
@ 2013-04-24 8:10 ` mpolacek at gcc dot gnu.org
2013-04-24 8:30 ` [Bug tree-optimization/57051] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2013-04-24 8:10 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> 2013-04-24 08:10:21 UTC ---
Well, one thing differs, 4.7 with -O3 aligns 'total' to
.align 16
whereas 4.8 with -O3 -fno-tree-vectorize has
.align 4
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] [4.8/4.9 Regression] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
2013-04-24 8:10 ` [Bug tree-optimization/57051] " mpolacek at gcc dot gnu.org
@ 2013-04-24 8:30 ` rguenth at gcc dot gnu.org
2013-04-24 10:44 ` jakub at gcc dot gnu.org
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-04-24 8:30 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Known to work| |4.7.3
Version|unknown |4.8.0
Keywords| |missed-optimization
Last reconfirmed| |2013-04-24
CC| |glisse at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
Ever Confirmed|0 |1
Summary|Optimization regression in |[4.8/4.9 Regression]
|4.8.0 from 4.7.2 |Optimization regression in
| |4.8.0 from 4.7.2
Target Milestone|--- |4.8.1
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-24 08:30:06 UTC ---
It seems scev_cprop doesn't do its job here.
(get_scalar_evolution
(scalar = total.1_8)
(scalar_evolution = {pretmp_14, +, _6 + 10}_1))
that's ok - SCCP doesn't provide any info in dumps, but I suppose it
fails to compute the number of iterations here(!?).
And we don't constant-fold the vectorized code:
pretmp_14 = total;
vect_total.18_44 = { 40, 60, 80, 100 } v>> 64;
vect_total.18_45 = vect_total.18_44 + { 40, 60, 80, 100 };
vect_total.18_46 = vect_total.18_45 v>> 32;
vect_total.18_47 = vect_total.18_46 + vect_total.18_45;
stmp_total.17_48 = BIT_FIELD_REF <vect_total.18_47, 32, 0>;
vect_total.19_49 = stmp_total.17_48 + pretmp_14;
total.1_9 = vect_total.19_49 + 80;
total.1_20 = vect_total.19_49 + 170;
total = total.1_20;
because we do not constant-fold vector shifts. Two ways to attack the
problem (SCCP failure needs to be analyzed). In 4.7 SCCP works.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] [4.8/4.9 Regression] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
2013-04-24 8:10 ` [Bug tree-optimization/57051] " mpolacek at gcc dot gnu.org
2013-04-24 8:30 ` [Bug tree-optimization/57051] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
@ 2013-04-24 10:44 ` jakub at gcc dot gnu.org
2013-04-26 13:17 ` jakub at gcc dot gnu.org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-04-24 10:44 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-24 10:44:13 UTC ---
Created attachment 29928
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29928
gcc49-pr57051.patch
It isn't that hard to fold VEC_RSHIFT_EXPR, at least for the cases where the
shift count is a multiple of element bitsize (the only case where GCC actually
ever emits VEC_RSHIFT_EXPR right now).
Untested (beyond checking this is folded into store of 450 again).
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] [4.8/4.9 Regression] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
` (2 preceding siblings ...)
2013-04-24 10:44 ` jakub at gcc dot gnu.org
@ 2013-04-26 13:17 ` jakub at gcc dot gnu.org
2013-05-03 13:57 ` [Bug tree-optimization/57051] [4.8 " jakub at gcc dot gnu.org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-04-26 13:17 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-26 13:16:58 UTC ---
Author: jakub
Date: Fri Apr 26 13:13:36 2013
New Revision: 198339
URL: http://gcc.gnu.org/viewcvs?rev=198339&root=gcc&view=rev
Log:
PR tree-optimization/57051
* fold-const.c (const_binop): Handle VEC_LSHIFT_EXPR
and VEC_RSHIFT_EXPR if shift count is a multiple of element
bitsize.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/fold-const.c
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] [4.8 Regression] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
` (3 preceding siblings ...)
2013-04-26 13:17 ` jakub at gcc dot gnu.org
@ 2013-05-03 13:57 ` jakub at gcc dot gnu.org
2013-05-03 14:00 ` [Bug tree-optimization/57051] " jakub at gcc dot gnu.org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-05-03 13:57 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-05-03 13:57:52 UTC ---
Author: jakub
Date: Fri May 3 13:16:13 2013
New Revision: 198580
URL: http://gcc.gnu.org/viewcvs?rev=198580&root=gcc&view=rev
Log:
Backported from mainline
2013-04-26 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/57051
* fold-const.c (const_binop): Handle VEC_LSHIFT_EXPR
and VEC_RSHIFT_EXPR if shift count is a multiple of element
bitsize.
2013-04-12 Marc Glisse <marc.glisse@inria.fr>
* fold-const.c (fold_binary_loc): Call const_binop also for mixed
vector-scalar operations.
Modified:
branches/gcc-4_8-branch/gcc/ChangeLog
branches/gcc-4_8-branch/gcc/fold-const.c
The testcase should now no longer regress, keeping open for Richard's SCEV
investigation.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
` (4 preceding siblings ...)
2013-05-03 13:57 ` [Bug tree-optimization/57051] [4.8 " jakub at gcc dot gnu.org
@ 2013-05-03 14:00 ` jakub at gcc dot gnu.org
2013-05-06 11:55 ` rguenth at gcc dot gnu.org
2013-05-17 12:27 ` jakub at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-05-03 14:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|4.8.1 |---
Summary|[4.8 Regression] |Optimization regression in
|Optimization regression in |4.8.0 from 4.7.2
|4.8.0 from 4.7.2 |
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
` (5 preceding siblings ...)
2013-05-03 14:00 ` [Bug tree-optimization/57051] " jakub at gcc dot gnu.org
@ 2013-05-06 11:55 ` rguenth at gcc dot gnu.org
2013-05-17 12:27 ` jakub at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-05-06 11:55 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> 2013-05-06 11:54:55 UTC ---
Mine.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/57051] Optimization regression in 4.8.0 from 4.7.2
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
` (6 preceding siblings ...)
2013-05-06 11:55 ` rguenth at gcc dot gnu.org
@ 2013-05-17 12:27 ` jakub at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: jakub at gcc dot gnu.org @ 2013-05-17 12:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57051
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Fri May 17 08:31:32 2013
New Revision: 199002
URL: http://gcc.gnu.org/viewcvs?rev=199002&root=gcc&view=rev
Log:
PR tree-optimization/57051
* fold-const.c (const_binop) <case VEC_LSHIFT_EXPR,
case VEC_RSHIFT_EXPR>: Fix BYTES_BIG_ENDIAN handling.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/fold-const.c
Author: jakub
Date: Fri May 17 08:52:36 2013
New Revision: 199004
URL: http://gcc.gnu.org/viewcvs?rev=199004&root=gcc&view=rev
Log:
PR tree-optimization/57051
* fold-const.c (const_binop) <case VEC_LSHIFT_EXPR,
case VEC_RSHIFT_EXPR>: Fix BYTES_BIG_ENDIAN handling.
Modified:
branches/gcc-4_8-branch/gcc/ChangeLog
branches/gcc-4_8-branch/gcc/fold-const.c
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2013-05-17 12:27 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-04-23 16:25 [Bug c/57051] New: Optimization regression in 4.8.0 from 4.7.2 tony.howard-co84udjx at yopmail dot com
2013-04-24 8:10 ` [Bug tree-optimization/57051] " mpolacek at gcc dot gnu.org
2013-04-24 8:30 ` [Bug tree-optimization/57051] [4.8/4.9 Regression] " rguenth at gcc dot gnu.org
2013-04-24 10:44 ` jakub at gcc dot gnu.org
2013-04-26 13:17 ` jakub at gcc dot gnu.org
2013-05-03 13:57 ` [Bug tree-optimization/57051] [4.8 " jakub at gcc dot gnu.org
2013-05-03 14:00 ` [Bug tree-optimization/57051] " jakub at gcc dot gnu.org
2013-05-06 11:55 ` rguenth at gcc dot gnu.org
2013-05-17 12:27 ` jakub at gcc dot gnu.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).