[Bug go/61303] gccgo: segfault, regression since 4.8.2

["maciej at opencsw dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61303

--- Comment #8 from Maciej Bliziński <maciej at opencsw dot org> ---
Here's my attempt to get some information:

experimental10s 14:35:13 ~/src/opencsw-gar/v2/go $ gcc -v
Reading specs from /opt/csw/lib/gcc/sparc-sun-solaris2.10/5.1.0/specs
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/opt/csw/libexec/gcc/sparc-sun-solaris2.10/5.1.0/lto-wrapper
Target: sparc-sun-solaris2.10
Configured with:
/home/dam/mgar/pkg/gcc5/trunk/work/solaris10-sparc/build-isa-sparcv8plus/gcc-5.1.0/configure
--prefix=/opt/csw --exec_prefix=/opt/csw --bindir=/opt/csw/bin
--sbindir=/opt/csw/sbin --libexs
Thread model: posix
gcc version 5.1.0 (GCC) 

experimental10s 14:31:43 ~/src/opencsw-gar/v2/go $ export CFLAGS="-g"
experimental10s 14:31:55 ~/src/opencsw-gar/v2/go $ gmake bin/package-gar-status
gccgo -o src/opencsw/diskformat/diskformat.o -g -c
src/opencsw/diskformat/diskformat.go
ginstall -m 755 src/opencsw/diskformat/diskformat.o opencsw/diskformat.o
gccgo -o src/opencsw/mantis/mantis.o -g -c src/opencsw/mantis/mantis.go
# ginstall
cp src/opencsw/mantis/mantis.o opencsw/mantis.o
gccgo -g -o bin/package-gar-status src/package-gar-status/package-gar-status.go
opencsw/diskformat.o opencsw/mantis.o
experimental10s 14:32:15 ~/src/opencsw-gar/v2/go $ # bin/package-gar-status
-output-file=foo.md 
experimental10s 14:32:29 ~/src/opencsw-gar/v2/go $ gdb bin/package-gar-status
GNU gdb (GDB) 7.7
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "sparc-sun-solaris2.10".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from bin/package-gar-status...done.
(gdb) run -output-file=foo.md
Starting program: /home/maciej/src/opencsw-gar/v2/go/bin/package-gar-status
-output-file=foo.md
[Thread debugging using libthread_db enabled]
[New Thread 1 (LWP 1)]
[New LWP    2        ]
[New LWP    3        ]
2015/05/04 14:33:05 Program start
2015/05/04 14:33:05 Looking at catalog  {unstable i386 SunOS5.10}  only.
2015/05/04 14:33:05 Making a request to
http://buildfarm.opencsw.org/pkgdb/rest/catalogs/unstable/i386/SunOS5.10/for-generation/as-dicts/
[New LWP    4        ]
[New LWP    5        ]
[New Thread 4 (LWP 4)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 4 (LWP 4)]
0xfe3c0d88 in memcpy () from
/platform/SUNW,SPARC-Enterprise-T5220/lib/libc_psr.so.1
(gdb) where
#0  0xfe3c0d88 in memcpy () from
/platform/SUNW,SPARC-Enterprise-T5220/lib/libc_psr.so.1
#1  0xfe9453d0 in runtime_netpoll (block=block@entry=1 '\001') at
/home/dam/mgar/pkg/gcc5/trunk/work/solaris10-sparc/build-isa-sparcv8plus/gcc-5.1.0/libgo/runtime/netpoll_select.c:163
#2  0xfe94a794 in findrunnable () at
/home/dam/mgar/pkg/gcc5/trunk/work/solaris10-sparc/build-isa-sparcv8plus/gcc-5.1.0/libgo/runtime/proc.c:1667
#3  schedule () at
/home/dam/mgar/pkg/gcc5/trunk/work/solaris10-sparc/build-isa-sparcv8plus/gcc-5.1.0/libgo/runtime/proc.c:1765
#4  0xfe94aad8 in runtime_mstart (mp=0xde315c00) at
/home/dam/mgar/pkg/gcc5/trunk/work/solaris10-sparc/build-isa-sparcv8plus/gcc-5.1.0/libgo/runtime/proc.c:1000
#5  0xff1baec8 in _lwp_start () from /lib/libc.so.1
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
>From gcc-bugs-return-485376-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Mon May 04 12:46:19 2015
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From: "hp at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/66004] New: [6 Regression]: performance of 26_numerics/random/negative_binomial_distribution/operators/values.cc
Date: Mon, 04 May 2015 12:46:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf004

            Bug ID: 66004
           Summary: [6 Regression]: performance of
                    26_numerics/random/negative_binomial_distribution/oper
                    ators/values.cc
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hp at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux-gnu
            Target: cris-elf

For r221618, this test took 34633750695 "basic clock cycles" in the CRIS
simulator.  For r222742 (aka. "now"), it takes 40111446541 (same unit).  This
is a performance regression of about 16% in less than 1.5 month!  I noticed
because the test started to fail on my autotester machine during times of load,
when it has been previously silent.  The cris-elf is a 32-bit soft-float
target.

Note that the situation is the opposite of that in PR65093.

I'm listing the libstdc++ component as the cause, will update as my
(low-intensity) investigation (which I guess will be mostly bisecting)
continues.  It is also a likely culprit, with the recent work alluded to in
PR65093 (either further work or another side of the coin, of changes there
improving performance).

My first reaction, before checking for regression, was the test can and should
be split up as in PR65093.  I still think it should, after the regression is
fixed.

(Revision r221618 happens to be the last regression-free revision for cris-elf;
after that no components outside the gcc repo have been updated.)

Relative performance numbers for other platforms at svn revisions near those
above would be interesting.