| Message ID | CAPrifDmyRQeeereCPY+KNsuCzyovcxwpLv4HZw1_tR6kQ-yNNg@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Sun, Jan 19, 2014 at 4:59 PM, Tim Shen <timshen91@gmail.com> wrote: > Tested and committed. It's quite interesting that after this change in the patch: - this->_M_quantifier(); + while (this->_M_quantifier()); ...even the regex input is nothing to do with quantifiers at all (say regex re(" ")), g++ -O3 generates slower code than -O2: ~ # g++ -O2 perf.cc && time ./a.out ./a.out 0.46s user 0.00s system 99% cpu 0.461 total ~ # g++ -O3 perf.cc && time ./a.out ./a.out 0.56s user 0.00s system 99% cpu 0.569 total perf.cc is almost the same as testsuite/performance/28_regex/split.cc. Following the man page, I found that g++ claims that the difference between -O3 and -O2 are: ~ # /usr/bin/g++ -c -Q -O3 --help=optimizers > /tmp/O3-opts ~ # /usr/bin/g++ -c -Q -O2 --help=optimizers > /tmp/O2-opts ~ # diff /tmp/O2-opts /tmp/O3-opts | grep enabled > -fgcse-after-reload [enabled] > -finline-functions [enabled] > -fipa-cp-clone [enabled] > -fpredictive-commoning [enabled] > -ftree-loop-distribute-patterns [enabled] > -ftree-loop-vectorize [enabled] > -ftree-partial-pre [enabled] > -ftree-slp-vectorize [enabled] > -funswitch-loops [enabled] However, -O2 with those flags give me a postive result: ~ # g++ -O2 perf.cc -fgcse-after-reload -finline-functions -fipa-cp-clone -fpredictive-commoning -ftree-loop-distribute-patterns -ftree-loop-vectorize -ftree-partial-pre -ftree-slp-vectorize -funswitch-loops && time ./a.out ./a.out 0.45s user 0.01s system 99% cpu 0.460 total By the way, my "g++" is alas to "g++ -g -Wall -std=c++11", and I'm sure -g doesn't matter. I don't know much about it. Is there any explanations as interesting as the question? ;) Thank you!
On Mon, 20 Jan 2014, Tim Shen wrote: > ...even the regex input is nothing to do with quantifiers at all (say > regex re(" ")), g++ -O3 generates slower code than -O2: > > ~ # g++ -O2 perf.cc && time ./a.out > ./a.out 0.46s user 0.00s system 99% cpu 0.461 total > ~ # g++ -O3 perf.cc && time ./a.out > ./a.out 0.56s user 0.00s system 99% cpu 0.569 total > > perf.cc is almost the same as testsuite/performance/28_regex/split.cc. > > Following the man page, I found that g++ claims that the difference > between -O3 and -O2 are: It is a FAQ that you can't get the effects of -Oy with -Ox and a bunch of -f flags. Some things depend directly on the optimization level. Note that you can also try the reverse: start from -O3 and use -fno-* flags. I would first add -march=native to make sure this isn't the result of optimizing for a different platform. I would suggest you use -fdump-tree-optimized and look at the generated files at -O2 and -O3 and see (they are in a vaguely C-like dialect) if you can find a difference that might explain the result. If so, then you can use -fdump-tree-all and find out where exactly gcc is going wrong. If not, there is -da, but the files will be much harder to read. In any case, reducing the testcase can only make it easier to understand the issue.
Hi, On 01/20/2014 09:31 AM, Marc Glisse wrote: > It is a FAQ that you can't get the effects of -Oy with -Ox and a bunch > of -f flags. Some things depend directly on the optimization level. For example, inlining of free functions. By the way, I think it is a *very* common experience that -O3 doesn't do better than -O2. Thus I'm not particularly surprised or worried ;) Paolo.
diff --git a/libstdc++-v3/include/bits/regex_compiler.h b/libstdc++-v3/include/bits/regex_compiler.h index 216f8fb..fe2e5f1 100644 --- a/libstdc++-v3/include/bits/regex_compiler.h +++ b/libstdc++-v3/include/bits/regex_compiler.h @@ -83,7 +83,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION bool _M_assertion(); - void + bool _M_quantifier(); bool diff --git a/libstdc++-v3/include/bits/regex_compiler.tcc b/libstdc++-v3/include/bits/regex_compiler.tcc index 621e43f..128dac1 100644 --- a/libstdc++-v3/include/bits/regex_compiler.tcc +++ b/libstdc++-v3/include/bits/regex_compiler.tcc @@ -135,7 +135,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION return true; if (this->_M_atom()) { - this->_M_quantifier(); + while (this->_M_quantifier()); return true; } return false; @@ -173,7 +173,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } template<typename _TraitsT> - void + bool _Compiler<_TraitsT>:: _M_quantifier() { @@ -276,6 +276,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } _M_stack.push(__e); } + else + return false; + return true; } #define __INSERT_REGEX_MATCHER(__func, args...)\ diff --git a/libstdc++-v3/testsuite/28_regex/basic_regex/multiple_quantifiers.cc b/libstdc++-v3/testsuite/28_regex/basic_regex/multiple_quantifiers.cc new file mode 100644 index 0000000..5670cbb --- /dev/null +++ b/libstdc++-v3/testsuite/28_regex/basic_regex/multiple_quantifiers.cc @@ -0,0 +1,33 @@ +// { dg-options "-std=gnu++11" } + +// Copyright (C) 2014 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. +// +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +// 28.8 basic_regex +// Tests multiple consecutive quantifiers + +#include <regex> + +using namespace std; + +int +main() +{ + regex re1("a++"); + regex re2("(a+)+"); + return 0; +}