| Message ID | 20181218155200.GA8769@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | Micro-optimization to avoid creating temporary path | expand |
On 18/12/18 15:52 +0000, Jonathan Wakely wrote: >Now that path::operator/=(basic_string_view<value_type>) works directly >from the string argument, instead of constructing a temporary path from >the string, it's potentially more efficient to do 'path(x) /= s' instead >of 'x / s'. This changes the only relevant place in the library. > > * src/filesystem/std-dir.cc (filesystem::_Dir::advance): Append > string to lvalue to avoid creating temporary path. This is only an optimization if it doesn't introduce a new copy! Fixed by the attached patch. Tested x86_64-linux, committed to trunk. commit c2cccc34e8d8c9db216b96bffaba018f50ec7b75 Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Dec 18 16:34:47 2018 +0000 Fix previous commit to move instead of copying * src/filesystem/std-dir.cc (filesystem::_Dir::advance): Move new path instead of copying. diff --git a/libstdc++-v3/src/filesystem/std-dir.cc b/libstdc++-v3/src/filesystem/std-dir.cc index 216182a2e56..b0f869fc8fd 100644 --- a/libstdc++-v3/src/filesystem/std-dir.cc +++ b/libstdc++-v3/src/filesystem/std-dir.cc @@ -63,7 +63,7 @@ struct fs::_Dir : _Dir_base { auto name = path; name /= entp->d_name; - entry = fs::directory_entry{name, get_file_type(*entp)}; + entry = fs::directory_entry{std::move(name), get_file_type(*entp)}; return true; } else if (!ec)
diff --git a/libstdc++-v3/src/filesystem/std-dir.cc b/libstdc++-v3/src/filesystem/std-dir.cc index 038f635a712..216182a2e56 100644 --- a/libstdc++-v3/src/filesystem/std-dir.cc +++ b/libstdc++-v3/src/filesystem/std-dir.cc @@ -61,7 +61,9 @@ struct fs::_Dir : _Dir_base { if (const auto entp = _Dir_base::advance(skip_permission_denied, ec)) { - entry = fs::directory_entry{path / entp->d_name, get_file_type(*entp)}; + auto name = path; + name /= entp->d_name; + entry = fs::directory_entry{name, get_file_type(*entp)}; return true; } else if (!ec)
Now that path::operator/=(basic_string_view<value_type>) works directly from the string argument, instead of constructing a temporary path from the string, it's potentially more efficient to do 'path(x) /= s' instead of 'x / s'. This changes the only relevant place in the library. * src/filesystem/std-dir.cc (filesystem::_Dir::advance): Append string to lvalue to avoid creating temporary path. Tested x86_64-linux, committed to trunk. commit e48b1b71c76d12f999d9cf4a12239845281a26e4 Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Dec 18 15:39:12 2018 +0000 Micro-optimization to avoid creating temporary path Now that path::operator/=(basic_string_view<value_type>) works directly from the string argument, instead of constructing a temporary path from the string, it's potentially more efficient to do 'path(x) /= s' instead of 'x / s'. This changes the only relevant place in the library. * src/filesystem/std-dir.cc (filesystem::_Dir::advance): Append string to lvalue to avoid creating temporary path.