Thank you for your encouraging replies, Johannes and Cristian.
In the meantime I created "default" Visual C++ projects on Visual Studio
2008, Visual Studio 2010, Visual Studio 2013, Visual Studio 2015 and
Visual Studio 2017 (from within the IDE, without using CMake). It
appears that each of these Visual Studio versions hast Link Time Code
Generation by default, for Release configurations.
I don't have access to a machine with Visual Studio 2005. Can someone
tell me whether this version also has Link Time Code Generation by
default, for Release configurations?
Kind regards, Niels
On 2018-01-25 14:54, Mueller-Roemer, Johannes Sebastian wrote:
This would be a great feature! Currently I override my release flags
by setting CMAKE_<LANG>_FLAGS_RELEASE_INIT and
CMAKE_<TYPE>_LINKER_FLAGS_RELEASE_INIT in a
CMAKE_USER_MAKE_RULES_OVERRIDE script. Direct support for /GL and
/LTCG in CMake would be great. Fewer target specifics to worry
about…
FROM: Cristian Adam
SENT: Wednesday, January 24, 2018 21:42
TO: Niels Dekker
CC: cmake <cmake@cmake.org>
SUBJECT: Re: [CMake] Link Time Code Generation (LTGC) by default, for
Release configurations of Visual Studio projects?
Hi,
I had a quick check to see if CMake 3.10 for which compilers it has
support for Interprocedural Optimization (IPO, or LTCG as known on
Visual C++).
Modules/Compiler had only for GNU, CLANG and PGI the following:
set(_CMAKE_${lang}_IPO_MAY_BE_SUPPORTED_BY_COMPILER YES)
QNX with QCC didn't have it set to YES even though nowdays QNX comes
with GCC 5.4.0 on QNX 7.0, which should be just fine.
It would be nice if CMake would have support for IPO on Visual C++.
The steps would be to set the right variables into
Modules/Compiler/MSVC-CXX.cmake, change the CheckIPOSupported
module, change some flags in some places,update tests, documentation,
and so on.
Shouldn't be hard to add this feature.
Cheers,
Cristian.
On Wed, Jan 24, 2018 at 9:06 PM, Niels Dekker wrote:
When a Visual C++ project is created within Visual Studio (by File
menu, New, Project...), it has Link Time Code Generation (LTGC) by
default, for its Release configurations: Compiler option /GL and
linker option /LTCG. However, when the Visual C++ project is
generated by CMake, it does not have LTGC, by default. LTCG looks
like a very useful feature to me. I think it's worth enabling the
feature by default, for Release configurations. What do you think?
Some details:
I created a "dummy" Visual C++ project in Visual Studio 2017
(Version 15.5.4), by File menu, New, Project..., and I also
generated one by CMake (version 3.10.2), using a very minimal
CMakeLists.txt
The Visual C++ project created by Visual Studio 2017 has the
following compile options, by default, for Release (x64):
/permissive- /GS /GL /W3 /Gy /Zc:wchar_t /Zi /Gm- /O2 /sdl
/Fd"x64\Release\vc141.pdb" /Zc:inline /fp:precise /D "_MBCS"
/errorReport:prompt /WX- /Zc:forScope /Gd /Oi /MD /Fa"x64\Release\"
/EHsc /nologo /Fo"x64\Release\" /Fp"x64\Release\MyVS2015Project.pch"
/diagnostics:classic
And the following linker options:
/OUT:"F:\X\Src\MyProject\MyVS2015Project\x64\Release\MyVS2015Project.exe"
/MANIFEST /LTCG:incremental /NXCOMPAT
/PDB:"F:\X\Src\MyProject\MyVS2015Project\x64\Release\MyVS2015Project.pdb"
/DYNAMICBASE "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib"
"comdlg32.lib" "advapi32.lib" "shell32.lib" "ole32.lib"
"oleaut32.lib" "uuid.lib" "odbc32.lib" "odbccp32.lib" /DEBUG:FULL
/MACHINE:X64 /OPT:REF
/PGD:"F:\X\Src\MyProject\MyVS2015Project\x64\Release\MyVS2015Project.pgd"
/MANIFESTUAC:"level='asInvoker' uiAccess='false'"
/ManifestFile:"x64\Release\MyVS2015Project.exe.intermediate.manifest"
/OPT:ICF /ERRORREPORT:PROMPT /NOLOGO /TLBID:1
The vcxproj file created by Visual Studio has
"<WholeProgramOptimization>true</WholeProgramOptimization>" for its
Release configurations.
The Visual C++ project generated by CMake (Generator: Visual Studio
15 2017 Win64) has the following compile options, for its Release
configuration:
/GS /TP /W3 /Zc:wchar_t /Gm- /O2 /Ob2
/Fd"MyExecutable.dir\Release\vc141.pdb" /Zc:inline /fp:precise /D
"WIN32" /D "_WINDOWS" /D "NDEBUG" /D "CMAKE_INTDIR=\"Release\"" /D
"_MBCS" /errorReport:prompt /WX- /Zc:forScope /GR /Gd /MD
/Fa"Release/" /EHsc /nologo /Fo"MyExecutable.dir\Release\"
/Fp"MyExecutable.dir\Release\MyExecutable.pch" /diagnostics:classic
And the following linker options:
/OUT:"F:\X\Bin\vc141-64\MyProject\Release\MyExecutable.exe"
/MANIFEST /NXCOMPAT
/PDB:"F:/X/Bin/vc141-64/MyProject/Release/MyExecutable.pdb"
/DYNAMICBASE "kernel32.lib" "user32.lib" "gdi32.lib" "winspool.lib"
"shell32.lib" "ole32.lib" "oleaut32.lib" "uuid.lib" "comdlg32.lib"
"advapi32.lib"
/IMPLIB:"F:/X/Bin/vc141-64/MyProject/Release/MyExecutable.lib"
/MACHINE:X64 /INCREMENTAL:NO
/PGD:"F:\X\Bin\vc141-64\MyProject\Release\MyExecutable.pgd"
/SUBSYSTEM:CONSOLE /MANIFESTUAC:"level='asInvoker' uiAccess='false'"
/ManifestFile:"MyExecutable.dir\Release\MyExecutable.exe.int
[1]ermediate.manifest" /ERRORREPORT:PROMPT /NOLOGO /TLBID:1
The vcxproj file generated by CMake does not have a
"<WholeProgramOptimization>" tag.
I hope you can consider adding LTCG to Release configurations of
Visual C++ projects generated by CMake, by default.
Kind regards, Niels
--
Niels Dekker
Scientific programmer
LKEB, Leiden University Medical Center
--
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