[CMake] CMake 3.13 Interprocedural Optimization for Visual C++: Whole Program Optimization (LTCG)

[Niels Dekker]

I'm very pleased that CMake 3.13 (just released) includes the "IPO for 
VS" feature that I implemented, with help from Brad Kind: it allows 
enabling Whole Program Optimization (Link Time Code Generation) on a 
Visual C++ project, by means of CMake flag INTERPROCEDURAL_OPTIMIZATION.

Visual Studio offers this option (LTCG) for more than a decade already, 
within the IDE. I'm glad that it's now also directly available to 
VS/CMake users.

In general, I would suggest to enable this option only for a Release 
build. As follows:

   project(MyProject)
   add_executable(MyProject MyMain.cpp MySource.cpp)
   set_property(TARGET MyProject PROPERTY 
INTERPROCEDURAL_OPTIMIZATION_RELEASE TRUE)

I'm interested to hear from other VS/CMake users if they find this new 
option helpful. And specifically whether they experience a significant 
performance gain from their application, after enabling IPO.

Note that my request to enable IPO "by default" for Release 
configurations has been rejected, at least for the time being: 
https://gitlab.kitware.com/cmake/cmake/issues/17720  So for now, users 
have to explicitly switch on this option.


Kind regards, Niels
-- 
Niels Dekker
Scientific programmer
LKEB, Leiden University Medical Center