I have the most recent cmake build and trying all build configurations (Debug, MinSizeRel, RelWithDebugInfo, Release, General) I see nowhere (text search) in generated makefiles the string -lto, so or the functionality is still not present, or it requires manual intervertion (in that case a text search for LTO or Link time optimization) over the documentation gives no result, so I see nowhere in official documentation a way to enable LTO.
Is there any way to enable LTO "globally" (for all compilers) without specifying manually flags that could be at worst supported only by GCC?
Edit: as of 28 October, 2015 on CMake IRC
jcelerier | I have a question about INTERPROCEDURAL_OPTIMIZATION
jcelerier | it sounds like it should enable -flto on gcc
+ngladitz | jcelerier: its only implemented for the intel compiler
jcelerier | ngladitz: ah, okay
jcelerier | are there other switches for pgo / lto ?
jcelerier | or must it be done by hand ?
+ngladitz | there currently is no first class support otherwise
Related CMake issue: https://gitlab.kitware.com/cmake/cmake/issues/15245
CMake has the INTERPROCEDURAL_OPTIMIZATION property on targets, which sounds like it may enable LTO on some platforms.
Link : http://www.cmake.org/cmake/help/v3.0/prop_tgt/INTERPROCEDURAL_OPTIMIZATION.html
To enable it on a target MyLib :
add_library(MyLib ...)
...
set_property(TARGET MyLib PROPERTY INTERPROCEDURAL_OPTIMIZATION True)