[CMake] How to use CMake with icc via configuration options when needing interprocedural optimization?

[Michael Jackson]

Not sure that is really going to work because by the time CMake has parsed your "option" code the compiler (and who knows how many other internal variables) has already been set. 
--
Mike Jackson <www.bluequartz.net>

On Feb 7, 2012, at 8:43 AM, janitor 048 wrote:

> Hello,
> 
> this is a question I recently asked on stackoverflow (http://stackoverflow.com/questions/9129233/recommended-ways-to-use-cmake-with-icc-via-configuration-options) but that has not received any response since then. Maybe this mailing list is a better place to ask... Here goes
> I would like to use the Intel compiler icc (or icpc) with a CMake-based project (on Linux for what it's worth). I can of course export the CXX variable when calling cmake, e.g. like
> 
> CXX=icpc cmake ../
> 
> and this works fine. I would however like to make this choice available via a custom option. For this I parse custom option, e.g.
> 
> cmake -DMY_COMPILER_OPTION=Intel ..
> 
> as
> 
> IF (MY_COMPILER_OPTION STREQUAL "Intel")
>   MESSAGE(STATUS "** Compiling with Intel settings **")
>   SET(CMAKE_CXX_COMPILER "icpc")
>   SET(CMAKE_CXX_FLAGS_RELEASE "-O3 -w")
>   SET(CMAKE_CXX_FLAGS_DEBUG "-g")
> ENDIF ()
> 
> and set CMAKE_CXX_COMPILER together with some compiler flags. This also works, however there is an important "but".
> 
> I would also like to use the option -ipo (interprocedural optimization) for my code when compiling with icc plus I need to compile a static library within the build process. For this to work, I need to use Intel's xiar (and also xilink I guess).
> 
> cmake actually offers a special property for this
> 
> set_property(TARGET mytarget PROPERTY INTERPROCEDURAL_OPTIMIZATION 1)
> 
> however this only seems to works properly when the compiler has been set via the environment variable (then xiar is used). When setting the compiler via CMAKE_CXX_COMPILER this property is ignored.
> 
> Is there another way to do this?. Some recommended way? Or at least a work-around?
> 
> 
> 
> Cheers, Oliver
> 
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