[llvm-commits] [PATCH] Add MSVC multi processor compilation to build system

[Óscar Fuentes]

Erik Olofsson <Erik.Olofsson at hansoft.se> writes:

>> Which are those options? If they are used on the future, having /MP active
>> by default may create some inconveniences. Changing the default value of
>> option(VAR ...) has no effect if VAR already is on CMakeCache.txt.
>
> Most notably incremental builds and creating a precompiled header. See
> http://msdn.microsoft.com/en-us/library/bb385193(v=VS.100).aspx
>
> Incremental builds are notoriously buggy, so I don't think we would
> ever want to enable that by default. If we ever want to add support
> for precompiled headers I do believe that msbuild automatically strips
> /MP if that option is enabled.

Okay, thanks. But IIRC last time I built LLVM with VS 10 it used all 4
cores. If you have checked that /MP is required for parallel builds, no
objection here. Don't forget documenting the option in docs/CMake.html.