[PATCH] D25337: [Modules] Add a command line option for enabling the modules feature exclusively for the Clang builtins.

[Elad Cohen via cfe-commits]

eladcohen added a comment.

Hi Bruno,

The short answer is yes. Essentially it can be done, but we would actually like for all the users to always get this behavior, implicitly.

The long answer is that there is a history of problems regarding the intrinsic files:
http://lists.llvm.org/pipermail/cfe-dev/2016-May/048837.html
http://lists.llvm.org/pipermail/cfe-dev/2016-September/050943.html
Mainly compatibility issues because MSVC makes all the intrinsics available all the time, while in clang this is not always the case (On Windows the different h files are not-included unless asked for explicitly since AVX512 was added which impacted compile-time).
A suggestion was made to try and mitigate this by reducing the compile time using modules (only for the x86 intrinsics). This patch aims at adding this option. The new compile flag is just a milestone - if all goes well, we can turn this on by default (Then we won't actually need to use a specific compile flag, and we could always include all the intrinsic h files without their long compile time).


https://reviews.llvm.org/D25337