Close https://github.com/llvm/llvm-project/issues/71034
See
https://discourse.llvm.org/t/rfc-c-20-modules-introduce-thin-bmi-and-decls-hash/74755
This patch introduces reduced BMI, which doesn't contain the definitions
of functions and variables if its definitions won't contribute to the
ABI.
Testing is a big part of the patch. We want to make sure the reduced BMI
contains the same behavior with the existing and relatively stable
fatBMI. This is pretty helpful for further reduction.
The user interfaces part it left to following patches to ease the
reviewing.
Make use of a physical copy, rather than real FS in unittests that
change working-directory to get rid of the side effect of changing cwd for the
whole process. It's triggering crashes depending on the test order.
Differential Revision: https://reviews.llvm.org/D152265
This patch forbids to write comment to BMIs for C++20 Named Modules.
Originally I thought this was helpful for language services like clangd.
But I found clangd don't want the BMI to contain comments actually. So
it is meaningless for C++20 Named Modules to keep such comments in
their BMI.
It is simple to enable this when someday we found we want this actually.
