The import and include problem is a long-standing issue with the use of
C++20 modules. This patch tried to improve this by skipping parsing
class and functions if their declaration is already defined in modules.
The scale of the patch itself is small as the patch reuses previous
optimization. Maybe we can skip parsing other declarations in the
future. But the patch itself should be good.
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.
See https://github.com/cplusplus/draft/pull/5204 for a detailed
background.
Simply, the test redundant-template-default-arg.cpp attached to this
patch should be accepted instead of being complained about the
redefinition.
Reviewed By: urnathan, rsmith, ChuanqiXu
Differential Revision: https://reviews.llvm.org/D118034
