[PATCH] D126189: [C++20][Modules] Build module static initializers per P1874R1.

[Iain Sandoe via Phabricator via cfe-commits]

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just updated description


Currently we only implement this for the Itanium ABI since the correct
mangling for the initializers in other ABIs is not yet known.

Intended result:

For a module (instead of the generic CXX initializer) we emit a module init
that:

- wraps the contained initializations in a control variable to ensure that the inits only happen once, even if a module is imported many times by imports of the main unit.
- calls module initialisers for imported modules first.  Note that the order of module import is not significant, and therefore neither is the order of imported module initializers.
- We then call initializers for the Global Module Fragment (if present)
- We then call initializers for the current module.
- We then call initializers for the Private Module Fragment (if present)

For a non-module TU that imports at least one module we emit a regular CXX
init that:

- Calls the initializers for any imported modules first.
- Then proceeds as normal with remaining inits.

Implementation:

- We provide the module pointer in the AST Context so that CodeGen can act on it and its sub-modules.
- We need to account for module build lines like this: ` clang -cc1 -std=c++20 Foo.pcm -emit-obj -o Foo.o` or ` clang -cc1 -std=c++20 -xc++-module Foo.cpp -emit-obj -o Foo.o`
- in order to do this, we add to ParseAST to set the module pointer in the ASTContext, once we establish that this is a module build and we know the module pointer. To be able to do this, we make the query for current module public in Sema.
- iIn CodeGen, we determine if the current build requires a CXX20-style module init and, if so, we defer any module initializers during the "Eagerly Emitted" phase.
- We then walk the module initializers at the end of the TU but before emitting deferred inits (which adds any hidden and static ones, fixing https://github.com/llvm/llvm-project/issues/51873 ).
- We then proceed to emit the deferred inits and continue to emit the CXX init function.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126189

Files:
  clang/include/clang/AST/ASTContext.h
  clang/include/clang/Sema/Sema.h
  clang/lib/CodeGen/CGDeclCXX.cpp
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/lib/CodeGen/CodeGenModule.h
  clang/lib/Parse/ParseAST.cpp
  clang/test/CodeGen/module-intializer.cpp

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