re-land [C++20][Modules] Build module static initializers per P1874R1.

The re-land fixes module map module dependencies seen on Greendragon, but
not in the clang test suite.

---

Currently we only

re-land [C++20][Modules] Build module static initializers per P1874R1.

The re-land fixes module map module dependencies seen on Greendragon, but
not in the clang test suite.

---

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 interface [which includes partition interface and implementation
units] (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 initializers 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 module implementation unit, or 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.

For all module unit kinds we include a global constructor entry, this allows
for the (in most cases unusual) possibility that a module object could be
included in a final binary without a specific call to its initializer.

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.

- In 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.

Differential Revision: https://reviews.llvm.org/D126189

show more ...

Revert "[C++20][Modules] Fix two tests for CTORs that return pointers [NFC]."

This reverts commit 4328b960176f4394416093e640ad4265bde65ad7.

reverting while we figure out why one of the Greendragon

Revert "[C++20][Modules] Fix two tests for CTORs that return pointers [NFC]."

This reverts commit 4328b960176f4394416093e640ad4265bde65ad7.

reverting while we figure out why one of the Greendragon lldb tests fails.

show more ...

[C++20][Modules] Fix two tests for CTORs that return pointers [NFC].

The test are to check that we call the correctly mangled CTORs, so that
the return values from them are irrelevant. I forgot tha

[C++20][Modules] Fix two tests for CTORs that return pointers [NFC].

The test are to check that we call the correctly mangled CTORs, so that
the return values from them are irrelevant. I forgot that some targets
return a pointer, apologies for the breakage.

show more ...

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

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

I

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

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 interface [which includes partition interface and implementation
units] (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 initializers 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 module implementation unit, or 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.

For all module unit kinds we include a global constructor entry, this allows
for the (in most cases unusual) possibility that a module object could be
included in a final binary without a specific call to its initializer.

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.

- In 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.

Differential Revision: https://reviews.llvm.org/D126189

show more ...