The PCH reader looks for `__clangast` section in the precompiled module file, which is not present in the file on AIX, and we don't support writing this custom section in XCOFF yet.
Reviewed By: daltenty
Differential Revision: https://reviews.llvm.org/D114481
During explicit modules build, when all modules are provided via `-fmodule-file=<path>` and implicit modules and implicit module maps are disabled (`-fno-implicit-modules`, `-fno-implicit-module-maps`), we don't need to load the original module map files at all. This patch stops emitting the `-fmodule-map-file=` arguments we don't need, saving some compilation time due to avoiding parsing such module maps and making the command line shorter.
Reviewed By: bnbarham
Differential Revision: https://reviews.llvm.org/D113473
The `ASTReader` populates `Module::PresumedModuleMapFile` only for top-level modules, not submodules. To avoid generating empty `-fmodule-map-file=` arguments, make discovered modules depend on top-level precompiled modules. The granularity of submodules is not important here.
The documentation of `Module::PresumedModuleMapFile` says this field is non-empty only when building from preprocessed source. This means there can still be cases where the dependency scanner generates empty `-fmodule-map-file=` arguments. That's being addressed in separate patch: D108544.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D108647
Steven Wan