[PATCH] D66710: ASTReader: Bypass overridden files when reading PCHs

[Duncan P. N. Exon Smith via Phabricator via cfe-commits]

dexonsmith created this revision.
dexonsmith added reviewers: rsmith, arphaman, akyrtzi, bruno.
Herald added a subscriber: ributzka.

If contents of a file that is part of a PCM are overridden when reading
it, but weren't overridden when the PCM was being built, the ASTReader
will emit an error.  Now it creates a separate FileEntry for recovery,
bypassing the overridden content instead of discarding it.  The
pre-existing testcase clang/test/PCH/remap-file-from-pch.cpp confirms
that the new recovery method works correctly.

This resolves a long-standing FIXME to avoid hypothetically invalidating
another precompiled module that's already using the overridden contents.

This also removes ContentCache-related API that would be unsafe to use
across `CompilerInstance`s in an implicit modules build.  This helps to
unblock us sinking it from SourceManager into FileManager in the future,
which would allow us to delete `InMemoryModuleCache`.


https://reviews.llvm.org/D66710

Files:
  clang/include/clang/Basic/FileManager.h
  clang/include/clang/Basic/SourceManager.h
  clang/lib/Basic/FileManager.cpp
  clang/lib/Basic/SourceManager.cpp
  clang/lib/Serialization/ASTReader.cpp

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