[PATCH] D28299: Module: use PCMCache to manage memory buffers for pcm files.

[Manman Ren via Phabricator via cfe-commits]

manmanren created this revision.
manmanren added reviewers: rsmith, benlangmuir, dexonsmith.
manmanren added subscribers: cfe-commits, bruno.

We create a PCMCache class to manage memory buffers associated with pcm files. With implicit modules, we currently use lock files to make
sure we are making progress when a single clang invocation builds a module file and then loads the module file immediately after. This
implementation requires lock file for correctness and causes all kinds of locking issues.

This patch tries to use PCMCache to share the content between writes and reads within a single clang invocation, so we can remove the
correctness-side of the lock file, and only use lock file for performance i.e to reduce chance of building the same pcm file from multiple
clang invocations.

We also add ThreadContext in PCMCache to diagnose cases where an ancestor validates a module and later on, a child thread tries
to invalidate it. Without the patch, this scenario will cause use-after-free of the FileEntry held by the ancestor.


https://reviews.llvm.org/D28299

Files:
  include/clang/Basic/DiagnosticSerializationKinds.td
  include/clang/Basic/FileManager.h
  include/clang/Serialization/ASTReader.h
  include/clang/Serialization/ASTWriter.h
  include/clang/Serialization/Module.h
  include/clang/Serialization/ModuleManager.h
  lib/Basic/FileManager.cpp
  lib/Frontend/ASTUnit.cpp
  lib/Frontend/ChainedIncludesSource.cpp
  lib/Frontend/CompilerInstance.cpp
  lib/Frontend/FrontendActions.cpp
  lib/Serialization/ASTReader.cpp
  lib/Serialization/ASTWriter.cpp
  lib/Serialization/GeneratePCH.cpp
  lib/Serialization/ModuleManager.cpp

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