Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/tools/clang/include/clang/Serialization/InMemoryModuleCache.h
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//===- InMemoryModuleCache.h - In-memory cache for modules ------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_SERIALIZATION_INMEMORYMODULECACHE_H
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#define LLVM_CLANG_SERIALIZATION_INMEMORYMODULECACHE_H
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#include "llvm/ADT/IntrusiveRefCntPtr.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include <memory>
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namespace clang {
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/// In-memory cache for modules.
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///
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/// This is a cache for modules for use across a compilation, sharing state
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/// between the CompilerInstances in an implicit modules build.  It must be
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/// shared by each CompilerInstance, ASTReader, ASTWriter, and ModuleManager
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/// that are coordinating.
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///
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/// Critically, it ensures that a single process has a consistent view of each
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/// PCM.  This is used by \a CompilerInstance when building PCMs to ensure that
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/// each \a ModuleManager sees the same files.
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class InMemoryModuleCache : public llvm::RefCountedBase<InMemoryModuleCache> {
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  struct PCM {
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    std::unique_ptr<llvm::MemoryBuffer> Buffer;
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    /// Track whether this PCM is known to be good (either built or
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    /// successfully imported by a CompilerInstance/ASTReader using this
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    /// cache).
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    bool IsFinal = false;
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    PCM() = default;
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    PCM(std::unique_ptr<llvm::MemoryBuffer> Buffer)
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        : Buffer(std::move(Buffer)) {}
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  };
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  /// Cache of buffers.
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  llvm::StringMap<PCM> PCMs;
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public:
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  /// There are four states for a PCM.  It must monotonically increase.
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  ///
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  ///  1. Unknown: the PCM has neither been read from disk nor built.
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  ///  2. Tentative: the PCM has been read from disk but not yet imported or
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  ///     built.  It might work.
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  ///  3. ToBuild: the PCM read from disk did not work but a new one has not
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  ///     been built yet.
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  ///  4. Final: indicating that the current PCM was either built in this
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  ///     process or has been successfully imported.
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  enum State { Unknown, Tentative, ToBuild, Final };
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  /// Get the state of the PCM.
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  State getPCMState(llvm::StringRef Filename) const;
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  /// Store the PCM under the Filename.
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  ///
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  /// \pre state is Unknown
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  /// \post state is Tentative
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  /// \return a reference to the buffer as a convenience.
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  llvm::MemoryBuffer &addPCM(llvm::StringRef Filename,
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                             std::unique_ptr<llvm::MemoryBuffer> Buffer);
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  /// Store a just-built PCM under the Filename.
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  ///
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  /// \pre state is Unknown or ToBuild.
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  /// \pre state is not Tentative.
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  /// \return a reference to the buffer as a convenience.
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  llvm::MemoryBuffer &addBuiltPCM(llvm::StringRef Filename,
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                                  std::unique_ptr<llvm::MemoryBuffer> Buffer);
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  /// Try to remove a buffer from the cache.  No effect if state is Final.
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  ///
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  /// \pre state is Tentative/Final.
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  /// \post Tentative => ToBuild or Final => Final.
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  /// \return false on success, i.e. if Tentative => ToBuild.
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  bool tryToDropPCM(llvm::StringRef Filename);
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  /// Mark a PCM as final.
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  ///
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  /// \pre state is Tentative or Final.
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  /// \post state is Final.
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  void finalizePCM(llvm::StringRef Filename);
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  /// Get a pointer to the pCM if it exists; else nullptr.
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  llvm::MemoryBuffer *lookupPCM(llvm::StringRef Filename) const;
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  /// Check whether the PCM is final and has been shown to work.
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  ///
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  /// \return true iff state is Final.
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  bool isPCMFinal(llvm::StringRef Filename) const;
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  /// Check whether the PCM is waiting to be built.
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  ///
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  /// \return true iff state is ToBuild.
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  bool shouldBuildPCM(llvm::StringRef Filename) const;
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};
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} // end namespace clang
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#endif // LLVM_CLANG_SERIALIZATION_INMEMORYMODULECACHE_H