1 files changed, 20 insertions, 7 deletions

diff --git a/include/clang/Frontend/PrecompiledPreamble.h b/include/clang/Frontend/PrecompiledPreamble.h
index 130fe60704a74..6abdbe3a1e1b1 100644
--- a/include/clang/Frontend/PrecompiledPreamble.h
+++ b/include/clang/Frontend/PrecompiledPreamble.h
@@ -38,7 +38,7 @@ class CompilerInvocation;
 class DeclGroupRef;
 class PCHContainerOperations;
 
-/// \brief Runs lexer to compute suggested preamble bounds.
+/// Runs lexer to compute suggested preamble bounds.
 PreambleBounds ComputePreambleBounds(const LangOptions &LangOpts,
                                      llvm::MemoryBuffer *Buffer,
                                      unsigned MaxLines);
@@ -53,7 +53,7 @@ class PrecompiledPreamble {
   struct PreambleFileHash;
 
 public:
-  /// \brief Try to build PrecompiledPreamble for \p Invocation. See
+  /// Try to build PrecompiledPreamble for \p Invocation. See
   /// BuildPreambleError for possible error codes.
   ///
   /// \param Invocation Original CompilerInvocation with options to compile the
@@ -104,14 +104,22 @@ public:
   /// Changes options inside \p CI to use PCH from this preamble. Also remaps
   /// main file to \p MainFileBuffer and updates \p VFS to ensure the preamble
   /// is accessible.
-  /// For in-memory preambles, PrecompiledPreamble instance continues to own
-  /// the MemoryBuffer with the Preamble after this method returns. The caller
-  /// is reponsible for making sure the PrecompiledPreamble instance outlives
-  /// the compiler run and the AST that will be using the PCH.
+  /// Requires that CanReuse() is true.
+  /// For in-memory preambles, PrecompiledPreamble instance continues to own the
+  /// MemoryBuffer with the Preamble after this method returns. The caller is
+  /// responsible for making sure the PrecompiledPreamble instance outlives the
+  /// compiler run and the AST that will be using the PCH.
   void AddImplicitPreamble(CompilerInvocation &CI,
                            IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
                            llvm::MemoryBuffer *MainFileBuffer) const;
 
+  /// Configure \p CI to use this preamble.
+  /// Like AddImplicitPreamble, but doesn't assume CanReuse() is true.
+  /// If this preamble does not match the file, it may parse differently.
+  void OverridePreamble(CompilerInvocation &CI,
+                        IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
+                        llvm::MemoryBuffer *MainFileBuffer) const;
+
 private:
   PrecompiledPreamble(PCHStorage Storage, std::vector<char> PreambleBytes,
                       bool PreambleEndsAtStartOfLine,
@@ -222,6 +230,12 @@ private:
     }
   };
 
+  /// Helper function to set up PCH for the preamble into \p CI and \p VFS to
+  /// with the specified \p Bounds.
+  void configurePreamble(PreambleBounds Bounds, CompilerInvocation &CI,
+                         IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
+                         llvm::MemoryBuffer *MainFileBuffer) const;
+
   /// Sets up the PreprocessorOptions and changes VFS, so that PCH stored in \p
   /// Storage is accessible to clang. This method is an implementation detail of
   /// AddImplicitPreamble.
@@ -275,7 +289,6 @@ enum class BuildPreambleError {
   PreambleIsEmpty = 1,
   CouldntCreateTempFile,
   CouldntCreateTargetInfo,
-  CouldntCreateVFSOverlay,
   BeginSourceFileFailed,
   CouldntEmitPCH
 };