3 files changed, 82 insertions, 16 deletions

diff --git a/include/clang-c/Index.h b/include/clang-c/Index.h
index 467a9826eb..30feb41f33 100644
--- a/include/clang-c/Index.h
+++ b/include/clang-c/Index.h
@@ -634,13 +634,13 @@ CINDEX_LINKAGE CXTranslationUnit clang_createTranslationUnitFromSourceFile(
 CINDEX_LINKAGE CXTranslationUnit clang_createTranslationUnit(CXIndex,
                                              const char *ast_filename);
 
-  /**
-   * \brief Flags that control the creation of translation units.
-   *
-   * The enumerators in this enumeration type are meant to be bitwise
-   * ORed together to specify which options should be used when
-   * constructing the translation unit.
-   */
+/**
+ * \brief Flags that control the creation of translation units.
+ *
+ * The enumerators in this enumeration type are meant to be bitwise
+ * ORed together to specify which options should be used when
+ * constructing the translation unit.
+ */
 enum CXTranslationUnit_Flags {
   /**
    * \brief Used to indicate that no special translation-unit options are
@@ -658,7 +658,35 @@ enum CXTranslationUnit_Flags {
    * applications that require more detailed information about the
    * behavior of the preprocessor.
    */
-  CXTranslationUnit_DetailedPreprocessingRecord = 0x01
+  CXTranslationUnit_DetailedPreprocessingRecord = 0x01,
+
+  /**
+   * \brief A flag that indicates that the intent of parsing the
+   * given translation unit is for live editing of the file.
+   *
+   * This flag is essentially a meta-flag that callers can use to indicate
+   * that the translation unit is being edited and, therefore, is likely to
+   * be reparsed many times. It enables an unspecified set of optimizations
+   * (e.g., the precompiled preamble) geared toward improving the performance
+   * of \c clang_reparseTranslationUnit().
+   */
+  CXTranslationUnit_Editing = 0x02,
+  
+  /**
+   * \brief Used to indicate that the translation unit should be built with an 
+   * implicit precompiled header for the preamble.
+   *
+   * An implicit precompiled header is used as an optimization when a
+   * particular translation unit is likely to be reparsed many times
+   * when the sources aren't changing that often. In this case, an
+   * implicit precompiled header will be built containing all of the
+   * initial includes at the top of the main file (what we refer to as
+   * the "preamble" of the file). In subsequent parses, if the
+   * preamble or the files in it have not changed, \c
+   * clang_reparseTranslationUnit() will re-use the implicit
+   * precompiled header to improve parsing performance.
+   */
+  CXTranslationUnit_PrecompiledPreamble = 0x04
 };
 
 /**
diff --git a/include/clang/Frontend/ASTUnit.h b/include/clang/Frontend/ASTUnit.h
index b7a48881ef..950da64c22 100644
--- a/include/clang/Frontend/ASTUnit.h
+++ b/include/clang/Frontend/ASTUnit.h
@@ -46,6 +46,14 @@ class TargetInfo;
 
 using namespace idx;
 
+class PrecompiledPreamble {
+  llvm::sys::Path PreambleFile;
+  
+public:
+  ~PrecompiledPreamble();
+  
+};
+  
 /// \brief Utility class for loading a ASTContext from a PCH file.
 ///
 class ASTUnit {
@@ -125,6 +133,7 @@ private:
 
   void CleanTemporaryFiles();
   bool Parse();
+  void BuildPrecompiledPreamble();
   
 public:
   class ConcurrencyCheck {
@@ -241,7 +250,8 @@ public:
   static ASTUnit *LoadFromCompilerInvocation(CompilerInvocation *CI,
                                      llvm::IntrusiveRefCntPtr<Diagnostic> Diags,
                                              bool OnlyLocalDecls = false,
-                                             bool CaptureDiagnostics = false);
+                                             bool CaptureDiagnostics = false,
+                                             bool PrecompilePreamble = false);
 
   /// LoadFromCommandLine - Create an ASTUnit from a vector of command line
   /// arguments, which must specify exactly one source file.
@@ -264,7 +274,8 @@ public:
                                       bool OnlyLocalDecls = false,
                                       RemappedFile *RemappedFiles = 0,
                                       unsigned NumRemappedFiles = 0,
-                                      bool CaptureDiagnostics = false);
+                                      bool CaptureDiagnostics = false,
+                                      bool PrecompilePreamble = false);
   
   /// \brief Reparse the source files using the same command-line options that
   /// were originally used to produce this translation unit.
diff --git a/include/clang/Frontend/PreprocessorOptions.h b/include/clang/Frontend/PreprocessorOptions.h
index e2c1ca25a2..05159335ad 100644
--- a/include/clang/Frontend/PreprocessorOptions.h
+++ b/include/clang/Frontend/PreprocessorOptions.h
@@ -62,21 +62,37 @@ public:
   std::vector<std::pair<std::string, const llvm::MemoryBuffer *> > 
     RemappedFileBuffers;
   
-  typedef std::vector<std::pair<std::string, std::string> >::const_iterator
+  typedef std::vector<std::pair<std::string, std::string> >::iterator
     remapped_file_iterator;
-  remapped_file_iterator remapped_file_begin() const { 
+  typedef std::vector<std::pair<std::string, std::string> >::const_iterator
+    const_remapped_file_iterator;
+  remapped_file_iterator remapped_file_begin() { 
     return RemappedFiles.begin();
   }
-  remapped_file_iterator remapped_file_end() const { 
+  const_remapped_file_iterator remapped_file_begin() const {
+    return RemappedFiles.begin();
+  }
+  remapped_file_iterator remapped_file_end() { 
+    return RemappedFiles.end();
+  }
+  const_remapped_file_iterator remapped_file_end() const { 
     return RemappedFiles.end();
   }
 
   typedef std::vector<std::pair<std::string, const llvm::MemoryBuffer *> >::
-                                  const_iterator remapped_file_buffer_iterator;
-  remapped_file_buffer_iterator remapped_file_buffer_begin() const {
+                                  iterator remapped_file_buffer_iterator;
+  typedef std::vector<std::pair<std::string, const llvm::MemoryBuffer *> >::
+                            const_iterator const_remapped_file_buffer_iterator;
+  remapped_file_buffer_iterator remapped_file_buffer_begin() {
+    return RemappedFileBuffers.begin();
+  }
+  const_remapped_file_buffer_iterator remapped_file_buffer_begin() const {
     return RemappedFileBuffers.begin();
   }
-  remapped_file_buffer_iterator remapped_file_buffer_end() const {
+  remapped_file_buffer_iterator remapped_file_buffer_end() {
+    return RemappedFileBuffers.end();
+  }
+  const_remapped_file_buffer_iterator remapped_file_buffer_end() const {
     return RemappedFileBuffers.end();
   }
   
@@ -92,9 +108,20 @@ public:
   void addRemappedFile(llvm::StringRef From, llvm::StringRef To) {
     RemappedFiles.push_back(std::make_pair(From, To));
   }
+  
+  remapped_file_iterator eraseRemappedFile(remapped_file_iterator Remapped) {
+    return RemappedFiles.erase(Remapped);
+  }
+  
   void addRemappedFile(llvm::StringRef From, const llvm::MemoryBuffer * To) {
     RemappedFileBuffers.push_back(std::make_pair(From, To));
   }
+  
+  remapped_file_buffer_iterator
+  eraseRemappedFile(remapped_file_buffer_iterator Remapped) {
+    return RemappedFileBuffers.erase(Remapped);
+  }
+  
   void clearRemappedFiles() {
     RemappedFiles.clear();
     RemappedFileBuffers.clear();