Introduce basic support for loading a precompiled preamble while

reparsing an ASTUnit. When saving a preamble, create a buffer larger
than the actual file we're working with but fill everything from the
end of the preamble to the end of the file with spaces (so the lexer
will quickly skip them). When we load the file, create a buffer of the
same size, filling it with the file and then spaces. Then, instruct
the lexer to start lexing after the preamble, therefore continuing the
parse from the spot where the preamble left off.

It's now possible to perform a simple preamble build + parse (+
reparse) with ASTUnit. However, one has to disable a bunch of checking
in the PCH reader to do so. That part isn't committed; it will likely
be handled with some other kind of flag (e.g., -fno-validate-pch).

As part of this, fix some issues with null termination of the memory
buffers created for the preamble; we were trying to explicitly
NULL-terminate them, even though they were also getting implicitly
NULL terminated, leading to excess warnings about NULL characters in
source files.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@109445 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 0 deletions

diff --git a/include/clang/Lex/Preprocessor.h b/include/clang/Lex/Preprocessor.h
index 1ee4bb6351..380f788d22 100644
--- a/include/clang/Lex/Preprocessor.h
+++ b/include/clang/Lex/Preprocessor.h
@@ -134,6 +134,12 @@ class Preprocessor {
   /// \brief The file that we're performing code-completion for, if any.
   const FileEntry *CodeCompletionFile;
 
+  /// \brief The number of bytes that we will initially skip when entering the
+  /// main file, which is used when loading a precompiled preamble, along
+  /// with a flag that indicates whether skipping this number of bytes will
+  /// place the lexer at the start of a line.
+  std::pair<unsigned, bool> SkipMainFilePreamble;
+  
   /// CurLexer - This is the current top of the stack that we're lexing from if
   /// not expanding a macro and we are lexing directly from source code.
   ///  Only one of CurLexer, CurPTHLexer, or CurTokenLexer will be non-null.
@@ -556,6 +562,18 @@ public:
   /// for which we are performing code completion.
   bool isCodeCompletionFile(SourceLocation FileLoc) const;
 
+  /// \brief Instruct the preprocessor to skip part of the main
+  /// the main source file.
+  ///
+  /// \brief Bytes The number of bytes in the preamble to skip.
+  ///
+  /// \brief StartOfLine Whether skipping these bytes puts the lexer at the
+  /// start of a line.
+  void setSkipMainFilePreamble(unsigned Bytes, bool StartOfLine) { 
+    SkipMainFilePreamble.first = Bytes;
+    SkipMainFilePreamble.second = StartOfLine;
+  }
+  
   /// Diag - Forwarding function for diagnostics.  This emits a diagnostic at
   /// the specified Token's location, translating the token's start
   /// position in the current buffer into a SourcePosition object for rendering.