Improve performance during cursor traversal when a region of interest

is present. 

Rather than using clang_getCursorExtent(), which requires
us to lex the token at the ending position to determine its
length. Then, we'd be comparing [a, b) source ranges that cover the
characters in the range rather than the normal behavior for Clang's
source ranges, which covers the tokens in the range. However, relexing
causes us to read the source file (which may come from a precompiled
header), which is rather unfortunate and affects performance.

In the new scheme, we only use Clang-style source ranges that cover
the tokens in the range. At the entry points where this matters
(clang_annotateTokens, clang_getCursor), we make sure to move source
locations to the start of the token.

Addresses most of <rdar://problem/8049381>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@109134 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/include/clang/Lex/Lexer.h b/include/clang/Lex/Lexer.h
index 96d7605e4d..8dd37d0348 100644
--- a/include/clang/Lex/Lexer.h
+++ b/include/clang/Lex/Lexer.h
@@ -219,6 +219,15 @@ public:
                                      const SourceManager &SM,
                                      const LangOptions &LangOpts);
 
+  /// \brief Given a location any where in a source buffer, find the location
+  /// that corresponds to the beginning of the token in which the original
+  /// source location lands.
+  ///
+  /// \param Loc 
+  static SourceLocation GetBeginningOfToken(SourceLocation Loc,
+                                            const SourceManager &SM,
+                                            const LangOptions &LangOpts);
+  
   /// \brief Compute the preamble of the given file.
   ///
   /// The preamble of a file contains the initial comments, include directives,