[clang] d604c57 - [NFC] Use find_last_of when seraching for code in getRawCommentForDeclNoCacheImpl

[Ivan Murashko via cfe-commits]

Author: Kugan Vivekanandarajah
Date: 2023-02-21T16:25:46Z
New Revision: d604c57164ecdb3084c8d00f9575158fddc30f81

URL: https://github.com/llvm/llvm-project/commit/d604c57164ecdb3084c8d00f9575158fddc30f81
DIFF: https://github.com/llvm/llvm-project/commit/d604c57164ecdb3084c8d00f9575158fddc30f81.diff

LOG: [NFC] Use find_last_of when seraching for code in getRawCommentForDeclNoCacheImpl

ASTContext::getRawCommentForDeclNoCacheImpl in this case, extracts the text between
the comment and declaration to make sure if there are  no other declarations or preprocessor
directives between  comment or declarations.

While using Text.find_first_of or Text.find_last_of  is functionally the same,
 using Text.find_last_of terminates fast in the presence of such.

Especially in generated code with sparse comments, it takes longer
to bailout when there is code in-between. Searching from last
(with find_last_of) bails out faster.

This shows up in perf profiles with clangd in some auto-generated code.
ASTContext::getRawCommentForDeclNoCacheImpl showing as much as 18.2% in this
case. With find_last_of, this drops to 2.8%.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D141950

Added: 
    

Modified: 
    clang/lib/AST/ASTContext.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 9b0d7b2b4b5a5..d852ac52ce8cf 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -349,7 +349,7 @@ RawComment *ASTContext::getRawCommentForDeclNoCacheImpl(
 
   // There should be no other declarations or preprocessor directives between
   // comment and declaration.
-  if (Text.find_first_of(";{}#@") != StringRef::npos)
+  if (Text.find_last_of(";{}#@") != StringRef::npos)
     return nullptr;
 
   return CommentBeforeDecl;