935bc7a214
AST file more lazy, so that we don't eagerly load that information for all known identifiers each time a new AST file is loaded. The eager reloading made some sense in the context of precompiled headers, since very few identifiers were defined before PCH load time. With modules, however, a huge amount of code can get parsed before we see an @import, so laziness becomes important here. The approach taken to make this information lazy is fairly simple: when we load a new AST file, we mark all of the existing identifiers as being out-of-date. Whenever we want to access information that may come from an AST (e.g., whether the identifier has a macro definition, or what top-level declarations have that name), we check the out-of-date bit and, if it's set, ask the AST reader to update the IdentifierInfo from the AST files. The update is a merge, and we now take care to merge declarations before/after imports with declarations from multiple imports. The results of this optimization are fairly dramatic. On a small application that brings in 14 non-trivial modules, this takes modules from being > 3x slower than a "perfect" PCH file down to 30% slower for a full rebuild. A partial rebuild (where the PCH file or modules can be re-used) is down to 7% slower. Making the PCH file just a little imperfect (e.g., adding two smallish modules used by a bunch of .m files that aren't in the PCH file) tips the scales in favor of the modules approach, with 24% faster partial rebuilds. This is just a first step; the lazy scheme could possibly be improved by adding versioning, so we don't search into modules we already searched. Moreover, we'll need similar lazy schemes for all of the other lookup data structures, such as DeclContexts. llvm-svn: 143100 |
||
|---|---|---|
| .. | ||
| INPUTS | ||
| bindings/python | ||
| docs | ||
| examples | ||
| include | ||
| lib | ||
| runtime | ||
| test | ||
| tools | ||
| unittests | ||
| utils | ||
| www | ||
| .gitignore | ||
| CMakeLists.txt | ||
| INSTALL.txt | ||
| LICENSE.TXT | ||
| Makefile | ||
| ModuleInfo.txt | ||
| NOTES.txt | ||
| README.txt | ||
README.txt
//===----------------------------------------------------------------------===// // C Language Family Front-end //===----------------------------------------------------------------------===// Welcome to Clang. This is a compiler front-end for the C family of languages (C, C++, Objective-C, and Objective-C++) which is built as part of the LLVM compiler infrastructure project. Unlike many other compiler frontends, Clang is useful for a number of things beyond just compiling code: we intend for Clang to be host to a number of different source level tools. One example of this is the Clang Static Analyzer. If you're interested in more (including how to build Clang) it is best to read the relevant web sites. Here are some pointers: Information on Clang: http://clang.llvm.org/ Building and using Clang: http://clang.llvm.org/get_started.html Clang Static Analyzer: http://clang-analyzer.llvm.org/ Information on the LLVM project: http://llvm.org/ If you have questions or comments about Clang, a great place to discuss them is on the Clang development mailing list: http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev If you find a bug in Clang, please file it in the LLVM bug tracker: http://llvm.org/bugs/