forked from OSchip/llvm-project
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this information lazy is fairly simple: when we load a new AST file, we mark all of the existing identifiers as being out-of-date.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AST (e.g., whether the identifier has a macro definition, or what top-level declarations have that name), we check the out-of-date bit and, if it's set, ask the AST reader to update the IdentifierInfo from the AST files.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 |
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| .. | ||
| CMakeLists.txt | ||
| HeaderMap.cpp | ||
| HeaderSearch.cpp | ||
| Lexer.cpp | ||
| LiteralSupport.cpp | ||
| MacroArgs.cpp | ||
| MacroArgs.h | ||
| MacroInfo.cpp | ||
| Makefile | ||
| PPCaching.cpp | ||
| PPDirectives.cpp | ||
| PPExpressions.cpp | ||
| PPLexerChange.cpp | ||
| PPMacroExpansion.cpp | ||
| PTHLexer.cpp | ||
| Pragma.cpp | ||
| PreprocessingRecord.cpp | ||
| Preprocessor.cpp | ||
| PreprocessorLexer.cpp | ||
| ScratchBuffer.cpp | ||
| TokenConcatenation.cpp | ||
| TokenLexer.cpp | ||