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cded1d3751
Summary: The LLVM SourceMgr class (which is used indirectly by Swift, though not Clang) has a routine for looking up line numbers of SMLocs. This routine uses a shared, special-purpose cache that handles exactly one access pattern efficiently: looking up the line number of an SMLoc that points into the same buffer as the last query made to the SourceMgr, at a location in the buffer at or ahead of the last query. When this works it's fine, but when it fails it's catastrophic for performancer: one recent out-of-order access from a Swift utility routine ran for tens of seconds, spending 99% of its time repeatedly scanning buffers for '\n'. This change removes the shared cache from the SourceMgr and installs a new cache in each SrcBuffer. The per-SrcBuffer caches are also "full", in the sense that rather than caching a single last-query pointer, they cache _all_ the line-ending offsets, in a binary-searchable array, such that once it's populated (on first access), all subsequent access patterns run at the same speed. Performance measurements I've done show this is actually a little bit faster on real codebases (though only a couple fractions of a percent). Memory usage is up by a few tens to hundreds of bytes per SrcBuffer that has a line lookup done on it; I've attempted to minimize this by using dynamic selection of integer sized when storing offset arrays. But the main motive here is to make-impossible the cases we don't always see, that show up by surprise when there is an out-of-order access pattern. Reviewers: jordan_rose Reviewed By: jordan_rose Subscribers: probinson, llvm-commits Differential Revision: https://reviews.llvm.org/D45003 llvm-svn: 329470 |
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| .. | ||
| MCDisassembler | ||
| MCParser | ||
| CMakeLists.txt | ||
| ConstantPools.cpp | ||
| ELFObjectWriter.cpp | ||
| LLVMBuild.txt | ||
| MachObjectWriter.cpp | ||
| MCAsmBackend.cpp | ||
| MCAsmInfo.cpp | ||
| MCAsmInfoCOFF.cpp | ||
| MCAsmInfoDarwin.cpp | ||
| MCAsmInfoELF.cpp | ||
| MCAsmInfoWasm.cpp | ||
| MCAsmMacro.cpp | ||
| MCAsmStreamer.cpp | ||
| MCAssembler.cpp | ||
| MCCodeEmitter.cpp | ||
| MCCodePadder.cpp | ||
| MCCodeView.cpp | ||
| MCContext.cpp | ||
| MCDwarf.cpp | ||
| MCELFObjectTargetWriter.cpp | ||
| MCELFStreamer.cpp | ||
| MCExpr.cpp | ||
| MCFragment.cpp | ||
| MCInst.cpp | ||
| MCInstPrinter.cpp | ||
| MCInstrAnalysis.cpp | ||
| MCInstrDesc.cpp | ||
| MCLabel.cpp | ||
| MCLinkerOptimizationHint.cpp | ||
| MCMachObjectTargetWriter.cpp | ||
| MCMachOStreamer.cpp | ||
| MCNullStreamer.cpp | ||
| MCObjectFileInfo.cpp | ||
| MCObjectStreamer.cpp | ||
| MCObjectWriter.cpp | ||
| MCRegisterInfo.cpp | ||
| MCSchedule.cpp | ||
| MCSection.cpp | ||
| MCSectionCOFF.cpp | ||
| MCSectionELF.cpp | ||
| MCSectionMachO.cpp | ||
| MCSectionWasm.cpp | ||
| MCStreamer.cpp | ||
| MCSubtargetInfo.cpp | ||
| MCSymbol.cpp | ||
| MCSymbolELF.cpp | ||
| MCTargetOptions.cpp | ||
| MCValue.cpp | ||
| MCWasmObjectTargetWriter.cpp | ||
| MCWasmStreamer.cpp | ||
| MCWin64EH.cpp | ||
| MCWinCOFFStreamer.cpp | ||
| MCWinEH.cpp | ||
| StringTableBuilder.cpp | ||
| SubtargetFeature.cpp | ||
| WasmObjectWriter.cpp | ||
| WinCOFFObjectWriter.cpp | ||