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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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| Unix | ||
| Windows | ||
| Allocator.cpp | ||
| AMDGPUMetadata.cpp | ||
| APFloat.cpp | ||
| APInt.cpp | ||
| APSInt.cpp | ||
| ARMAttributeParser.cpp | ||
| ARMBuildAttrs.cpp | ||
| ARMWinEH.cpp | ||
| Atomic.cpp | ||
| BinaryStreamError.cpp | ||
| BinaryStreamReader.cpp | ||
| BinaryStreamRef.cpp | ||
| BinaryStreamWriter.cpp | ||
| BlockFrequency.cpp | ||
| BranchProbability.cpp | ||
| CachePruning.cpp | ||
| Chrono.cpp | ||
| circular_raw_ostream.cpp | ||
| CMakeLists.txt | ||
| CodeGenCoverage.cpp | ||
| COM.cpp | ||
| CommandLine.cpp | ||
| Compression.cpp | ||
| ConvertUTF.cpp | ||
| ConvertUTFWrapper.cpp | ||
| COPYRIGHT.regex | ||
| CrashRecoveryContext.cpp | ||
| DAGDeltaAlgorithm.cpp | ||
| DataExtractor.cpp | ||
| Debug.cpp | ||
| DebugCounter.cpp | ||
| DeltaAlgorithm.cpp | ||
| DJB.cpp | ||
| DynamicLibrary.cpp | ||
| Errno.cpp | ||
| Error.cpp | ||
| ErrorHandling.cpp | ||
| FileOutputBuffer.cpp | ||
| FileUtilities.cpp | ||
| FoldingSet.cpp | ||
| FormattedStream.cpp | ||
| FormatVariadic.cpp | ||
| GlobPattern.cpp | ||
| GraphWriter.cpp | ||
| Hashing.cpp | ||
| Host.cpp | ||
| IntEqClasses.cpp | ||
| IntervalMap.cpp | ||
| JamCRC.cpp | ||
| KnownBits.cpp | ||
| LEB128.cpp | ||
| LineIterator.cpp | ||
| LLVMBuild.txt | ||
| Locale.cpp | ||
| LockFileManager.cpp | ||
| LowLevelType.cpp | ||
| ManagedStatic.cpp | ||
| MathExtras.cpp | ||
| MD5.cpp | ||
| Memory.cpp | ||
| MemoryBuffer.cpp | ||
| Mutex.cpp | ||
| NativeFormatting.cpp | ||
| Options.cpp | ||
| Parallel.cpp | ||
| Path.cpp | ||
| PluginLoader.cpp | ||
| PrettyStackTrace.cpp | ||
| Process.cpp | ||
| Program.cpp | ||
| RandomNumberGenerator.cpp | ||
| raw_os_ostream.cpp | ||
| raw_ostream.cpp | ||
| README.txt.system | ||
| regcomp.c | ||
| regengine.inc | ||
| regerror.c | ||
| regex2.h | ||
| regex_impl.h | ||
| Regex.cpp | ||
| regexec.c | ||
| regfree.c | ||
| regstrlcpy.c | ||
| regutils.h | ||
| RWMutex.cpp | ||
| ScaledNumber.cpp | ||
| ScopedPrinter.cpp | ||
| SHA1.cpp | ||
| Signals.cpp | ||
| SmallPtrSet.cpp | ||
| SmallVector.cpp | ||
| SourceMgr.cpp | ||
| SpecialCaseList.cpp | ||
| Statistic.cpp | ||
| StringExtras.cpp | ||
| StringMap.cpp | ||
| StringPool.cpp | ||
| StringRef.cpp | ||
| StringSaver.cpp | ||
| SystemUtils.cpp | ||
| TargetParser.cpp | ||
| TargetRegistry.cpp | ||
| TarWriter.cpp | ||
| Threading.cpp | ||
| ThreadLocal.cpp | ||
| ThreadPool.cpp | ||
| Timer.cpp | ||
| ToolOutputFile.cpp | ||
| TrigramIndex.cpp | ||
| Triple.cpp | ||
| Twine.cpp | ||
| Unicode.cpp | ||
| UnicodeCaseFold.cpp | ||
| Valgrind.cpp | ||
| Watchdog.cpp | ||
| WithColor.cpp | ||
| xxhash.cpp | ||
| YAMLParser.cpp | ||
| YAMLTraits.cpp | ||
Design Of lib/System
====================
The software in this directory is designed to completely shield LLVM from any
and all operating system specific functionality. It is not intended to be a
complete operating system wrapper (such as ACE), but only to provide the
functionality necessary to support LLVM.
The software located here, of necessity, has very specific and stringent design
rules. Violation of these rules means that cracks in the shield could form and
the primary goal of the library is defeated. By consistently using this library,
LLVM becomes more easily ported to new platforms since the only thing requiring
porting is this library.
Complete documentation for the library can be found in the file:
llvm/docs/SystemLibrary.html
or at this URL:
http://llvm.org/docs/SystemLibrary.html
While we recommend that you read the more detailed documentation, for the
impatient, here's a high level summary of the library's requirements.
1. No system header files are to be exposed through the interface.
2. Std C++ and Std C header files are okay to be exposed through the interface.
3. No exposed system-specific functions.
4. No exposed system-specific data.
5. Data in lib/System classes must use only simple C++ intrinsic types.
6. Errors are handled by returning "true" and setting an optional std::string
7. Library must not throw any exceptions, period.
8. Interface functions must not have throw() specifications.
9. No duplicate function impementations are permitted within an operating
system class.
To accomplish these requirements, the library has numerous design criteria that
must be satisfied. Here's a high level summary of the library's design criteria:
1. No unused functionality (only what LLVM needs)
2. High-Level Interfaces
3. Use Opaque Classes
4. Common Implementations
5. Multiple Implementations
6. Minimize Memory Allocation
7. No Virtual Methods