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SmallVectorTemplateCommon wants to know the address of the first element so it can detect whether it's in "small size" mode. The old implementation split the small array, creating the storage for the first element in SmallVectorTemplateCommon, and pulling the rest into SmallVectorStorage where we know the size of the array. This bloats SmallVector size 0 by the larger of sizeof(void*) and sizeof(T), and we're not even using the storage. The new implementation leaves the full small storage to SmallVectorStorage. To calculate the offset of the first element in SmallVectorTemplateCommon, we just need to know how far to jump, which we can calculate out-of-band. One subtlety is that we need SmallVectorStorage to be properly aligned even when the size is 0, to be sure that (for large alignments) we actually have the padding and it's well defined to do the pointer math. llvm-svn: 337820 |
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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 | ||
| InitLLVM.cpp | ||
| IntEqClasses.cpp | ||
| IntervalMap.cpp | ||
| JamCRC.cpp | ||
| JSON.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 | ||
| VersionTuple.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