LCOV - code coverage report
Current view: top level - include/llvm/LTO - LTO.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 16 16 100.0 %
Date: 2017-09-14 15:23:50 Functions: 6 7 85.7 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===-LTO.h - LLVM Link Time Optimizer ------------------------------------===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file declares functions and classes used to support LTO. It is intended
      11             : // to be used both by LTO classes as well as by clients (gold-plugin) that
      12             : // don't utilize the LTO code generator interfaces.
      13             : //
      14             : //===----------------------------------------------------------------------===//
      15             : 
      16             : #ifndef LLVM_LTO_LTO_H
      17             : #define LLVM_LTO_LTO_H
      18             : 
      19             : #include "llvm/ADT/MapVector.h"
      20             : #include "llvm/ADT/StringMap.h"
      21             : #include "llvm/ADT/StringSet.h"
      22             : #include "llvm/Analysis/ObjectUtils.h"
      23             : #include "llvm/IR/DiagnosticInfo.h"
      24             : #include "llvm/IR/ModuleSummaryIndex.h"
      25             : #include "llvm/LTO/Config.h"
      26             : #include "llvm/Linker/IRMover.h"
      27             : #include "llvm/Object/IRSymtab.h"
      28             : #include "llvm/Support/Error.h"
      29             : #include "llvm/Support/ToolOutputFile.h"
      30             : #include "llvm/Support/thread.h"
      31             : #include "llvm/Target/TargetOptions.h"
      32             : #include "llvm/Transforms/IPO/FunctionImport.h"
      33             : 
      34             : namespace llvm {
      35             : 
      36             : class BitcodeModule;
      37             : class Error;
      38             : class LLVMContext;
      39             : class MemoryBufferRef;
      40             : class Module;
      41             : class Target;
      42             : class raw_pwrite_stream;
      43             : 
      44             : /// Resolve Weak and LinkOnce values in the \p Index. Linkage changes recorded
      45             : /// in the index and the ThinLTO backends must apply the changes to the Module
      46             : /// via thinLTOResolveWeakForLinkerModule.
      47             : ///
      48             : /// This is done for correctness (if value exported, ensure we always
      49             : /// emit a copy), and compile-time optimization (allow drop of duplicates).
      50             : void thinLTOResolveWeakForLinkerInIndex(
      51             :     ModuleSummaryIndex &Index,
      52             :     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
      53             :         isPrevailing,
      54             :     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
      55             :         recordNewLinkage);
      56             : 
      57             : /// Update the linkages in the given \p Index to mark exported values
      58             : /// as external and non-exported values as internal. The ThinLTO backends
      59             : /// must apply the changes to the Module via thinLTOInternalizeModule.
      60             : void thinLTOInternalizeAndPromoteInIndex(
      61             :     ModuleSummaryIndex &Index,
      62             :     function_ref<bool(StringRef, GlobalValue::GUID)> isExported);
      63             : 
      64             : namespace lto {
      65             : 
      66             : /// Given the original \p Path to an output file, replace any path
      67             : /// prefix matching \p OldPrefix with \p NewPrefix. Also, create the
      68             : /// resulting directory if it does not yet exist.
      69             : std::string getThinLTOOutputFile(const std::string &Path,
      70             :                                  const std::string &OldPrefix,
      71             :                                  const std::string &NewPrefix);
      72             : 
      73             : /// Setup optimization remarks.
      74             : Expected<std::unique_ptr<tool_output_file>>
      75             : setupOptimizationRemarks(LLVMContext &Context, StringRef LTORemarksFilename,
      76             :                          bool LTOPassRemarksWithHotness, int Count = -1);
      77             : 
      78             : class LTO;
      79             : struct SymbolResolution;
      80             : class ThinBackendProc;
      81             : 
      82             : /// An input file. This is a symbol table wrapper that only exposes the
      83             : /// information that an LTO client should need in order to do symbol resolution.
      84        4038 : class InputFile {
      85             : public:
      86             :   class Symbol;
      87             : 
      88             : private:
      89             :   // FIXME: Remove LTO class friendship once we have bitcode symbol tables.
      90             :   friend LTO;
      91        6075 :   InputFile() = default;
      92             : 
      93             :   std::vector<BitcodeModule> Mods;
      94             :   SmallVector<char, 0> Strtab;
      95             :   std::vector<Symbol> Symbols;
      96             : 
      97             :   // [begin, end) for each module
      98             :   std::vector<std::pair<size_t, size_t>> ModuleSymIndices;
      99             : 
     100             :   StringRef TargetTriple, SourceFileName, COFFLinkerOpts;
     101             :   std::vector<StringRef> ComdatTable;
     102             : 
     103             : public:
     104             :   ~InputFile();
     105             : 
     106             :   /// Create an InputFile.
     107             :   static Expected<std::unique_ptr<InputFile>> create(MemoryBufferRef Object);
     108             : 
     109             :   /// The purpose of this class is to only expose the symbol information that an
     110             :   /// LTO client should need in order to do symbol resolution.
     111             :   class Symbol : irsymtab::Symbol {
     112             :     friend LTO;
     113             : 
     114             :   public:
     115        1364 :     Symbol(const irsymtab::Symbol &S) : irsymtab::Symbol(S) {}
     116             : 
     117             :     using irsymtab::Symbol::isUndefined;
     118             :     using irsymtab::Symbol::isCommon;
     119             :     using irsymtab::Symbol::isWeak;
     120             :     using irsymtab::Symbol::isIndirect;
     121             :     using irsymtab::Symbol::getName;
     122             :     using irsymtab::Symbol::getVisibility;
     123             :     using irsymtab::Symbol::canBeOmittedFromSymbolTable;
     124             :     using irsymtab::Symbol::isTLS;
     125             :     using irsymtab::Symbol::getComdatIndex;
     126             :     using irsymtab::Symbol::getCommonSize;
     127             :     using irsymtab::Symbol::getCommonAlignment;
     128             :     using irsymtab::Symbol::getCOFFWeakExternalFallback;
     129             :     using irsymtab::Symbol::getSectionName;
     130             :     using irsymtab::Symbol::isExecutable;
     131             :   };
     132             : 
     133             :   /// A range over the symbols in this InputFile.
     134        2124 :   ArrayRef<Symbol> symbols() const { return Symbols; }
     135             : 
     136             :   /// Returns linker options specified in the input file.
     137             :   StringRef getCOFFLinkerOpts() const { return COFFLinkerOpts; }
     138             : 
     139             :   /// Returns the path to the InputFile.
     140             :   StringRef getName() const;
     141             : 
     142             :   /// Returns the input file's target triple.
     143             :   StringRef getTargetTriple() const { return TargetTriple; }
     144             : 
     145             :   /// Returns the source file path specified at compile time.
     146             :   StringRef getSourceFileName() const { return SourceFileName; }
     147             : 
     148             :   // Returns a table with all the comdats used by this file.
     149         360 :   ArrayRef<StringRef> getComdatTable() const { return ComdatTable; }
     150             : 
     151             : private:
     152             :   ArrayRef<Symbol> module_symbols(unsigned I) const {
     153        1014 :     const auto &Indices = ModuleSymIndices[I];
     154        2028 :     return {Symbols.data() + Indices.first, Symbols.data() + Indices.second};
     155             :   }
     156             : };
     157             : 
     158             : /// This class wraps an output stream for a native object. Most clients should
     159             : /// just be able to return an instance of this base class from the stream
     160             : /// callback, but if a client needs to perform some action after the stream is
     161             : /// written to, that can be done by deriving from this class and overriding the
     162             : /// destructor.
     163             : class NativeObjectStream {
     164             : public:
     165         830 :   NativeObjectStream(std::unique_ptr<raw_pwrite_stream> OS) : OS(std::move(OS)) {}
     166             :   std::unique_ptr<raw_pwrite_stream> OS;
     167         829 :   virtual ~NativeObjectStream() = default;
     168             : };
     169             : 
     170             : /// This type defines the callback to add a native object that is generated on
     171             : /// the fly.
     172             : ///
     173             : /// Stream callbacks must be thread safe.
     174             : typedef std::function<std::unique_ptr<NativeObjectStream>(unsigned Task)>
     175             :     AddStreamFn;
     176             : 
     177             : /// This is the type of a native object cache. To request an item from the
     178             : /// cache, pass a unique string as the Key. For hits, the cached file will be
     179             : /// added to the link and this function will return AddStreamFn(). For misses,
     180             : /// the cache will return a stream callback which must be called at most once to
     181             : /// produce content for the stream. The native object stream produced by the
     182             : /// stream callback will add the file to the link after the stream is written
     183             : /// to.
     184             : ///
     185             : /// Clients generally look like this:
     186             : ///
     187             : /// if (AddStreamFn AddStream = Cache(Task, Key))
     188             : ///   ProduceContent(AddStream);
     189             : typedef std::function<AddStreamFn(unsigned Task, StringRef Key)>
     190             :     NativeObjectCache;
     191             : 
     192             : /// A ThinBackend defines what happens after the thin-link phase during ThinLTO.
     193             : /// The details of this type definition aren't important; clients can only
     194             : /// create a ThinBackend using one of the create*ThinBackend() functions below.
     195             : typedef std::function<std::unique_ptr<ThinBackendProc>(
     196             :     Config &C, ModuleSummaryIndex &CombinedIndex,
     197             :     StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries,
     198             :     AddStreamFn AddStream, NativeObjectCache Cache)>
     199             :     ThinBackend;
     200             : 
     201             : /// This ThinBackend runs the individual backend jobs in-process.
     202             : ThinBackend createInProcessThinBackend(unsigned ParallelismLevel);
     203             : 
     204             : /// This ThinBackend writes individual module indexes to files, instead of
     205             : /// running the individual backend jobs. This backend is for distributed builds
     206             : /// where separate processes will invoke the real backends.
     207             : ///
     208             : /// To find the path to write the index to, the backend checks if the path has a
     209             : /// prefix of OldPrefix; if so, it replaces that prefix with NewPrefix. It then
     210             : /// appends ".thinlto.bc" and writes the index to that path. If
     211             : /// ShouldEmitImportsFiles is true it also writes a list of imported files to a
     212             : /// similar path with ".imports" appended instead.
     213             : ThinBackend createWriteIndexesThinBackend(std::string OldPrefix,
     214             :                                           std::string NewPrefix,
     215             :                                           bool ShouldEmitImportsFiles,
     216             :                                           std::string LinkedObjectsFile);
     217             : 
     218             : /// This class implements a resolution-based interface to LLVM's LTO
     219             : /// functionality. It supports regular LTO, parallel LTO code generation and
     220             : /// ThinLTO. You can use it from a linker in the following way:
     221             : /// - Set hooks and code generation options (see lto::Config struct defined in
     222             : ///   Config.h), and use the lto::Config object to create an lto::LTO object.
     223             : /// - Create lto::InputFile objects using lto::InputFile::create(), then use
     224             : ///   the symbols() function to enumerate its symbols and compute a resolution
     225             : ///   for each symbol (see SymbolResolution below).
     226             : /// - After the linker has visited each input file (and each regular object
     227             : ///   file) and computed a resolution for each symbol, take each lto::InputFile
     228             : ///   and pass it and an array of symbol resolutions to the add() function.
     229             : /// - Call the getMaxTasks() function to get an upper bound on the number of
     230             : ///   native object files that LTO may add to the link.
     231             : /// - Call the run() function. This function will use the supplied AddStream
     232             : ///   and Cache functions to add up to getMaxTasks() native object files to
     233             : ///   the link.
     234         325 : class LTO {
     235             :   friend InputFile;
     236             : 
     237             : public:
     238             :   /// Create an LTO object. A default constructed LTO object has a reasonable
     239             :   /// production configuration, but you can customize it by passing arguments to
     240             :   /// this constructor.
     241             :   /// FIXME: We do currently require the DiagHandler field to be set in Conf.
     242             :   /// Until that is fixed, a Config argument is required.
     243             :   LTO(Config Conf, ThinBackend Backend = nullptr,
     244             :       unsigned ParallelCodeGenParallelismLevel = 1);
     245             :   ~LTO();
     246             : 
     247             :   /// Add an input file to the LTO link, using the provided symbol resolutions.
     248             :   /// The symbol resolutions must appear in the enumeration order given by
     249             :   /// InputFile::symbols().
     250             :   Error add(std::unique_ptr<InputFile> Obj, ArrayRef<SymbolResolution> Res);
     251             : 
     252             :   /// Returns an upper bound on the number of tasks that the client may expect.
     253             :   /// This may only be called after all IR object files have been added. For a
     254             :   /// full description of tasks see LTOBackend.h.
     255             :   unsigned getMaxTasks() const;
     256             : 
     257             :   /// Runs the LTO pipeline. This function calls the supplied AddStream
     258             :   /// function to add native object files to the link.
     259             :   ///
     260             :   /// The Cache parameter is optional. If supplied, it will be used to cache
     261             :   /// native object files and add them to the link.
     262             :   ///
     263             :   /// The client will receive at most one callback (via either AddStream or
     264             :   /// Cache) for each task identifier.
     265             :   Error run(AddStreamFn AddStream, NativeObjectCache Cache = nullptr);
     266             : 
     267             : private:
     268             :   Config Conf;
     269             : 
     270         650 :   struct RegularLTOState {
     271             :     RegularLTOState(unsigned ParallelCodeGenParallelismLevel, Config &Conf);
     272             :     struct CommonResolution {
     273             :       uint64_t Size = 0;
     274             :       unsigned Align = 0;
     275             :       /// Record if at least one instance of the common was marked as prevailing
     276             :       bool Prevailing = false;
     277             :     };
     278             :     std::map<std::string, CommonResolution> Commons;
     279             : 
     280             :     unsigned ParallelCodeGenParallelismLevel;
     281             :     LTOLLVMContext Ctx;
     282             :     bool HasModule = false;
     283             :     std::unique_ptr<Module> CombinedModule;
     284             :     std::unique_ptr<IRMover> Mover;
     285             : 
     286             :     // This stores the information about a regular LTO module that we have added
     287             :     // to the link. It will either be linked immediately (for modules without
     288             :     // summaries) or after summary-based dead stripping (for modules with
     289             :     // summaries).
     290        4845 :     struct AddedModule {
     291             :       std::unique_ptr<Module> M;
     292             :       std::vector<GlobalValue *> Keep;
     293             :     };
     294             :     std::vector<AddedModule> ModsWithSummaries;
     295             :   } RegularLTO;
     296             : 
     297         975 :   struct ThinLTOState {
     298             :     ThinLTOState(ThinBackend Backend);
     299             : 
     300             :     ThinBackend Backend;
     301             :     ModuleSummaryIndex CombinedIndex;
     302             :     MapVector<StringRef, BitcodeModule> ModuleMap;
     303             :     DenseMap<GlobalValue::GUID, StringRef> PrevailingModuleForGUID;
     304             :   } ThinLTO;
     305             : 
     306             :   // The global resolution for a particular (mangled) symbol name. This is in
     307             :   // particular necessary to track whether each symbol can be internalized.
     308             :   // Because any input file may introduce a new cross-partition reference, we
     309             :   // cannot make any final internalization decisions until all input files have
     310             :   // been added and the client has called run(). During run() we apply
     311             :   // internalization decisions either directly to the module (for regular LTO)
     312             :   // or to the combined index (for ThinLTO).
     313        3176 :   struct GlobalResolution {
     314             :     /// The unmangled name of the global.
     315             :     std::string IRName;
     316             : 
     317             :     /// Keep track if the symbol is visible outside of a module with a summary
     318             :     /// (i.e. in either a regular object or a regular LTO module without a
     319             :     /// summary).
     320             :     bool VisibleOutsideSummary = false;
     321             : 
     322             :     bool UnnamedAddr = true;
     323             : 
     324             :     /// This field keeps track of the partition number of this global. The
     325             :     /// regular LTO object is partition 0, while each ThinLTO object has its own
     326             :     /// partition number from 1 onwards.
     327             :     ///
     328             :     /// Any global that is defined or used by more than one partition, or that
     329             :     /// is referenced externally, may not be internalized.
     330             :     ///
     331             :     /// Partitions generally have a one-to-one correspondence with tasks, except
     332             :     /// that we use partition 0 for all parallel LTO code generation partitions.
     333             :     /// Any partitioning of the combined LTO object is done internally by the
     334             :     /// LTO backend.
     335             :     unsigned Partition = Unknown;
     336             : 
     337             :     /// Special partition numbers.
     338             :     enum : unsigned {
     339             :       /// A partition number has not yet been assigned to this global.
     340             :       Unknown = -1u,
     341             : 
     342             :       /// This global is either used by more than one partition or has an
     343             :       /// external reference, and therefore cannot be internalized.
     344             :       External = -2u,
     345             : 
     346             :       /// The RegularLTO partition
     347             :       RegularLTO = 0,
     348             :     };
     349             :   };
     350             : 
     351             :   // Global mapping from mangled symbol names to resolutions.
     352             :   StringMap<GlobalResolution> GlobalResolutions;
     353             : 
     354             :   void addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
     355             :                             ArrayRef<SymbolResolution> Res, unsigned Partition,
     356             :                             bool InSummary);
     357             : 
     358             :   // These functions take a range of symbol resolutions [ResI, ResE) and consume
     359             :   // the resolutions used by a single input module by incrementing ResI. After
     360             :   // these functions return, [ResI, ResE) will refer to the resolution range for
     361             :   // the remaining modules in the InputFile.
     362             :   Error addModule(InputFile &Input, unsigned ModI,
     363             :                   const SymbolResolution *&ResI, const SymbolResolution *ResE);
     364             : 
     365             :   Expected<RegularLTOState::AddedModule>
     366             :   addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
     367             :                 const SymbolResolution *&ResI, const SymbolResolution *ResE);
     368             :   Error linkRegularLTO(RegularLTOState::AddedModule Mod,
     369             :                        bool LivenessFromIndex);
     370             : 
     371             :   Error addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
     372             :                    const SymbolResolution *&ResI, const SymbolResolution *ResE);
     373             : 
     374             :   Error runRegularLTO(AddStreamFn AddStream);
     375             :   Error runThinLTO(AddStreamFn AddStream, NativeObjectCache Cache,
     376             :                    bool HasRegularLTO);
     377             : 
     378             :   mutable bool CalledGetMaxTasks = false;
     379             : };
     380             : 
     381             : /// The resolution for a symbol. The linker must provide a SymbolResolution for
     382             : /// each global symbol based on its internal resolution of that symbol.
     383             : struct SymbolResolution {
     384             :   SymbolResolution()
     385        1006 :       : Prevailing(0), FinalDefinitionInLinkageUnit(0), VisibleToRegularObj(0),
     386        1006 :         LinkerRedefined(0) {}
     387             : 
     388             :   /// The linker has chosen this definition of the symbol.
     389             :   unsigned Prevailing : 1;
     390             : 
     391             :   /// The definition of this symbol is unpreemptable at runtime and is known to
     392             :   /// be in this linkage unit.
     393             :   unsigned FinalDefinitionInLinkageUnit : 1;
     394             : 
     395             :   /// The definition of this symbol is visible outside of the LTO unit.
     396             :   unsigned VisibleToRegularObj : 1;
     397             : 
     398             :   /// Linker redefined version of the symbol which appeared in -wrap or -defsym
     399             :   /// linker option.
     400             :   unsigned LinkerRedefined : 1;
     401             : };
     402             : 
     403             : } // namespace lto
     404             : } // namespace llvm
     405             : 
     406             : #endif

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