include/llvm/MC/MCAssembler.h

   1 //===- MCAssembler.h - Object File Generation -------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_MC_MCASSEMBLER_H
  10 #define LLVM_MC_MCASSEMBLER_H
  11
  12 #include "llvm/ADT/ArrayRef.h"
  13 #include "llvm/ADT/STLExtras.h"
  14 #include "llvm/ADT/SmallPtrSet.h"
  15 #include "llvm/ADT/StringRef.h"
  16 #include "llvm/ADT/iterator.h"
  17 #include "llvm/ADT/iterator_range.h"
  18 #include "llvm/BinaryFormat/MachO.h"
  19 #include "llvm/MC/MCDirectives.h"
  20 #include "llvm/MC/MCDwarf.h"
  21 #include "llvm/MC/MCFixup.h"
  22 #include "llvm/MC/MCFragment.h"
  23 #include "llvm/MC/MCLinkerOptimizationHint.h"
  24 #include "llvm/MC/MCSymbol.h"
  25 #include "llvm/Support/VersionTuple.h"
  26 #include <cassert>
  27 #include <cstddef>
  28 #include <cstdint>
  29 #include <string>
  30 #include <utility>
  31 #include <vector>
  32
  33 namespace llvm {
  34
  35 class MCAsmBackend;
  36 class MCAsmLayout;
  37 class MCContext;
  38 class MCCodeEmitter;
  39 class MCFragment;
  40 class MCObjectWriter;
  41 class MCSection;
  42 class MCValue;
  43
  44 // FIXME: This really doesn't belong here. See comments below.
  45 struct IndirectSymbolData {
  46   MCSymbol *Symbol;
  47   MCSection *Section;
  48 };
  49
  50 // FIXME: Ditto this. Purely so the Streamer and the ObjectWriter can talk
  51 // to one another.
  52 struct DataRegionData {
  53   // This enum should be kept in sync w/ the mach-o definition in
  54   // llvm/Object/MachOFormat.h.
  55   enum KindTy { Data = 1, JumpTable8, JumpTable16, JumpTable32 } Kind;
  56   MCSymbol *Start;
  57   MCSymbol *End;
  58 };
  59
  60 class MCAssembler {
  61   friend class MCAsmLayout;
  62
  63 public:
  64   using SectionListType = std::vector<MCSection *>;
  65   using SymbolDataListType = std::vector<const MCSymbol *>;
  66
  67   using const_iterator = pointee_iterator<SectionListType::const_iterator>;
  68   using iterator = pointee_iterator<SectionListType::iterator>;
  69
  70   using const_symbol_iterator =
  71       pointee_iterator<SymbolDataListType::const_iterator>;
  72   using symbol_iterator = pointee_iterator<SymbolDataListType::iterator>;
  73
  74   using symbol_range = iterator_range<symbol_iterator>;
  75   using const_symbol_range = iterator_range<const_symbol_iterator>;
  76
  77   using const_indirect_symbol_iterator =
  78       std::vector<IndirectSymbolData>::const_iterator;
  79   using indirect_symbol_iterator = std::vector<IndirectSymbolData>::iterator;
  80
  81   using const_data_region_iterator =
  82       std::vector<DataRegionData>::const_iterator;
  83   using data_region_iterator = std::vector<DataRegionData>::iterator;
  84
  85   /// MachO specific deployment target version info.
  86   // A Major version of 0 indicates that no version information was supplied
  87   // and so the corresponding load command should not be emitted.
  88   using VersionInfoType = struct {
  89     bool EmitBuildVersion;
  90     union {
  91       MCVersionMinType Type;          ///< Used when EmitBuildVersion==false.
  92       MachO::PlatformType Platform;   ///< Used when EmitBuildVersion==true.
  93     } TypeOrPlatform;
  94     unsigned Major;
  95     unsigned Minor;
  96     unsigned Update;
  97     /// An optional version of the SDK that was used to build the source.
  98     VersionTuple SDKVersion;
  99   };
 100
 101 private:
 102   MCContext &Context;
 103
 104   std::unique_ptr<MCAsmBackend> Backend;
 105
 106   std::unique_ptr<MCCodeEmitter> Emitter;
 107
 108   std::unique_ptr<MCObjectWriter> Writer;
 109
 110   SectionListType Sections;
 111
 112   SymbolDataListType Symbols;
 113
 114   std::vector<IndirectSymbolData> IndirectSymbols;
 115
 116   std::vector<DataRegionData> DataRegions;
 117
 118   /// The list of linker options to propagate into the object file.
 119   std::vector<std::vector<std::string>> LinkerOptions;
 120
 121   /// List of declared file names
 122   std::vector<std::string> FileNames;
 123
 124   MCDwarfLineTableParams LTParams;
 125
 126   /// The set of function symbols for which a .thumb_func directive has
 127   /// been seen.
 128   //
 129   // FIXME: We really would like this in target specific code rather than
 130   // here. Maybe when the relocation stuff moves to target specific,
 131   // this can go with it? The streamer would need some target specific
 132   // refactoring too.
 133   mutable SmallPtrSet<const MCSymbol *, 32> ThumbFuncs;
 134
 135   /// The bundle alignment size currently set in the assembler.
 136   ///
 137   /// By default it's 0, which means bundling is disabled.
 138   unsigned BundleAlignSize;
 139
 140   bool RelaxAll : 1;
 141   bool SubsectionsViaSymbols : 1;
 142   bool IncrementalLinkerCompatible : 1;
 143
 144   /// ELF specific e_header flags
 145   // It would be good if there were an MCELFAssembler class to hold this.
 146   // ELF header flags are used both by the integrated and standalone assemblers.
 147   // Access to the flags is necessary in cases where assembler directives affect
 148   // which flags to be set.
 149   unsigned ELFHeaderEFlags;
 150
 151   /// Used to communicate Linker Optimization Hint information between
 152   /// the Streamer and the .o writer
 153   MCLOHContainer LOHContainer;
 154
 155   VersionInfoType VersionInfo;
 156
 157   /// Evaluate a fixup to a relocatable expression and the value which should be
 158   /// placed into the fixup.
 159   ///
 160   /// \param Layout The layout to use for evaluation.
 161   /// \param Fixup The fixup to evaluate.
 162   /// \param DF The fragment the fixup is inside.
 163   /// \param Target [out] On return, the relocatable expression the fixup
 164   /// evaluates to.
 165   /// \param Value [out] On return, the value of the fixup as currently laid
 166   /// out.
 167   /// \param WasForced [out] On return, the value in the fixup is set to the
 168   /// correct value if WasForced is true, even if evaluateFixup returns false.
 169   /// \return Whether the fixup value was fully resolved. This is true if the
 170   /// \p Value result is fixed, otherwise the value may change due to
 171   /// relocation.
 172   bool evaluateFixup(const MCAsmLayout &Layout, const MCFixup &Fixup,
 173                      const MCFragment *DF, MCValue &Target,
 174                      uint64_t &Value, bool &WasForced) const;
 175
 176   /// Check whether a fixup can be satisfied, or whether it needs to be relaxed
 177   /// (increased in size, in order to hold its value correctly).
 178   bool fixupNeedsRelaxation(const MCFixup &Fixup, const MCRelaxableFragment *DF,
 179                             const MCAsmLayout &Layout) const;
 180
 181   /// Check whether the given fragment needs relaxation.
 182   bool fragmentNeedsRelaxation(const MCRelaxableFragment *IF,
 183                                const MCAsmLayout &Layout) const;
 184
 185   /// Perform one layout iteration and return true if any offsets
 186   /// were adjusted.
 187   bool layoutOnce(MCAsmLayout &Layout);
 188
 189   /// Perform one layout iteration of the given section and return true
 190   /// if any offsets were adjusted.
 191   bool layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec);
 192
 193   bool relaxInstruction(MCAsmLayout &Layout, MCRelaxableFragment &IF);
 194
 195   bool relaxPaddingFragment(MCAsmLayout &Layout, MCPaddingFragment &PF);
 196
 197   bool relaxLEB(MCAsmLayout &Layout, MCLEBFragment &IF);
 198
 199   bool relaxDwarfLineAddr(MCAsmLayout &Layout, MCDwarfLineAddrFragment &DF);
 200   bool relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
 201                                    MCDwarfCallFrameFragment &DF);
 202   bool relaxCVInlineLineTable(MCAsmLayout &Layout,
 203                               MCCVInlineLineTableFragment &DF);
 204   bool relaxCVDefRange(MCAsmLayout &Layout, MCCVDefRangeFragment &DF);
 205
 206   /// finishLayout - Finalize a layout, including fragment lowering.
 207   void finishLayout(MCAsmLayout &Layout);
 208
 209   std::tuple<MCValue, uint64_t, bool>
 210   handleFixup(const MCAsmLayout &Layout, MCFragment &F, const MCFixup &Fixup);
 211
 212 public:
 213   std::vector<std::pair<StringRef, const MCSymbol *>> Symvers;
 214
 215   /// Construct a new assembler instance.
 216   //
 217   // FIXME: How are we going to parameterize this? Two obvious options are stay
 218   // concrete and require clients to pass in a target like object. The other
 219   // option is to make this abstract, and have targets provide concrete
 220   // implementations as we do with AsmParser.
 221   MCAssembler(MCContext &Context, std::unique_ptr<MCAsmBackend> Backend,
 222               std::unique_ptr<MCCodeEmitter> Emitter,
 223               std::unique_ptr<MCObjectWriter> Writer);
 224   MCAssembler(const MCAssembler &) = delete;
 225   MCAssembler &operator=(const MCAssembler &) = delete;
 226   ~MCAssembler();
 227
 228   /// Compute the effective fragment size assuming it is laid out at the given
 229   /// \p SectionAddress and \p FragmentOffset.
 230   uint64_t computeFragmentSize(const MCAsmLayout &Layout,
 231                                const MCFragment &F) const;
 232
 233   /// Find the symbol which defines the atom containing the given symbol, or
 234   /// null if there is no such symbol.
 235   const MCSymbol *getAtom(const MCSymbol &S) const;
 236
 237   /// Check whether a particular symbol is visible to the linker and is required
 238   /// in the symbol table, or whether it can be discarded by the assembler. This
 239   /// also effects whether the assembler treats the label as potentially
 240   /// defining a separate atom.
 241   bool isSymbolLinkerVisible(const MCSymbol &SD) const;
 242
 243   /// Emit the section contents to \p OS.
 244   void writeSectionData(raw_ostream &OS, const MCSection *Section,
 245                         const MCAsmLayout &Layout) const;
 246
 247   /// Check whether a given symbol has been flagged with .thumb_func.
 248   bool isThumbFunc(const MCSymbol *Func) const;
 249
 250   /// Flag a function symbol as the target of a .thumb_func directive.
 251   void setIsThumbFunc(const MCSymbol *Func) { ThumbFuncs.insert(Func); }
 252
 253   /// ELF e_header flags
 254   unsigned getELFHeaderEFlags() const { return ELFHeaderEFlags; }
 255   void setELFHeaderEFlags(unsigned Flags) { ELFHeaderEFlags = Flags; }
 256
 257   /// MachO deployment target version information.
 258   const VersionInfoType &getVersionInfo() const { return VersionInfo; }
 259   void setVersionMin(MCVersionMinType Type, unsigned Major, unsigned Minor,
 260                      unsigned Update,
 261                      VersionTuple SDKVersion = VersionTuple()) {
 262     VersionInfo.EmitBuildVersion = false;
 263     VersionInfo.TypeOrPlatform.Type = Type;
 264     VersionInfo.Major = Major;
 265     VersionInfo.Minor = Minor;
 266     VersionInfo.Update = Update;
 267     VersionInfo.SDKVersion = SDKVersion;
 268   }
 269   void setBuildVersion(MachO::PlatformType Platform, unsigned Major,
 270                        unsigned Minor, unsigned Update,
 271                        VersionTuple SDKVersion = VersionTuple()) {
 272     VersionInfo.EmitBuildVersion = true;
 273     VersionInfo.TypeOrPlatform.Platform = Platform;
 274     VersionInfo.Major = Major;
 275     VersionInfo.Minor = Minor;
 276     VersionInfo.Update = Update;
 277     VersionInfo.SDKVersion = SDKVersion;
 278   }
 279
 280   /// Reuse an assembler instance
 281   ///
 282   void reset();
 283
 284   MCContext &getContext() const { return Context; }
 285
 286   MCAsmBackend *getBackendPtr() const { return Backend.get(); }
 287
 288   MCCodeEmitter *getEmitterPtr() const { return Emitter.get(); }
 289
 290   MCObjectWriter *getWriterPtr() const { return Writer.get(); }
 291
 292   MCAsmBackend &getBackend() const { return *Backend; }
 293
 294   MCCodeEmitter &getEmitter() const { return *Emitter; }
 295
 296   MCObjectWriter &getWriter() const { return *Writer; }
 297
 298   MCDwarfLineTableParams getDWARFLinetableParams() const { return LTParams; }
 299   void setDWARFLinetableParams(MCDwarfLineTableParams P) { LTParams = P; }
 300
 301   /// Finish - Do final processing and write the object to the output stream.
 302   /// \p Writer is used for custom object writer (as the MCJIT does),
 303   /// if not specified it is automatically created from backend.
 304   void Finish();
 305
 306   // Layout all section and prepare them for emission.
 307   void layout(MCAsmLayout &Layout);
 308
 309   // FIXME: This does not belong here.
 310   bool getSubsectionsViaSymbols() const { return SubsectionsViaSymbols; }
 311   void setSubsectionsViaSymbols(bool Value) { SubsectionsViaSymbols = Value; }
 312
 313   bool isIncrementalLinkerCompatible() const {
 314     return IncrementalLinkerCompatible;
 315   }
 316   void setIncrementalLinkerCompatible(bool Value) {
 317     IncrementalLinkerCompatible = Value;
 318   }
 319
 320   bool getRelaxAll() const { return RelaxAll; }
 321   void setRelaxAll(bool Value) { RelaxAll = Value; }
 322
 323   bool isBundlingEnabled() const { return BundleAlignSize != 0; }
 324
 325   unsigned getBundleAlignSize() const { return BundleAlignSize; }
 326
 327   void setBundleAlignSize(unsigned Size) {
 328     assert((Size == 0 || !(Size & (Size - 1))) &&
 329            "Expect a power-of-two bundle align size");
 330     BundleAlignSize = Size;
 331   }
 332
 333   /// \name Section List Access
 334   /// @{
 335
 336   iterator begin() { return Sections.begin(); }
 337   const_iterator begin() const { return Sections.begin(); }
 338
 339   iterator end() { return Sections.end(); }
 340   const_iterator end() const { return Sections.end(); }
 341
 342   size_t size() const { return Sections.size(); }
 343
 344   /// @}
 345   /// \name Symbol List Access
 346   /// @{
 347   symbol_iterator symbol_begin() { return Symbols.begin(); }
 348   const_symbol_iterator symbol_begin() const { return Symbols.begin(); }
 349
 350   symbol_iterator symbol_end() { return Symbols.end(); }
 351   const_symbol_iterator symbol_end() const { return Symbols.end(); }
 352
 353   symbol_range symbols() { return make_range(symbol_begin(), symbol_end()); }
 354   const_symbol_range symbols() const {
 355     return make_range(symbol_begin(), symbol_end());
 356   }
 357
 358   size_t symbol_size() const { return Symbols.size(); }
 359
 360   /// @}
 361   /// \name Indirect Symbol List Access
 362   /// @{
 363
 364   // FIXME: This is a total hack, this should not be here. Once things are
 365   // factored so that the streamer has direct access to the .o writer, it can
 366   // disappear.
 367   std::vector<IndirectSymbolData> &getIndirectSymbols() {
 368     return IndirectSymbols;
 369   }
 370
 371   indirect_symbol_iterator indirect_symbol_begin() {
 372     return IndirectSymbols.begin();
 373   }
 374   const_indirect_symbol_iterator indirect_symbol_begin() const {
 375     return IndirectSymbols.begin();
 376   }
 377
 378   indirect_symbol_iterator indirect_symbol_end() {
 379     return IndirectSymbols.end();
 380   }
 381   const_indirect_symbol_iterator indirect_symbol_end() const {
 382     return IndirectSymbols.end();
 383   }
 384
 385   size_t indirect_symbol_size() const { return IndirectSymbols.size(); }
 386
 387   /// @}
 388   /// \name Linker Option List Access
 389   /// @{
 390
 391   std::vector<std::vector<std::string>> &getLinkerOptions() {
 392     return LinkerOptions;
 393   }
 394
 395   /// @}
 396   /// \name Data Region List Access
 397   /// @{
 398
 399   // FIXME: This is a total hack, this should not be here. Once things are
 400   // factored so that the streamer has direct access to the .o writer, it can
 401   // disappear.
 402   std::vector<DataRegionData> &getDataRegions() { return DataRegions; }
 403
 404   data_region_iterator data_region_begin() { return DataRegions.begin(); }
 405   const_data_region_iterator data_region_begin() const {
 406     return DataRegions.begin();
 407   }
 408
 409   data_region_iterator data_region_end() { return DataRegions.end(); }
 410   const_data_region_iterator data_region_end() const {
 411     return DataRegions.end();
 412   }
 413
 414   size_t data_region_size() const { return DataRegions.size(); }
 415
 416   /// @}
 417   /// \name Data Region List Access
 418   /// @{
 419
 420   // FIXME: This is a total hack, this should not be here. Once things are
 421   // factored so that the streamer has direct access to the .o writer, it can
 422   // disappear.
 423   MCLOHContainer &getLOHContainer() { return LOHContainer; }
 424   const MCLOHContainer &getLOHContainer() const {
 425     return const_cast<MCAssembler *>(this)->getLOHContainer();
 426   }
 427
 428   struct CGProfileEntry {
 429     const MCSymbolRefExpr *From;
 430     const MCSymbolRefExpr *To;
 431     uint64_t Count;
 432   };
 433   std::vector<CGProfileEntry> CGProfile;
 434   /// @}
 435   /// \name Backend Data Access
 436   /// @{
 437
 438   bool registerSection(MCSection &Section);
 439
 440   void registerSymbol(const MCSymbol &Symbol, bool *Created = nullptr);
 441
 442   ArrayRef<std::string> getFileNames() { return FileNames; }
 443
 444   void addFileName(StringRef FileName) {
 445     if (!is_contained(FileNames, FileName))
 446       FileNames.push_back(FileName);
 447   }
 448
 449   /// Write the necessary bundle padding to \p OS.
 450   /// Expects a fragment \p F containing instructions and its size \p FSize.
 451   void writeFragmentPadding(raw_ostream &OS, const MCEncodedFragment &F,
 452                             uint64_t FSize) const;
 453
 454   /// @}
 455
 456   void dump() const;
 457 };
 458
 459 /// Compute the amount of padding required before the fragment \p F to
 460 /// obey bundling restrictions, where \p FOffset is the fragment's offset in
 461 /// its section and \p FSize is the fragment's size.
 462 uint64_t computeBundlePadding(const MCAssembler &Assembler,
 463                               const MCEncodedFragment *F, uint64_t FOffset,
 464                               uint64_t FSize);
 465
 466 } // end namespace llvm
 467
 468 #endif // LLVM_MC_MCASSEMBLER_H