LLVM  6.0.0svn
WasmObjectWriter.cpp
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1 //===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===//
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 implements Wasm object file writer information.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/STLExtras.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/BinaryFormat/Wasm.h"
17 #include "llvm/MC/MCAsmBackend.h"
18 #include "llvm/MC/MCAsmInfo.h"
19 #include "llvm/MC/MCAsmLayout.h"
20 #include "llvm/MC/MCAssembler.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
25 #include "llvm/MC/MCObjectWriter.h"
26 #include "llvm/MC/MCSectionWasm.h"
27 #include "llvm/MC/MCSymbolWasm.h"
28 #include "llvm/MC/MCValue.h"
30 #include "llvm/Support/Casting.h"
31 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/LEB128.h"
35 #include <vector>
36 
37 using namespace llvm;
38 
39 #define DEBUG_TYPE "mc"
40 
41 namespace {
42 
43 // For patching purposes, we need to remember where each section starts, both
44 // for patching up the section size field, and for patching up references to
45 // locations within the section.
46 struct SectionBookkeeping {
47  // Where the size of the section is written.
48  uint64_t SizeOffset;
49  // Where the contents of the section starts (after the header).
50  uint64_t ContentsOffset;
51 };
52 
53 // The signature of a wasm function, in a struct capable of being used as a
54 // DenseMap key.
55 struct WasmFunctionType {
56  // Support empty and tombstone instances, needed by DenseMap.
57  enum { Plain, Empty, Tombstone } State;
58 
59  // The return types of the function.
61 
62  // The parameter types of the function.
64 
65  WasmFunctionType() : State(Plain) {}
66 
67  bool operator==(const WasmFunctionType &Other) const {
68  return State == Other.State && Returns == Other.Returns &&
69  Params == Other.Params;
70  }
71 };
72 
73 // Traits for using WasmFunctionType in a DenseMap.
74 struct WasmFunctionTypeDenseMapInfo {
75  static WasmFunctionType getEmptyKey() {
76  WasmFunctionType FuncTy;
77  FuncTy.State = WasmFunctionType::Empty;
78  return FuncTy;
79  }
80  static WasmFunctionType getTombstoneKey() {
81  WasmFunctionType FuncTy;
82  FuncTy.State = WasmFunctionType::Tombstone;
83  return FuncTy;
84  }
85  static unsigned getHashValue(const WasmFunctionType &FuncTy) {
86  uintptr_t Value = FuncTy.State;
87  for (wasm::ValType Ret : FuncTy.Returns)
88  Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Ret));
89  for (wasm::ValType Param : FuncTy.Params)
90  Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Param));
91  return Value;
92  }
93  static bool isEqual(const WasmFunctionType &LHS,
94  const WasmFunctionType &RHS) {
95  return LHS == RHS;
96  }
97 };
98 
99 // A wasm data segment. A wasm binary contains only a single data section
100 // but that can contain many segments, each with their own virtual location
101 // in memory. Each MCSection data created by llvm is modeled as its own
102 // wasm data segment.
103 struct WasmDataSegment {
105  StringRef Name;
107  uint32_t Alignment;
108  uint32_t Flags;
110 };
111 
112 // A wasm import to be written into the import section.
113 struct WasmImport {
114  StringRef ModuleName;
115  StringRef FieldName;
116  unsigned Kind;
117  int32_t Type;
118 };
119 
120 // A wasm function to be written into the function section.
121 struct WasmFunction {
122  int32_t Type;
123  const MCSymbolWasm *Sym;
124 };
125 
126 // A wasm export to be written into the export section.
127 struct WasmExport {
128  StringRef FieldName;
129  unsigned Kind;
130  uint32_t Index;
131 };
132 
133 // A wasm global to be written into the global section.
134 struct WasmGlobal {
136  bool IsMutable;
137  bool HasImport;
138  uint64_t InitialValue;
139  uint32_t ImportIndex;
140 };
141 
142 // Information about a single relocation.
143 struct WasmRelocationEntry {
144  uint64_t Offset; // Where is the relocation.
145  const MCSymbolWasm *Symbol; // The symbol to relocate with.
146  int64_t Addend; // A value to add to the symbol.
147  unsigned Type; // The type of the relocation.
148  const MCSectionWasm *FixupSection;// The section the relocation is targeting.
149 
150  WasmRelocationEntry(uint64_t Offset, const MCSymbolWasm *Symbol,
151  int64_t Addend, unsigned Type,
152  const MCSectionWasm *FixupSection)
153  : Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type),
154  FixupSection(FixupSection) {}
155 
156  bool hasAddend() const {
157  switch (Type) {
158  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
159  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
160  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
161  return true;
162  default:
163  return false;
164  }
165  }
166 
167  void print(raw_ostream &Out) const {
168  Out << "Off=" << Offset << ", Sym=" << *Symbol << ", Addend=" << Addend
169  << ", Type=" << Type
170  << ", FixupSection=" << FixupSection->getSectionName();
171  }
172 
173 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
174  LLVM_DUMP_METHOD void dump() const { print(dbgs()); }
175 #endif
176 };
177 
178 #if !defined(NDEBUG)
179 raw_ostream &operator<<(raw_ostream &OS, const WasmRelocationEntry &Rel) {
180  Rel.print(OS);
181  return OS;
182 }
183 #endif
184 
185 class WasmObjectWriter : public MCObjectWriter {
186  /// Helper struct for containing some precomputed information on symbols.
187  struct WasmSymbolData {
188  const MCSymbolWasm *Symbol;
189  StringRef Name;
190 
191  // Support lexicographic sorting.
192  bool operator<(const WasmSymbolData &RHS) const { return Name < RHS.Name; }
193  };
194 
195  /// The target specific Wasm writer instance.
196  std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter;
197 
198  // Relocations for fixing up references in the code section.
199  std::vector<WasmRelocationEntry> CodeRelocations;
200 
201  // Relocations for fixing up references in the data section.
202  std::vector<WasmRelocationEntry> DataRelocations;
203 
204  // Index values to use for fixing up call_indirect type indices.
205  // Maps function symbols to the index of the type of the function
207  // Maps function symbols to the table element index space. Used
208  // for TABLE_INDEX relocation types (i.e. address taken functions).
209  DenseMap<const MCSymbolWasm *, uint32_t> IndirectSymbolIndices;
210  // Maps function/global symbols to the function/global index space.
212 
214  FunctionTypeIndices;
215  SmallVector<WasmFunctionType, 4> FunctionTypes;
217  unsigned NumGlobalImports = 0;
218 
219  // TargetObjectWriter wrappers.
220  bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
221  unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup) const {
222  return TargetObjectWriter->getRelocType(Target, Fixup);
223  }
224 
225  void startSection(SectionBookkeeping &Section, unsigned SectionId,
226  const char *Name = nullptr);
227  void endSection(SectionBookkeeping &Section);
228 
229 public:
230  WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
231  raw_pwrite_stream &OS)
232  : MCObjectWriter(OS, /*IsLittleEndian=*/true),
233  TargetObjectWriter(std::move(MOTW)) {}
234 
235 private:
236  ~WasmObjectWriter() override;
237 
238  void reset() override {
239  CodeRelocations.clear();
240  DataRelocations.clear();
241  TypeIndices.clear();
242  SymbolIndices.clear();
243  IndirectSymbolIndices.clear();
244  FunctionTypeIndices.clear();
245  FunctionTypes.clear();
246  Globals.clear();
248  NumGlobalImports = 0;
249  }
250 
251  void writeHeader(const MCAssembler &Asm);
252 
253  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
254  const MCFragment *Fragment, const MCFixup &Fixup,
255  MCValue Target, uint64_t &FixedValue) override;
256 
257  void executePostLayoutBinding(MCAssembler &Asm,
258  const MCAsmLayout &Layout) override;
259 
260  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
261 
262  void writeString(const StringRef Str) {
263  encodeULEB128(Str.size(), getStream());
264  writeBytes(Str);
265  }
266 
267  void writeValueType(wasm::ValType Ty) {
268  encodeSLEB128(int32_t(Ty), getStream());
269  }
270 
271  void writeTypeSection(ArrayRef<WasmFunctionType> FunctionTypes);
272  void writeImportSection(ArrayRef<WasmImport> Imports);
273  void writeFunctionSection(ArrayRef<WasmFunction> Functions);
274  void writeTableSection(uint32_t NumElements);
275  void writeMemorySection(uint32_t DataSize);
276  void writeGlobalSection();
277  void writeExportSection(ArrayRef<WasmExport> Exports);
278  void writeElemSection(ArrayRef<uint32_t> TableElems);
279  void writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
280  ArrayRef<WasmFunction> Functions);
281  void writeDataSection(ArrayRef<WasmDataSegment> Segments);
282  void writeNameSection(ArrayRef<WasmFunction> Functions,
283  ArrayRef<WasmImport> Imports,
284  uint32_t NumFuncImports);
285  void writeCodeRelocSection();
286  void writeDataRelocSection();
287  void writeLinkingMetaDataSection(
288  ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
289  SmallVector<std::pair<StringRef, uint32_t>, 4> SymbolFlags,
290  bool HasStackPointer, uint32_t StackPointerGlobal);
291 
292  uint32_t getProvisionalValue(const WasmRelocationEntry &RelEntry);
293  void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations,
294  uint64_t ContentsOffset);
295 
296  void writeRelocations(ArrayRef<WasmRelocationEntry> Relocations);
297  uint32_t getRelocationIndexValue(const WasmRelocationEntry &RelEntry);
298  uint32_t getFunctionType(const MCSymbolWasm& Symbol);
299  uint32_t registerFunctionType(const MCSymbolWasm& Symbol);
300 };
301 
302 } // end anonymous namespace
303 
304 WasmObjectWriter::~WasmObjectWriter() {}
305 
306 // Write out a section header and a patchable section size field.
307 void WasmObjectWriter::startSection(SectionBookkeeping &Section,
308  unsigned SectionId,
309  const char *Name) {
310  assert((Name != nullptr) == (SectionId == wasm::WASM_SEC_CUSTOM) &&
311  "Only custom sections can have names");
312 
313  DEBUG(dbgs() << "startSection " << SectionId << ": " << Name << "\n");
314  encodeULEB128(SectionId, getStream());
315 
316  Section.SizeOffset = getStream().tell();
317 
318  // The section size. We don't know the size yet, so reserve enough space
319  // for any 32-bit value; we'll patch it later.
320  encodeULEB128(UINT32_MAX, getStream());
321 
322  // The position where the section starts, for measuring its size.
323  Section.ContentsOffset = getStream().tell();
324 
325  // Custom sections in wasm also have a string identifier.
326  if (SectionId == wasm::WASM_SEC_CUSTOM) {
327  assert(Name);
328  writeString(StringRef(Name));
329  }
330 }
331 
332 // Now that the section is complete and we know how big it is, patch up the
333 // section size field at the start of the section.
334 void WasmObjectWriter::endSection(SectionBookkeeping &Section) {
335  uint64_t Size = getStream().tell() - Section.ContentsOffset;
336  if (uint32_t(Size) != Size)
337  report_fatal_error("section size does not fit in a uint32_t");
338 
339  DEBUG(dbgs() << "endSection size=" << Size << "\n");
340 
341  // Write the final section size to the payload_len field, which follows
342  // the section id byte.
343  uint8_t Buffer[16];
344  unsigned SizeLen = encodeULEB128(Size, Buffer, 5);
345  assert(SizeLen == 5);
346  getStream().pwrite((char *)Buffer, SizeLen, Section.SizeOffset);
347 }
348 
349 // Emit the Wasm header.
350 void WasmObjectWriter::writeHeader(const MCAssembler &Asm) {
351  writeBytes(StringRef(wasm::WasmMagic, sizeof(wasm::WasmMagic)));
352  writeLE32(wasm::WasmVersion);
353 }
354 
355 void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
356  const MCAsmLayout &Layout) {
357 }
358 
359 void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
360  const MCAsmLayout &Layout,
361  const MCFragment *Fragment,
362  const MCFixup &Fixup, MCValue Target,
363  uint64_t &FixedValue) {
364  MCAsmBackend &Backend = Asm.getBackend();
365  bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
367  const auto &FixupSection = cast<MCSectionWasm>(*Fragment->getParent());
368  uint64_t C = Target.getConstant();
369  uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
370  MCContext &Ctx = Asm.getContext();
371 
372  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
373  assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
374  "Should not have constructed this");
375 
376  // Let A, B and C being the components of Target and R be the location of
377  // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
378  // If it is pcrel, we want to compute (A - B + C - R).
379 
380  // In general, Wasm has no relocations for -B. It can only represent (A + C)
381  // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
382  // replace B to implement it: (A - R - K + C)
383  if (IsPCRel) {
384  Ctx.reportError(
385  Fixup.getLoc(),
386  "No relocation available to represent this relative expression");
387  return;
388  }
389 
390  const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol());
391 
392  if (SymB.isUndefined()) {
393  Ctx.reportError(Fixup.getLoc(),
394  Twine("symbol '") + SymB.getName() +
395  "' can not be undefined in a subtraction expression");
396  return;
397  }
398 
399  assert(!SymB.isAbsolute() && "Should have been folded");
400  const MCSection &SecB = SymB.getSection();
401  if (&SecB != &FixupSection) {
402  Ctx.reportError(Fixup.getLoc(),
403  "Cannot represent a difference across sections");
404  return;
405  }
406 
407  uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
408  uint64_t K = SymBOffset - FixupOffset;
409  IsPCRel = true;
410  C -= K;
411  }
412 
413  // We either rejected the fixup or folded B into C at this point.
414  const MCSymbolRefExpr *RefA = Target.getSymA();
415  const auto *SymA = RefA ? cast<MCSymbolWasm>(&RefA->getSymbol()) : nullptr;
416 
417  if (SymA && SymA->isVariable()) {
418  const MCExpr *Expr = SymA->getVariableValue();
419  const auto *Inner = cast<MCSymbolRefExpr>(Expr);
420  if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
421  llvm_unreachable("weakref used in reloc not yet implemented");
422  }
423 
424  // Put any constant offset in an addend. Offsets can be negative, and
425  // LLVM expects wrapping, in contrast to wasm's immediates which can't
426  // be negative and don't wrap.
427  FixedValue = 0;
428 
429  if (SymA)
430  SymA->setUsedInReloc();
431 
432  assert(!IsPCRel);
433  assert(SymA);
434 
435  unsigned Type = getRelocType(Target, Fixup);
436 
437  WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection);
438  DEBUG(dbgs() << "WasmReloc: " << Rec << "\n");
439 
440  if (FixupSection.isWasmData())
441  DataRelocations.push_back(Rec);
442  else if (FixupSection.getKind().isText())
443  CodeRelocations.push_back(Rec);
444  else if (!FixupSection.getKind().isMetadata())
445  // TODO(sbc): Add support for debug sections.
446  llvm_unreachable("unexpected section type");
447 }
448 
449 // Write X as an (unsigned) LEB value at offset Offset in Stream, padded
450 // to allow patching.
451 static void
453  uint8_t Buffer[5];
454  unsigned SizeLen = encodeULEB128(X, Buffer, 5);
455  assert(SizeLen == 5);
456  Stream.pwrite((char *)Buffer, SizeLen, Offset);
457 }
458 
459 // Write X as an signed LEB value at offset Offset in Stream, padded
460 // to allow patching.
461 static void
462 WritePatchableSLEB(raw_pwrite_stream &Stream, int32_t X, uint64_t Offset) {
463  uint8_t Buffer[5];
464  unsigned SizeLen = encodeSLEB128(X, Buffer, 5);
465  assert(SizeLen == 5);
466  Stream.pwrite((char *)Buffer, SizeLen, Offset);
467 }
468 
469 // Write X as a plain integer value at offset Offset in Stream.
470 static void WriteI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
471  uint8_t Buffer[4];
472  support::endian::write32le(Buffer, X);
473  Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset);
474 }
475 
477  if (Symbol.isVariable()) {
478  const MCExpr *Expr = Symbol.getVariableValue();
479  auto *Inner = cast<MCSymbolRefExpr>(Expr);
480  return cast<MCSymbolWasm>(&Inner->getSymbol());
481  }
482  return &Symbol;
483 }
484 
485 // Compute a value to write into the code at the location covered
486 // by RelEntry. This value isn't used by the static linker, since
487 // we have addends; it just serves to make the code more readable
488 // and to make standalone wasm modules directly usable.
489 uint32_t
490 WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry) {
491  const MCSymbolWasm *Sym = ResolveSymbol(*RelEntry.Symbol);
492 
493  // For undefined symbols, use a hopefully invalid value.
494  if (!Sym->isDefined(/*SetUsed=*/false))
495  return UINT32_MAX;
496 
497  uint32_t GlobalIndex = SymbolIndices[Sym];
498  const WasmGlobal& Global = Globals[GlobalIndex - NumGlobalImports];
499  uint64_t Address = Global.InitialValue + RelEntry.Addend;
500 
501  // Ignore overflow. LLVM allows address arithmetic to silently wrap.
503 
504  return Value;
505 }
506 
507 static void addData(SmallVectorImpl<char> &DataBytes,
508  MCSectionWasm &DataSection) {
509  DEBUG(errs() << "addData: " << DataSection.getSectionName() << "\n");
510 
511  DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment()));
512 
513  size_t LastFragmentSize = 0;
514  for (const MCFragment &Frag : DataSection) {
515  if (Frag.hasInstructions())
516  report_fatal_error("only data supported in data sections");
517 
518  if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) {
519  if (Align->getValueSize() != 1)
520  report_fatal_error("only byte values supported for alignment");
521  // If nops are requested, use zeros, as this is the data section.
522  uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
523  uint64_t Size = std::min<uint64_t>(alignTo(DataBytes.size(),
524  Align->getAlignment()),
525  DataBytes.size() +
526  Align->getMaxBytesToEmit());
527  DataBytes.resize(Size, Value);
528  } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
529  DataBytes.insert(DataBytes.end(), Fill->getSize(), Fill->getValue());
530  } else {
531  const auto &DataFrag = cast<MCDataFragment>(Frag);
532  const SmallVectorImpl<char> &Contents = DataFrag.getContents();
533 
534  DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
535  LastFragmentSize = Contents.size();
536  }
537  }
538 
539  // Don't allow empty segments, or segments that end with zero-sized
540  // fragment, otherwise the linker cannot map symbols to a unique
541  // data segment. This can be triggered by zero-sized structs
542  // See: test/MC/WebAssembly/bss.ll
543  if (LastFragmentSize == 0)
544  DataBytes.resize(DataBytes.size() + 1);
545  DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n");
546 }
547 
548 uint32_t WasmObjectWriter::getRelocationIndexValue(
549  const WasmRelocationEntry &RelEntry) {
550  switch (RelEntry.Type) {
551  case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
552  case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
553  if (!IndirectSymbolIndices.count(RelEntry.Symbol))
554  report_fatal_error("symbol not found table index space: " +
555  RelEntry.Symbol->getName());
556  return IndirectSymbolIndices[RelEntry.Symbol];
557  case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
558  case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
559  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
560  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
561  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
562  if (!SymbolIndices.count(RelEntry.Symbol))
563  report_fatal_error("symbol not found function/global index space: " +
564  RelEntry.Symbol->getName());
565  return SymbolIndices[RelEntry.Symbol];
566  case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
567  if (!TypeIndices.count(RelEntry.Symbol))
568  report_fatal_error("symbol not found in type index space: " +
569  RelEntry.Symbol->getName());
570  return TypeIndices[RelEntry.Symbol];
571  default:
572  llvm_unreachable("invalid relocation type");
573  }
574 }
575 
576 // Apply the portions of the relocation records that we can handle ourselves
577 // directly.
578 void WasmObjectWriter::applyRelocations(
579  ArrayRef<WasmRelocationEntry> Relocations, uint64_t ContentsOffset) {
580  raw_pwrite_stream &Stream = getStream();
581  for (const WasmRelocationEntry &RelEntry : Relocations) {
582  uint64_t Offset = ContentsOffset +
583  RelEntry.FixupSection->getSectionOffset() +
584  RelEntry.Offset;
585 
586  DEBUG(dbgs() << "applyRelocation: " << RelEntry << "\n");
587  switch (RelEntry.Type) {
588  case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
589  case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
590  case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
591  case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB: {
592  uint32_t Index = getRelocationIndexValue(RelEntry);
593  WritePatchableSLEB(Stream, Index, Offset);
594  break;
595  }
596  case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32: {
597  uint32_t Index = getRelocationIndexValue(RelEntry);
598  WriteI32(Stream, Index, Offset);
599  break;
600  }
601  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB: {
602  uint32_t Value = getProvisionalValue(RelEntry);
603  WritePatchableSLEB(Stream, Value, Offset);
604  break;
605  }
606  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB: {
607  uint32_t Value = getProvisionalValue(RelEntry);
608  WritePatchableLEB(Stream, Value, Offset);
609  break;
610  }
611  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32: {
612  uint32_t Value = getProvisionalValue(RelEntry);
613  WriteI32(Stream, Value, Offset);
614  break;
615  }
616  default:
617  llvm_unreachable("invalid relocation type");
618  }
619  }
620 }
621 
622 // Write out the portions of the relocation records that the linker will
623 // need to handle.
624 void WasmObjectWriter::writeRelocations(
625  ArrayRef<WasmRelocationEntry> Relocations) {
626  raw_pwrite_stream &Stream = getStream();
627  for (const WasmRelocationEntry& RelEntry : Relocations) {
628 
629  uint64_t Offset = RelEntry.Offset +
630  RelEntry.FixupSection->getSectionOffset();
631  uint32_t Index = getRelocationIndexValue(RelEntry);
632 
633  encodeULEB128(RelEntry.Type, Stream);
634  encodeULEB128(Offset, Stream);
635  encodeULEB128(Index, Stream);
636  if (RelEntry.hasAddend())
637  encodeSLEB128(RelEntry.Addend, Stream);
638  }
639 }
640 
641 void WasmObjectWriter::writeTypeSection(
642  ArrayRef<WasmFunctionType> FunctionTypes) {
643  if (FunctionTypes.empty())
644  return;
645 
646  SectionBookkeeping Section;
647  startSection(Section, wasm::WASM_SEC_TYPE);
648 
649  encodeULEB128(FunctionTypes.size(), getStream());
650 
651  for (const WasmFunctionType &FuncTy : FunctionTypes) {
652  encodeSLEB128(wasm::WASM_TYPE_FUNC, getStream());
653  encodeULEB128(FuncTy.Params.size(), getStream());
654  for (wasm::ValType Ty : FuncTy.Params)
655  writeValueType(Ty);
656  encodeULEB128(FuncTy.Returns.size(), getStream());
657  for (wasm::ValType Ty : FuncTy.Returns)
658  writeValueType(Ty);
659  }
660 
661  endSection(Section);
662 }
663 
664 void WasmObjectWriter::writeImportSection(ArrayRef<WasmImport> Imports) {
665  if (Imports.empty())
666  return;
667 
668  SectionBookkeeping Section;
669  startSection(Section, wasm::WASM_SEC_IMPORT);
670 
671  encodeULEB128(Imports.size(), getStream());
672  for (const WasmImport &Import : Imports) {
673  writeString(Import.ModuleName);
674  writeString(Import.FieldName);
675 
676  encodeULEB128(Import.Kind, getStream());
677 
678  switch (Import.Kind) {
680  encodeULEB128(Import.Type, getStream());
681  break;
683  encodeSLEB128(int32_t(Import.Type), getStream());
684  encodeULEB128(0, getStream()); // mutability
685  break;
686  default:
687  llvm_unreachable("unsupported import kind");
688  }
689  }
690 
691  endSection(Section);
692 }
693 
694 void WasmObjectWriter::writeFunctionSection(ArrayRef<WasmFunction> Functions) {
695  if (Functions.empty())
696  return;
697 
698  SectionBookkeeping Section;
699  startSection(Section, wasm::WASM_SEC_FUNCTION);
700 
701  encodeULEB128(Functions.size(), getStream());
702  for (const WasmFunction &Func : Functions)
703  encodeULEB128(Func.Type, getStream());
704 
705  endSection(Section);
706 }
707 
708 void WasmObjectWriter::writeTableSection(uint32_t NumElements) {
709  // For now, always emit the table section, since indirect calls are not
710  // valid without it. In the future, we could perhaps be more clever and omit
711  // it if there are no indirect calls.
712 
713  SectionBookkeeping Section;
714  startSection(Section, wasm::WASM_SEC_TABLE);
715 
716  encodeULEB128(1, getStream()); // The number of tables.
717  // Fixed to 1 for now.
718  encodeSLEB128(wasm::WASM_TYPE_ANYFUNC, getStream()); // Type of table
719  encodeULEB128(0, getStream()); // flags
720  encodeULEB128(NumElements, getStream()); // initial
721 
722  endSection(Section);
723 }
724 
725 void WasmObjectWriter::writeMemorySection(uint32_t DataSize) {
726  // For now, always emit the memory section, since loads and stores are not
727  // valid without it. In the future, we could perhaps be more clever and omit
728  // it if there are no loads or stores.
729  SectionBookkeeping Section;
730  uint32_t NumPages = (DataSize + wasm::WasmPageSize - 1) / wasm::WasmPageSize;
731 
732  startSection(Section, wasm::WASM_SEC_MEMORY);
733  encodeULEB128(1, getStream()); // number of memory spaces
734 
735  encodeULEB128(0, getStream()); // flags
736  encodeULEB128(NumPages, getStream()); // initial
737 
738  endSection(Section);
739 }
740 
741 void WasmObjectWriter::writeGlobalSection() {
742  if (Globals.empty())
743  return;
744 
745  SectionBookkeeping Section;
746  startSection(Section, wasm::WASM_SEC_GLOBAL);
747 
748  encodeULEB128(Globals.size(), getStream());
749  for (const WasmGlobal &Global : Globals) {
750  writeValueType(Global.Type);
751  write8(Global.IsMutable);
752 
753  if (Global.HasImport) {
754  assert(Global.InitialValue == 0);
756  encodeULEB128(Global.ImportIndex, getStream());
757  } else {
758  assert(Global.ImportIndex == 0);
760  encodeSLEB128(Global.InitialValue, getStream()); // offset
761  }
762  write8(wasm::WASM_OPCODE_END);
763  }
764 
765  endSection(Section);
766 }
767 
768 void WasmObjectWriter::writeExportSection(ArrayRef<WasmExport> Exports) {
769  if (Exports.empty())
770  return;
771 
772  SectionBookkeeping Section;
773  startSection(Section, wasm::WASM_SEC_EXPORT);
774 
775  encodeULEB128(Exports.size(), getStream());
776  for (const WasmExport &Export : Exports) {
777  writeString(Export.FieldName);
778  encodeSLEB128(Export.Kind, getStream());
779  encodeULEB128(Export.Index, getStream());
780  }
781 
782  endSection(Section);
783 }
784 
785 void WasmObjectWriter::writeElemSection(ArrayRef<uint32_t> TableElems) {
786  if (TableElems.empty())
787  return;
788 
789  SectionBookkeeping Section;
790  startSection(Section, wasm::WASM_SEC_ELEM);
791 
792  encodeULEB128(1, getStream()); // number of "segments"
793  encodeULEB128(0, getStream()); // the table index
794 
795  // init expr for starting offset
797  encodeSLEB128(0, getStream());
798  write8(wasm::WASM_OPCODE_END);
799 
800  encodeULEB128(TableElems.size(), getStream());
801  for (uint32_t Elem : TableElems)
802  encodeULEB128(Elem, getStream());
803 
804  endSection(Section);
805 }
806 
807 void WasmObjectWriter::writeCodeSection(const MCAssembler &Asm,
808  const MCAsmLayout &Layout,
809  ArrayRef<WasmFunction> Functions) {
810  if (Functions.empty())
811  return;
812 
813  SectionBookkeeping Section;
814  startSection(Section, wasm::WASM_SEC_CODE);
815 
816  encodeULEB128(Functions.size(), getStream());
817 
818  for (const WasmFunction &Func : Functions) {
819  auto &FuncSection = static_cast<MCSectionWasm &>(Func.Sym->getSection());
820 
821  int64_t Size = 0;
822  if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout))
823  report_fatal_error(".size expression must be evaluatable");
824 
825  encodeULEB128(Size, getStream());
826  FuncSection.setSectionOffset(getStream().tell() - Section.ContentsOffset);
827  Asm.writeSectionData(&FuncSection, Layout);
828  }
829 
830  // Apply fixups.
831  applyRelocations(CodeRelocations, Section.ContentsOffset);
832 
833  endSection(Section);
834 }
835 
836 void WasmObjectWriter::writeDataSection(ArrayRef<WasmDataSegment> Segments) {
837  if (Segments.empty())
838  return;
839 
840  SectionBookkeeping Section;
841  startSection(Section, wasm::WASM_SEC_DATA);
842 
843  encodeULEB128(Segments.size(), getStream()); // count
844 
845  for (const WasmDataSegment & Segment : Segments) {
846  encodeULEB128(0, getStream()); // memory index
848  encodeSLEB128(Segment.Offset, getStream()); // offset
849  write8(wasm::WASM_OPCODE_END);
850  encodeULEB128(Segment.Data.size(), getStream()); // size
851  Segment.Section->setSectionOffset(getStream().tell() - Section.ContentsOffset);
852  writeBytes(Segment.Data); // data
853  }
854 
855  // Apply fixups.
856  applyRelocations(DataRelocations, Section.ContentsOffset);
857 
858  endSection(Section);
859 }
860 
861 void WasmObjectWriter::writeNameSection(
862  ArrayRef<WasmFunction> Functions,
863  ArrayRef<WasmImport> Imports,
864  unsigned NumFuncImports) {
865  uint32_t TotalFunctions = NumFuncImports + Functions.size();
866  if (TotalFunctions == 0)
867  return;
868 
869  SectionBookkeeping Section;
870  startSection(Section, wasm::WASM_SEC_CUSTOM, "name");
871  SectionBookkeeping SubSection;
872  startSection(SubSection, wasm::WASM_NAMES_FUNCTION);
873 
874  encodeULEB128(TotalFunctions, getStream());
875  uint32_t Index = 0;
876  for (const WasmImport &Import : Imports) {
877  if (Import.Kind == wasm::WASM_EXTERNAL_FUNCTION) {
878  encodeULEB128(Index, getStream());
879  writeString(Import.FieldName);
880  ++Index;
881  }
882  }
883  for (const WasmFunction &Func : Functions) {
884  encodeULEB128(Index, getStream());
885  writeString(Func.Sym->getName());
886  ++Index;
887  }
888 
889  endSection(SubSection);
890  endSection(Section);
891 }
892 
893 void WasmObjectWriter::writeCodeRelocSection() {
894  // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
895  // for descriptions of the reloc sections.
896 
897  if (CodeRelocations.empty())
898  return;
899 
900  SectionBookkeeping Section;
901  startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.CODE");
902 
903  encodeULEB128(wasm::WASM_SEC_CODE, getStream());
904  encodeULEB128(CodeRelocations.size(), getStream());
905 
906  writeRelocations(CodeRelocations);
907 
908  endSection(Section);
909 }
910 
911 void WasmObjectWriter::writeDataRelocSection() {
912  // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
913  // for descriptions of the reloc sections.
914 
915  if (DataRelocations.empty())
916  return;
917 
918  SectionBookkeeping Section;
919  startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.DATA");
920 
921  encodeULEB128(wasm::WASM_SEC_DATA, getStream());
922  encodeULEB128(DataRelocations.size(), getStream());
923 
924  writeRelocations(DataRelocations);
925 
926  endSection(Section);
927 }
928 
929 void WasmObjectWriter::writeLinkingMetaDataSection(
930  ArrayRef<WasmDataSegment> Segments, uint32_t DataSize,
931  SmallVector<std::pair<StringRef, uint32_t>, 4> SymbolFlags,
932  bool HasStackPointer, uint32_t StackPointerGlobal) {
933  SectionBookkeeping Section;
934  startSection(Section, wasm::WASM_SEC_CUSTOM, "linking");
935  SectionBookkeeping SubSection;
936 
937  if (HasStackPointer) {
938  startSection(SubSection, wasm::WASM_STACK_POINTER);
939  encodeULEB128(StackPointerGlobal, getStream()); // id
940  endSection(SubSection);
941  }
942 
943  if (SymbolFlags.size() != 0) {
944  startSection(SubSection, wasm::WASM_SYMBOL_INFO);
945  encodeULEB128(SymbolFlags.size(), getStream());
946  for (auto Pair: SymbolFlags) {
947  writeString(Pair.first);
948  encodeULEB128(Pair.second, getStream());
949  }
950  endSection(SubSection);
951  }
952 
953  if (DataSize > 0) {
954  startSection(SubSection, wasm::WASM_DATA_SIZE);
955  encodeULEB128(DataSize, getStream());
956  endSection(SubSection);
957  }
958 
959  if (Segments.size()) {
960  startSection(SubSection, wasm::WASM_SEGMENT_INFO);
961  encodeULEB128(Segments.size(), getStream());
962  for (const WasmDataSegment &Segment : Segments) {
963  writeString(Segment.Name);
964  encodeULEB128(Segment.Alignment, getStream());
965  encodeULEB128(Segment.Flags, getStream());
966  }
967  endSection(SubSection);
968  }
969 
970  endSection(Section);
971 }
972 
973 uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm& Symbol) {
974  assert(Symbol.isFunction());
975  assert(TypeIndices.count(&Symbol));
976  return TypeIndices[&Symbol];
977 }
978 
979 uint32_t WasmObjectWriter::registerFunctionType(const MCSymbolWasm& Symbol) {
980  assert(Symbol.isFunction());
981 
982  WasmFunctionType F;
983  const MCSymbolWasm* ResolvedSym = ResolveSymbol(Symbol);
984  F.Returns = ResolvedSym->getReturns();
985  F.Params = ResolvedSym->getParams();
986 
987  auto Pair =
988  FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));
989  if (Pair.second)
990  FunctionTypes.push_back(F);
991  TypeIndices[&Symbol] = Pair.first->second;
992 
993  DEBUG(dbgs() << "registerFunctionType: " << Symbol << " new:" << Pair.second << "\n");
994  DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n");
995  return Pair.first->second;
996 }
997 
998 void WasmObjectWriter::writeObject(MCAssembler &Asm,
999  const MCAsmLayout &Layout) {
1000  DEBUG(dbgs() << "WasmObjectWriter::writeObject\n");
1001  MCContext &Ctx = Asm.getContext();
1003 
1004  // Collect information from the available symbols.
1005  SmallVector<WasmFunction, 4> Functions;
1006  SmallVector<uint32_t, 4> TableElems;
1010  SmallPtrSet<const MCSymbolWasm *, 4> IsAddressTaken;
1011  unsigned NumFuncImports = 0;
1012  SmallVector<WasmDataSegment, 4> DataSegments;
1013  uint32_t StackPointerGlobal = 0;
1014  uint32_t DataSize = 0;
1015  bool HasStackPointer = false;
1016 
1017  // Populate the IsAddressTaken set.
1018  for (const WasmRelocationEntry &RelEntry : CodeRelocations) {
1019  switch (RelEntry.Type) {
1020  case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
1021  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
1022  IsAddressTaken.insert(RelEntry.Symbol);
1023  break;
1024  default:
1025  break;
1026  }
1027  }
1028  for (const WasmRelocationEntry &RelEntry : DataRelocations) {
1029  switch (RelEntry.Type) {
1030  case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
1031  case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
1032  IsAddressTaken.insert(RelEntry.Symbol);
1033  break;
1034  default:
1035  break;
1036  }
1037  }
1038 
1039  // Populate FunctionTypeIndices and Imports.
1040  for (const MCSymbol &S : Asm.symbols()) {
1041  const auto &WS = static_cast<const MCSymbolWasm &>(S);
1042 
1043  if (WS.isTemporary())
1044  continue;
1045 
1046  if (WS.isFunction())
1047  registerFunctionType(WS);
1048 
1049  // If the symbol is not defined in this translation unit, import it.
1050  if (!WS.isDefined(/*SetUsed=*/false)) {
1051  WasmImport Import;
1052  Import.ModuleName = WS.getModuleName();
1053  Import.FieldName = WS.getName();
1054 
1055  if (WS.isFunction()) {
1056  Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1057  Import.Type = getFunctionType(WS);
1058  SymbolIndices[&WS] = NumFuncImports;
1059  ++NumFuncImports;
1060  } else {
1061  Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1062  Import.Type = int32_t(PtrType);
1063  SymbolIndices[&WS] = NumGlobalImports;
1064  ++NumGlobalImports;
1065  }
1066 
1067  Imports.push_back(Import);
1068  }
1069  }
1070 
1071  // In the special .global_variables section, we've encoded global
1072  // variables used by the function. Translate them into the Globals
1073  // list.
1074  MCSectionWasm *GlobalVars =
1075  Ctx.getWasmSection(".global_variables", SectionKind::getMetadata());
1076  if (!GlobalVars->getFragmentList().empty()) {
1077  if (GlobalVars->getFragmentList().size() != 1)
1078  report_fatal_error("only one .global_variables fragment supported");
1079  const MCFragment &Frag = *GlobalVars->begin();
1080  if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
1081  report_fatal_error("only data supported in .global_variables");
1082  const auto &DataFrag = cast<MCDataFragment>(Frag);
1083  if (!DataFrag.getFixups().empty())
1084  report_fatal_error("fixups not supported in .global_variables");
1085  const SmallVectorImpl<char> &Contents = DataFrag.getContents();
1086  for (const uint8_t *p = (const uint8_t *)Contents.data(),
1087  *end = (const uint8_t *)Contents.data() + Contents.size();
1088  p != end; ) {
1089  WasmGlobal G;
1090  if (end - p < 3)
1091  report_fatal_error("truncated global variable encoding");
1092  G.Type = wasm::ValType(int8_t(*p++));
1093  G.IsMutable = bool(*p++);
1094  G.HasImport = bool(*p++);
1095  if (G.HasImport) {
1096  G.InitialValue = 0;
1097 
1098  WasmImport Import;
1099  Import.ModuleName = (const char *)p;
1100  const uint8_t *nul = (const uint8_t *)memchr(p, '\0', end - p);
1101  if (!nul)
1102  report_fatal_error("global module name must be nul-terminated");
1103  p = nul + 1;
1104  nul = (const uint8_t *)memchr(p, '\0', end - p);
1105  if (!nul)
1106  report_fatal_error("global base name must be nul-terminated");
1107  Import.FieldName = (const char *)p;
1108  p = nul + 1;
1109 
1110  Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1111  Import.Type = int32_t(G.Type);
1112 
1113  G.ImportIndex = NumGlobalImports;
1114  ++NumGlobalImports;
1115 
1116  Imports.push_back(Import);
1117  } else {
1118  unsigned n;
1119  G.InitialValue = decodeSLEB128(p, &n);
1120  G.ImportIndex = 0;
1121  if ((ptrdiff_t)n > end - p)
1122  report_fatal_error("global initial value must be valid SLEB128");
1123  p += n;
1124  }
1125  Globals.push_back(G);
1126  }
1127  }
1128 
1129  // In the special .stack_pointer section, we've encoded the stack pointer
1130  // index.
1131  MCSectionWasm *StackPtr =
1132  Ctx.getWasmSection(".stack_pointer", SectionKind::getMetadata());
1133  if (!StackPtr->getFragmentList().empty()) {
1134  if (StackPtr->getFragmentList().size() != 1)
1135  report_fatal_error("only one .stack_pointer fragment supported");
1136  const MCFragment &Frag = *StackPtr->begin();
1137  if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
1138  report_fatal_error("only data supported in .stack_pointer");
1139  const auto &DataFrag = cast<MCDataFragment>(Frag);
1140  if (!DataFrag.getFixups().empty())
1141  report_fatal_error("fixups not supported in .stack_pointer");
1142  const SmallVectorImpl<char> &Contents = DataFrag.getContents();
1143  if (Contents.size() != 4)
1144  report_fatal_error("only one entry supported in .stack_pointer");
1145  HasStackPointer = true;
1146  StackPointerGlobal = NumGlobalImports + *(const int32_t *)Contents.data();
1147  }
1148 
1149  for (MCSection &Sec : Asm) {
1150  auto &Section = static_cast<MCSectionWasm &>(Sec);
1151  if (!Section.isWasmData())
1152  continue;
1153 
1154  DataSize = alignTo(DataSize, Section.getAlignment());
1155  DataSegments.emplace_back();
1156  WasmDataSegment &Segment = DataSegments.back();
1157  Segment.Name = Section.getSectionName();
1158  Segment.Offset = DataSize;
1159  Segment.Section = &Section;
1160  addData(Segment.Data, Section);
1161  Segment.Alignment = Section.getAlignment();
1162  Segment.Flags = 0;
1163  DataSize += Segment.Data.size();
1164  Section.setMemoryOffset(Segment.Offset);
1165  }
1166 
1167  // Handle regular defined and undefined symbols.
1168  for (const MCSymbol &S : Asm.symbols()) {
1169  // Ignore unnamed temporary symbols, which aren't ever exported, imported,
1170  // or used in relocations.
1171  if (S.isTemporary() && S.getName().empty())
1172  continue;
1173 
1174  const auto &WS = static_cast<const MCSymbolWasm &>(S);
1175  DEBUG(dbgs() << "MCSymbol: '" << S << "'"
1176  << " isDefined=" << S.isDefined() << " isExternal="
1177  << S.isExternal() << " isTemporary=" << S.isTemporary()
1178  << " isFunction=" << WS.isFunction()
1179  << " isWeak=" << WS.isWeak()
1180  << " isVariable=" << WS.isVariable() << "\n");
1181 
1182  if (WS.isWeak())
1183  SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_WEAK);
1184 
1185  if (WS.isVariable())
1186  continue;
1187 
1188  unsigned Index;
1189 
1190  if (WS.isFunction()) {
1191  if (WS.isDefined(/*SetUsed=*/false)) {
1192  if (WS.getOffset() != 0)
1194  "function sections must contain one function each");
1195 
1196  if (WS.getSize() == 0)
1198  "function symbols must have a size set with .size");
1199 
1200  // A definition. Take the next available index.
1201  Index = NumFuncImports + Functions.size();
1202 
1203  // Prepare the function.
1204  WasmFunction Func;
1205  Func.Type = getFunctionType(WS);
1206  Func.Sym = &WS;
1207  SymbolIndices[&WS] = Index;
1208  Functions.push_back(Func);
1209  } else {
1210  // An import; the index was assigned above.
1211  Index = SymbolIndices.find(&WS)->second;
1212  }
1213 
1214  DEBUG(dbgs() << " -> function index: " << Index << "\n");
1215 
1216  // If needed, prepare the function to be called indirectly.
1217  if (IsAddressTaken.count(&WS) != 0) {
1218  IndirectSymbolIndices[&WS] = TableElems.size();
1219  DEBUG(dbgs() << " -> adding to table: " << TableElems.size() << "\n");
1220  TableElems.push_back(Index);
1221  }
1222  } else {
1223  if (WS.isTemporary() && !WS.getSize())
1224  continue;
1225 
1226  if (!WS.isDefined(/*SetUsed=*/false))
1227  continue;
1228 
1229  if (!WS.getSize())
1230  report_fatal_error("data symbols must have a size set with .size: " +
1231  WS.getName());
1232 
1233  int64_t Size = 0;
1234  if (!WS.getSize()->evaluateAsAbsolute(Size, Layout))
1235  report_fatal_error(".size expression must be evaluatable");
1236 
1237  // For each global, prepare a corresponding wasm global holding its
1238  // address. For externals these will also be named exports.
1239  Index = NumGlobalImports + Globals.size();
1240  auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection());
1241 
1242  WasmGlobal Global;
1243  Global.Type = PtrType;
1244  Global.IsMutable = false;
1245  Global.HasImport = false;
1246  Global.InitialValue = DataSection.getMemoryOffset() + Layout.getSymbolOffset(WS);
1247  Global.ImportIndex = 0;
1248  SymbolIndices[&WS] = Index;
1249  DEBUG(dbgs() << " -> global index: " << Index << "\n");
1250  Globals.push_back(Global);
1251  }
1252 
1253  // If the symbol is visible outside this translation unit, export it.
1254  if (WS.isDefined(/*SetUsed=*/false)) {
1255  WasmExport Export;
1256  Export.FieldName = WS.getName();
1257  Export.Index = Index;
1258  if (WS.isFunction())
1259  Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1260  else
1261  Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1262  DEBUG(dbgs() << " -> export " << Exports.size() << "\n");
1263  Exports.push_back(Export);
1264  if (!WS.isExternal())
1265  SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
1266  }
1267  }
1268 
1269  // Handle weak aliases. We need to process these in a separate pass because
1270  // we need to have processed the target of the alias before the alias itself
1271  // and the symbols are not necessarily ordered in this way.
1272  for (const MCSymbol &S : Asm.symbols()) {
1273  if (!S.isVariable())
1274  continue;
1275 
1276  assert(S.isDefined(/*SetUsed=*/false));
1277 
1278  // Find the target symbol of this weak alias and export that index
1279  const auto &WS = static_cast<const MCSymbolWasm &>(S);
1280  const MCSymbolWasm *ResolvedSym = ResolveSymbol(WS);
1281  DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *ResolvedSym << "'\n");
1282  assert(SymbolIndices.count(ResolvedSym) > 0);
1283  uint32_t Index = SymbolIndices.find(ResolvedSym)->second;
1284  DEBUG(dbgs() << " -> index:" << Index << "\n");
1285 
1286  SymbolIndices[&WS] = Index;
1287  WasmExport Export;
1288  Export.FieldName = WS.getName();
1289  Export.Index = Index;
1290  if (WS.isFunction())
1291  Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
1292  else
1293  Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
1294  DEBUG(dbgs() << " -> export " << Exports.size() << "\n");
1295  Exports.push_back(Export);
1296 
1297  if (!WS.isExternal())
1298  SymbolFlags.emplace_back(WS.getName(), wasm::WASM_SYMBOL_BINDING_LOCAL);
1299  }
1300 
1301  // Add types for indirect function calls.
1302  for (const WasmRelocationEntry &Fixup : CodeRelocations) {
1303  if (Fixup.Type != wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB)
1304  continue;
1305 
1306  registerFunctionType(*Fixup.Symbol);
1307  }
1308 
1309  // Write out the Wasm header.
1310  writeHeader(Asm);
1311 
1312  writeTypeSection(FunctionTypes);
1313  writeImportSection(Imports);
1314  writeFunctionSection(Functions);
1315  writeTableSection(TableElems.size());
1316  writeMemorySection(DataSize);
1317  writeGlobalSection();
1318  writeExportSection(Exports);
1319  // TODO: Start Section
1320  writeElemSection(TableElems);
1321  writeCodeSection(Asm, Layout, Functions);
1322  writeDataSection(DataSegments);
1323  writeNameSection(Functions, Imports, NumFuncImports);
1324  writeCodeRelocSection();
1325  writeDataRelocSection();
1326  writeLinkingMetaDataSection(DataSegments, DataSize, SymbolFlags,
1327  HasStackPointer, StackPointerGlobal);
1328 
1329  // TODO: Translate the .comment section to the output.
1330  // TODO: Translate debug sections to the output.
1331 }
1332 
1333 std::unique_ptr<MCObjectWriter>
1334 llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW,
1335  raw_pwrite_stream &OS) {
1336  // FIXME: Can't use make_unique<WasmObjectWriter>(...) as WasmObjectWriter's
1337  // destructor is private. Is that necessary?
1338  return std::unique_ptr<MCObjectWriter>(
1339  new WasmObjectWriter(std::move(MOTW), OS));
1340 }
bool isFunction() const
Definition: MCSymbolWasm.h:42
uint64_t CallInst * C
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
static const MCSymbolWasm * ResolveSymbol(const MCSymbolWasm &Symbol)
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:244
constexpr char Align[]
Key for Kernel::Arg::Metadata::mAlign.
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:115
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
bool isVariable() const
isVariable - Check if this is a variable symbol.
Definition: MCSymbol.h:295
#define LLVM_DUMP_METHOD
Mark debug helper function definitions like dump() that should not be stripped from debug builds...
Definition: Compiler.h:449
This represents an "assembler immediate".
Definition: MCValue.h:40
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
static void WriteI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset)
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE size_t size() const
size - Get the string size.
Definition: StringRef.h:138
virtual const MCFixupKindInfo & getFixupKindInfo(MCFixupKind Kind) const
Get information on a fixup kind.
MCSectionWasm * getWasmSection(const Twine &Section, SectionKind K)
Definition: MCContext.h:444
StringRef getSectionName() const
Definition: MCSectionWasm.h:63
FragmentType getKind() const
Definition: MCFragment.h:102
void write32le(void *P, uint32_t V)
Definition: Endian.h:404
F(f)
uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew=0)
Returns the next integer (mod 2**64) that is greater than or equal to Value and is a multiple of Alig...
Definition: MathExtras.h:677
Defines the object file and target independent interfaces used by the assembler backend to write nati...
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:66
unsigned getAlignment() const
Definition: MCSection.h:117
Export information to summary.
Is this fixup kind PCrelative? This is used by the assembler backend to evaluate fixup values in a ta...
MCContext & getContext() const
Definition: MCAssembler.h:259
static void WritePatchableSLEB(raw_pwrite_stream &Stream, int32_t X, uint64_t Offset)
int64_t getConstant() const
Definition: MCValue.h:47
const MCSymbolRefExpr * getSymB() const
Definition: MCValue.h:49
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:29
int64_t decodeSLEB128(const uint8_t *p, unsigned *n=nullptr, const uint8_t *end=nullptr, const char **error=nullptr)
Utility function to decode a SLEB128 value.
Definition: LEB128.h:157
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:36
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:165
static unsigned getRelocType(const MCValue &Target, const MCFixupKind FixupKind, const bool IsPCRel)
Translates generic PPC fixup kind to Mach-O/PPC relocation type enum.
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:736
const uint32_t WasmVersion
Definition: Wasm.h:26
void writeSectionData(const MCSection *Section, const MCAsmLayout &Layout) const
Emit the section contents using the given object writer.
Context object for machine code objects.
Definition: MCContext.h:59
static bool isEqual(const Function &Caller, const Function &Callee)
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
void encodeULEB128(uint64_t Value, raw_ostream &OS, unsigned PadTo=0)
Utility function to encode a ULEB128 value to an output stream.
Definition: LEB128.h:77
void dump(const SparseBitVector< ElementSize > &LHS, raw_ostream &out)
Import information from summary.
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:149
This represents a section on wasm.
Definition: MCSectionWasm.h:28
static bool is64Bit(const char *name)
virtual void reset()
lifetime management
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
bool getSymbolOffset(const MCSymbol &S, uint64_t &Val) const
Get the offset of the given symbol, as computed in the current layout.
Definition: MCFragment.cpp:129
void pwrite(const char *Ptr, size_t Size, uint64_t Offset)
Definition: raw_ostream.h:343
std::unique_ptr< MCObjectWriter > createWasmObjectWriter(std::unique_ptr< MCWasmObjectTargetWriter > MOTW, raw_pwrite_stream &OS)
Construct a new Wasm writer instance.
const MCSymbolRefExpr * getSymA() const
Definition: MCValue.h:48
void encodeSLEB128(int64_t Value, raw_ostream &OS, unsigned PadTo=0)
Utility function to encode a SLEB128 value to an output stream.
Definition: LEB128.h:23
void reportError(SMLoc L, const Twine &Msg)
Definition: MCContext.cpp:570
const SmallVector< wasm::ValType, 1 > & getReturns() const
Definition: MCSymbolWasm.h:50
static void addData(SmallVectorImpl< char > &DataBytes, MCSectionWasm &DataSection)
static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val)
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
uint32_t getOffset() const
Definition: MCFixup.h:95
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
uint64_t getFragmentOffset(const MCFragment *F) const
Get the offset of the given fragment inside its containing section.
Definition: MCFragment.cpp:77
PowerPC TLS Dynamic Call Fixup
const char WasmMagic[]
Definition: Wasm.h:24
SMLoc getLoc() const
Definition: MCFixup.h:112
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
MCAsmBackend & getBackend() const
Definition: MCAssembler.h:261
const MCSymbol & getSymbol() const
Definition: MCExpr.h:318
const DataFlowGraph & G
Definition: RDFGraph.cpp:211
static SectionKind getMetadata()
Definition: SectionKind.h:179
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
Target - Wrapper for Target specific information.
MCSection * getParent() const
Definition: MCFragment.h:104
bool hasInstructions() const
Does this fragment have instructions emitted into it? By default this is false, but specific fragment...
Definition: MCFragment.h:115
iterator insert(iterator I, T &&Elt)
Definition: SmallVector.h:482
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:120
pointer data()
Return a pointer to the vector&#39;s buffer, even if empty().
Definition: SmallVector.h:143
void emplace_back(ArgTypes &&... Args)
Definition: SmallVector.h:656
bool isDefined(bool SetUsed=true) const
isDefined - Check if this symbol is defined (i.e., it has an address).
Definition: MCSymbol.h:249
symbol_range symbols()
Definition: MCAssembler.h:322
raw_ostream & operator<<(raw_ostream &OS, const APInt &I)
Definition: APInt.h:2018
An abstract base class for streams implementations that also support a pwrite operation.
Definition: raw_ostream.h:337
const SmallVector< wasm::ValType, 4 > & getParams() const
Definition: MCSymbolWasm.h:60
const unsigned Kind
static void WritePatchableLEB(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset)
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const MCExpr * getVariableValue(bool SetUsed=true) const
getVariableValue - Get the value for variable symbols.
Definition: MCSymbol.h:300
bool operator<(int64_t V1, const APSInt &V2)
Definition: APSInt.h:326
LLVM Value Representation.
Definition: Value.h:73
Generic interface to target specific assembler backends.
Definition: MCAsmBackend.h:40
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:44
#define DEBUG(X)
Definition: Debug.h:118
const uint32_t WasmPageSize
Definition: Wasm.h:28
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
bool operator==(uint64_t V1, const APInt &V2)
Definition: APInt.h:1946
MCSection::FragmentListType & getFragmentList()
Definition: MCSection.h:143
MCFixupKind getKind() const
Definition: MCFixup.h:93
bool empty() const
empty - Check if the array is empty.
Definition: ArrayRef.h:144
iterator begin()
Definition: MCSection.h:156
void resize(size_type N)
Definition: SmallVector.h:355