llvm/lib/ObjectYAML/WasmEmitter.cpp

   1 //===- yaml2wasm - Convert YAML to a Wasm object file --------------------===//
   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 /// \file
  10 /// The Wasm component of yaml2obj.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13 //
  14
  15 #include "llvm/Object/Wasm.h"
  16 #include "llvm/ObjectYAML/ObjectYAML.h"
  17 #include "llvm/ObjectYAML/yaml2obj.h"
  18 #include "llvm/Support/Endian.h"
  19 #include "llvm/Support/LEB128.h"
  20
  21 using namespace llvm;
  22
  23 namespace {
  24 /// This parses a yaml stream that represents a Wasm object file.
  25 /// See docs/yaml2obj for the yaml scheema.
  26 class WasmWriter {
  27 public:
  28   WasmWriter(WasmYAML::Object &Obj, yaml::ErrorHandler EH)
  29       : Obj(Obj), ErrHandler(EH) {}
  30   bool writeWasm(raw_ostream &OS);
  31
  32 private:
  33   void writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
  34                          uint32_t SectionIndex);
  35
  36   void writeInitExpr(raw_ostream &OS, const WasmYAML::InitExpr &InitExpr);
  37
  38   void writeSectionContent(raw_ostream &OS, WasmYAML::CustomSection &Section);
  39   void writeSectionContent(raw_ostream &OS, WasmYAML::TypeSection &Section);
  40   void writeSectionContent(raw_ostream &OS, WasmYAML::ImportSection &Section);
  41   void writeSectionContent(raw_ostream &OS, WasmYAML::FunctionSection &Section);
  42   void writeSectionContent(raw_ostream &OS, WasmYAML::TableSection &Section);
  43   void writeSectionContent(raw_ostream &OS, WasmYAML::MemorySection &Section);
  44   void writeSectionContent(raw_ostream &OS, WasmYAML::TagSection &Section);
  45   void writeSectionContent(raw_ostream &OS, WasmYAML::GlobalSection &Section);
  46   void writeSectionContent(raw_ostream &OS, WasmYAML::ExportSection &Section);
  47   void writeSectionContent(raw_ostream &OS, WasmYAML::StartSection &Section);
  48   void writeSectionContent(raw_ostream &OS, WasmYAML::ElemSection &Section);
  49   void writeSectionContent(raw_ostream &OS, WasmYAML::CodeSection &Section);
  50   void writeSectionContent(raw_ostream &OS, WasmYAML::DataSection &Section);
  51   void writeSectionContent(raw_ostream &OS, WasmYAML::DataCountSection &Section);
  52
  53   // Custom section types
  54   void writeSectionContent(raw_ostream &OS, WasmYAML::DylinkSection &Section);
  55   void writeSectionContent(raw_ostream &OS, WasmYAML::NameSection &Section);
  56   void writeSectionContent(raw_ostream &OS, WasmYAML::LinkingSection &Section);
  57   void writeSectionContent(raw_ostream &OS, WasmYAML::ProducersSection &Section);
  58   void writeSectionContent(raw_ostream &OS,
  59                           WasmYAML::TargetFeaturesSection &Section);
  60   WasmYAML::Object &Obj;
  61   uint32_t NumImportedFunctions = 0;
  62   uint32_t NumImportedGlobals = 0;
  63   uint32_t NumImportedTables = 0;
  64   uint32_t NumImportedTags = 0;
  65
  66   bool HasError = false;
  67   yaml::ErrorHandler ErrHandler;
  68   void reportError(const Twine &Msg);
  69 };
  70
  71 class SubSectionWriter {
  72   raw_ostream &OS;
  73   std::string OutString;
  74   raw_string_ostream StringStream;
  75
  76 public:
  77   SubSectionWriter(raw_ostream &OS) : OS(OS), StringStream(OutString) {}
  78
  79   void done() {
  80     StringStream.flush();
  81     encodeULEB128(OutString.size(), OS);
  82     OS << OutString;
  83     OutString.clear();
  84   }
  85
  86   raw_ostream &getStream() { return StringStream; }
  87 };
  88
  89 } // end anonymous namespace
  90
  91 static int writeUint64(raw_ostream &OS, uint64_t Value) {
  92   char Data[sizeof(Value)];
  93   support::endian::write64le(Data, Value);
  94   OS.write(Data, sizeof(Data));
  95   return 0;
  96 }
  97
  98 static int writeUint32(raw_ostream &OS, uint32_t Value) {
  99   char Data[sizeof(Value)];
 100   support::endian::write32le(Data, Value);
 101   OS.write(Data, sizeof(Data));
 102   return 0;
 103 }
 104
 105 static int writeUint8(raw_ostream &OS, uint8_t Value) {
 106   char Data[sizeof(Value)];
 107   memcpy(Data, &Value, sizeof(Data));
 108   OS.write(Data, sizeof(Data));
 109   return 0;
 110 }
 111
 112 static int writeStringRef(const StringRef &Str, raw_ostream &OS) {
 113   encodeULEB128(Str.size(), OS);
 114   OS << Str;
 115   return 0;
 116 }
 117
 118 static int writeLimits(const WasmYAML::Limits &Lim, raw_ostream &OS) {
 119   writeUint8(OS, Lim.Flags);
 120   encodeULEB128(Lim.Minimum, OS);
 121   if (Lim.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX)
 122     encodeULEB128(Lim.Maximum, OS);
 123   return 0;
 124 }
 125
 126 void WasmWriter::reportError(const Twine &Msg) {
 127   ErrHandler(Msg);
 128   HasError = true;
 129 }
 130
 131 void WasmWriter::writeInitExpr(raw_ostream &OS,
 132                                const WasmYAML::InitExpr &InitExpr) {
 133   if (InitExpr.Extended) {
 134     InitExpr.Body.writeAsBinary(OS);
 135   } else {
 136     writeUint8(OS, InitExpr.Inst.Opcode);
 137     switch (InitExpr.Inst.Opcode) {
 138     case wasm::WASM_OPCODE_I32_CONST:
 139       encodeSLEB128(InitExpr.Inst.Value.Int32, OS);
 140       break;
 141     case wasm::WASM_OPCODE_I64_CONST:
 142       encodeSLEB128(InitExpr.Inst.Value.Int64, OS);
 143       break;
 144     case wasm::WASM_OPCODE_F32_CONST:
 145       writeUint32(OS, InitExpr.Inst.Value.Float32);
 146       break;
 147     case wasm::WASM_OPCODE_F64_CONST:
 148       writeUint64(OS, InitExpr.Inst.Value.Float64);
 149       break;
 150     case wasm::WASM_OPCODE_GLOBAL_GET:
 151       encodeULEB128(InitExpr.Inst.Value.Global, OS);
 152       break;
 153     default:
 154       reportError("unknown opcode in init_expr: " +
 155                   Twine(InitExpr.Inst.Opcode));
 156       return;
 157     }
 158     writeUint8(OS, wasm::WASM_OPCODE_END);
 159   }
 160 }
 161
 162 void WasmWriter::writeSectionContent(raw_ostream &OS,
 163                                      WasmYAML::DylinkSection &Section) {
 164   writeStringRef(Section.Name, OS);
 165
 166   writeUint8(OS, wasm::WASM_DYLINK_MEM_INFO);
 167   SubSectionWriter SubSection(OS);
 168   raw_ostream &SubOS = SubSection.getStream();
 169   encodeULEB128(Section.MemorySize, SubOS);
 170   encodeULEB128(Section.MemoryAlignment, SubOS);
 171   encodeULEB128(Section.TableSize, SubOS);
 172   encodeULEB128(Section.TableAlignment, SubOS);
 173   SubSection.done();
 174
 175   if (Section.Needed.size()) {
 176     writeUint8(OS, wasm::WASM_DYLINK_NEEDED);
 177     raw_ostream &SubOS = SubSection.getStream();
 178     encodeULEB128(Section.Needed.size(), SubOS);
 179     for (StringRef Needed : Section.Needed)
 180       writeStringRef(Needed, SubOS);
 181     SubSection.done();
 182   }
 183 }
 184
 185 void WasmWriter::writeSectionContent(raw_ostream &OS,
 186                                      WasmYAML::LinkingSection &Section) {
 187   writeStringRef(Section.Name, OS);
 188   encodeULEB128(Section.Version, OS);
 189
 190   SubSectionWriter SubSection(OS);
 191
 192   // SYMBOL_TABLE subsection
 193   if (Section.SymbolTable.size()) {
 194     writeUint8(OS, wasm::WASM_SYMBOL_TABLE);
 195     encodeULEB128(Section.SymbolTable.size(), SubSection.getStream());
 196     for (auto Sym : llvm::enumerate(Section.SymbolTable)) {
 197       const WasmYAML::SymbolInfo &Info = Sym.value();
 198       assert(Info.Index == Sym.index());
 199       writeUint8(SubSection.getStream(), Info.Kind);
 200       encodeULEB128(Info.Flags, SubSection.getStream());
 201       switch (Info.Kind) {
 202       case wasm::WASM_SYMBOL_TYPE_FUNCTION:
 203       case wasm::WASM_SYMBOL_TYPE_GLOBAL:
 204       case wasm::WASM_SYMBOL_TYPE_TABLE:
 205       case wasm::WASM_SYMBOL_TYPE_TAG:
 206         encodeULEB128(Info.ElementIndex, SubSection.getStream());
 207         if ((Info.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0 ||
 208             (Info.Flags & wasm::WASM_SYMBOL_EXPLICIT_NAME) != 0)
 209           writeStringRef(Info.Name, SubSection.getStream());
 210         break;
 211       case wasm::WASM_SYMBOL_TYPE_DATA:
 212         writeStringRef(Info.Name, SubSection.getStream());
 213         if ((Info.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0) {
 214           encodeULEB128(Info.DataRef.Segment, SubSection.getStream());
 215           encodeULEB128(Info.DataRef.Offset, SubSection.getStream());
 216           encodeULEB128(Info.DataRef.Size, SubSection.getStream());
 217         }
 218         break;
 219       case wasm::WASM_SYMBOL_TYPE_SECTION:
 220         encodeULEB128(Info.ElementIndex, SubSection.getStream());
 221         break;
 222       default:
 223         llvm_unreachable("unexpected kind");
 224       }
 225     }
 226
 227     SubSection.done();
 228   }
 229
 230   // SEGMENT_NAMES subsection
 231   if (Section.SegmentInfos.size()) {
 232     writeUint8(OS, wasm::WASM_SEGMENT_INFO);
 233     encodeULEB128(Section.SegmentInfos.size(), SubSection.getStream());
 234     for (const WasmYAML::SegmentInfo &SegmentInfo : Section.SegmentInfos) {
 235       writeStringRef(SegmentInfo.Name, SubSection.getStream());
 236       encodeULEB128(SegmentInfo.Alignment, SubSection.getStream());
 237       encodeULEB128(SegmentInfo.Flags, SubSection.getStream());
 238     }
 239     SubSection.done();
 240   }
 241
 242   // INIT_FUNCS subsection
 243   if (Section.InitFunctions.size()) {
 244     writeUint8(OS, wasm::WASM_INIT_FUNCS);
 245     encodeULEB128(Section.InitFunctions.size(), SubSection.getStream());
 246     for (const WasmYAML::InitFunction &Func : Section.InitFunctions) {
 247       encodeULEB128(Func.Priority, SubSection.getStream());
 248       encodeULEB128(Func.Symbol, SubSection.getStream());
 249     }
 250     SubSection.done();
 251   }
 252
 253   // COMDAT_INFO subsection
 254   if (Section.Comdats.size()) {
 255     writeUint8(OS, wasm::WASM_COMDAT_INFO);
 256     encodeULEB128(Section.Comdats.size(), SubSection.getStream());
 257     for (const auto &C : Section.Comdats) {
 258       writeStringRef(C.Name, SubSection.getStream());
 259       encodeULEB128(0, SubSection.getStream()); // flags for future use
 260       encodeULEB128(C.Entries.size(), SubSection.getStream());
 261       for (const WasmYAML::ComdatEntry &Entry : C.Entries) {
 262         writeUint8(SubSection.getStream(), Entry.Kind);
 263         encodeULEB128(Entry.Index, SubSection.getStream());
 264       }
 265     }
 266     SubSection.done();
 267   }
 268 }
 269
 270 void WasmWriter::writeSectionContent(raw_ostream &OS,
 271                                      WasmYAML::NameSection &Section) {
 272   writeStringRef(Section.Name, OS);
 273   if (Section.FunctionNames.size()) {
 274     writeUint8(OS, wasm::WASM_NAMES_FUNCTION);
 275
 276     SubSectionWriter SubSection(OS);
 277
 278     encodeULEB128(Section.FunctionNames.size(), SubSection.getStream());
 279     for (const WasmYAML::NameEntry &NameEntry : Section.FunctionNames) {
 280       encodeULEB128(NameEntry.Index, SubSection.getStream());
 281       writeStringRef(NameEntry.Name, SubSection.getStream());
 282     }
 283
 284     SubSection.done();
 285   }
 286   if (Section.GlobalNames.size()) {
 287     writeUint8(OS, wasm::WASM_NAMES_GLOBAL);
 288
 289     SubSectionWriter SubSection(OS);
 290
 291     encodeULEB128(Section.GlobalNames.size(), SubSection.getStream());
 292     for (const WasmYAML::NameEntry &NameEntry : Section.GlobalNames) {
 293       encodeULEB128(NameEntry.Index, SubSection.getStream());
 294       writeStringRef(NameEntry.Name, SubSection.getStream());
 295     }
 296
 297     SubSection.done();
 298   }
 299   if (Section.DataSegmentNames.size()) {
 300     writeUint8(OS, wasm::WASM_NAMES_DATA_SEGMENT);
 301
 302     SubSectionWriter SubSection(OS);
 303
 304     encodeULEB128(Section.DataSegmentNames.size(), SubSection.getStream());
 305     for (const WasmYAML::NameEntry &NameEntry : Section.DataSegmentNames) {
 306       encodeULEB128(NameEntry.Index, SubSection.getStream());
 307       writeStringRef(NameEntry.Name, SubSection.getStream());
 308     }
 309
 310     SubSection.done();
 311   }
 312 }
 313
 314 void WasmWriter::writeSectionContent(raw_ostream &OS,
 315                                      WasmYAML::ProducersSection &Section) {
 316   writeStringRef(Section.Name, OS);
 317   int Fields = int(!Section.Languages.empty()) + int(!Section.Tools.empty()) +
 318                int(!Section.SDKs.empty());
 319   if (Fields == 0)
 320     return;
 321   encodeULEB128(Fields, OS);
 322   for (auto &Field : {std::make_pair(StringRef("language"), &Section.Languages),
 323                       std::make_pair(StringRef("processed-by"), &Section.Tools),
 324                       std::make_pair(StringRef("sdk"), &Section.SDKs)}) {
 325     if (Field.second->empty())
 326       continue;
 327     writeStringRef(Field.first, OS);
 328     encodeULEB128(Field.second->size(), OS);
 329     for (auto &Entry : *Field.second) {
 330       writeStringRef(Entry.Name, OS);
 331       writeStringRef(Entry.Version, OS);
 332     }
 333   }
 334 }
 335
 336 void WasmWriter::writeSectionContent(raw_ostream &OS,
 337                                      WasmYAML::TargetFeaturesSection &Section) {
 338   writeStringRef(Section.Name, OS);
 339   encodeULEB128(Section.Features.size(), OS);
 340   for (auto &E : Section.Features) {
 341     writeUint8(OS, E.Prefix);
 342     writeStringRef(E.Name, OS);
 343   }
 344 }
 345
 346 void WasmWriter::writeSectionContent(raw_ostream &OS,
 347                                      WasmYAML::CustomSection &Section) {
 348   if (auto S = dyn_cast<WasmYAML::DylinkSection>(&Section)) {
 349     writeSectionContent(OS, *S);
 350   } else if (auto S = dyn_cast<WasmYAML::NameSection>(&Section)) {
 351     writeSectionContent(OS, *S);
 352   } else if (auto S = dyn_cast<WasmYAML::LinkingSection>(&Section)) {
 353     writeSectionContent(OS, *S);
 354   } else if (auto S = dyn_cast<WasmYAML::ProducersSection>(&Section)) {
 355     writeSectionContent(OS, *S);
 356   } else if (auto S = dyn_cast<WasmYAML::TargetFeaturesSection>(&Section)) {
 357     writeSectionContent(OS, *S);
 358   } else {
 359     writeStringRef(Section.Name, OS);
 360     Section.Payload.writeAsBinary(OS);
 361   }
 362 }
 363
 364 void WasmWriter::writeSectionContent(raw_ostream &OS,
 365                                     WasmYAML::TypeSection &Section) {
 366   encodeULEB128(Section.Signatures.size(), OS);
 367   uint32_t ExpectedIndex = 0;
 368   for (const WasmYAML::Signature &Sig : Section.Signatures) {
 369     if (Sig.Index != ExpectedIndex) {
 370       reportError("unexpected type index: " + Twine(Sig.Index));
 371       return;
 372     }
 373     ++ExpectedIndex;
 374     writeUint8(OS, Sig.Form);
 375     encodeULEB128(Sig.ParamTypes.size(), OS);
 376     for (auto ParamType : Sig.ParamTypes)
 377       writeUint8(OS, ParamType);
 378     encodeULEB128(Sig.ReturnTypes.size(), OS);
 379     for (auto ReturnType : Sig.ReturnTypes)
 380       writeUint8(OS, ReturnType);
 381   }
 382 }
 383
 384 void WasmWriter::writeSectionContent(raw_ostream &OS,
 385                                     WasmYAML::ImportSection &Section) {
 386   encodeULEB128(Section.Imports.size(), OS);
 387   for (const WasmYAML::Import &Import : Section.Imports) {
 388     writeStringRef(Import.Module, OS);
 389     writeStringRef(Import.Field, OS);
 390     writeUint8(OS, Import.Kind);
 391     switch (Import.Kind) {
 392     case wasm::WASM_EXTERNAL_FUNCTION:
 393       encodeULEB128(Import.SigIndex, OS);
 394       NumImportedFunctions++;
 395       break;
 396     case wasm::WASM_EXTERNAL_GLOBAL:
 397       writeUint8(OS, Import.GlobalImport.Type);
 398       writeUint8(OS, Import.GlobalImport.Mutable);
 399       NumImportedGlobals++;
 400       break;
 401     case wasm::WASM_EXTERNAL_TAG:
 402       writeUint8(OS, 0); // Reserved 'attribute' field
 403       encodeULEB128(Import.SigIndex, OS);
 404       NumImportedTags++;
 405       break;
 406     case wasm::WASM_EXTERNAL_MEMORY:
 407       writeLimits(Import.Memory, OS);
 408       break;
 409     case wasm::WASM_EXTERNAL_TABLE:
 410       writeUint8(OS, Import.TableImport.ElemType);
 411       writeLimits(Import.TableImport.TableLimits, OS);
 412       NumImportedTables++;
 413       break;
 414     default:
 415       reportError("unknown import type: " +Twine(Import.Kind));
 416       return;
 417     }
 418   }
 419 }
 420
 421 void WasmWriter::writeSectionContent(raw_ostream &OS,
 422                                      WasmYAML::FunctionSection &Section) {
 423   encodeULEB128(Section.FunctionTypes.size(), OS);
 424   for (uint32_t FuncType : Section.FunctionTypes)
 425     encodeULEB128(FuncType, OS);
 426 }
 427
 428 void WasmWriter::writeSectionContent(raw_ostream &OS,
 429                                     WasmYAML::ExportSection &Section) {
 430   encodeULEB128(Section.Exports.size(), OS);
 431   for (const WasmYAML::Export &Export : Section.Exports) {
 432     writeStringRef(Export.Name, OS);
 433     writeUint8(OS, Export.Kind);
 434     encodeULEB128(Export.Index, OS);
 435   }
 436 }
 437
 438 void WasmWriter::writeSectionContent(raw_ostream &OS,
 439                                      WasmYAML::StartSection &Section) {
 440   encodeULEB128(Section.StartFunction, OS);
 441 }
 442
 443 void WasmWriter::writeSectionContent(raw_ostream &OS,
 444                                      WasmYAML::TableSection &Section) {
 445   encodeULEB128(Section.Tables.size(), OS);
 446   uint32_t ExpectedIndex = NumImportedTables;
 447   for (auto &Table : Section.Tables) {
 448     if (Table.Index != ExpectedIndex) {
 449       reportError("unexpected table index: " + Twine(Table.Index));
 450       return;
 451     }
 452     ++ExpectedIndex;
 453     writeUint8(OS, Table.ElemType);
 454     writeLimits(Table.TableLimits, OS);
 455   }
 456 }
 457
 458 void WasmWriter::writeSectionContent(raw_ostream &OS,
 459                                      WasmYAML::MemorySection &Section) {
 460   encodeULEB128(Section.Memories.size(), OS);
 461   for (const WasmYAML::Limits &Mem : Section.Memories)
 462     writeLimits(Mem, OS);
 463 }
 464
 465 void WasmWriter::writeSectionContent(raw_ostream &OS,
 466                                      WasmYAML::TagSection &Section) {
 467   encodeULEB128(Section.TagTypes.size(), OS);
 468   for (uint32_t TagType : Section.TagTypes) {
 469     writeUint8(OS, 0); // Reserved 'attribute' field
 470     encodeULEB128(TagType, OS);
 471   }
 472 }
 473
 474 void WasmWriter::writeSectionContent(raw_ostream &OS,
 475                                      WasmYAML::GlobalSection &Section) {
 476   encodeULEB128(Section.Globals.size(), OS);
 477   uint32_t ExpectedIndex = NumImportedGlobals;
 478   for (auto &Global : Section.Globals) {
 479     if (Global.Index != ExpectedIndex) {
 480       reportError("unexpected global index: " + Twine(Global.Index));
 481       return;
 482     }
 483     ++ExpectedIndex;
 484     writeUint8(OS, Global.Type);
 485     writeUint8(OS, Global.Mutable);
 486     writeInitExpr(OS, Global.Init);
 487   }
 488 }
 489
 490 void WasmWriter::writeSectionContent(raw_ostream &OS,
 491                                      WasmYAML::ElemSection &Section) {
 492   encodeULEB128(Section.Segments.size(), OS);
 493   for (auto &Segment : Section.Segments) {
 494     encodeULEB128(Segment.Flags, OS);
 495     if (Segment.Flags & wasm::WASM_ELEM_SEGMENT_HAS_TABLE_NUMBER)
 496       encodeULEB128(Segment.TableNumber, OS);
 497
 498     writeInitExpr(OS, Segment.Offset);
 499
 500     if (Segment.Flags & wasm::WASM_ELEM_SEGMENT_MASK_HAS_ELEM_KIND) {
 501       // We only support active function table initializers, for which the elem
 502       // kind is specified to be written as 0x00 and interpreted to mean
 503       // "funcref".
 504       if (Segment.ElemKind != uint32_t(wasm::ValType::FUNCREF)) {
 505         reportError("unexpected elemkind: " + Twine(Segment.ElemKind));
 506         return;
 507       }
 508       const uint8_t ElemKind = 0;
 509       writeUint8(OS, ElemKind);
 510     }
 511
 512     encodeULEB128(Segment.Functions.size(), OS);
 513     for (auto &Function : Segment.Functions)
 514       encodeULEB128(Function, OS);
 515   }
 516 }
 517
 518 void WasmWriter::writeSectionContent(raw_ostream &OS,
 519                                     WasmYAML::CodeSection &Section) {
 520   encodeULEB128(Section.Functions.size(), OS);
 521   uint32_t ExpectedIndex = NumImportedFunctions;
 522   for (auto &Func : Section.Functions) {
 523     std::string OutString;
 524     raw_string_ostream StringStream(OutString);
 525     if (Func.Index != ExpectedIndex) {
 526       reportError("unexpected function index: " + Twine(Func.Index));
 527       return;
 528     }
 529     ++ExpectedIndex;
 530
 531     encodeULEB128(Func.Locals.size(), StringStream);
 532     for (auto &LocalDecl : Func.Locals) {
 533       encodeULEB128(LocalDecl.Count, StringStream);
 534       writeUint8(StringStream, LocalDecl.Type);
 535     }
 536
 537     Func.Body.writeAsBinary(StringStream);
 538
 539     // Write the section size followed by the content
 540     StringStream.flush();
 541     encodeULEB128(OutString.size(), OS);
 542     OS << OutString;
 543   }
 544 }
 545
 546 void WasmWriter::writeSectionContent(raw_ostream &OS,
 547                                      WasmYAML::DataSection &Section) {
 548   encodeULEB128(Section.Segments.size(), OS);
 549   for (auto &Segment : Section.Segments) {
 550     encodeULEB128(Segment.InitFlags, OS);
 551     if (Segment.InitFlags & wasm::WASM_DATA_SEGMENT_HAS_MEMINDEX)
 552       encodeULEB128(Segment.MemoryIndex, OS);
 553     if ((Segment.InitFlags & wasm::WASM_DATA_SEGMENT_IS_PASSIVE) == 0)
 554       writeInitExpr(OS, Segment.Offset);
 555     encodeULEB128(Segment.Content.binary_size(), OS);
 556     Segment.Content.writeAsBinary(OS);
 557   }
 558 }
 559
 560 void WasmWriter::writeSectionContent(raw_ostream &OS,
 561                                      WasmYAML::DataCountSection &Section) {
 562   encodeULEB128(Section.Count, OS);
 563 }
 564
 565 void WasmWriter::writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec,
 566                                   uint32_t SectionIndex) {
 567   switch (Sec.Type) {
 568   case wasm::WASM_SEC_CODE:
 569     writeStringRef("reloc.CODE", OS);
 570     break;
 571   case wasm::WASM_SEC_DATA:
 572     writeStringRef("reloc.DATA", OS);
 573     break;
 574   case wasm::WASM_SEC_CUSTOM: {
 575     auto *CustomSection = cast<WasmYAML::CustomSection>(&Sec);
 576     writeStringRef(("reloc." + CustomSection->Name).str(), OS);
 577     break;
 578   }
 579   default:
 580     llvm_unreachable("not yet implemented");
 581   }
 582
 583   encodeULEB128(SectionIndex, OS);
 584   encodeULEB128(Sec.Relocations.size(), OS);
 585
 586   for (auto Reloc : Sec.Relocations) {
 587     writeUint8(OS, Reloc.Type);
 588     encodeULEB128(Reloc.Offset, OS);
 589     encodeULEB128(Reloc.Index, OS);
 590     if (wasm::relocTypeHasAddend(Reloc.Type))
 591       encodeSLEB128(Reloc.Addend, OS);
 592   }
 593 }
 594
 595 bool WasmWriter::writeWasm(raw_ostream &OS) {
 596   // Write headers
 597   OS.write(wasm::WasmMagic, sizeof(wasm::WasmMagic));
 598   writeUint32(OS, Obj.Header.Version);
 599
 600   // Write each section
 601   llvm::object::WasmSectionOrderChecker Checker;
 602   for (const std::unique_ptr<WasmYAML::Section> &Sec : Obj.Sections) {
 603     StringRef SecName = "";
 604     if (auto S = dyn_cast<WasmYAML::CustomSection>(Sec.get()))
 605       SecName = S->Name;
 606     if (!Checker.isValidSectionOrder(Sec->Type, SecName)) {
 607       reportError("out of order section type: " + Twine(Sec->Type));
 608       return false;
 609     }
 610     encodeULEB128(Sec->Type, OS);
 611     std::string OutString;
 612     raw_string_ostream StringStream(OutString);
 613     if (auto S = dyn_cast<WasmYAML::CustomSection>(Sec.get()))
 614       writeSectionContent(StringStream, *S);
 615     else if (auto S = dyn_cast<WasmYAML::TypeSection>(Sec.get()))
 616       writeSectionContent(StringStream, *S);
 617     else if (auto S = dyn_cast<WasmYAML::ImportSection>(Sec.get()))
 618       writeSectionContent(StringStream, *S);
 619     else if (auto S = dyn_cast<WasmYAML::FunctionSection>(Sec.get()))
 620       writeSectionContent(StringStream, *S);
 621     else if (auto S = dyn_cast<WasmYAML::TableSection>(Sec.get()))
 622       writeSectionContent(StringStream, *S);
 623     else if (auto S = dyn_cast<WasmYAML::MemorySection>(Sec.get()))
 624       writeSectionContent(StringStream, *S);
 625     else if (auto S = dyn_cast<WasmYAML::TagSection>(Sec.get()))
 626       writeSectionContent(StringStream, *S);
 627     else if (auto S = dyn_cast<WasmYAML::GlobalSection>(Sec.get()))
 628       writeSectionContent(StringStream, *S);
 629     else if (auto S = dyn_cast<WasmYAML::ExportSection>(Sec.get()))
 630       writeSectionContent(StringStream, *S);
 631     else if (auto S = dyn_cast<WasmYAML::StartSection>(Sec.get()))
 632       writeSectionContent(StringStream, *S);
 633     else if (auto S = dyn_cast<WasmYAML::ElemSection>(Sec.get()))
 634       writeSectionContent(StringStream, *S);
 635     else if (auto S = dyn_cast<WasmYAML::CodeSection>(Sec.get()))
 636       writeSectionContent(StringStream, *S);
 637     else if (auto S = dyn_cast<WasmYAML::DataSection>(Sec.get()))
 638       writeSectionContent(StringStream, *S);
 639     else if (auto S = dyn_cast<WasmYAML::DataCountSection>(Sec.get()))
 640       writeSectionContent(StringStream, *S);
 641     else
 642       reportError("unknown section type: " + Twine(Sec->Type));
 643
 644     if (HasError)
 645       return false;
 646
 647     StringStream.flush();
 648
 649     unsigned HeaderSecSizeEncodingLen =
 650         Sec->HeaderSecSizeEncodingLen ? *Sec->HeaderSecSizeEncodingLen : 5;
 651     unsigned RequiredLen = getULEB128Size(OutString.size());
 652     // Wasm spec does not allow LEBs larger than 5 bytes
 653     assert(RequiredLen <= 5);
 654     if (HeaderSecSizeEncodingLen < RequiredLen) {
 655       reportError("section header length can't be encoded in a LEB of size " +
 656                   Twine(HeaderSecSizeEncodingLen));
 657       return false;
 658     }
 659     // Write the section size followed by the content
 660     encodeULEB128(OutString.size(), OS, HeaderSecSizeEncodingLen);
 661     OS << OutString;
 662   }
 663
 664   // write reloc sections for any section that have relocations
 665   uint32_t SectionIndex = 0;
 666   for (const std::unique_ptr<WasmYAML::Section> &Sec : Obj.Sections) {
 667     if (Sec->Relocations.empty()) {
 668       SectionIndex++;
 669       continue;
 670     }
 671
 672     writeUint8(OS, wasm::WASM_SEC_CUSTOM);
 673     std::string OutString;
 674     raw_string_ostream StringStream(OutString);
 675     writeRelocSection(StringStream, *Sec, SectionIndex++);
 676     StringStream.flush();
 677
 678     encodeULEB128(OutString.size(), OS);
 679     OS << OutString;
 680   }
 681
 682   return true;
 683 }
 684
 685 namespace llvm {
 686 namespace yaml {
 687
 688 bool yaml2wasm(WasmYAML::Object &Doc, raw_ostream &Out, ErrorHandler EH) {
 689   WasmWriter Writer(Doc, EH);
 690   return Writer.writeWasm(Out);
 691 }
 692
 693 } // namespace yaml
 694 } // namespace llvm