diff --git a/llvm/include/llvm/ObjectYAML/WasmYAML.h b/llvm/include/llvm/ObjectYAML/WasmYAML.h
@@ -0,0 +1,338 @@
+//===- WasmYAML.h - Wasm YAMLIO implementation ------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file declares classes for handling the YAML representation
+/// of wasm binaries.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECTYAML_WASMYAML_H
+#define LLVM_OBJECTYAML_WASMYAML_H
+
+#include "llvm/ObjectYAML/YAML.h"
+#include "llvm/Support/Wasm.h"
+
+namespace llvm {
+namespace WasmYAML {
+
+LLVM_YAML_STRONG_TYPEDEF(uint32_t, SectionType)
+LLVM_YAML_STRONG_TYPEDEF(int32_t, ValueType)
+LLVM_YAML_STRONG_TYPEDEF(int32_t, TableType)
+LLVM_YAML_STRONG_TYPEDEF(int32_t, SignatureForm)
+LLVM_YAML_STRONG_TYPEDEF(uint32_t, ExportKind)
+LLVM_YAML_STRONG_TYPEDEF(uint32_t, Opcode)
+LLVM_YAML_STRONG_TYPEDEF(uint32_t, RelocType)
+
+struct FileHeader {
+  yaml::Hex32 Version;
+};
+
+struct Import {
+  StringRef Module;
+  StringRef Field;
+  ExportKind Kind;
+  union {
+    uint32_t SigIndex;
+    ValueType GlobalType;
+  };
+  bool GlobalMutable;
+};
+
+struct Limits {
+  yaml::Hex32 Flags;
+  yaml::Hex32 Initial;
+  yaml::Hex32 Maximum;
+};
+
+struct Table {
+  TableType ElemType;
+  Limits TableLimits;
+};
+
+struct Export {
+  StringRef Name;
+  ExportKind Kind;
+  uint32_t Index;
+};
+
+struct ElemSegment {
+  uint32_t TableIndex;
+  wasm::WasmInitExpr Offset;
+  std::vector<uint32_t> Functions;
+};
+
+struct Global {
+  ValueType Type;
+  bool Mutable;
+  wasm::WasmInitExpr InitExpr;
+};
+
+struct LocalDecl {
+  ValueType Type;
+  uint32_t Count;
+};
+
+struct Function {
+  std::vector<LocalDecl> Locals;
+  yaml::BinaryRef Body;
+};
+
+struct Relocation {
+  RelocType Type;
+  uint32_t Index;
+  yaml::Hex32 Offset;
+  yaml::Hex32 Addend;
+};
+
+struct DataSegment {
+  uint32_t Index;
+  wasm::WasmInitExpr Offset;
+  yaml::BinaryRef Content;
+};
+
+struct Signature {
+  Signature() : Form(wasm::WASM_TYPE_FUNC) {}
+
+  uint32_t Index;
+  SignatureForm Form;
+  std::vector<ValueType> ParamTypes;
+  ValueType ReturnType;
+};
+
+struct Section {
+  Section(SectionType SecType) : Type(SecType) {}
+
+  SectionType Type;
+  std::vector<Relocation> Relocations;
+};
+
+struct CustomSection : Section {
+  CustomSection() : Section(wasm::WASM_SEC_CUSTOM) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_CUSTOM;
+  }
+
+  StringRef Name;
+  yaml::BinaryRef Payload;
+};
+
+struct TypeSection : Section {
+  TypeSection() : Section(wasm::WASM_SEC_TYPE) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_TYPE;
+  }
+
+  std::vector<Signature> Signatures;
+};
+
+struct ImportSection : Section {
+  ImportSection() : Section(wasm::WASM_SEC_IMPORT) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_IMPORT;
+  }
+
+  std::vector<Import> Imports;
+};
+
+struct FunctionSection : Section {
+  FunctionSection() : Section(wasm::WASM_SEC_FUNCTION) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_FUNCTION;
+  }
+
+  std::vector<uint32_t> FunctionTypes;
+};
+
+struct TableSection : Section {
+  TableSection() : Section(wasm::WASM_SEC_TABLE) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_TABLE;
+  }
+
+  std::vector<Table> Tables;
+};
+
+struct MemorySection : Section {
+  MemorySection() : Section(wasm::WASM_SEC_MEMORY) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_MEMORY;
+  }
+
+  std::vector<Limits> Memories;
+};
+
+struct GlobalSection : Section {
+  GlobalSection() : Section(wasm::WASM_SEC_GLOBAL) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_GLOBAL;
+  }
+
+  std::vector<Global> Globals;
+};
+
+struct ExportSection : Section {
+  ExportSection() : Section(wasm::WASM_SEC_EXPORT) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_EXPORT;
+  }
+
+  std::vector<Export> Exports;
+};
+
+struct StartSection : Section {
+  StartSection() : Section(wasm::WASM_SEC_START) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_START;
+  }
+
+  uint32_t StartFunction;
+};
+
+struct ElemSection : Section {
+  ElemSection() : Section(wasm::WASM_SEC_ELEM) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_ELEM;
+  }
+
+  std::vector<ElemSegment> Segments;
+};
+
+struct CodeSection : Section {
+  CodeSection() : Section(wasm::WASM_SEC_CODE) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_CODE;
+  }
+
+  std::vector<Function> Functions;
+};
+
+struct DataSection : Section {
+  DataSection() : Section(wasm::WASM_SEC_DATA) {}
+  static bool classof(const Section *S) {
+    return S->Type == wasm::WASM_SEC_DATA;
+  }
+
+  std::vector<DataSegment> Segments;
+};
+
+struct Object {
+  FileHeader Header;
+  std::vector<std::unique_ptr<Section>> Sections;
+};
+
+} // end namespace WasmYAML
+} // end namespace llvm
+
+LLVM_YAML_IS_SEQUENCE_VECTOR(std::unique_ptr<llvm::WasmYAML::Section>)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Signature)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::ValueType)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Table)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Import)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Export)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::ElemSegment)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Limits)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::DataSegment)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Global)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Function)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::LocalDecl)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::WasmYAML::Relocation)
+LLVM_YAML_IS_SEQUENCE_VECTOR(uint32_t)
+
+namespace llvm {
+namespace yaml {
+
+template <> struct MappingTraits<WasmYAML::FileHeader> {
+  static void mapping(IO &IO, WasmYAML::FileHeader &FileHdr);
+};
+
+template <> struct MappingTraits<std::unique_ptr<WasmYAML::Section>> {
+  static void mapping(IO &IO, std::unique_ptr<WasmYAML::Section> &Section);
+};
+
+template <> struct MappingTraits<WasmYAML::Object> {
+  static void mapping(IO &IO, WasmYAML::Object &Object);
+};
+
+template <> struct MappingTraits<WasmYAML::Import> {
+  static void mapping(IO &IO, WasmYAML::Import &Import);
+};
+
+template <> struct MappingTraits<WasmYAML::Export> {
+  static void mapping(IO &IO, WasmYAML::Export &Export);
+};
+
+template <> struct MappingTraits<WasmYAML::Global> {
+  static void mapping(IO &IO, WasmYAML::Global &Global);
+};
+
+template <> struct ScalarEnumerationTraits<WasmYAML::SectionType> {
+  static void enumeration(IO &IO, WasmYAML::SectionType &Type);
+};
+
+template <> struct MappingTraits<WasmYAML::Signature> {
+  static void mapping(IO &IO, WasmYAML::Signature &Signature);
+};
+
+template <> struct MappingTraits<WasmYAML::Table> {
+  static void mapping(IO &IO, WasmYAML::Table &Table);
+};
+
+template <> struct MappingTraits<WasmYAML::Limits> {
+  static void mapping(IO &IO, WasmYAML::Limits &Limits);
+};
+
+template <> struct MappingTraits<WasmYAML::Function> {
+  static void mapping(IO &IO, WasmYAML::Function &Function);
+};
+
+template <> struct MappingTraits<WasmYAML::Relocation> {
+  static void mapping(IO &IO, WasmYAML::Relocation &Relocation);
+};
+
+template <> struct MappingTraits<WasmYAML::LocalDecl> {
+  static void mapping(IO &IO, WasmYAML::LocalDecl &LocalDecl);
+};
+
+template <> struct MappingTraits<wasm::WasmInitExpr> {
+  static void mapping(IO &IO, wasm::WasmInitExpr &Expr);
+};
+
+template <> struct MappingTraits<WasmYAML::DataSegment> {
+  static void mapping(IO &IO, WasmYAML::DataSegment &Segment);
+};
+
+template <> struct MappingTraits<WasmYAML::ElemSegment> {
+  static void mapping(IO &IO, WasmYAML::ElemSegment &Segment);
+};
+
+template <> struct ScalarEnumerationTraits<WasmYAML::ValueType> {
+  static void enumeration(IO &IO, WasmYAML::ValueType &Type);
+};
+
+template <> struct ScalarEnumerationTraits<WasmYAML::ExportKind> {
+  static void enumeration(IO &IO, WasmYAML::ExportKind &Kind);
+};
+
+template <> struct ScalarEnumerationTraits<WasmYAML::TableType> {
+  static void enumeration(IO &IO, WasmYAML::TableType &Type);
+};
+
+template <> struct ScalarEnumerationTraits<WasmYAML::Opcode> {
+  static void enumeration(IO &IO, WasmYAML::Opcode &Opcode);
+};
+
+template <> struct ScalarEnumerationTraits<WasmYAML::RelocType> {
+  static void enumeration(IO &IO, WasmYAML::RelocType &Kind);
+};
+
+} // end namespace yaml
+} // end namespace llvm
+
+#endif
diff --git a/llvm/include/llvm/Support/Wasm.h b/llvm/include/llvm/Support/Wasm.h
@@ -30,11 +30,83 @@ struct WasmObjectHeader {
   uint32_t Version;
 };
 
-struct WasmSection {
-  uint32_t Type;             // Section type (See below)
-  uint32_t Offset;           // Offset with in the file
-  StringRef Name;            // Section name (User-defined sections only)
-  ArrayRef<uint8_t> Content; // Section content
+struct WasmSignature {
+  std::vector<int32_t> ParamTypes;
+  int32_t ReturnType;
+};
+
+struct WasmImport {
+  StringRef Module;
+  StringRef Field;
+  uint32_t Kind;
+  union {
+    uint32_t SigIndex;
+    int32_t GlobalType;
+  };
+  bool GlobalMutable;
+};
+
+struct WasmExport {
+  StringRef Name;
+  uint32_t Kind;
+  uint32_t Index;
+};
+
+struct WasmLimits {
+  uint32_t Flags;
+  uint32_t Initial;
+  uint32_t Maximum;
+};
+
+struct WasmTable {
+  int32_t ElemType;
+  WasmLimits Limits;
+};
+
+struct WasmInitExpr {
+  uint8_t Opcode;
+  union {
+    int32_t Int32;
+    int64_t Int64;
+    int32_t Float32;
+    int64_t Float64;
+    uint32_t Global;
+  } Value;
+};
+
+struct WasmGlobal {
+  int32_t Type;
+  bool Mutable;
+  WasmInitExpr InitExpr;
+};
+
+struct WasmLocalDecl {
+  int32_t Type;
+  uint32_t Count;
+};
+
+struct WasmFunction {
+  std::vector<WasmLocalDecl> Locals;
+  ArrayRef<uint8_t> Body;
+};
+
+struct WasmDataSegment {
+  uint32_t Index;
+  WasmInitExpr Offset;
+  ArrayRef<uint8_t> Content;
+};
+
+struct WasmElemSegment {
+  uint32_t TableIndex;
+  WasmInitExpr Offset;
+  std::vector<uint32_t> Functions;
+};
+
+struct WasmRelocation {
+  uint32_t Type;         // The type of the relocation.
+  int32_t Index;         // Index into function to global index space.
+  uint64_t Offset;       // Offset from the start of the section.
+  uint64_t Addend;       // A value to add to the symbol.
 };
 
 enum : unsigned {
@@ -86,6 +158,10 @@ enum : unsigned {
   WASM_NAMES_LOCAL       = 0x2,
 };
 
+enum : unsigned {
+  WASM_LIMITS_FLAG_HAS_MAX = 0x1,
+};
+
 // Subset of types that a value can have
 enum class ValType {
   I32 = WASM_TYPE_I32,
@@ -100,6 +176,8 @@ enum : unsigned {
 #include "WasmRelocs/WebAssembly.def"
 };
 
+#undef WASM_RELOC
+
 } // end namespace wasm
 } // end namespace llvm
 

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
diff --git a/llvm/lib/ObjectYAML/CMakeLists.txt b/llvm/lib/ObjectYAML/CMakeLists.txt
@@ -6,5 +6,6 @@ add_llvm_library(LLVMObjectYAML
   ELFYAML.cpp
   MachOYAML.cpp
   ObjectYAML.cpp
+  WasmYAML.cpp
   YAML.cpp
   )
diff --git a/llvm/lib/ObjectYAML/ObjectYAML.cpp b/llvm/lib/ObjectYAML/ObjectYAML.cpp
@@ -43,6 +43,9 @@ void MappingTraits<YamlObjectFile>::mapping(IO &IO,
       ObjectFile.FatMachO.reset(new MachOYAML::UniversalBinary());
       MappingTraits<MachOYAML::UniversalBinary>::mapping(IO,
                                                          *ObjectFile.FatMachO);
+    } else if (IO.mapTag("!WASM")) {
+      ObjectFile.Wasm.reset(new WasmYAML::Object());
+      MappingTraits<WasmYAML::Object>::mapping(IO, *ObjectFile.Wasm);
     } else {
       Input &In = (Input &)IO;
       std::string Tag = In.getCurrentNode()->getRawTag();

diff --git a/llvm/lib/ObjectYAML/WasmYAML.cpp b/llvm/lib/ObjectYAML/WasmYAML.cpp
@@ -0,0 +1,348 @@
+//===- WasmYAML.cpp - Wasm YAMLIO implementation --------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines classes for handling the YAML representation of wasm.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ObjectYAML/WasmYAML.h"
+#include "llvm/Object/Wasm.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/MipsABIFlags.h"
+
+namespace llvm {
+namespace yaml {
+
+void MappingTraits<WasmYAML::FileHeader>::mapping(
+    IO &IO, WasmYAML::FileHeader &FileHdr) {
+  IO.mapRequired("Version", FileHdr.Version);
+}
+
+void MappingTraits<WasmYAML::Object>::mapping(IO &IO,
+                                              WasmYAML::Object &Object) {
+  IO.setContext(&Object);
+  IO.mapTag("!WASM", true);
+  IO.mapRequired("FileHeader", Object.Header);
+  IO.mapOptional("Sections", Object.Sections);
+  IO.setContext(nullptr);
+}
+
+static void commonSectionMapping(IO &IO, WasmYAML::Section &Section) {
+  IO.mapRequired("Type", Section.Type);
+  IO.mapOptional("Relocations", Section.Relocations);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::CustomSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapRequired("Name", Section.Name);
+  IO.mapRequired("Payload", Section.Payload);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::TypeSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Signatures", Section.Signatures);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::ImportSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Imports", Section.Imports);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::FunctionSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("FunctionTypes", Section.FunctionTypes);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::TableSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Tables", Section.Tables);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::MemorySection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Memories", Section.Memories);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::GlobalSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Globals", Section.Globals);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::ExportSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Exports", Section.Exports);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::StartSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("StartFunction", Section.StartFunction);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::ElemSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Segments", Section.Segments);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::CodeSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapRequired("Functions", Section.Functions);
+}
+
+static void sectionMapping(IO &IO, WasmYAML::DataSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapRequired("Segments", Section.Segments);
+}
+
+void MappingTraits<std::unique_ptr<WasmYAML::Section>>::mapping(
+    IO &IO, std::unique_ptr<WasmYAML::Section> &Section) {
+  WasmYAML::SectionType SectionType;
+  if (IO.outputting())
+    SectionType = Section->Type;
+  else
+    IO.mapRequired("Type", SectionType);
+
+  switch (SectionType) {
+  case wasm::WASM_SEC_CUSTOM:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::CustomSection());
+    sectionMapping(IO, *cast<WasmYAML::CustomSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_TYPE:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::TypeSection());
+    sectionMapping(IO, *cast<WasmYAML::TypeSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_IMPORT:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::ImportSection());
+    sectionMapping(IO, *cast<WasmYAML::ImportSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_FUNCTION:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::FunctionSection());
+    sectionMapping(IO, *cast<WasmYAML::FunctionSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_TABLE:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::TableSection());
+    sectionMapping(IO, *cast<WasmYAML::TableSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_MEMORY:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::MemorySection());
+    sectionMapping(IO, *cast<WasmYAML::MemorySection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_GLOBAL:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::GlobalSection());
+    sectionMapping(IO, *cast<WasmYAML::GlobalSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_EXPORT:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::ExportSection());
+    sectionMapping(IO, *cast<WasmYAML::ExportSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_START:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::StartSection());
+    sectionMapping(IO, *cast<WasmYAML::StartSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_ELEM:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::ElemSection());
+    sectionMapping(IO, *cast<WasmYAML::ElemSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_CODE:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::CodeSection());
+    sectionMapping(IO, *cast<WasmYAML::CodeSection>(Section.get()));
+    break;
+  case wasm::WASM_SEC_DATA:
+    if (!IO.outputting())
+      Section.reset(new WasmYAML::DataSection());
+    sectionMapping(IO, *cast<WasmYAML::DataSection>(Section.get()));
+    break;
+  default:
+    llvm_unreachable("Unknown section type");
+  }
+}
+
+void ScalarEnumerationTraits<WasmYAML::SectionType>::enumeration(
+    IO &IO, WasmYAML::SectionType &Type) {
+#define ECase(X) IO.enumCase(Type, #X, wasm::WASM_SEC_##X);
+  ECase(CUSTOM);
+  ECase(TYPE);
+  ECase(IMPORT);
+  ECase(FUNCTION);
+  ECase(TABLE);
+  ECase(MEMORY);
+  ECase(GLOBAL);
+  ECase(EXPORT);
+  ECase(START);
+  ECase(ELEM);
+  ECase(CODE);
+  ECase(DATA);
+#undef ECase
+}
+
+void MappingTraits<WasmYAML::Signature>::mapping(
+    IO &IO, WasmYAML::Signature &Signature) {
+  IO.mapOptional("Index", Signature.Index);
+  IO.mapRequired("ReturnType", Signature.ReturnType);
+  IO.mapRequired("ParamTypes", Signature.ParamTypes);
+}
+
+void MappingTraits<WasmYAML::Table>::mapping(IO &IO, WasmYAML::Table &Table) {
+  IO.mapRequired("ElemType", Table.ElemType);
+  IO.mapRequired("Limits", Table.TableLimits);
+}
+
+void MappingTraits<WasmYAML::Function>::mapping(IO &IO,
+                                                WasmYAML::Function &Function) {
+  IO.mapRequired("Locals", Function.Locals);
+  IO.mapRequired("Body", Function.Body);
+}
+
+void MappingTraits<WasmYAML::Relocation>::mapping(
+    IO &IO, WasmYAML::Relocation &Relocation) {
+  IO.mapRequired("Type", Relocation.Type);
+  IO.mapRequired("Index", Relocation.Index);
+  IO.mapRequired("Offset", Relocation.Offset);
+  IO.mapRequired("Addend", Relocation.Addend);
+}
+
+void MappingTraits<WasmYAML::LocalDecl>::mapping(
+    IO &IO, WasmYAML::LocalDecl &LocalDecl) {
+  IO.mapRequired("Type", LocalDecl.Type);
+  IO.mapRequired("Count", LocalDecl.Count);
+}
+
+void MappingTraits<WasmYAML::Limits>::mapping(IO &IO,
+                                              WasmYAML::Limits &Limits) {
+  if (!IO.outputting() || Limits.Flags)
+    IO.mapOptional("Flags", Limits.Flags);
+  IO.mapRequired("Initial", Limits.Initial);
+  if (!IO.outputting() || Limits.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX)
+    IO.mapOptional("Maximum", Limits.Maximum);
+}
+
+void MappingTraits<WasmYAML::ElemSegment>::mapping(
+    IO &IO, WasmYAML::ElemSegment &Segment) {
+  IO.mapRequired("Offset", Segment.Offset);
+  IO.mapRequired("Functions", Segment.Functions);
+}
+
+void MappingTraits<WasmYAML::Import>::mapping(IO &IO,
+                                              WasmYAML::Import &Import) {
+  IO.mapRequired("Module", Import.Module);
+  IO.mapRequired("Field", Import.Field);
+  IO.mapRequired("Kind", Import.Kind);
+  if (Import.Kind == wasm::WASM_EXTERNAL_FUNCTION) {
+    IO.mapRequired("SigIndex", Import.SigIndex);
+  } else if (Import.Kind == wasm::WASM_EXTERNAL_GLOBAL) {
+    IO.mapRequired("GlobalType", Import.GlobalType);
+    IO.mapRequired("GlobalMutable", Import.GlobalMutable);
+  } else {
+    llvm_unreachable("unhandled import type");
+  }
+}
+
+void MappingTraits<WasmYAML::Export>::mapping(IO &IO,
+                                              WasmYAML::Export &Export) {
+  IO.mapRequired("Name", Export.Name);
+  IO.mapRequired("Kind", Export.Kind);
+  IO.mapRequired("Index", Export.Index);
+}
+
+void MappingTraits<WasmYAML::Global>::mapping(IO &IO,
+                                              WasmYAML::Global &Global) {
+  IO.mapRequired("Type", Global.Type);
+  IO.mapRequired("Mutable", Global.Mutable);
+  IO.mapRequired("InitExpr", Global.InitExpr);
+}
+
+void MappingTraits<wasm::WasmInitExpr>::mapping(IO &IO,
+                                                wasm::WasmInitExpr &Expr) {
+  WasmYAML::Opcode Op = Expr.Opcode;
+  IO.mapRequired("Opcode", Op);
+  Expr.Opcode = Op;
+  switch (Expr.Opcode) {
+  case wasm::WASM_OPCODE_I32_CONST:
+    IO.mapRequired("Value", Expr.Value.Int32);
+    break;
+  case wasm::WASM_OPCODE_I64_CONST:
+    IO.mapRequired("Value", Expr.Value.Int64);
+    break;
+  case wasm::WASM_OPCODE_F32_CONST:
+    IO.mapRequired("Value", Expr.Value.Float32);
+    break;
+  case wasm::WASM_OPCODE_F64_CONST:
+    IO.mapRequired("Value", Expr.Value.Float64);
+    break;
+  }
+}
+
+void MappingTraits<WasmYAML::DataSegment>::mapping(
+    IO &IO, WasmYAML::DataSegment &Segment) {
+  IO.mapRequired("Index", Segment.Index);
+  IO.mapRequired("Offset", Segment.Offset);
+  IO.mapRequired("Content", Segment.Content);
+}
+
+void ScalarEnumerationTraits<WasmYAML::ValueType>::enumeration(
+    IO &IO, WasmYAML::ValueType &Type) {
+#define ECase(X) IO.enumCase(Type, #X, wasm::WASM_TYPE_##X);
+  ECase(I32);
+  ECase(I64);
+  ECase(F32);
+  ECase(F64);
+  ECase(ANYFUNC);
+  ECase(FUNC);
+  ECase(NORESULT);
+#undef ECase
+}
+
+void ScalarEnumerationTraits<WasmYAML::ExportKind>::enumeration(
+    IO &IO, WasmYAML::ExportKind &Kind) {
+#define ECase(X) IO.enumCase(Kind, #X, wasm::WASM_EXTERNAL_##X);
+  ECase(FUNCTION);
+  ECase(TABLE);
+  ECase(MEMORY);
+  ECase(GLOBAL);
+#undef ECase
+}
+
+void ScalarEnumerationTraits<WasmYAML::Opcode>::enumeration(
+    IO &IO, WasmYAML::Opcode &Code) {
+#define ECase(X) IO.enumCase(Code, #X, wasm::WASM_OPCODE_##X);
+  ECase(END);
+  ECase(I32_CONST);
+  ECase(I64_CONST);
+  ECase(F64_CONST);
+  ECase(F32_CONST);
+  ECase(GET_GLOBAL);
+#undef ECase
+}
+
+void ScalarEnumerationTraits<WasmYAML::TableType>::enumeration(
+    IO &IO, WasmYAML::TableType &Type) {
+#define ECase(X) IO.enumCase(Type, #X, wasm::WASM_TYPE_##X);
+  ECase(ANYFUNC);
+#undef ECase
+}
+
+void ScalarEnumerationTraits<WasmYAML::RelocType>::enumeration(
+    IO &IO, WasmYAML::RelocType &Type) {
+#define WASM_RELOC(name, value) IO.enumCase(Type, #name, wasm::name);
+#include "llvm/Support/WasmRelocs/WebAssembly.def"
+#undef WASM_RELOC
+}
+
+} // end namespace yaml
+} // end namespace llvm
diff --git a/llvm/test/ObjectYAML/wasm/code_section.yaml b/llvm/test/ObjectYAML/wasm/code_section.yaml
@@ -0,0 +1,72 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TYPE
+    Signatures:
+      - ReturnType:      F32
+        ParamTypes:
+          - I32
+      - ReturnType:      NORESULT
+        ParamTypes:
+          - I32
+          - I64
+  - Type:            FUNCTION
+    FunctionTypes:
+      - 0
+      - 1
+  - Type:            CODE
+    Relocations:
+      - Type:            R_WEBASSEMBLY_TABLE_INDEX_SLEB
+        Index:           0
+        Offset:          0x00000006
+        Addend:          0x00000000
+      - Type:            R_WEBASSEMBLY_FUNCTION_INDEX_LEB
+        Index:           1
+        Offset:          0x00000025
+        Addend:          0x00000000
+    Functions:
+      - Locals:
+         - Type:            I32
+           Count:           3
+        Body:            418080808000210020002101200111808080800000210220020F0B
+      - Locals:
+         - Type:            I32
+           Count:           1
+        Body:            108180808000210020000F0B
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:  - Type:            TYPE
+# CHECK:    Signatures:
+# CHECK:      - Index:           0
+# CHECK:        ReturnType:      F32
+# CHECK:        ParamTypes:
+# CHECK:          - I32
+# CHECK:      - Index:           1
+# CHECK:        ReturnType:      NORESULT
+# CHECK:        ParamTypes:
+# CHECK:          - I32
+# CHECK:          - I64
+# CHECK:  - Type:            CODE
+# CHECK:    Relocations:
+# CHECK:      - Type:            R_WEBASSEMBLY_TABLE_INDEX_SLEB
+# CHECK:        Index:           0
+# CHECK:        Offset:          0x00000006
+# CHECK:        Addend:          0x00000000
+# CHECK:      - Type:            R_WEBASSEMBLY_FUNCTION_INDEX_LEB
+# CHECK:        Index:           1
+# CHECK:        Offset:          0x00000025
+# CHECK:        Addend:          0x00000000
+# CHECK:    Functions:
+# CHECK:      - Locals:
+# CHECK:         - Type:            I32
+# CHECK:           Count:           3
+# CHECK:        Body:            418080808000210020002101200111808080800000210220020F0B
+# CHECK:      - Locals:
+# CHECK:         - Type:            I32
+# CHECK:           Count:           1
+# CHECK:        Body:            108180808000210020000F0B
diff --git a/llvm/test/ObjectYAML/wasm/custom_section.yaml b/llvm/test/ObjectYAML/wasm/custom_section.yaml
@@ -0,0 +1,17 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            CUSTOM
+    Name:            foo
+    Payload:         03666F6F0401020304
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:  - Type:            CUSTOM
+# CHECK:    Name:            foo
+# CHECK:    Payload:         03666F6F0401020304
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/data_section.yaml b/llvm/test/ObjectYAML/wasm/data_section.yaml
@@ -0,0 +1,28 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            MEMORY
+    Memories:
+      - Initial:         0x00000003
+  - Type:            DATA
+    Segments:
+      - Index:           0
+        Offset:
+          Opcode:          I32_CONST
+          Value:           4
+        Content:         '10001000'
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:   - Type:            DATA
+# CHECK:     Segments:
+# CHECK:       - Index:           0
+# CHECK:         Offset:
+# CHECK:           Opcode:          I32_CONST
+# CHECK:           Value:           4
+# CHECK:         Content:         '10001000'
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/elem_section.yaml b/llvm/test/ObjectYAML/wasm/elem_section.yaml
@@ -0,0 +1,42 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TABLE
+    Tables:         
+      - ElemType:          ANYFUNC
+        Limits:
+          Flags:           0x00000001
+          Initial:         0x00000010
+          Maximum:         0x00000011
+  - Type:            ELEM
+    Segments:
+      - Offset:
+          Opcode:        I32_CONST
+          Value:         3
+        Functions:
+          - 1
+      - Offset:
+          Opcode:        I32_CONST
+          Value:         5
+        Functions:
+          - 4
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:   - Type:            ELEM
+# CHECK:     Segments:
+# CHECK:       - Offset:
+# CHECK:           Opcode:           I32_CONST
+# CHECK:           Value:            3
+# CHECK:         Functions:
+# CHECK:           - 1
+# CHECK:       - Offset:
+# CHECK:           Opcode:           I32_CONST
+# CHECK:           Value:            5
+# CHECK:         Functions:
+# CHECK:           - 4
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/export_section.yaml b/llvm/test/ObjectYAML/wasm/export_section.yaml
@@ -0,0 +1,27 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            EXPORT
+    Exports:         
+      - Name:            foo
+        Kind:            FUNCTION
+        Index:           0
+      - Name:            bar
+        Kind:            FUNCTION
+        Index:           1
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:   - Type:            EXPORT
+# CHECK:     Exports:         
+# CHECK:       - Name:            foo
+# CHECK:         Kind:            FUNCTION
+# CHECK:         Index:           0
+# CHECK:       - Name:            bar
+# CHECK:         Kind:            FUNCTION
+# CHECK:         Index:           1
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/function_section.yaml b/llvm/test/ObjectYAML/wasm/function_section.yaml
@@ -0,0 +1,19 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            FUNCTION
+    FunctionTypes:   
+      - 1
+      - 0
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:   - Type:            FUNCTION
+# CHECK:     FunctionTypes:   
+# CHECK:       - 1
+# CHECK:       - 0
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/global_section.yaml b/llvm/test/ObjectYAML/wasm/global_section.yaml
@@ -0,0 +1,25 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            GLOBAL
+    Globals:         
+      - Type:        I32
+        Mutable:     false
+        InitExpr:
+          Opcode:          I64_CONST
+          Value:           -5
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:  - Type:            GLOBAL
+# CHECK:    Globals:         
+# CHECK:      - Type:        I32
+# CHECK:        Mutable:     false
+# CHECK:        InitExpr:
+# CHECK:          Opcode:          I64_CONST
+# CHECK:          Value:           -5
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/header.yaml b/llvm/test/ObjectYAML/wasm/header.yaml
@@ -0,0 +1,9 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/header_invalid_version.yaml b/llvm/test/ObjectYAML/wasm/header_invalid_version.yaml
@@ -0,0 +1,8 @@
+# RUN: yaml2obj %s | not obj2yaml 2>&1 | FileCheck %s
+
+--- !WASM
+FileHeader:
+  Version:         0x00000002
+...
+
+# CHECK: Error: 'Invalid data was encountered while parsing the file'
diff --git a/llvm/test/ObjectYAML/wasm/import_section.yaml b/llvm/test/ObjectYAML/wasm/import_section.yaml
@@ -0,0 +1,41 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TYPE
+    Signatures:
+      - ReturnType:      I32
+        ParamTypes:
+          - I32
+  - Type:            IMPORT
+    Imports:         
+      - Module:          foo
+        Field:           bar
+        Kind:            FUNCTION
+        SigIndex:        0
+      - Module:          fiz
+        Field:           baz
+        Kind:            GLOBAL
+        GlobalType:      I32
+        GlobalMutable:   false
+  - Type:            FUNCTION
+    FunctionTypes:
+      - 0
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:   - Type:            IMPORT
+# CHECK:     Imports:         
+# CHECK:       - Module:          foo
+# CHECK:         Field:           bar
+# CHECK:         Kind:            FUNCTION
+# CHECK:         SigIndex:        0
+# CHECK:       - Module:          fiz
+# CHECK:         Field:           baz
+# CHECK:         Kind:            GLOBAL
+# CHECK:         GlobalType:      I32
+# CHECK:         GlobalMutable:   false
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/memory_section.yaml b/llvm/test/ObjectYAML/wasm/memory_section.yaml
@@ -0,0 +1,23 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            MEMORY
+    Memories:         
+      - Flags:           0x00000001
+        Initial:         0x00000002
+        Maximum:         0x000000FF
+      - Initial:         0x00000003
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:   - Type:            MEMORY
+# CHECK:     Memories:         
+# CHECK:       - Flags:            0x00000001
+# CHECK:         Initial:          0x00000002
+# CHECK:         Maximum:          0x000000FF
+# CHECK:       - Initial:          0x00000003
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/start_section.yaml b/llvm/test/ObjectYAML/wasm/start_section.yaml
@@ -0,0 +1,15 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            START
+    StartFunction:   1
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:  - Type:            START
+# CHECK:    StartFunction:   1
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/table_section.yaml b/llvm/test/ObjectYAML/wasm/table_section.yaml
@@ -0,0 +1,25 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TABLE
+    Tables:         
+      - ElemType:        ANYFUNC
+        Limits:
+          Flags:           0x00000001
+          Initial:         0x00000010
+          Maximum:         0x00000011
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:  - Type:            TABLE
+# CHECK:    Tables:         
+# CHECK:      - ElemType:        ANYFUNC
+# CHECK:        Limits:
+# CHECK:          Flags:           0x00000001
+# CHECK:          Initial:         0x00000010
+# CHECK:          Maximum:         0x00000011
+# CHECK: ...
diff --git a/llvm/test/ObjectYAML/wasm/type_section.yaml b/llvm/test/ObjectYAML/wasm/type_section.yaml
@@ -0,0 +1,33 @@
+# RUN: yaml2obj %s | obj2yaml | FileCheck %s
+--- !WASM
+FileHeader:
+  Version:         0x00000001
+Sections:
+  - Type:            TYPE
+    Signatures:
+      - ReturnType:      I32
+        ParamTypes:
+          - F32
+          - F32
+      - ReturnType:      I64
+        ParamTypes:
+          - F64
+          - F64
+...
+# CHECK: --- !WASM
+# CHECK: FileHeader:
+# CHECK:   Version:           0x00000001
+# CHECK: Sections:
+# CHECK:  - Type:            TYPE
+# CHECK:    Signatures:
+# CHECK:      - Index:           0
+# CHECK:        ReturnType:      I32
+# CHECK:        ParamTypes:
+# CHECK:          - F32
+# CHECK:          - F32
+# CHECK:      - Index:           1
+# CHECK:        ReturnType:      I64
+# CHECK:        ParamTypes:
+# CHECK:          - F64
+# CHECK:          - F64
+# CHECK: ...
diff --git a/llvm/test/tools/llvm-objdump/Inputs/test.wasm b/llvm/test/tools/llvm-objdump/Inputs/test.wasm
diff --git a/llvm/test/tools/llvm-objdump/wasm.txt b/llvm/test/tools/llvm-objdump/wasm.txt
@@ -9,7 +9,7 @@
 # CHECK:   4 EXPORT        0000000e 0000000000000000 
 # CHECK:   5 ELEM          00000007 0000000000000000 
 # CHECK:   6 CODE          0000002a 0000000000000000 TEXT 
-# CHECK:   7 name          0000002c 0000000000000000 
+# CHECK:   7 name          0000003c 0000000000000000 
 
 # RUN: llvm-objdump -p %p/Inputs/test.wasm | FileCheck %s -check-prefix CHECK-HEADER
 

diff --git a/llvm/test/tools/llvm-readobj/Inputs/trivial.obj.wasm b/llvm/test/tools/llvm-readobj/Inputs/trivial.obj.wasm
diff --git a/llvm/test/tools/llvm-readobj/sections.test b/llvm/test/tools/llvm-readobj/sections.test
@@ -531,7 +531,7 @@ WASM-NEXT:     Offset: 75
 WASM-NEXT:   }
 WASM-NEXT:   Section {
 WASM-NEXT:     Type: CUSTOM (0x0)
-WASM-NEXT:     Size: 44
+WASM-NEXT:     Size: 60
 WASM-NEXT:     Offset: 119
 WASM-NEXT:     Name: name
 WASM-NEXT:   }

diff --git a/llvm/tools/llvm-readobj/WasmDumper.cpp b/llvm/tools/llvm-readobj/WasmDumper.cpp
@@ -55,14 +55,14 @@ class WasmDumper : public ObjDumper {
   void printSections() override {
     ListScope Group(W, "Sections");
     for (const SectionRef &Section : Obj->sections()) {
-      const wasm::WasmSection *WasmSec = Obj->getWasmSection(Section);
+      const WasmSection &WasmSec = Obj->getWasmSection(Section);
       DictScope SectionD(W, "Section");
-      const char *Type = wasmSectionTypeToString(WasmSec->Type);
-      W.printHex("Type", Type, WasmSec->Type);
-      W.printNumber("Size", (uint64_t)WasmSec->Content.size());
-      W.printNumber("Offset", WasmSec->Offset);
-      if (WasmSec->Type == wasm::WASM_SEC_CUSTOM) {
-        W.printString("Name", WasmSec->Name);
+      const char *Type = wasmSectionTypeToString(WasmSec.Type);
+      W.printHex("Type", Type, WasmSec.Type);
+      W.printNumber("Size", (uint64_t)WasmSec.Content.size());
+      W.printNumber("Offset", WasmSec.Offset);
+      if (WasmSec.Type == wasm::WASM_SEC_CUSTOM) {
+        W.printString("Name", WasmSec.Name);
       }
     }
   }

diff --git a/llvm/tools/obj2yaml/CMakeLists.txt b/llvm/tools/obj2yaml/CMakeLists.txt
@@ -11,5 +11,6 @@ add_llvm_tool(obj2yaml
   dwarf2yaml.cpp
   elf2yaml.cpp
   macho2yaml.cpp
+  wasm2yaml.cpp
   Error.cpp
   )
diff --git a/llvm/tools/obj2yaml/obj2yaml.cpp b/llvm/tools/obj2yaml/obj2yaml.cpp
@@ -24,6 +24,8 @@ static std::error_code dumpObject(const ObjectFile &Obj) {
     return coff2yaml(outs(), cast<COFFObjectFile>(Obj));
   if (Obj.isELF())
     return elf2yaml(outs(), Obj);
+  if (Obj.isWasm())
+    return wasm2yaml(outs(), cast<WasmObjectFile>(Obj));
 
   return obj2yaml_error::unsupported_obj_file_format;
 }

diff --git a/llvm/tools/obj2yaml/obj2yaml.h b/llvm/tools/obj2yaml/obj2yaml.h
@@ -14,6 +14,7 @@
 #define LLVM_TOOLS_OBJ2YAML_OBJ2YAML_H
 
 #include "llvm/Object/COFF.h"
+#include "llvm/Object/Wasm.h"
 #include "llvm/Support/raw_ostream.h"
 #include <system_error>
 
@@ -23,6 +24,8 @@ std::error_code elf2yaml(llvm::raw_ostream &Out,
                          const llvm::object::ObjectFile &Obj);
 std::error_code macho2yaml(llvm::raw_ostream &Out,
                            const llvm::object::Binary &Obj);
+std::error_code wasm2yaml(llvm::raw_ostream &Out,
+                          const llvm::object::WasmObjectFile &Obj);
 
 // Forward decls for dwarf2yaml
 namespace llvm {

diff --git a/llvm/tools/obj2yaml/wasm2yaml.cpp b/llvm/tools/obj2yaml/wasm2yaml.cpp
@@ -0,0 +1,219 @@
+//===------ utils/wasm2yaml.cpp - obj2yaml conversion tool ------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "obj2yaml.h"
+#include "llvm/Object/COFF.h"
+#include "llvm/ObjectYAML/WasmYAML.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/YAMLTraits.h"
+
+using namespace llvm;
+
+namespace {
+
+class WasmDumper {
+  const object::WasmObjectFile &Obj;
+
+public:
+  WasmDumper(const object::WasmObjectFile &O) : Obj(O) {}
+  ErrorOr<WasmYAML::Object *> dump();
+};
+
+ErrorOr<WasmYAML::Object *> WasmDumper::dump() {
+  auto Y = make_unique<WasmYAML::Object>();
+
+  // Dump header
+  Y->Header.Version = Obj.getHeader().Version;
+
+  // Dump sections
+  for (const auto &Sec : Obj.sections()) {
+    const object::WasmSection &WasmSec = Obj.getWasmSection(Sec);
+    std::unique_ptr<WasmYAML::Section> S;
+    switch (WasmSec.Type) {
+    case wasm::WASM_SEC_CUSTOM: {
+      if (WasmSec.Name.startswith("reloc.")) {
+        // Relocations are attached the sections they apply to rather than
+        // being represented as a custom section in the YAML output.
+        continue;
+      }
+      auto CustomSec = make_unique<WasmYAML::CustomSection>();
+      CustomSec->Name = WasmSec.Name;
+      CustomSec->Payload = yaml::BinaryRef(WasmSec.Content);
+      S = std::move(CustomSec);
+      break;
+    }
+    case wasm::WASM_SEC_TYPE: {
+      auto TypeSec = make_unique<WasmYAML::TypeSection>();
+      uint32_t Index = 0;
+      for (const auto &FunctionSig : Obj.types()) {
+        WasmYAML::Signature Sig;
+        Sig.Index = Index++;
+        Sig.ReturnType = FunctionSig.ReturnType;
+        for (const auto &ParamType : FunctionSig.ParamTypes)
+          Sig.ParamTypes.push_back(ParamType);
+        TypeSec->Signatures.push_back(Sig);
+      }
+      S = std::move(TypeSec);
+      break;
+    }
+    case wasm::WASM_SEC_IMPORT: {
+      auto ImportSec = make_unique<WasmYAML::ImportSection>();
+      for (auto &Import : Obj.imports()) {
+        WasmYAML::Import Ex;
+        Ex.Module = Import.Module;
+        Ex.Field = Import.Field;
+        Ex.Kind = Import.Kind;
+        if (Ex.Kind == wasm::WASM_EXTERNAL_FUNCTION) {
+          Ex.SigIndex = Import.SigIndex;
+        } else if (Ex.Kind == wasm::WASM_EXTERNAL_GLOBAL) {
+          Ex.GlobalType = Import.GlobalType;
+          Ex.GlobalMutable = Import.GlobalMutable;
+        }
+        ImportSec->Imports.push_back(Ex);
+      }
+      S = std::move(ImportSec);
+      break;
+    }
+    case wasm::WASM_SEC_FUNCTION: {
+      auto FuncSec = make_unique<WasmYAML::FunctionSection>();
+      for (const auto &Func : Obj.functionTypes()) {
+        FuncSec->FunctionTypes.push_back(Func);
+      }
+      S = std::move(FuncSec);
+      break;
+    }
+    case wasm::WASM_SEC_TABLE: {
+      auto TableSec = make_unique<WasmYAML::TableSection>();
+      for (auto &Table : Obj.tables()) {
+        WasmYAML::Table T;
+        T.ElemType = Table.ElemType;
+        T.TableLimits.Flags = Table.Limits.Flags;
+        T.TableLimits.Initial = Table.Limits.Initial;
+        T.TableLimits.Maximum = Table.Limits.Maximum;
+        TableSec->Tables.push_back(T);
+      }
+      S = std::move(TableSec);
+      break;
+    }
+    case wasm::WASM_SEC_MEMORY: {
+      auto MemorySec = make_unique<WasmYAML::MemorySection>();
+      for (auto &Memory : Obj.memories()) {
+        WasmYAML::Limits L;
+        L.Flags = Memory.Flags;
+        L.Initial = Memory.Initial;
+        L.Maximum = Memory.Maximum;
+        MemorySec->Memories.push_back(L);
+      }
+      S = std::move(MemorySec);
+      break;
+    }
+    case wasm::WASM_SEC_GLOBAL: {
+      auto GlobalSec = make_unique<WasmYAML::GlobalSection>();
+      for (auto &Global : Obj.globals()) {
+        WasmYAML::Global G;
+        G.Type = Global.Type;
+        G.Mutable = Global.Mutable;
+        G.InitExpr = Global.InitExpr;
+        GlobalSec->Globals.push_back(G);
+      }
+      S = std::move(GlobalSec);
+      break;
+    }
+    case wasm::WASM_SEC_START: {
+      auto StartSec = make_unique<WasmYAML::StartSection>();
+      StartSec->StartFunction = Obj.startFunction();
+      S = std::move(StartSec);
+      break;
+    }
+    case wasm::WASM_SEC_EXPORT: {
+      auto ExportSec = make_unique<WasmYAML::ExportSection>();
+      for (auto &Export : Obj.exports()) {
+        WasmYAML::Export Ex;
+        Ex.Name = Export.Name;
+        Ex.Kind = Export.Kind;
+        Ex.Index = Export.Index;
+        ExportSec->Exports.push_back(Ex);
+      }
+      S = std::move(ExportSec);
+      break;
+    }
+    case wasm::WASM_SEC_ELEM: {
+      auto ElemSec = make_unique<WasmYAML::ElemSection>();
+      for (auto &Segment : Obj.elements()) {
+        WasmYAML::ElemSegment Seg;
+        Seg.TableIndex = Segment.TableIndex;
+        Seg.Offset = Segment.Offset;
+        for (auto &Func : Segment.Functions) {
+          Seg.Functions.push_back(Func);
+        }
+        ElemSec->Segments.push_back(Seg);
+      }
+      S = std::move(ElemSec);
+      break;
+    }
+    case wasm::WASM_SEC_CODE: {
+      auto CodeSec = make_unique<WasmYAML::CodeSection>();
+      for (auto &Func : Obj.functions()) {
+        WasmYAML::Function Function;
+        for (auto &Local : Func.Locals) {
+          WasmYAML::LocalDecl LocalDecl;
+          LocalDecl.Type = Local.Type;
+          LocalDecl.Count = Local.Count;
+          Function.Locals.push_back(LocalDecl);
+        }
+        Function.Body = yaml::BinaryRef(Func.Body);
+        CodeSec->Functions.push_back(Function);
+      }
+      S = std::move(CodeSec);
+      break;
+    }
+    case wasm::WASM_SEC_DATA: {
+      auto DataSec = make_unique<WasmYAML::DataSection>();
+      for (auto &Segment : Obj.dataSegments()) {
+        WasmYAML::DataSegment Seg;
+        Seg.Index = Segment.Index;
+        Seg.Offset = Segment.Offset;
+        Seg.Content = yaml::BinaryRef(Segment.Content);
+        DataSec->Segments.push_back(Seg);
+      }
+      S = std::move(DataSec);
+      break;
+    }
+    default:
+      llvm_unreachable("Unknown section type");
+      break;
+    }
+    for (const wasm::WasmRelocation &Reloc: WasmSec.Relocations) {
+      WasmYAML::Relocation R;
+      R.Type = Reloc.Type;
+      R.Index = Reloc.Index;
+      R.Offset = Reloc.Offset;
+      R.Addend = Reloc.Addend;
+      S->Relocations.push_back(R);
+    }
+    Y->Sections.push_back(std::move(S));
+  }
+
+  return Y.release();
+}
+
+} // namespace
+
+std::error_code wasm2yaml(raw_ostream &Out, const object::WasmObjectFile &Obj) {
+  WasmDumper Dumper(Obj);
+  ErrorOr<WasmYAML::Object *> YAMLOrErr = Dumper.dump();
+  if (std::error_code EC = YAMLOrErr.getError())
+    return EC;
+
+  std::unique_ptr<WasmYAML::Object> YAML(YAMLOrErr.get());
+  yaml::Output Yout(Out);
+  Yout << *YAML;
+
+  return std::error_code();
+}
diff --git a/llvm/tools/yaml2obj/CMakeLists.txt b/llvm/tools/yaml2obj/CMakeLists.txt
@@ -10,4 +10,5 @@ add_llvm_tool(yaml2obj
   yaml2coff.cpp
   yaml2elf.cpp
   yaml2macho.cpp
+  yaml2wasm.cpp
   )
diff --git a/llvm/tools/yaml2obj/yaml2obj.cpp b/llvm/tools/yaml2obj/yaml2obj.cpp
@@ -57,6 +57,8 @@ static int convertYAML(yaml::Input &YIn, raw_ostream &Out) {
         return yaml2coff(*Doc.Coff, Out);
       if (Doc.MachO || Doc.FatMachO)
         return yaml2macho(Doc, Out);
+      if (Doc.Wasm)
+        return yaml2wasm(*Doc.Wasm, Out);
       errs() << "yaml2obj: Unknown document type!\n";
       return 1;
     }

diff --git a/llvm/tools/yaml2obj/yaml2obj.h b/llvm/tools/yaml2obj/yaml2obj.h
@@ -23,6 +23,10 @@ namespace ELFYAML {
 struct Object;
 }
 
+namespace WasmYAML {
+struct Object;
+}
+
 namespace yaml {
 class Input;
 struct YamlObjectFile;
@@ -32,5 +36,6 @@ struct YamlObjectFile;
 int yaml2coff(llvm::COFFYAML::Object &Doc, llvm::raw_ostream &Out);
 int yaml2elf(llvm::ELFYAML::Object &Doc, llvm::raw_ostream &Out);
 int yaml2macho(llvm::yaml::YamlObjectFile &Doc, llvm::raw_ostream &Out);
+int yaml2wasm(llvm::WasmYAML::Object &Doc, llvm::raw_ostream &Out);
 
 #endif
diff --git a/llvm/tools/yaml2obj/yaml2wasm.cpp b/llvm/tools/yaml2obj/yaml2wasm.cpp
@@ -0,0 +1,377 @@
+//===- yaml2wasm - Convert YAML to a Wasm object file --------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief The Wasm component of yaml2obj.
+///
+//===----------------------------------------------------------------------===//
+//
+#include "yaml2obj.h"
+#include "llvm/Object/Wasm.h"
+#include "llvm/ObjectYAML/ObjectYAML.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/LEB128.h"
+
+using namespace llvm;
+
+/// This parses a yaml stream that represents a Wasm object file.
+/// See docs/yaml2obj for the yaml scheema.
+class WasmWriter {
+public:
+  WasmWriter(WasmYAML::Object &Obj) : Obj(Obj) {}
+  int writeWasm(raw_ostream &OS);
+  int writeRelocSection(raw_ostream &OS, WasmYAML::Section &Sec);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::CustomSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::TypeSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::ImportSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::FunctionSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::TableSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::MemorySection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::GlobalSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::ExportSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::StartSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::ElemSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::CodeSection &Section);
+  int writeSectionContent(raw_ostream &OS, WasmYAML::DataSection &Section);
+
+private:
+  WasmYAML::Object &Obj;
+};
+
+static int writeUint64(raw_ostream &OS, uint64_t Value) {
+  char Data[sizeof(Value)];
+  support::endian::write64le(Data, Value);
+  OS.write(Data, sizeof(Data));
+  return 0;
+}
+
+static int writeUint32(raw_ostream &OS, uint32_t Value) {
+  char Data[sizeof(Value)];
+  support::endian::write32le(Data, Value);
+  OS.write(Data, sizeof(Data));
+  return 0;
+}
+
+static int writeUint8(raw_ostream &OS, uint8_t Value) {
+  char Data[sizeof(Value)];
+  memcpy(Data, &Value, sizeof(Data));
+  OS.write(Data, sizeof(Data));
+  return 0;
+}
+
+static int writeStringRef(StringRef &Str, raw_ostream &OS) {
+  encodeULEB128(Str.size(), OS);
+  OS << Str;
+  return 0;
+}
+
+static int writeLimits(WasmYAML::Limits Lim, raw_ostream &OS) {
+  encodeULEB128(Lim.Flags, OS);
+  encodeULEB128(Lim.Initial, OS);
+  if (Lim.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX)
+    encodeULEB128(Lim.Maximum, OS);
+  return 0;
+}
+
+static int writeInitExpr(wasm::WasmInitExpr InitExpr, raw_ostream &OS) {
+  writeUint8(OS, InitExpr.Opcode);
+  switch (InitExpr.Opcode) {
+  case wasm::WASM_OPCODE_I32_CONST:
+    encodeSLEB128(InitExpr.Value.Int32, OS);
+    break;
+  case wasm::WASM_OPCODE_I64_CONST:
+    encodeSLEB128(InitExpr.Value.Int64, OS);
+    break;
+  case wasm::WASM_OPCODE_F32_CONST:
+    writeUint32(OS, InitExpr.Value.Float32);
+    break;
+  case wasm::WASM_OPCODE_F64_CONST:
+    writeUint64(OS, InitExpr.Value.Float64);
+    break;
+  case wasm::WASM_OPCODE_GET_GLOBAL:
+    encodeULEB128(InitExpr.Value.Global, OS);
+    break;
+  default:
+    errs() << "Unknown opcode in init_expr: " << InitExpr.Opcode;
+    return 1;
+  }
+  writeUint8(OS, wasm::WASM_OPCODE_END);
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::CustomSection &Section) {
+  // writeStringRef(Section.Name, OS);
+  // encodeULEB128(Section.Payload.binary_size(), OS);
+  Section.Payload.writeAsBinary(OS);
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::TypeSection &Section) {
+  encodeULEB128(Section.Signatures.size(), OS);
+  for (auto &Sig : Section.Signatures) {
+    encodeSLEB128(Sig.Form, OS);
+    encodeULEB128(Sig.ParamTypes.size(), OS);
+    for (auto ParamType : Sig.ParamTypes)
+      encodeSLEB128(ParamType, OS);
+    if (Sig.ReturnType == wasm::WASM_TYPE_NORESULT) {
+      encodeSLEB128(0, OS);
+    } else {
+      encodeULEB128(1, OS);
+      encodeSLEB128(Sig.ReturnType, OS);
+    }
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::ImportSection &Section) {
+  encodeULEB128(Section.Imports.size(), OS);
+  for (auto &Import : Section.Imports) {
+    writeStringRef(Import.Module, OS);
+    writeStringRef(Import.Field, OS);
+    encodeULEB128(Import.Kind, OS);
+    switch (Import.Kind) {
+    case wasm::WASM_EXTERNAL_FUNCTION:
+      encodeULEB128(Import.SigIndex, OS);
+      break;
+    case wasm::WASM_EXTERNAL_GLOBAL:
+      encodeSLEB128(Import.GlobalType, OS);
+      writeUint8(OS, Import.GlobalMutable);
+      break;
+    default:
+      errs() << "Unknown import type: " << Import.Kind;
+      return 1;
+    }
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::FunctionSection &Section) {
+  encodeULEB128(Section.FunctionTypes.size(), OS);
+  for (uint32_t FuncType : Section.FunctionTypes) {
+    encodeULEB128(FuncType, OS);
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::ExportSection &Section) {
+  encodeULEB128(Section.Exports.size(), OS);
+  for (auto &Export : Section.Exports) {
+    writeStringRef(Export.Name, OS);
+    encodeULEB128(Export.Kind, OS);
+    encodeULEB128(Export.Index, OS);
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::StartSection &Section) {
+  encodeULEB128(Section.StartFunction, OS);
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::TableSection &Section) {
+  encodeULEB128(Section.Tables.size(), OS);
+  for (auto &Table : Section.Tables) {
+    encodeSLEB128(Table.ElemType, OS);
+    writeLimits(Table.TableLimits, OS);
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::MemorySection &Section) {
+  encodeULEB128(Section.Memories.size(), OS);
+  for (auto &Mem : Section.Memories) {
+    writeLimits(Mem, OS);
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::GlobalSection &Section) {
+  encodeULEB128(Section.Globals.size(), OS);
+  for (auto &Global : Section.Globals) {
+    encodeSLEB128(Global.Type, OS);
+    writeUint8(OS, Global.Mutable);
+    writeInitExpr(Global.InitExpr, OS);
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::ElemSection &Section) {
+  encodeULEB128(Section.Segments.size(), OS);
+  for (auto &Segment : Section.Segments) {
+    encodeULEB128(Segment.TableIndex, OS);
+    writeInitExpr(Segment.Offset, OS);
+
+    encodeULEB128(Segment.Functions.size(), OS);
+    for (auto &Function : Segment.Functions) {
+      encodeULEB128(Function, OS);
+    }
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::CodeSection &Section) {
+  encodeULEB128(Section.Functions.size(), OS);
+  for (auto &Func : Section.Functions) {
+    std::string OutString;
+    raw_string_ostream StringStream(OutString);
+
+    encodeULEB128(Func.Locals.size(), StringStream);
+    for (auto &LocalDecl : Func.Locals) {
+      encodeULEB128(LocalDecl.Count, StringStream);
+      encodeSLEB128(LocalDecl.Type, StringStream);
+    }
+
+    Func.Body.writeAsBinary(StringStream);
+
+    // Write the section size followed by the content
+    StringStream.flush();
+    encodeULEB128(OutString.size(), OS);
+    OS << OutString;
+  }
+  return 0;
+}
+
+int WasmWriter::writeSectionContent(raw_ostream &OS,
+                                    WasmYAML::DataSection &Section) {
+  encodeULEB128(Section.Segments.size(), OS);
+  for (auto &Segment : Section.Segments) {
+    encodeULEB128(Segment.Index, OS);
+    writeInitExpr(Segment.Offset, OS);
+    encodeULEB128(Segment.Content.binary_size(), OS);
+    Segment.Content.writeAsBinary(OS);
+  }
+  return 0;
+}
+
+int WasmWriter::writeRelocSection(raw_ostream &OS,
+                                  WasmYAML::Section &Sec) {
+  StringRef Name;
+  switch (Sec.Type) {
+    case wasm::WASM_SEC_CODE:
+      Name = "reloc.CODE";
+      break;
+    case wasm::WASM_SEC_DATA:
+      Name = "reloc.DATA";
+      break;
+    default:
+      llvm_unreachable("not yet implemented");
+      return 1;
+  }
+
+  writeStringRef(Name, OS);
+  encodeULEB128(Sec.Type, OS);
+  encodeULEB128(Sec.Relocations.size(), OS);
+
+  for (auto Reloc: Sec.Relocations) {
+    encodeULEB128(Reloc.Type, OS);
+    encodeULEB128(Reloc.Offset, OS);
+    encodeULEB128(Reloc.Index, OS);
+    switch (Reloc.Type) {
+      case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB:
+      case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB:
+      case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32:
+        encodeULEB128(Reloc.Addend, OS);
+    }
+  }
+  return 0;
+}
+
+
+int WasmWriter::writeWasm(raw_ostream &OS) {
+  // Write headers
+  OS.write(wasm::WasmMagic, sizeof(wasm::WasmMagic));
+  writeUint32(OS, Obj.Header.Version);
+
+  // Write each section
+  for (const std::unique_ptr<WasmYAML::Section> &Sec : Obj.Sections) {
+    encodeULEB128(Sec->Type, OS);
+
+    std::string OutString;
+    raw_string_ostream StringStream(OutString);
+    if (auto S = dyn_cast<WasmYAML::CustomSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::TypeSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::ImportSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::FunctionSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::TableSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::MemorySection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::GlobalSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::ExportSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::StartSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::ElemSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::CodeSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else if (auto S = dyn_cast<WasmYAML::DataSection>(Sec.get())) {
+      if (auto Err = writeSectionContent(StringStream, *S))
+        return Err;
+    } else {
+      errs() << "Unknown section type: " << Sec->Type << "\n";
+      return 1;
+    }
+    StringStream.flush();
+
+    // Write the section size followed by the content
+    encodeULEB128(OutString.size(), OS);
+    OS << OutString;
+  }
+
+  // write reloc sections for any section that have relocations
+  for (const std::unique_ptr<WasmYAML::Section> &Sec : Obj.Sections) {
+    if (Sec->Relocations.empty())
+      continue;
+
+    encodeULEB128(wasm::WASM_SEC_CUSTOM, OS);
+    std::string OutString;
+    raw_string_ostream StringStream(OutString);
+    writeRelocSection(StringStream, *Sec);
+    StringStream.flush();
+
+    encodeULEB128(OutString.size(), OS);
+    OS << OutString;
+  }
+
+  return 0;
+}
+
+int yaml2wasm(llvm::WasmYAML::Object &Doc, raw_ostream &Out) {
+  WasmWriter Writer(Doc);
+
+  return Writer.writeWasm(Out);
+}