Index: lib/MC/WasmObjectWriter.cpp
===================================================================
--- lib/MC/WasmObjectWriter.cpp
+++ lib/MC/WasmObjectWriter.cpp
@@ -184,6 +184,9 @@
   // Relocations for fixing up references in the data section.
   std::vector<WasmRelocationEntry> DataRelocations;
 
+  // Relocations for fixing up references in the debug sections.
+  std::vector<WasmRelocationEntry> DebugRelocations;
+
   // Index values to use for fixing up call_indirect type indices.
   // Maps function symbols to the index of the type of the function
   DenseMap<const MCSymbolWasm *, uint32_t> TypeIndices;
@@ -227,6 +230,7 @@
   void reset() override {
     CodeRelocations.clear();
     DataRelocations.clear();
+    DebugRelocations.clear();
     TypeIndices.clear();
     SymbolIndices.clear();
     WasmIndices.clear();
@@ -273,11 +277,13 @@
   void writeDataSection();
   void writeCodeRelocSection();
   void writeDataRelocSection();
+  void writeDebugRelocSection(const MCAsmLayout &Layout);
   void writeLinkingMetaDataSection(
       ArrayRef<wasm::WasmSymbolInfo> SymbolInfos,
       ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
       const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats);
 
+  void writeDebugSections(const MCAssembler &Asm, const MCAsmLayout &Layout);
   uint32_t getProvisionalValue(const WasmRelocationEntry &RelEntry);
   void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations,
                         uint64_t ContentsOffset);
@@ -362,9 +368,11 @@
   if (FixupSection.getSectionName().startswith(".init_array"))
     return;
 
-  // TODO(sbc): Add support for debug sections.
-  if (FixupSection.getKind().isMetadata())
-    return;
+  // TODO: Add support for non-debug metadata sections?
+  if (FixupSection.getKind().isMetadata()) {
+    if (!FixupSection.getSectionName().startswith(".debug_"))
+      return;
+  }
 
   if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
     assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
@@ -439,7 +447,9 @@
   // TODO(sbc): Add support for relocations against unnamed temporaries such
   // as those generated by llvm's `blockaddress`.
   // See: test/MC/WebAssembly/blockaddress.ll
-  if (SymA->getName().empty() && Type != wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB)
+  if (SymA->getName().empty() &&
+      (Type != wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB &&
+       (!FixupSection.getKind().isMetadata() || Type != wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32)))
     report_fatal_error("relocations against un-named temporaries are not yet "
                        "supported by wasm");
 
@@ -447,6 +457,8 @@
     DataRelocations.push_back(Rec);
   else if (FixupSection.getKind().isText())
     CodeRelocations.push_back(Rec);
+  else if (FixupSection.getKind().isMetadata())
+    DebugRelocations.push_back(Rec);
   else
     llvm_unreachable("unexpected section type");
 }
@@ -861,6 +873,60 @@
   endSection(Section);
 }
 
+void WasmObjectWriter::writeDebugRelocSection(const MCAsmLayout &Layout) {
+  if (DebugRelocations.empty())
+    return;
+
+  SectionBookkeeping Section;
+  startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.DEBUG");
+
+  encodeULEB128(DebugRelocations.size(), getStream());
+
+  // Write all entries in following format:
+  //   type ULEB128 = R_WEBASSEMBLY_MEMORY_ADDR_I32
+  //   fixup section code (+maybe custom section name)
+  //   fixup offset
+  //   target section code (+maybe name)
+  //   target
+  //   addend
+  // TODO: It is possible to have running table of section codes to compress
+  // custom name, e.g. have an index in the table instead of code + name, and
+  // if it's out of table bounds append table with following code + name.
+  raw_pwrite_stream &Stream = getStream();
+  for (const WasmRelocationEntry& RelEntry : DebugRelocations) {
+
+    auto WriteSectionCode = [&] (const MCSectionWasm& Section) {
+      if (Section.isWasmData()) {
+	encodeULEB128(wasm::WASM_SEC_DATA, Stream);
+      } else if (Section.getKind().isText()) {
+	encodeULEB128(wasm::WASM_SEC_CODE, Stream);
+      } else if (Section.getSectionName().startswith(".debug_")) {
+	encodeULEB128(wasm::WASM_SEC_CUSTOM, Stream);
+        writeString(Section.getSectionName().str());
+      } else
+	llvm_unreachable("unexpected section type/kind");
+    };
+
+    assert(RelEntry.Type == wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32);
+
+    uint64_t Offset = RelEntry.Offset + RelEntry.FixupSection->getSectionOffset();
+
+    auto& TargetSection = static_cast<MCSectionWasm&>(RelEntry.Symbol->getSection());
+    uint32_t TargetOffset = Layout.getSymbolOffset(*RelEntry.Symbol) +
+                            TargetSection.getSectionOffset();
+
+    write8(RelEntry.Type);
+    WriteSectionCode(*RelEntry.FixupSection);
+    encodeULEB128(Offset, Stream);
+    WriteSectionCode(TargetSection);
+    encodeULEB128(TargetOffset, Stream);
+    if (RelEntry.hasAddend())
+      encodeSLEB128(RelEntry.Addend, Stream);
+  }
+
+  endSection(Section);
+}
+
 void WasmObjectWriter::writeLinkingMetaDataSection(
     ArrayRef<wasm::WasmSymbolInfo> SymbolInfos,
     ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs,
@@ -936,6 +1002,26 @@
   endSection(Section);
 }
 
+void WasmObjectWriter::writeDebugSections(const MCAssembler &Asm, const MCAsmLayout &Layout) {
+  for (MCSection &Sec : Asm) {
+    auto &DebugSection = static_cast<MCSectionWasm &>(Sec);
+    StringRef SectionName = DebugSection.getSectionName();
+    if (!SectionName.startswith(".debug_")) {
+      continue;
+    }
+
+    SectionBookkeeping Section;
+    startSection(Section, wasm::WASM_SEC_CUSTOM, SectionName.str().c_str());
+
+    DebugSection.setSectionOffset(getStream().tell() - Section.ContentsOffset);
+    Asm.writeSectionData(&DebugSection, Layout);
+
+    endSection(Section);
+
+    //writeDebugSection(Asm, DebugSection, Layout);
+  }
+}
+
 uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm& Symbol) {
   assert(Symbol.isFunction());
   assert(TypeIndices.count(&Symbol));
@@ -1307,12 +1393,13 @@
   writeElemSection(TableElems);
   writeCodeSection(Asm, Layout, Functions);
   writeDataSection();
+  writeDebugSections(Asm, Layout);
   writeLinkingMetaDataSection(SymbolInfos, InitFuncs, Comdats);
   writeCodeRelocSection();
   writeDataRelocSection();
+  writeDebugRelocSection(Layout);
 
   // TODO: Translate the .comment section to the output.
-  // TODO: Translate debug sections to the output.
 }
 
 std::unique_ptr<MCObjectWriter>