Index: llvm/trunk/include/llvm/MC/MCMachObjectWriter.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCMachObjectWriter.h
+++ llvm/trunk/include/llvm/MC/MCMachObjectWriter.h
@@ -265,7 +265,7 @@
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
-  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
+  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
 };
 
 /// Construct a new Mach-O writer instance.
Index: llvm/trunk/include/llvm/MC/MCObjectWriter.h
===================================================================
--- llvm/trunk/include/llvm/MC/MCObjectWriter.h
+++ llvm/trunk/include/llvm/MC/MCObjectWriter.h
@@ -109,12 +109,12 @@
                                                       bool InSet,
                                                       bool IsPCRel) const;
 
-  /// Write the object file.
+  /// Write the object file and returns the number of bytes written.
   ///
   /// This routine is called by the assembler after layout and relaxation is
   /// complete, fixups have been evaluated and applied, and relocations
   /// generated.
-  virtual void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) = 0;
+  virtual uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) = 0;
 
   /// @}
   /// \name Binary Output
Index: llvm/trunk/lib/MC/ELFObjectWriter.cpp
===================================================================
--- llvm/trunk/lib/MC/ELFObjectWriter.cpp
+++ llvm/trunk/lib/MC/ELFObjectWriter.cpp
@@ -247,7 +247,7 @@
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
-  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
+  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
   void writeSection(const SectionIndexMapTy &SectionIndexMap,
                     uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
                     const MCSectionELF &Section);
@@ -1205,8 +1205,10 @@
   }
 }
 
-void ELFObjectWriter::writeObject(MCAssembler &Asm,
-                                  const MCAsmLayout &Layout) {
+uint64_t ELFObjectWriter::writeObject(MCAssembler &Asm,
+                                      const MCAsmLayout &Layout) {
+  uint64_t StartOffset = W.OS.tell();
+
   MCContext &Ctx = Asm.getContext();
   MCSectionELF *StrtabSection =
       Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
@@ -1334,6 +1336,8 @@
   }
   Stream.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
                 NumSectionsOffset);
+
+  return W.OS.tell() - StartOffset;
 }
 
 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
Index: llvm/trunk/lib/MC/MCAssembler.cpp
===================================================================
--- llvm/trunk/lib/MC/MCAssembler.cpp
+++ llvm/trunk/lib/MC/MCAssembler.cpp
@@ -815,13 +815,8 @@
   MCAsmLayout Layout(*this);
   layout(Layout);
 
-  raw_ostream &OS = getWriter().getStream();
-  uint64_t StartOffset = OS.tell();
-
   // Write the object file.
-  getWriter().writeObject(*this, Layout);
-
-  stats::ObjectBytes += OS.tell() - StartOffset;
+  stats::ObjectBytes += getWriter().writeObject(*this, Layout);
 }
 
 bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
Index: llvm/trunk/lib/MC/MachObjectWriter.cpp
===================================================================
--- llvm/trunk/lib/MC/MachObjectWriter.cpp
+++ llvm/trunk/lib/MC/MachObjectWriter.cpp
@@ -735,8 +735,10 @@
   llvm_unreachable("Invalid mc version min type");
 }
 
-void MachObjectWriter::writeObject(MCAssembler &Asm,
-                                   const MCAsmLayout &Layout) {
+uint64_t MachObjectWriter::writeObject(MCAssembler &Asm,
+                                       const MCAsmLayout &Layout) {
+  uint64_t StartOffset = W.OS.tell();
+
   // Compute symbol table information and bind symbol indices.
   computeSymbolTable(Asm, LocalSymbolData, ExternalSymbolData,
                      UndefinedSymbolData);
@@ -1011,6 +1013,8 @@
     // Write the string table.
     StringTable.write(W.OS);
   }
+
+  return W.OS.tell() - StartOffset;
 }
 
 std::unique_ptr<MCObjectWriter>
Index: llvm/trunk/lib/MC/WasmObjectWriter.cpp
===================================================================
--- llvm/trunk/lib/MC/WasmObjectWriter.cpp
+++ llvm/trunk/lib/MC/WasmObjectWriter.cpp
@@ -285,7 +285,7 @@
   void executePostLayoutBinding(MCAssembler &Asm,
                                 const MCAsmLayout &Layout) override;
 
-  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
+  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
 
   void writeString(const StringRef Str) {
     encodeULEB128(Str.size(), W.OS);
@@ -1075,8 +1075,10 @@
   return true;
 }
 
-void WasmObjectWriter::writeObject(MCAssembler &Asm,
-                                   const MCAsmLayout &Layout) {
+uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
+                                       const MCAsmLayout &Layout) {
+  uint64_t StartOffset = W.OS.tell();
+
   LLVM_DEBUG(dbgs() << "WasmObjectWriter::writeObject\n");
   MCContext &Ctx = Asm.getContext();
 
@@ -1472,6 +1474,7 @@
   writeCustomRelocSections();
 
   // TODO: Translate the .comment section to the output.
+  return W.OS.tell() - StartOffset;
 }
 
 std::unique_ptr<MCObjectWriter>
Index: llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp
===================================================================
--- llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp
+++ llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp
@@ -206,7 +206,7 @@
   void assignSectionNumbers();
   void assignFileOffsets(MCAssembler &Asm, const MCAsmLayout &Layout);
 
-  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
+  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
 };
 
 } // end anonymous namespace
@@ -963,8 +963,10 @@
   Header.PointerToSymbolTable = Offset;
 }
 
-void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
-                                      const MCAsmLayout &Layout) {
+uint64_t WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
+                                          const MCAsmLayout &Layout) {
+  uint64_t StartOffset = W.OS.tell();
+
   if (Sections.size() > INT32_MAX)
     report_fatal_error(
         "PE COFF object files can't have more than 2147483647 sections");
@@ -1070,6 +1072,8 @@
 
   // Write a string table, which completes the entire COFF file.
   Strings.write(W.OS);
+
+  return W.OS.tell() - StartOffset;
 }
 
 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)