diff --git a/include/llvm/MC/MCAssembler.h b/include/llvm/MC/MCAssembler.h
index a308030ff6b..e2ba91de2a7 100644
--- a/include/llvm/MC/MCAssembler.h
+++ b/include/llvm/MC/MCAssembler.h
@@ -113,8 +113,8 @@ public:
   typedef SmallVectorImpl<MCFixup>::const_iterator const_fixup_iterator;
   typedef SmallVectorImpl<MCFixup>::iterator fixup_iterator;
 
-  virtual SmallString<32> &getContents() = 0;
-  virtual const SmallString<32> &getContents() const = 0;
+  virtual SmallVectorImpl<char> &getContents() = 0;
+  virtual const SmallVectorImpl<char> &getContents() const = 0;
 
   virtual SmallVectorImpl<MCFixup> &getFixups() = 0;
   virtual const SmallVectorImpl<MCFixup> &getFixups() const = 0;
@@ -132,7 +132,7 @@ public:
 
 class MCDataFragment : public MCEncodedFragment {
   virtual void anchor();
-  SmallString<32> Contents;
+  SmallVector<char, 32> Contents;
 
   /// Fixups - The list of fixups in this fragment.
   SmallVector<MCFixup, 4> Fixups;
@@ -142,8 +142,8 @@ public:
     : MCEncodedFragment(FT_Data, SD) {
   }
 
-  SmallString<32> &getContents() { return Contents; }
-  const SmallString<32> &getContents() const { return Contents; }
+  virtual SmallVectorImpl<char> &getContents() { return Contents; }
+  virtual const SmallVectorImpl<char> &getContents() const { return Contents; }
 
   SmallVectorImpl<MCFixup> &getFixups() {
     return Fixups;
@@ -171,7 +171,7 @@ class MCInstFragment : public MCEncodedFragment {
   MCInst Inst;
 
   /// Contents - Binary data for the currently encoded instruction.
-  SmallString<32> Contents;
+  SmallVector<char, 8> Contents;
 
   /// Fixups - The list of fixups in this fragment.
   SmallVector<MCFixup, 1> Fixups;
@@ -181,8 +181,8 @@ public:
     : MCEncodedFragment(FT_Inst, SD), Inst(_Inst) {
   }
 
-  SmallString<32> &getContents() { return Contents; }
-  const SmallString<32> &getContents() const { return Contents; }
+  virtual SmallVectorImpl<char> &getContents() { return Contents; }
+  virtual const SmallVectorImpl<char> &getContents() const { return Contents; }
 
   unsigned getInstSize() const { return Contents.size(); }
   const MCInst &getInst() const { return Inst; }
diff --git a/include/llvm/MC/MCObjectWriter.h b/include/llvm/MC/MCObjectWriter.h
index 22f10ffa271..f77b7d853db 100644
--- a/include/llvm/MC/MCObjectWriter.h
+++ b/include/llvm/MC/MCObjectWriter.h
@@ -173,7 +173,13 @@ public:
     OS << StringRef(Zeros, N % 16);
   }
 
+  void WriteBytes(SmallVectorImpl<char> &ByteVec, unsigned ZeroFillSize = 0) {
+    WriteBytes(StringRef(ByteVec.data(), ByteVec.size()), ZeroFillSize);
+  }
+
   void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
+    // TODO: this version may need to go away once all fragment contents are
+    // converted to SmallVector<char, N>
     assert((ZeroFillSize == 0 || Str.size () <= ZeroFillSize) &&
       "data size greater than fill size, unexpected large write will occur");
     OS << Str;
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index b0623d35a9e..bfe17094628 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -203,7 +203,7 @@ class ELFObjectWriter : public MCObjectWriter {
     void String8(MCDataFragment &F, uint8_t Value) {
       char buf[1];
       buf[0] = Value;
-      F.getContents() += StringRef(buf, 1);
+      F.getContents().append(&buf[0], &buf[1]);
     }
 
     void String16(MCDataFragment &F, uint16_t Value) {
@@ -212,7 +212,7 @@ class ELFObjectWriter : public MCObjectWriter {
         StringLE16(buf, Value);
       else
         StringBE16(buf, Value);
-      F.getContents() += StringRef(buf, 2);
+      F.getContents().append(&buf[0], &buf[2]);
     }
 
     void String32(MCDataFragment &F, uint32_t Value) {
@@ -221,7 +221,7 @@ class ELFObjectWriter : public MCObjectWriter {
         StringLE32(buf, Value);
       else
         StringBE32(buf, Value);
-      F.getContents() += StringRef(buf, 4);
+      F.getContents().append(&buf[0], &buf[4]);
     }
 
     void String64(MCDataFragment &F, uint64_t Value) {
@@ -230,7 +230,7 @@ class ELFObjectWriter : public MCObjectWriter {
         StringLE64(buf, Value);
       else
         StringBE64(buf, Value);
-      F.getContents() += StringRef(buf, 8);
+      F.getContents().append(&buf[0], &buf[8]);
     }
 
     void WriteHeader(uint64_t SectionDataSize,
@@ -1186,7 +1186,7 @@ void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
   // The first entry of a string table holds a null character so skip
   // section 0.
   uint64_t Index = 1;
-  F->getContents() += '\x00';
+  F->getContents().push_back('\x00');
 
   for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
     const MCSectionELF &Section = *Sections[I];
@@ -1204,8 +1204,8 @@ void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
     SectionStringTableIndex[&Section] = Index;
 
     Index += Name.size() + 1;
-    F->getContents() += Name;
-    F->getContents() += '\x00';
+    F->getContents().append(Name.begin(), Name.end());
+    F->getContents().push_back('\x00');
   }
 }
 
@@ -1380,7 +1380,7 @@ void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
          ++i) {
       const MCFragment &F = *i;
       assert(F.getKind() == MCFragment::FT_Data);
-      WriteBytes(cast<MCDataFragment>(F).getContents().str());
+      WriteBytes(cast<MCDataFragment>(F).getContents());
     }
   } else {
     Asm.writeSectionData(&SD, Layout);
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index b2136e553e2..989d8be0af5 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -391,7 +391,7 @@ void MCAsmLayout::LayoutFragment(MCFragment *F) {
 ///        a MCEncodedFragment.
 static void writeFragmentContents(const MCFragment &F, MCObjectWriter *OW) {
   MCEncodedFragment &EF = cast<MCEncodedFragment>(F);
-  OW->WriteBytes(EF.getContents().str());
+  OW->WriteBytes(EF.getContents());
 }
 
 /// \brief Write the fragment \p F to the output file.