6 files changed, 38 insertions, 21 deletions
diff --git a/include/llvm/Analysis/CFGPrinter.h b/include/llvm/Analysis/CFGPrinter.h
index e6d2ed1a68..759afcaee1 100644
--- a/include/llvm/Analysis/CFGPrinter.h
+++ b/include/llvm/Analysis/CFGPrinter.h
@@ -36,9 +36,7 @@ struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {
     if (!Node->getName().empty())
       return Node->getName().str();
 
-    std::string Str;
-    raw_string_ostream OS(Str);
-
+    string_ostream OS;
     Node->printAsOperand(OS, false);
     return OS.str();
   }
@@ -46,8 +44,7 @@ struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {
   static std::string getCompleteNodeLabel(const BasicBlock *Node,
                                           const Function *) {
     enum { MaxColumns = 80 };
-    std::string Str;
-    raw_string_ostream OS(Str);
+    string_ostream OS;
 
     if (Node->getName().empty()) {
       Node->printAsOperand(OS, false);
@@ -109,8 +106,7 @@ struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {
 
       if (SuccNo == 0) return "def";
 
-      std::string Str;
-      raw_string_ostream OS(Str);
+      string_ostream OS;
       SwitchInst::ConstCaseIt Case =
           SwitchInst::ConstCaseIt::fromSuccessorIndex(SI, SuccNo);
       OS << Case.getCaseValue()->getValue();
diff --git a/include/llvm/ExecutionEngine/ObjectBuffer.h b/include/llvm/ExecutionEngine/ObjectBuffer.h
index 071a42b6b7..81dc88dcd0 100644
--- a/include/llvm/ExecutionEngine/ObjectBuffer.h
+++ b/include/llvm/ExecutionEngine/ObjectBuffer.h
@@ -58,23 +58,18 @@ protected:
 class ObjectBufferStream : public ObjectBuffer {
   void anchor() override;
 public:
-  ObjectBufferStream() : OS(SV) {}
+  ObjectBufferStream() {}
   virtual ~ObjectBufferStream() {}
 
   raw_ostream &getOStream() { return OS; }
   void flush()
   {
-    OS.flush();
-
     // Make the data accessible via the ObjectBuffer::Buffer
-    Buffer.reset(MemoryBuffer::getMemBuffer(StringRef(SV.data(), SV.size()),
-                                            "",
-                                            false));
+    Buffer.reset(MemoryBuffer::getMemBuffer(OS.str(), "", false));
   }
 
 protected:
-  SmallVector<char, 4096> SV; // Working buffer into which we JIT.
-  raw_svector_ostream     OS; // streaming wrapper
+  small_string_ostream<4096> OS; // Working buffer into which we JIT.
 };
 
 } // namespace llvm
diff --git a/include/llvm/Support/GraphWriter.h b/include/llvm/Support/GraphWriter.h
index 2f02aa7a1c..a6bd1afa16 100644
--- a/include/llvm/Support/GraphWriter.h
+++ b/include/llvm/Support/GraphWriter.h
@@ -184,8 +184,7 @@ public:
         O << "|" << DOT::EscapeString(NodeDesc);
     }
 
-    std::string edgeSourceLabels;
-    raw_string_ostream EdgeSourceLabels(edgeSourceLabels);
+    string_ostream EdgeSourceLabels;
     bool hasEdgeSourceLabels = getEdgeSourceLabels(EdgeSourceLabels, Node);
 
     if (hasEdgeSourceLabels) {
diff --git a/include/llvm/Support/YAMLTraits.h b/include/llvm/Support/YAMLTraits.h
index a23faf65bb..14ca2db932 100644
--- a/include/llvm/Support/YAMLTraits.h
+++ b/include/llvm/Support/YAMLTraits.h
@@ -612,8 +612,7 @@ template<typename T>
 typename std::enable_if<has_ScalarTraits<T>::value,void>::type
 yamlize(IO &io, T &Val, bool) {
   if ( io.outputting() ) {
-    std::string Storage;
-    llvm::raw_string_ostream Buffer(Storage);
+    llvm::string_ostream Buffer;
     ScalarTraits<T>::output(Val, io.getContext(), Buffer);
     StringRef Str = Buffer.str();
     io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
diff --git a/include/llvm/Support/raw_ostream.h b/include/llvm/Support/raw_ostream.h
index 34fbe082cd..77e473f2f6 100644
--- a/include/llvm/Support/raw_ostream.h
+++ b/include/llvm/Support/raw_ostream.h
@@ -15,6 +15,7 @@
 #define LLVM_SUPPORT_RAW_OSTREAM_H
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/DataTypes.h"
 
@@ -461,6 +462,14 @@ class raw_svector_ostream : public raw_ostream {
   /// current_pos - Return the current position within the stream, not
   /// counting the bytes currently in the buffer.
   uint64_t current_pos() const override;
+
+protected:
+  // This constructor is specified not to access \p O provided for storage as it
+  // may not yet be initialized at construction time.
+  explicit raw_svector_ostream(SmallVectorImpl<char> &O, std::nullptr_t)
+      : OS(O){};
+  void init();
+
 public:
   /// Construct a new raw_svector_ostream.
   ///
@@ -493,6 +502,25 @@ public:
   ~raw_null_ostream();
 };
 
+/// string_ostream - A raw_ostream that builds a string.  This is a
+/// raw_svector_ostream with storage.
+template <unsigned InternalLen>
+class small_string_ostream : public raw_svector_ostream {
+  SmallVector<char, InternalLen> Buffer;
+  // There's no need to flush explicitly.
+  using raw_svector_ostream::flush;
+
+public:
+  small_string_ostream() : raw_svector_ostream(Buffer, nullptr) { init(); }
+
+  void clear() {
+    flush();
+    Buffer.clear();
+  }
+};
+
+typedef small_string_ostream<128> string_ostream;
+
 } // end llvm namespace
 
 #endif
diff --git a/include/llvm/TableGen/StringToOffsetTable.h b/include/llvm/TableGen/StringToOffsetTable.h
index c924bd8ec5..01829a10b2 100644
--- a/include/llvm/TableGen/StringToOffsetTable.h
+++ b/include/llvm/TableGen/StringToOffsetTable.h
@@ -42,8 +42,8 @@ public:
 
   void EmitString(raw_ostream &O) {
     // Escape the string.
-    SmallString<256> Str;
-    raw_svector_ostream(Str).write_escaped(AggregateString);
+    small_string_ostream<256> Str;
+    Str.write_escaped(AggregateString);
     AggregateString = Str.str();
 
     O << "    \"";