Index: llvm/trunk/include/llvm/DebugInfo/CodeView/SymbolSerializer.h
===================================================================
--- llvm/trunk/include/llvm/DebugInfo/CodeView/SymbolSerializer.h
+++ llvm/trunk/include/llvm/DebugInfo/CodeView/SymbolSerializer.h
@@ -28,7 +28,10 @@
 
 class SymbolSerializer : public SymbolVisitorCallbacks {
   BumpPtrAllocator &Storage;
-  std::vector<uint8_t> RecordBuffer;
+  // Since this is a fixed size buffer, use a stack allocated buffer.  This
+  // yields measurable performance increase over the repeated heap allocations
+  // when serializing many independent records via writeOneSymbol.
+  std::array<uint8_t, MaxRecordLength> RecordBuffer;
   MutableBinaryByteStream Stream;
   BinaryStreamWriter Writer;
   SymbolRecordMapping Mapping;
Index: llvm/trunk/lib/DebugInfo/CodeView/SymbolSerializer.cpp
===================================================================
--- llvm/trunk/lib/DebugInfo/CodeView/SymbolSerializer.cpp
+++ llvm/trunk/lib/DebugInfo/CodeView/SymbolSerializer.cpp
@@ -21,8 +21,7 @@
 
 SymbolSerializer::SymbolSerializer(BumpPtrAllocator &Allocator,
                                    CodeViewContainer Container)
-    : Storage(Allocator), RecordBuffer(MaxRecordLength),
-      Stream(RecordBuffer, support::little), Writer(Stream),
+    : Storage(Allocator), Stream(RecordBuffer, support::little), Writer(Stream),
       Mapping(Writer, Container) {}
 
 Error SymbolSerializer::visitSymbolBegin(CVSymbol &Record) {