[llvm] r210747 - Avoid redundant allocations in the linker optimisation hint

[Alp Toker]

Author: alp
Date: Wed Jun 11 23:02:46 2014
New Revision: 210747

URL: http://llvm.org/viewvc/llvm-project?rev=210747&view=rev
Log:
Avoid redundant allocations in the linker optimisation hint

Modified:
    llvm/trunk/include/llvm/MC/MCLinkerOptimizationHint.h

Modified: llvm/trunk/include/llvm/MC/MCLinkerOptimizationHint.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCLinkerOptimizationHint.h?rev=210747&r1=210746&r2=210747&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCLinkerOptimizationHint.h (original)
+++ llvm/trunk/include/llvm/MC/MCLinkerOptimizationHint.h Wed Jun 11 23:02:46 2014
@@ -96,6 +96,19 @@ static inline int MCLOHIdToNbArgs(MCLOHT
   return -1;
 }
 
+namespace {
+class raw_counting_ostream : public raw_ostream {
+  uint64_t Count = 0;
+
+  void write_impl(const char *, size_t size) override { Count += size; }
+
+  uint64_t current_pos() const override { return Count; }
+
+public:
+  ~raw_counting_ostream() { flush(); }
+};
+}
+
 /// Store Linker Optimization Hint information (LOH).
 class MCLOHDirective {
   MCLOHType Kind;
@@ -132,8 +145,7 @@ public:
   /// the given @p Layout.
   uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
                        const MCAsmLayout &Layout) const {
-    std::string Buffer;
-    raw_string_ostream OutStream(Buffer);
+    raw_counting_ostream OutStream;
     Emit_impl(OutStream, ObjWriter, Layout);
     return OutStream.tell();
   }