MC: virtualise EmitWindowsUnwindTables

This makes EmitWindowsUnwindTables a virtual function and lowers the
implementation of the function to the X86WinCOFFStreamer.  This method is a
target specific operation.  This enables making the behaviour target dependent
by isolating it entirely to the target specific streamer.

llvm-svn: 214664

llvm/include/llvm/MC/MCStreamer.h

@@ -208,7 +208,7 @@ protected:
     return CurrentWinFrameInfo;
   }
 
-  void EmitWindowsUnwindTables();
+  virtual void EmitWindowsUnwindTables();
 
   virtual void EmitRawTextImpl(StringRef String);
 

llvm/lib/MC/MCStreamer.cpp

@@ -601,10 +601,6 @@ void MCStreamer::EmitRawText(const Twine &T) {
 }
 
 void MCStreamer::EmitWindowsUnwindTables() {
-  if (!getNumWinFrameInfos())
-    return;
-
-  MCWin64EHUnwindEmitter::Emit(*this);
 }
 
 void MCStreamer::Finish() {

llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp

@@ -20,6 +20,7 @@ public:
     : MCWinCOFFStreamer(C, AB, *CE, OS) { }
 
   void EmitWinEHHandlerData() override;
+  void EmitWindowsUnwindTables() override;
   void FinishImpl() override;
 };
 
@@ -31,6 +32,12 @@ void X86WinCOFFStreamer::EmitWinEHHandlerData() {
   MCWin64EHUnwindEmitter::EmitUnwindInfo(*this, getCurrentWinFrameInfo());
 }
 
+void X86WinCOFFStreamer::EmitWindowsUnwindTables() {
+  if (!getNumWinFrameInfos())
+    return;
+  MCWin64EHUnwindEmitter::Emit(*this);
+}
+
 void X86WinCOFFStreamer::FinishImpl() {
   EmitFrames(nullptr);
   EmitWindowsUnwindTables();