Give the MCStreamer class hierarchy LLVM RTTI facilities for use with

isa<> and dyn_cast<>. In several places, code is already hacking around
the absence of this, and there seem to be several interfaces that might
be lifted and/or devirtualized using this.

This change was based on a discussion with Jim Grosbach about how best
to handle testing for specific MCStreamer subclasses. He said that this
was the correct end state, and everything else was too hacky so
I decided to just make it so.

No functionality should be changed here, this is just threading the kind
through all the constructors and setting up the classof overloads.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174113 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 41 insertions, 10 deletions

diff --git a/include/llvm/MC/MCELFStreamer.h b/include/llvm/MC/MCELFStreamer.h
index 60a360f896..0413613232 100644
--- a/include/llvm/MC/MCELFStreamer.h
+++ b/include/llvm/MC/MCELFStreamer.h
@@ -28,15 +28,20 @@ class MCSymbolData;
 class raw_ostream;
 
 class MCELFStreamer : public MCObjectStreamer {
-public:
-  MCELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+protected:
+  MCELFStreamer(StreamerKind Kind, MCContext &Context, MCAsmBackend &TAB,
                 raw_ostream &OS, MCCodeEmitter *Emitter)
-    : MCObjectStreamer(Context, TAB, OS, Emitter) {}
+      : MCObjectStreamer(Kind, Context, TAB, OS, Emitter) {}
+
+public:
+  MCELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+                MCCodeEmitter *Emitter)
+      : MCObjectStreamer(SK_ELFStreamer, Context, TAB, OS, Emitter) {}
 
-  MCELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                raw_ostream &OS, MCCodeEmitter *Emitter,
-                MCAssembler *Assembler)
-    : MCObjectStreamer(Context, TAB, OS, Emitter, Assembler) {}
+  MCELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+                MCCodeEmitter *Emitter, MCAssembler *Assembler)
+      : MCObjectStreamer(SK_ELFStreamer, Context, TAB, OS, Emitter,
+                         Assembler) {}
 
   virtual ~MCELFStreamer();
 
@@ -81,6 +86,10 @@ public:
   virtual void FinishImpl();
   /// @}
 
+  static bool classof(const MCStreamer *S) {
+    return S->getKind() == SK_ELFStreamer && S->getKind() == SK_ARMELFStreamer;
+  }
+
 private:
   virtual void EmitInstToFragment(const MCInst &Inst);
   virtual void EmitInstToData(const MCInst &Inst);
diff --git a/include/llvm/MC/MCObjectStreamer.h b/include/llvm/MC/MCObjectStreamer.h
index d73fe3abd0..f06c49ff08 100644
--- a/include/llvm/MC/MCObjectStreamer.h
+++ b/include/llvm/MC/MCObjectStreamer.h
@@ -38,9 +38,9 @@ class MCObjectStreamer : public MCStreamer {
   virtual void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame);
 
 protected:
-  MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
+  MCObjectStreamer(StreamerKind Kind, MCContext &Context, MCAsmBackend &TAB,
                    raw_ostream &_OS, MCCodeEmitter *_Emitter);
-  MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
+  MCObjectStreamer(StreamerKind Kind, MCContext &Context, MCAsmBackend &TAB,
                    raw_ostream &_OS, MCCodeEmitter *_Emitter,
                    MCAssembler *_Assembler);
   ~MCObjectStreamer();
@@ -107,6 +107,10 @@ public:
   virtual void FinishImpl();
 
   /// @}
+
+  static bool classof(const MCStreamer *S) {
+    return S->getKind() >= SK_ELFStreamer && S->getKind() <= SK_WinCOFFStreamer;
+  }
 };
 
 } // end namespace llvm
diff --git a/include/llvm/MC/MCStreamer.h b/include/llvm/MC/MCStreamer.h
index c6246e102f..36313258c7 100644
--- a/include/llvm/MC/MCStreamer.h
+++ b/include/llvm/MC/MCStreamer.h
@@ -46,6 +46,22 @@ namespace llvm {
   /// a .s file, and implementations that write out .o files of various formats.
   ///
   class MCStreamer {
+  public:
+    enum StreamerKind {
+      SK_AsmStreamer,
+      SK_NullStreamer,
+      SK_RecordStreamer,
+
+      // MCObjectStreamer subclasses.
+      SK_ELFStreamer,
+      SK_ARMELFStreamer,
+      SK_MachOStreamer,
+      SK_PureStreamer,
+      SK_WinCOFFStreamer
+    };
+
+  private:
+    const StreamerKind Kind;
     MCContext &Context;
 
     MCStreamer(const MCStreamer&) LLVM_DELETED_FUNCTION;
@@ -74,7 +90,7 @@ namespace llvm {
     bool AutoInitSections;
 
   protected:
-    MCStreamer(MCContext &Ctx);
+    MCStreamer(StreamerKind Kind, MCContext &Ctx);
 
     const MCExpr *BuildSymbolDiff(MCContext &Context, const MCSymbol *A,
                                   const MCSymbol *B);
@@ -93,6 +109,8 @@ namespace llvm {
   public:
     virtual ~MCStreamer();
 
+    StreamerKind getKind() const { return Kind; }
+
     /// State management
     ///
     virtual void reset();