llvm-mc: Add dummy MCStreamer implementation, (eventually) for use in profiling.

- Currently unused.

 - A few other random comment fixes lumped in.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78960 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCStreamer.h

@@ -221,6 +221,10 @@ namespace llvm {
     virtual void Finish() = 0;
   };
 
+  /// createNullStreamer - Create a dummy machine code streamer, which does
+  /// nothing. This is useful for timing the assembler front end.
+  MCStreamer *createNullStreamer(MCContext &Ctx);
+
   /// createAsmStreamer - Create a machine code streamer which will print out
   /// assembly for the native target, suitable for compiling with a native
   /// assembler.

include/llvm/Target/TargetRegistry.h

@@ -217,7 +217,7 @@ namespace llvm {
     /// the current host.  If no close target can be found, this returns null
     /// and sets the Error string to a reason.
     ///
-    /// Mainted for compatibility through 2.6.
+    /// Maintained for compatibility through 2.6.
     static const Target *getClosestTargetForJIT(std::string &Error);
 
     /// @}

lib/MC/MCAsmStreamer.cpp

@@ -155,6 +155,7 @@ void MCAsmStreamer::EmitLabel(MCSymbol *Symbol) {
 
 void MCAsmStreamer::EmitAssemblerFlag(AssemblerFlag Flag) {
   switch (Flag) {
+  default: assert(0 && "Invalid flag!");
   case SubsectionsViaSymbols: OS << ".subsections_via_symbols"; break;
   }
   OS << '\n';
@@ -215,10 +216,7 @@ void MCAsmStreamer::EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
 
 void MCAsmStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
                                  unsigned Size, unsigned Pow2Alignment) {
-  // Note: a .zerofill directive does not switch sections
-  // FIXME: Really we would like the segment and section names as well as the
-  // section type to be separate values instead of embedded in the name. Not
-  // all assemblers understand all this stuff though.
+  // Note: a .zerofill directive does not switch sections.
   OS << ".zerofill ";
   
   // This is a mach-o specific directive.
@@ -226,7 +224,6 @@ void MCAsmStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
   OS << '"' << MOSection->getSegmentName() << ","
      << MOSection->getSectionName() << '"';
   
-  
   if (Symbol != NULL) {
     OS << ',' << Symbol << ',' << Size;
     if (Pow2Alignment != 0)

lib/MC/MCNullStreamer.cpp

@@ -0,0 +1,72 @@
+//===- lib/MC/MCNullStreamer.cpp - Dummy Streamer Implementation ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCStreamer.h"
+
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+
+using namespace llvm;
+
+namespace {
+
+  class MCNullStreamer : public MCStreamer {
+  public:
+    MCNullStreamer(MCContext &Context) : MCStreamer(Context) {}
+
+    /// @name MCStreamer Interface
+    /// @{
+
+    virtual void SwitchSection(MCSection *Section) {}
+
+    virtual void EmitLabel(MCSymbol *Symbol) {}
+
+    virtual void EmitAssemblerFlag(AssemblerFlag Flag) {}
+
+    virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
+                                bool MakeAbsolute = false) {}
+
+    virtual void EmitSymbolAttribute(MCSymbol *Symbol, SymbolAttr Attribute) {}
+
+    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
+
+    virtual void EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) {}
+
+    virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
+                                  unsigned Pow2Alignment, bool IsLocal) {}
+
+    virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = NULL,
+                              unsigned Size = 0, unsigned Pow2Alignment = 0) {}
+
+    virtual void EmitBytes(const StringRef &Data) {}
+
+    virtual void EmitValue(const MCValue &Value, unsigned Size) {}
+
+    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
+                                      unsigned ValueSize = 1,
+                                      unsigned MaxBytesToEmit = 0) {}
+
+    virtual void EmitValueToOffset(const MCValue &Offset, 
+                                   unsigned char Value = 0) {}
+    
+    virtual void EmitInstruction(const MCInst &Inst) {}
+
+    virtual void Finish() {}
+    
+    /// @}
+  };
+
+}
+    
+MCStreamer *llvm::createNullStreamer(MCContext &Context) {
+  return new MCNullStreamer(Context);
+}