[mips] Add custom MCELFStreamer.

[matheusalmeida]

Summary

Add custom MCELFStreamer. This allows us to insert some hooks before emitting data into an actual object file. For example, we can capture the register usage for a translation unit by overriding the EmitInstruction method. The register usage information is needed to generate .reginfo and .Mips.options ELF sections.

No functional changes.

[jacksprat]

Great idea!

[dsanders]

LGTM

[matheusalmeida]

Closed by commit rL204917 (authored by @matheusalmeida).

llvm/trunk/lib/Target/Mips/MCTargetDesc/CMakeLists.txt

 add_llvm_library(LLVMMipsDesc
   MipsAsmBackend.cpp
   MipsELFObjectWriter.cpp
+  MipsELFStreamer.cpp
   MipsMCAsmInfo.cpp
   MipsMCCodeEmitter.cpp
   MipsMCExpr.cpp
   MipsMCTargetDesc.cpp
   MipsNaClELFStreamer.cpp
   MipsTargetStreamer.cpp
   )

llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.h

+//===-------- MipsELFStreamer.h - ELF Object Output -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is a custom MCELFStreamer which allows us to insert some hooks before
+// emitting data into an actual object file.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MIPSELFSTREAMER_H
+#define MIPSELFSTREAMER_H
+
+#include "llvm/MC/MCELFStreamer.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+class MCAsmBackend;
+class MCCodeEmitter;
+class MCContext;
+class MCSubtargetInfo;
+
+class MipsELFStreamer : public MCELFStreamer {
+  const MCSubtargetInfo &STI;
+
+public:
+  MipsELFStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
+                  MCCodeEmitter *Emitter, const MCSubtargetInfo &STI)
+      : MCELFStreamer(Context, MAB, OS, Emitter), STI(STI) {}
+
+  virtual ~MipsELFStreamer() {}
+};
+
+MCELFStreamer *createMipsELFStreamer(MCContext &Context, MCAsmBackend &MAB,
+                                     raw_ostream &OS, MCCodeEmitter *Emitter,
+                                     const MCSubtargetInfo &STI, bool RelaxAll,
+                                     bool NoExecStack);
+} // namespace llvm.
+#endif

llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.cpp

+//===-------- MipsELFStreamer.cpp - ELF Object Output ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MipsELFStreamer.h"
+
+namespace llvm {
+MCELFStreamer *createMipsELFStreamer(MCContext &Context, MCAsmBackend &MAB,
+                                     raw_ostream &OS, MCCodeEmitter *Emitter,
+                                     const MCSubtargetInfo &STI, bool RelaxAll,
+                                     bool NoExecStack) {
+  return new MipsELFStreamer(Context, MAB, OS, Emitter, STI);
+}
+}

llvm/trunk/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp

 //===-- MipsMCTargetDesc.cpp - Mips Target Descriptions -------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file provides Mips specific target descriptions.
 //
 //===----------------------------------------------------------------------===//
 
 #include "InstPrinter/MipsInstPrinter.h"
+#include "MipsELFStreamer.h"
 #include "MipsMCAsmInfo.h"
 #include "MipsMCNaCl.h"
 #include "MipsMCTargetDesc.h"
 #include "MipsTargetStreamer.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCCodeGenInfo.h"
 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCInstrInfo.h"

 
 static MCStreamer *createMCStreamer(const Target &T, StringRef TT,
                                     MCContext &Context, MCAsmBackend &MAB,
                                     raw_ostream &OS, MCCodeEmitter *Emitter,
                                     const MCSubtargetInfo &STI,
                                     bool RelaxAll, bool NoExecStack) {
   MCStreamer *S;
   if (!Triple(TT).isOSNaCl())
-    S = createELFStreamer(Context, MAB, OS, Emitter, RelaxAll, NoExecStack);
+    S = createMipsELFStreamer(Context, MAB, OS, Emitter, STI, RelaxAll,
+                              NoExecStack);
   else
     S = createMipsNaClELFStreamer(Context, MAB, OS, Emitter, RelaxAll,
                                   NoExecStack);
   new MipsTargetELFStreamer(*S, STI);
   return S;
 }
 
 static MCStreamer *