TargetLoweringObjectFile.h

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//===-- llvm/Target/TargetLoweringObjectFile.h - Object Info ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements classes used to handle lowerings specific to common
// object file formats.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TARGET_TARGETLOWERINGOBJECTFILE_H
#define LLVM_TARGET_TARGETLOWERINGOBJECTFILE_H

#include "llvm/ADT/ArrayRef.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/SectionKind.h"

namespace llvm {
  class MachineModuleInfo;
  class Mangler;
  class MCContext;
  class MCExpr;
  class MCSection;
  class MCSymbol;
  class MCSymbolRefExpr;
  class MCStreamer;
  class ConstantExpr;
  class GlobalValue;
  class TargetMachine;

class TargetLoweringObjectFile : public MCObjectFileInfo {
  MCContext *Ctx;
  const DataLayout *DL;

  TargetLoweringObjectFile(
    const TargetLoweringObjectFile&) LLVM_DELETED_FUNCTION;
  void operator=(const TargetLoweringObjectFile&) LLVM_DELETED_FUNCTION;

public:
  MCContext &getContext() const { return *Ctx; }

  TargetLoweringObjectFile() : MCObjectFileInfo(), Ctx(nullptr), DL(nullptr) {}

  virtual ~TargetLoweringObjectFile();

  /// This method must be called before any actual lowering is done.  This
  /// specifies the current context for codegen, and gives the lowering
  /// implementations a chance to set up their default sections.
  virtual void Initialize(MCContext &ctx, const TargetMachine &TM);

  virtual void emitPersonalityValue(MCStreamer &Streamer,
                                    const TargetMachine &TM,
                                    const MCSymbol *Sym) const;

  /// Extract the dependent library name from a linker option string. Returns
  /// StringRef() if the option does not specify a library.
  virtual StringRef getDepLibFromLinkerOpt(StringRef LinkerOption) const {
    return StringRef();
  }

  /// Emit the module flags that the platform cares about.
  virtual void emitModuleFlags(MCStreamer &Streamer,
                               ArrayRef<Module::ModuleFlagEntry> Flags,
                               Mangler &Mang, const TargetMachine &TM) const {}

  /// Given a constant with the SectionKind, return a section that it should be
  /// placed in.
  virtual const MCSection *getSectionForConstant(SectionKind Kind,
                                                 const Constant *C) const;

  /// Classify the specified global variable into a set of target independent
  /// categories embodied in SectionKind.
  static SectionKind getKindForGlobal(const GlobalValue *GV,
                                      const TargetMachine &TM);

  /// This method computes the appropriate section to emit the specified global
  /// variable or function definition. This should not be passed external (or
  /// available externally) globals.
  const MCSection *SectionForGlobal(const GlobalValue *GV,
                                    SectionKind Kind, Mangler &Mang,
                                    const TargetMachine &TM) const;

  /// This method computes the appropriate section to emit the specified global
  /// variable or function definition. This should not be passed external (or
  /// available externally) globals.
  const MCSection *SectionForGlobal(const GlobalValue *GV,
                                    Mangler &Mang,
                                    const TargetMachine &TM) const {
    return SectionForGlobal(GV, getKindForGlobal(GV, TM), Mang, TM);
  }

  /// Targets should implement this method to assign a section to globals with
  /// an explicit section specfied. The implementation of this method can
  /// assume that GV->hasSection() is true.
  virtual const MCSection *
  getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
                           Mangler &Mang, const TargetMachine &TM) const = 0;

  /// Allow the target to completely override section assignment of a global.
  virtual const MCSection *getSpecialCasedSectionGlobals(const GlobalValue *GV,
                                                         SectionKind Kind,
                                                         Mangler &Mang) const {
    return nullptr;
  }

  /// Return an MCExpr to use for a reference to the specified global variable
  /// from exception handling information.
  virtual const MCExpr *
  getTTypeGlobalReference(const GlobalValue *GV, unsigned Encoding,
                          Mangler &Mang, const TargetMachine &TM,
                          MachineModuleInfo *MMI, MCStreamer &Streamer) const;

  /// Return the MCSymbol for a private symbol with global value name as its
  /// base, with the specified suffix.
  MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
                                         StringRef Suffix, Mangler &Mang,
                                         const TargetMachine &TM) const;

  // The symbol that gets passed to .cfi_personality.
  virtual MCSymbol *getCFIPersonalitySymbol(const GlobalValue *GV,
                                            Mangler &Mang,
                                            const TargetMachine &TM,
                                            MachineModuleInfo *MMI) const;

  const MCExpr *
  getTTypeReference(const MCSymbolRefExpr *Sym, unsigned Encoding,
                    MCStreamer &Streamer) const;

  virtual const MCSection *getStaticCtorSection(unsigned Priority,
                                                const MCSymbol *KeySym) const {
    return StaticCtorSection;
  }

  virtual const MCSection *getStaticDtorSection(unsigned Priority,
                                                const MCSymbol *KeySym) const {
    return StaticDtorSection;
  }

  /// \brief Create a symbol reference to describe the given TLS variable when
  /// emitting the address in debug info.
  virtual const MCExpr *getDebugThreadLocalSymbol(const MCSymbol *Sym) const;

  virtual const MCExpr *
  getExecutableRelativeSymbol(const ConstantExpr *CE, Mangler &Mang,
                              const TargetMachine &TM) const {
    return nullptr;
  }

  /// \brief True if the section is atomized using the symbols in it.
  /// This is false if the section is not atomized at all (most ELF sections) or
  /// if it is atomized based on its contents (MachO' __TEXT,__cstring for
  /// example).
  virtual bool isSectionAtomizableBySymbols(const MCSection &Section) const;

protected:
  virtual const MCSection *
  SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
                         Mangler &Mang, const TargetMachine &TM) const;
};

} // end namespace llvm

#endif