MCWinEH.h

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//===- MCWinEH.h - Windows Unwinding Support --------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_MC_MCWINEH_H
#define LLVM_MC_MCWINEH_H
 
#include "llvm/ADT/MapVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/SMLoc.h"
#include <vector>
 
namespace llvm {
class MCSection;
class MCStreamer;
class MCSymbol;
 
namespace WinEH {
struct Instruction {
  const MCSymbol *Label;
  unsigned Offset;
  uint16_t Register;
  uint16_t Register2; // For 2-register ops (e.g. PUSH2)
  uint8_t Operation;
 
  Instruction(unsigned Op, MCSymbol *L, unsigned Reg, unsigned Off)
      : Label(L), Offset(Off), Register(Reg), Register2(0), Operation(Op) {}
 
  Instruction(unsigned Op, MCSymbol *L, unsigned Reg1, unsigned Reg2,
              unsigned Off)
      : Label(L), Offset(Off), Register(Reg1), Register2(Reg2), Operation(Op) {}
 
  bool operator==(const Instruction &I) const {
    // Check whether two instructions refer to the same operation
    // applied at a different spot (i.e. pointing at a different label).
    return Offset == I.Offset && Register == I.Register &&
           Register2 == I.Register2 && Operation == I.Operation;
  }
  bool operator!=(const Instruction &I) const { return !(*this == I); }
};
 
struct FrameInfo {
  const MCSymbol *Begin = nullptr;
  const MCSymbol *End = nullptr;
  const MCSymbol *FuncletOrFuncEnd = nullptr;
  const MCSymbol *ExceptionHandler = nullptr;
  const MCSymbol *Function = nullptr;
  SMLoc FunctionLoc;
  const MCSymbol *PrologEnd = nullptr;
  const MCSymbol *Symbol = nullptr;
  MCSection *TextSection = nullptr;
  uint32_t PackedInfo = 0;
  uint32_t PrologCodeBytes = 0;
 
  bool HandlesUnwind = false;
  bool HandlesExceptions = false;
  bool EmitAttempted = false;
  bool Fragment = false;
  constexpr static uint8_t DefaultVersion = 1;
  uint8_t Version = DefaultVersion;
 
  int LastFrameInst = -1;
  FrameInfo *ChainedParent = nullptr;
  std::vector<Instruction> Instructions;
  struct Epilog {
    std::vector<Instruction> Instructions;
    unsigned Condition;
    const MCSymbol *Start = nullptr;
    const MCSymbol *End = nullptr;
    const MCSymbol *UnwindV2Start = nullptr;
    SMLoc Loc;
  };
  MapVector<MCSymbol *, Epilog> EpilogMap;
 
  // For splitting unwind info of large functions
  struct Segment {
    int64_t Offset;
    int64_t Length;
    bool HasProlog;
    MCSymbol *Symbol = nullptr;
    // Map an Epilog's symbol to its offset within the function.
    MapVector<MCSymbol *, int64_t> Epilogs;
 
    Segment(int64_t Offset, int64_t Length, bool HasProlog = false)
        : Offset(Offset), Length(Length), HasProlog(HasProlog) {}
  };
 
  std::vector<Segment> Segments;
 
  FrameInfo() = default;
  FrameInfo(const MCSymbol *Function, const MCSymbol *BeginFuncEHLabel)
      : Begin(BeginFuncEHLabel), Function(Function) {}
  FrameInfo(const MCSymbol *Function, const MCSymbol *BeginFuncEHLabel,
            FrameInfo *ChainedParent)
      : Begin(BeginFuncEHLabel), Function(Function),
        Version(ChainedParent->Version), ChainedParent(ChainedParent) {}
 
  bool empty() const {
    if (!Instructions.empty())
      return false;
    for (const auto &E : EpilogMap)
      if (!E.second.Instructions.empty())
        return false;
    return true;
  }
};
 
class LLVM_ABI UnwindEmitter {
public:
  virtual ~UnwindEmitter();
 
  /// This emits the unwind info sections (.pdata and .xdata in PE/COFF).
  virtual void Emit(MCStreamer &Streamer) const = 0;
  virtual void EmitUnwindInfo(MCStreamer &Streamer, FrameInfo *FI,
                              bool HandlerData) const = 0;
};
} // namespace WinEH
} // namespace llvm
 
#endif