path: root/lib/CodeGen/AsmPrinter/DwarfException.cpp

//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing dwarf exception info into asm files.
//
//===----------------------------------------------------------------------===//

#include "DwarfException.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
using namespace llvm;

static TimerGroup &getDwarfTimerGroup() {
  static TimerGroup DwarfTimerGroup("Dwarf Exception");
  return DwarfTimerGroup;
}

DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
                               const MCAsmInfo *T)
  : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
    shouldEmitTableModule(false), shouldEmitMovesModule(false),
    ExceptionTimer(0) {
  if (TimePassesIsEnabled)
    ExceptionTimer = new Timer("Dwarf Exception Writer",
                               getDwarfTimerGroup());
}

DwarfException::~DwarfException() {
  delete ExceptionTimer;
}

/// SizeOfEncodedValue - Return the size of the encoding in bytes.
unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
  if (Encoding == dwarf::DW_EH_PE_omit)
    return 0;

  switch (Encoding & 0x07) {
  case dwarf::DW_EH_PE_absptr:
    return TD->getPointerSize();
  case dwarf::DW_EH_PE_udata2:
    return 2;
  case dwarf::DW_EH_PE_udata4:
    return 4;
  case dwarf::DW_EH_PE_udata8:
    return 8;
  }

  llvm_unreachable("Invalid encoded value.");
  return 0;
}

/// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
/// is shared among many Frame Description Entries.  There is at least one CIE
/// in every non-empty .debug_frame section.
void DwarfException::EmitCIE(const Function *Personality, unsigned Index) {
  // Size and sign of stack growth.
  int stackGrowth =
    Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
    TargetFrameInfo::StackGrowsUp ?
    TD->getPointerSize() : -TD->getPointerSize();

  // Begin eh frame section.
  Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());

  if (MAI->is_EHSymbolPrivate())
    O << MAI->getPrivateGlobalPrefix();

  O << "EH_frame" << Index << ":\n";
  EmitLabel("section_eh_frame", Index);

  // Define base labels.
  EmitLabel("eh_frame_common", Index);

  // Define the eh frame length.
  EmitDifference("eh_frame_common_end", Index,
                 "eh_frame_common_begin", Index, true);
  Asm->EOL("Length of Common Information Entry");

  // EH frame header.
  EmitLabel("eh_frame_common_begin", Index);
  Asm->EmitInt32((int)0);
  Asm->EOL("CIE Identifier Tag");
  Asm->EmitInt8(dwarf::DW_CIE_VERSION);
  Asm->EOL("CIE Version");

  // The personality presence indicates that language specific information will
  // show up in the eh frame.

  // FIXME: Don't hardcode these encodings.
  unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
  if (Personality && MAI->getNeedsIndirectEncoding())
    PerEncoding |= dwarf::DW_EH_PE_indirect;
  unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
  unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;

  char Augmentation[5] = { 0 };
  unsigned AugmentationSize = 0;
  char *APtr = Augmentation + 1;

  if (Personality) {
    // There is a personality function.
    *APtr++ = 'P';
    AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
  }

  if (UsesLSDA[Index]) {
    // An LSDA pointer is in the FDE augmentation.
    *APtr++ = 'L';
    ++AugmentationSize;
  }

  if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
    // A non-default pointer encoding for the FDE.
    *APtr++ = 'R';
    ++AugmentationSize;
  }

  if (APtr != Augmentation + 1)
    Augmentation[0] = 'z';

  Asm->EmitString(Augmentation);
  Asm->EOL("CIE Augmentation");

  // Round out reader.
  Asm->EmitULEB128Bytes(1);
  Asm->EOL("CIE Code Alignment Factor");
  Asm->EmitSLEB128Bytes(stackGrowth);
  Asm->EOL("CIE Data Alignment Factor");
  Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
  Asm->EOL("CIE Return Address Column"