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/AsmPrinter.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
using namespace llvm;

DwarfException::DwarfException(AsmPrinter *A)
  : Asm(A), MMI(Asm->MMI), shouldEmitTable(false), shouldEmitMoves(false),
    shouldEmitTableModule(false), shouldEmitMovesModule(false) {}

DwarfException::~DwarfException() {}

/// 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 *PersonalityFn, unsigned Index) {
  // Size and sign of stack growth.
  int stackGrowth = Asm->getTargetData().getPointerSize();
  if (Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
      TargetFrameInfo::StackGrowsDown)
    stackGrowth *= -1;

  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();

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

  MCSymbol *EHFrameSym;
  if (TLOF.isFunctionEHFrameSymbolPrivate())
    EHFrameSym = Asm->GetTempSymbol("EH_frame", Index);
  else
    EHFrameSym = Asm->OutContext.GetOrCreateSymbol(Twine("EH_frame") + 
                                                   Twine(Index));
  Asm->OutStreamer.EmitLabel(EHFrameSym);
  
  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("section_eh_frame", Index));

  // Define base labels.
  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common", Index));

  // Define the eh frame length.
  Asm->OutStreamer.AddComment("Length of Common Information Entry");
  Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_frame_common_end", Index),
                           Asm->GetTempSymbol("eh_frame_common_begin", Index),
                           4);

  // EH frame header.
  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_begin",Index));
  Asm->OutStreamer.AddComment("CIE Identifier Tag");
  Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
  Asm->OutStreamer.AddComment("DW_CIE_VERSION");
  Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);

  // The personality presence indicates that language specific information will
  // show up in the eh frame.  Find out how we are supposed to lower the
  // personality function reference:

  unsigned LSDAEncoding = TLOF.getLSDAEncoding();
  unsigned FDEEncoding = TLOF.getFDEEncoding();
  unsigned PerEncoding = TLOF.getPersonalityEncoding();

  char Augmentation[6] = { 0 };
  unsigned AugmentationSize = 0;
  char *APtr = Augmentation + 1;

  if (PersonalityFn) {
    // There is a personality function.
    *APtr++ = 'P';
    AugmentationSize += 1 + Asm->GetSizeOfEncodedValue(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->OutStreamer.AddComment("CIE Augmentation");
  Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);

  // Round out reader.
  Asm->EmitULEB128(1, "CIE Code Alignment Factor");
  Asm->EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
  Asm->OutStreamer.AddComment("CIE Return Address Column");

  const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo();
  Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));

  if (Augmentation[0]) {
    Asm->EmitULEB128