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/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/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/Timer.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
using namespace llvm;

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

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

/// CreateLabelDiff - Emit a label and subtract it from the expression we
/// already have.  This is equivalent to emitting "foo - .", but we have to emit
/// the label for "." directly.
const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
                                              const char *LabelName,
                                              unsigned Index) {
  SmallString<64> Name;
  raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
                            << LabelName << Asm->getFunctionNumber()
                            << "_" << Index;
  MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
  Asm->OutStreamer.EmitLabel(DotSym);

  return MCBinaryExpr::CreateSub(ExprRef,
                                 MCSymbolRefExpr::Create(DotSym,
                                                         Asm->OutContext),
                                 Asm->OutContext);
}

/// 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->TM.getFrameInfo()->getStackGrowthDirection() ==
    TargetFrameInfo::StackGrowsUp ?
    TD->getPointerSize() : -TD->getPointerSize();

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

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

  if (MAI->is_EHSymbolPrivate())
    O << MAI->getPrivateGlobalPrefix();
  O << "EH_frame" << Index << ":\n";
  
  Asm->OutStreamer.EmitLabel(getDWLabel("section_eh_frame", Index));

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

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

  // EH frame header.
  Asm->OutStreamer.EmitLabel(getDWLabel("eh_frame_common_begin", Index));
  if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("CIE Identifier Tag");
  Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
  if (Asm->VerboseAsm) 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 + SizeOfEncodedValue(PerEncoding);
  }

  if (UsesLSDA[Index]) {
    // An LSDA pointer is in the FDE augmentation.