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/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
using namespace llvm;

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");
}

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;
  }

  assert(0 && "Invalid encoded value.");
  return 0;
}

/// 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";
  
  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.  Find out how we are supposed to lower the
  // personality function reference:
  const MCExpr *PersonalityRef = 0;
  bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
  if (PersonalityFn) {
    // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
    
    // In non-static mode, ask the object file how to represent this reference.
    PersonalityRef =
      TLOF.getSymbolForDwarfGlobalReference(