lib/CodeGen/AsmPrinter/DwarfPrinter.cpp

//===--- lib/CodeGen/DwarfPrinter.cpp - Dwarf Printer ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Emit general DWARF directives.
//
//===----------------------------------------------------------------------===//

#include "DwarfPrinter.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/ADT/SmallString.h"
using namespace llvm;

DwarfPrinter::DwarfPrinter(AsmPrinter *A)
: Asm(A), MAI(A->MAI), TD(Asm->TM.getTargetData()),
  RI(Asm->TM.getRegisterInfo()), M(NULL), MF(NULL), MMI(NULL),
  SubprogramCount(0) {}

/// SizeOfEncodedValue - Return the size of the encoding in bytes.
unsigned DwarfPrinter::SizeOfEncodedValue(unsigned Encoding) const {
  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;
}

static const char *DecodeDWARFEncoding(unsigned Encoding) {
  switch (Encoding) {
  case dwarf::DW_EH_PE_absptr: return "absptr";
  case dwarf::DW_EH_PE_omit:   return "omit";
  case dwarf::DW_EH_PE_pcrel:  return "pcrel";
  case dwarf::DW_EH_PE_udata4: return "udata4";
  case dwarf::DW_EH_PE_udata8: return "udata8";
  case dwarf::DW_EH_PE_sdata4: return "sdata4";
  case dwarf::DW_EH_PE_sdata8: return "sdata8";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4: return "pcrel udata4";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4: return "pcrel sdata4";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8: return "pcrel udata8";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8: return "pcrel sdata8";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
    return "indirect pcrel udata4";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
    return "indirect pcrel sdata4";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
    return "indirect pcrel udata8";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
    return "indirect pcrel sdata8";
  }
  
  return "<unknown encoding>";
}

/// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
/// encoding.  If verbose assembly output is enabled, we output comments
/// describing the encoding.  Desc is an optional string saying what the
/// encoding is specifying (e.g. "LSDA").
void DwarfPrinter::EmitEncodingByte(unsigned Val, const char *Desc) {
  if (Asm->isVerbose()) {
    if (Desc != 0)
      Asm->OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
                                  Twine(DecodeDWARFEncoding(Val)));
    else
      Asm->OutStreamer.AddComment(Twine("Encoding = ") +
                                  DecodeDWARFEncoding(Val));
  }

  Asm->OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
}

/// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
void DwarfPrinter::EmitCFAByte(unsigned Val) {
  if (Asm->isVerbose()) {
    if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset+64)
      Asm->OutStreamer.AddComment("DW_CFA_offset + Reg (" + 
                                  Twine(Val-dwarf::DW_CFA_offset) + ")");
    else
      Asm->OutStreamer.AddComment(dwarf::CallFrameString(Val));
  }
  Asm->OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
}

void DwarfPrinter::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();

  const MCExpr *Exp = TLOF.getExprForDwarfReference(Sym, Asm->Mang,
                                                    Asm->MMI, Encoding,
                                                    Asm->OutStreamer);
  Asm->OutStreamer.EmitValue(Exp, SizeOfEncodedValue(Encoding), /*addrspace*/0);
}

void DwarfPrinter::EmitReference(const GlobalValue *GV, unsigned Encoding)const{
  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();

  const MCExpr *Exp =
    TLOF.getExprForDwarfGlobalReference(GV, Asm->Mang, Asm->MMI, Encoding,
                                        Asm->OutStreamer);
  Asm->OutStreamer.EmitValue(Exp, SizeOfEncodedValue(Encoding), /*addrspace*/0);
}

/// EmitDifference - Emit the difference between two labels.  If this assembler
/// supports .set, we emit a .set of a temporary and then use it in the .word.
void DwarfPrinter::EmitDifference(const MCSymbol *TagHi, const MCSymbol *TagLo,
                                  bool IsSmall) {
  unsigned Size = IsSmall ? 4 : TD->getPointerSize();
  Asm->EmitLabelDifference(TagHi, TagLo, Size);
}

void DwarfPrinter::EmitSectionOffset(const MCSymbol *Label,
                                     const MCSymbol *Section,
                                     bool IsSmall, bool isEH) {
  bool isAbsolute;
  if (isEH)
    isAbsolute = MAI->isAbsoluteEHSectionOffsets();
  else
    isAbsolute = MAI->isAbsoluteDebugSectionOffsets();

  if (!isAbsolute)
    return EmitDifference(Label, Section, IsSmall);
  
  // On COFF targets, we have to emit the weird .secrel32 directive.
  if (const char *SecOffDir = MAI->getDwarfSectionOffsetDirective()) {
    // FIXME: MCize.
    Asm->OutStreamer.EmitRawText(SecOffDir + Twine(Label->getName()));
  } else {
    unsigned Size = IsSmall ? 4 : TD->getPointerSize();
    Asm->OutStreamer.EmitSymbolValue(Label, Size, 0/*AddrSpace*/);
  }
}

/// EmitFrameMoves - Emit frame instructions to describe the layout of the
/// frame.
void DwarfPrinter::EmitFrameMoves(MCSymbol *BaseLabel,
                                  const std::vector<MachineMove> &Moves,
                                  bool isEH) {
  int stackGrowth = TD->getPointerSize();
  if (Asm->TM.getFrameInfo()->getStackGrowthDirection() !=
      TargetFrameInfo::StackGrowsUp)
    stackGrowth *= -1;
  
  for (unsigned i = 0, N = Moves.size(); i < N; ++i) {
    const MachineMove &Move = Moves[i];
    MCSymbol *Label = Move.getLabel();
    // Throw out move if the label is invalid.
    if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.

    const MachineLocation &Dst = Move.getDestination();
    const MachineLocation &Src = Move.getSource();

    // Advance row if new location.
    if (BaseLabel && Label) {
      MCSymbol *ThisSym = Label;
      if (ThisSym != BaseLabel) {
        EmitCFAByte(dwarf::DW_CFA_advance_loc4);
        EmitDifference(ThisSym, BaseLabel, true);
        BaseLabel = ThisSym;
      }
    }

    // If advancing cfa.
    if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
      if (!Src.isReg()) {
        if (Src.getReg() == MachineLocation::VirtualFP) {
          EmitCFAByte(dwarf::DW_CFA_def_cfa_offset);
        } else {
          EmitCFAByte(dwarf::DW_CFA_def_cfa);
          Asm->EmitULEB128(RI->getDwarfRegNum(Src.getReg(), isEH), "Register");
        }

        int Offset = -Src.getOffset();
        Asm->EmitULEB128(Offset, "Offset");
      } else {
        llvm_unreachable("Machine move not supported yet.");
      }
    } else if (Src.isReg() &&
               Src.getReg() == MachineLocation::VirtualFP) {
      if (Dst.isReg()) {
        EmitCFAByte(dwarf::DW_CFA_def_cfa_register);
        Asm->EmitULEB128(RI->getDwarfRegNum(Dst.getReg(), isEH), "Register");
      } else {
        llvm_unreachable("Machine move not supported yet.");
      }
    } else {
      unsigned Reg = RI->getDwarfRegNum(Src.getReg(), isEH);
      int Offset = Dst.getOffset() / stackGrowth;

      if (Offset < 0) {
        EmitCFAByte(dwarf::DW_CFA_offset_extended_sf);
        Asm->EmitULEB128(Reg, "Reg");
        Asm->EmitSLEB128(Offset, "Offset");
      } else if (Reg < 64) {
        EmitCFAByte(dwarf::DW_CFA_offset + Reg);
        Asm->EmitULEB128(Offset, "Offset");
      } else {
        EmitCFAByte(dwarf::DW_CFA_offset_extended);
        Asm->EmitULEB128(Reg, "Reg");
        Asm->EmitULEB128(Offset, "Offset");
      }
    }
  }
}