lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp

//===-- AsmPrinterDwarf.cpp - AsmPrinter Dwarf Support --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Dwarf emissions parts of AsmPrinter.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "asm-printer"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/Dwarf.h"
using namespace llvm;

/// EmitSLEB128 - emit the specified signed leb128 value.
void AsmPrinter::EmitSLEB128(int Value, const char *Desc) const {
  if (isVerbose() && Desc)
    OutStreamer.AddComment(Desc);
    
  if (MAI->hasLEB128()) {
    // FIXME: MCize.
    OutStreamer.EmitRawText("\t.sleb128\t" + Twine(Value));
    return;
  }

  // If we don't have .sleb128, emit as .bytes.
  int Sign = Value >> (8 * sizeof(Value) - 1);
  bool IsMore;
  
  do {
    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
    Value >>= 7;
    IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
    if (IsMore) Byte |= 0x80;
    OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
  } while (IsMore);
}

/// EmitULEB128 - emit the specified signed leb128 value.
void AsmPrinter::EmitULEB128(unsigned Value, const char *Desc,
                             unsigned PadTo) const {
  if (isVerbose() && Desc)
    OutStreamer.AddComment(Desc);
 
  if (MAI->hasLEB128() && PadTo == 0) {
    // FIXME: MCize.
    OutStreamer.EmitRawText("\t.uleb128\t" + Twine(Value));
    return;
  }
  
  // If we don't have .uleb128 or we want to emit padding, emit as .bytes.
  do {
    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
    Value >>= 7;
    if (Value || PadTo != 0) Byte |= 0x80;
    OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
  } while (Value);

  if (PadTo) {
    if (PadTo > 1)
      OutStreamer.EmitFill(PadTo - 1, 0x80/*fillval*/, 0/*addrspace*/);
    OutStreamer.EmitFill(1, 0/*fillval*/, 0/*addrspace*/);
  }
}

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

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 AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) {
  if (isVerbose()) {
    if (Desc != 0)
      OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
                             Twine(DecodeDWARFEncoding(Val)));
    else
      OutStreamer.AddComment(Twine("Encoding = ") +
                             DecodeDWARFEncoding(Val));
  }
  
  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
}