llvm/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.
//
//===----------------------------------------------------------------------===//

#include "ByteStreamer.h"
#include "DwarfExpression.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/ADT/Twine.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MachineLocation.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;

#define DEBUG_TYPE "asm-printer"

/// DwarfExpression implementation for .debug_loc entries.
class DebugLocDwarfExpression : public DwarfExpression {
  ByteStreamer &BS;

public:
  DebugLocDwarfExpression(TargetMachine &TM, ByteStreamer &BS)
      : DwarfExpression(TM), BS(BS) {}

  void EmitOp(uint8_t Op, const char *Comment) override;
  void EmitSigned(int Value) override;
  void EmitUnsigned(unsigned Value) override;
  unsigned getFrameRegister() override { llvm_unreachable("not available"); };
};

void DebugLocDwarfExpression::EmitOp(uint8_t Op, const char *Comment) {
  BS.EmitInt8(
      Op, Comment ? Twine(Comment) + " " + dwarf::OperationEncodingString(Op)
                  : dwarf::OperationEncodingString(Op));
}
void DebugLocDwarfExpression::EmitSigned(int Value) {
  BS.EmitSLEB128(Value, Twine(Value));
}
void DebugLocDwarfExpression::EmitUnsigned(unsigned Value) {
  BS.EmitULEB128(Value, Twine(Value));
}

//===----------------------------------------------------------------------===//
// Dwarf Emission Helper Routines
//===----------------------------------------------------------------------===//

/// EmitSLEB128 - emit the specified signed leb128 value.
void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
  if (isVerbose() && Desc)
    OutStreamer.AddComment(Desc);

  OutStreamer.EmitSLEB128IntValue(Value);
}

/// EmitULEB128 - emit the specified signed leb128 value.
void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc,
                             unsigned PadTo) const {
  if (isVerbose() && Desc)
    OutStreamer.AddComment(Desc);

  OutStreamer.EmitULEB128IntValue(Value, PadTo);
}

/// 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);
}

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) const {
  if (isVerbose()) {
    if (Desc)
      OutStreamer.AddComment(Twine(Desc) + " Encoding = " +
                             Twine(DecodeDWARFEncoding(Val)));
    else
      OutStreamer.AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
  }

  OutStreamer.EmitIntValue(Val, 1);
}

/// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
  if (Encoding == dwarf::DW_EH_PE_omit)
    return 0;

  switch (Encoding & 0x07) {
  default:
    llvm_unreachable("Invalid encoded value.");
  case dwarf::DW_EH_PE_absptr:
    return TM.getSubtargetImpl()->getDataLayout()->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;
  }
}

void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
                                    unsigned Encoding) const {
  if (GV) {
    const TargetLoweringObjectFile &TLOF = getObjFileLowering();

    const MCExpr *Exp =
        TLOF.getTTypeGlobalReference(GV, Encoding, *Mang, TM, MMI, OutStreamer);
    OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
  } else
    OutStreamer.EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
}

/// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
/// section.  This can be done with a special directive if the target supports
/// it (e.g. cygwin) or by emitting it as an offset from a label at the start
/// of the section.
///
/// SectionLabel is a temporary label emitted at the start of the section that
/// Label lives in.
void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
                                   const MCSymbol *SectionLabel) const {
  // On COFF targets, we have to emit the special .secrel32 directive.
  if (MAI->needsDwarfSectionOffsetDirective()) {
    OutStreamer.EmitCOFFSecRel32(Label);
    return;
  }

  // Get the section that we're referring to, based on SectionLabel.
  const MCSection &Section = SectionLabel->getSection();

  // If Label has already been emitted, verify that it is in the same section as
  // section label for sanity.
  assert((!Label->isInSection() || &Label->getSection() == &Section) &&
         "Section offset using wrong section base for label");

  // If the section in question will end up with an address of 0 anyway, we can
  // just emit an absolute reference to save a relocation.
  if (Section.isBaseAddressKnownZero()) {
    OutStreamer.EmitSymbolValue(Label, 4);
    return;
  }

  // Otherwise, emit it as a label difference from the start of the section.
  EmitLabelDifference(Label, SectionLabel, 4);
}

// Some targets do not provide a DWARF register number for every
// register.  This function attempts to emit a DWARF register by
// emitting a piece of a super-register or by piecing together
// multiple subregisters that alias the register.
void AsmPrinter::EmitDwarfRegOpPiece(ByteStreamer &Streamer,
                                     const MachineLocation &MLoc,
                                     unsigned PieceSizeInBits,
                                     unsigned PieceOffsetInBits) const {
  assert(MLoc.isReg() && "MLoc must be a register");
  DebugLocDwarfExpression Expr(TM, Streamer);
  Expr.AddMachineRegPiece(MLoc.getReg(), PieceSizeInBits, PieceOffsetInBits);
}

void AsmPrinter::EmitDwarfOpPiece(ByteStreamer &Streamer,
                                  unsigned PieceSizeInBits,
                                  unsigned PieceOffsetInBits) const {
  DebugLocDwarfExpression Expr(TM, Streamer);
  Expr.AddOpPiece(PieceSizeInBits, PieceOffsetInBits);
}

/// EmitDwarfRegOp - Emit dwarf register operation.
void AsmPrinter::EmitDwarfRegOp(ByteStreamer &Streamer,
                                const MachineLocation &MLoc,
                                bool Indirect) const {
  DebugLocDwarfExpression Expr(TM, Streamer);
  const TargetRegisterInfo *TRI = TM.getSubtargetImpl()->getRegisterInfo();
  int Reg = TRI->getDwarfRegNum(MLoc.getReg(), false);
  if (Reg < 0) {
    // We assume that pointers are always in an addressable register.
    if (Indirect || MLoc.isIndirect())
      // FIXME: We have no reasonable way of handling errors in here. The
      // caller might be in the middle of a dwarf expression. We should
      // probably assert that Reg >= 0 once debug info generation is more
      // mature.
      return Expr.EmitOp(dwarf::DW_OP_nop,
                         "nop (could not find a dwarf register number)");

    // Attempt to find a valid super- or sub-register.
    return Expr.AddMachineRegPiece(MLoc.getReg());
  }

  if (MLoc.isIndirect())
    Expr.AddRegIndirect(Reg, MLoc.getOffset(), Indirect);
  else if (Indirect)
    Expr.AddRegIndirect(Reg, 0, false);
  else
    Expr.AddReg(Reg);
}

//===----------------------------------------------------------------------===//
// Dwarf Lowering Routines
//===----------------------------------------------------------------------===//

void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
  switch (Inst.getOperation()) {
  default:
    llvm_unreachable("Unexpected instruction");
  case MCCFIInstruction::OpDefCfaOffset:
    OutStreamer.EmitCFIDefCfaOffset(Inst.getOffset());
    break;
  case MCCFIInstruction::OpDefCfa:
    OutStreamer.EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
    break;
  case MCCFIInstruction::OpDefCfaRegister:
    OutStreamer.EmitCFIDefCfaRegister(Inst.getRegister());
    break;
  case MCCFIInstruction::OpOffset:
    OutStreamer.EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
    break;
  case MCCFIInstruction::OpRegister:
    OutStreamer.EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
    break;
  case MCCFIInstruction::OpWindowSave:
    OutStreamer.EmitCFIWindowSave();
    break;
  case MCCFIInstruction::OpSameValue:
    OutStreamer.EmitCFISameValue(Inst.getRegister());
    break;
  }
}