AsmPrinterDwarf.cpp

//===-- AsmPrinterDwarf.cpp - AsmPrinter Dwarf Support --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the Dwarf emissions parts of AsmPrinter.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/DIE.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include <cstdint>
using namespace llvm;

#define DEBUG_TYPE "asm-printer"

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

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_uleb128:
    return "uleb128";
  case dwarf::DW_EH_PE_sleb128:
    return "sleb128";
  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";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_datarel |
      dwarf::DW_EH_PE_sdata4:
    return "indirect datarel sdata4";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_datarel |
      dwarf::DW_EH_PE_sdata8:
    return "indirect datarel 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 MAI->getCodePointerSize();
  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) {
  if (GV) {
    const TargetLoweringObjectFile &TLOF = getObjFileLowering();

    const MCExpr *Exp =
        TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
    OutStreamer->emitValue(Exp, GetSizeOfEncodedValue(Encoding));
  } else
    OutStreamer->emitIntValue(0, GetSizeOfEncodedValue(Encoding));
}

void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
                                          bool ForceOffset) const {
  if (!ForceOffset) {
    // On COFF targets, we have to emit the special .secrel32 directive.
    if (MAI->needsDwarfSectionOffsetDirective()) {
      assert(!isDwarf64() &&
             "emitting DWARF64 is not implemented for COFF targets");
      OutStreamer->emitCOFFSecRel32(Label, /*Offset=*/0);
      return;
    }

    // If the format uses relocations with dwarf, refer to the symbol directly.
    if (doesDwarfUseRelocationsAcrossSections()) {
      OutStreamer->emitSymbolValue(Label, getDwarfOffsetByteSize());
      return;
    }
  }

  // Otherwise, emit it as a label difference from the start of the section.
  emitLabelDifference(Label, Label->getSection().getBeginSymbol(),
                      getDwarfOffsetByteSize());
}

void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntry S) const {
  if (doesDwarfUseRelocationsAcrossSections()) {
    assert(S.Symbol && "No symbol available");
    emitDwarfSymbolReference(S.Symbol);
    return;
  }

  // Just emit the offset directly; no need for symbol math.
  OutStreamer->emitIntValue(S.Offset, getDwarfOffsetByteSize());
}

void AsmPrinter::emitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
  emitLabelPlusOffset(Label, Offset, getDwarfOffsetByteSize());
}

void AsmPrinter::emitDwarfLengthOrOffset(uint64_t Value) const {
  assert(isDwarf64() || Value <= UINT32_MAX);
  OutStreamer->emitIntValue(Value, getDwarfOffsetByteSize());
}

void AsmPrinter::emitDwarfUnitLength(uint64_t Length,
                                     const Twine &Comment) const {
  OutStreamer->emitDwarfUnitLength(Length, Comment);
}

MCSymbol *AsmPrinter::emitDwarfUnitLength(const Twine &Prefix,
                                          const Twine &Comment) const {
  return OutStreamer->emitDwarfUnitLength(Prefix, Comment);
}

void AsmPrinter::emitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
                                    unsigned Encoding) const {
  // The least significant 3 bits specify the width of the encoding
  if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
    emitLabelDifferenceAsULEB128(Hi, Lo);
  else
    emitLabelDifference(Hi, Lo, GetSizeOfEncodedValue(Encoding));
}

void AsmPrinter::emitCallSiteValue(uint64_t Value, unsigned Encoding) const {
  // The least significant 3 bits specify the width of the encoding
  if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
    emitULEB128(Value);
  else
    OutStreamer->emitIntValue(Value, GetSizeOfEncodedValue(Encoding));
}

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

void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
  SMLoc Loc = Inst.getLoc();
  switch (Inst.getOperation()) {
  default:
    llvm_unreachable("Unexpected instruction");
  case MCCFIInstruction::OpDefCfaOffset:
    OutStreamer->emitCFIDefCfaOffset(Inst.getOffset(), Loc);
    break;
  case MCCFIInstruction::OpAdjustCfaOffset:
    OutStreamer->emitCFIAdjustCfaOffset(Inst.getOffset(), Loc);
    break;
  case MCCFIInstruction::OpDefCfa:
    OutStreamer->emitCFIDefCfa(Inst.getRegister(), Inst.getOffset(), Loc);
    break;
  case MCCFIInstruction::OpDefCfaRegister:
    OutStreamer->emitCFIDefCfaRegister(Inst.getRegister(), Loc);
    break;
  case MCCFIInstruction::OpLLVMDefAspaceCfa:
    OutStreamer->emitCFILLVMDefAspaceCfa(Inst.getRegister(), Inst.getOffset(),
                                         Inst.getAddressSpace(), Loc);
    break;
  case MCCFIInstruction::OpOffset:
    OutStreamer->emitCFIOffset(Inst.getRegister(), Inst.getOffset(), Loc);
    break;
  case MCCFIInstruction::OpRegister:
    OutStreamer->emitCFIRegister(Inst.getRegister(), Inst.getRegister2(), Loc);
    break;
  case MCCFIInstruction::OpWindowSave:
    OutStreamer->emitCFIWindowSave(Loc);
    break;
  case MCCFIInstruction::OpNegateRAState:
    OutStreamer->emitCFINegateRAState(Loc);
    break;
  case MCCFIInstruction::OpSameValue:
    OutStreamer->emitCFISameValue(Inst.getRegister(), Loc);
    break;
  case MCCFIInstruction::OpGnuArgsSize:
    OutStreamer->emitCFIGnuArgsSize(Inst.getOffset(), Loc);
    break;
  case MCCFIInstruction::OpEscape:
    OutStreamer->AddComment(Inst.getComment());
    OutStreamer->emitCFIEscape(Inst.getValues(), Loc);
    break;
  case MCCFIInstruction::OpRestore:
    OutStreamer->emitCFIRestore(Inst.getRegister(), Loc);
    break;
  case MCCFIInstruction::OpUndefined:
    OutStreamer->emitCFIUndefined(Inst.getRegister(), Loc);
    break;
  case MCCFIInstruction::OpRememberState:
    OutStreamer->emitCFIRememberState(Loc);
    break;
  case MCCFIInstruction::OpRestoreState:
    OutStreamer->emitCFIRestoreState(Loc);
    break;
  }
}

void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
  // Emit the code (index) for the abbreviation.
  if (isVerbose())
    OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
                            Twine::utohexstr(Die.getOffset()) + ":0x" +
                            Twine::utohexstr(Die.getSize()) + " " +
                            dwarf::TagString(Die.getTag()));
  emitULEB128(Die.getAbbrevNumber());

  // Emit the DIE attribute values.
  for (const auto &V : Die.values()) {
    dwarf::Attribute Attr = V.getAttribute();
    assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");

    if (isVerbose()) {
      OutStreamer->AddComment(dwarf::AttributeString(Attr));
      if (Attr == dwarf::DW_AT_accessibility)
        OutStreamer->AddComment(
            dwarf::AccessibilityString(V.getDIEInteger().getValue()));
    }

    // Emit an attribute using the defined form.
    V.emitValue(this);
  }

  // Emit the DIE children if any.
  if (Die.hasChildren()) {
    for (const auto &Child : Die.children())
      emitDwarfDIE(Child);

    OutStreamer->AddComment("End Of Children Mark");
    emitInt8(0);
  }
}

void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
  // Emit the abbreviations code (base 1 index.)
  emitULEB128(Abbrev.getNumber(), "Abbreviation Code");

  // Emit the abbreviations data.
  Abbrev.Emit(this);
}