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      1 //===-- AsmPrinterDwarf.cpp - AsmPrinter Dwarf Support --------------------===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 //
      9 // This file implements the Dwarf emissions parts of AsmPrinter.
     10 //
     11 //===----------------------------------------------------------------------===//
     12 
     13 #include "ByteStreamer.h"
     14 #include "llvm/ADT/Twine.h"
     15 #include "llvm/BinaryFormat/Dwarf.h"
     16 #include "llvm/CodeGen/AsmPrinter.h"
     17 #include "llvm/CodeGen/DIE.h"
     18 #include "llvm/CodeGen/MachineFunction.h"
     19 #include "llvm/IR/DataLayout.h"
     20 #include "llvm/MC/MCAsmInfo.h"
     21 #include "llvm/MC/MCDwarf.h"
     22 #include "llvm/MC/MCRegisterInfo.h"
     23 #include "llvm/MC/MCSection.h"
     24 #include "llvm/MC/MCStreamer.h"
     25 #include "llvm/MC/MCSymbol.h"
     26 #include "llvm/MC/MachineLocation.h"
     27 #include "llvm/Support/ErrorHandling.h"
     28 #include "llvm/Target/TargetLoweringObjectFile.h"
     29 #include "llvm/Target/TargetMachine.h"
     30 #include <cstdint>
     31 using namespace llvm;
     32 
     33 #define DEBUG_TYPE "asm-printer"
     34 
     35 //===----------------------------------------------------------------------===//
     36 // Dwarf Emission Helper Routines
     37 //===----------------------------------------------------------------------===//
     38 
     39 /// EmitSLEB128 - emit the specified signed leb128 value.
     40 void AsmPrinter::emitSLEB128(int64_t Value, const char *Desc) const {
     41   if (isVerbose() && Desc)
     42     OutStreamer->AddComment(Desc);
     43 
     44   OutStreamer->emitSLEB128IntValue(Value);
     45 }
     46 
     47 void AsmPrinter::emitULEB128(uint64_t Value, const char *Desc,
     48                              unsigned PadTo) const {
     49   if (isVerbose() && Desc)
     50     OutStreamer->AddComment(Desc);
     51 
     52   OutStreamer->emitULEB128IntValue(Value, PadTo);
     53 }
     54 
     55 /// Emit something like ".uleb128 Hi-Lo".
     56 void AsmPrinter::emitLabelDifferenceAsULEB128(const MCSymbol *Hi,
     57                                               const MCSymbol *Lo) const {
     58   OutStreamer->emitAbsoluteSymbolDiffAsULEB128(Hi, Lo);
     59 }
     60 
     61 static const char *DecodeDWARFEncoding(unsigned Encoding) {
     62   switch (Encoding) {
     63   case dwarf::DW_EH_PE_absptr:
     64     return "absptr";
     65   case dwarf::DW_EH_PE_omit:
     66     return "omit";
     67   case dwarf::DW_EH_PE_pcrel:
     68     return "pcrel";
     69   case dwarf::DW_EH_PE_uleb128:
     70     return "uleb128";
     71   case dwarf::DW_EH_PE_sleb128:
     72     return "sleb128";
     73   case dwarf::DW_EH_PE_udata4:
     74     return "udata4";
     75   case dwarf::DW_EH_PE_udata8:
     76     return "udata8";
     77   case dwarf::DW_EH_PE_sdata4:
     78     return "sdata4";
     79   case dwarf::DW_EH_PE_sdata8:
     80     return "sdata8";
     81   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
     82     return "pcrel udata4";
     83   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
     84     return "pcrel sdata4";
     85   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
     86     return "pcrel udata8";
     87   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
     88     return "pcrel sdata8";
     89   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
     90       :
     91     return "indirect pcrel udata4";
     92   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
     93       :
     94     return "indirect pcrel sdata4";
     95   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
     96       :
     97     return "indirect pcrel udata8";
     98   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
     99       :
    100     return "indirect pcrel sdata8";
    101   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_datarel |
    102       dwarf::DW_EH_PE_sdata4:
    103     return "indirect datarel sdata4";
    104   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_datarel |
    105       dwarf::DW_EH_PE_sdata8:
    106     return "indirect datarel sdata8";
    107   }
    108 
    109   return "<unknown encoding>";
    110 }
    111 
    112 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
    113 /// encoding.  If verbose assembly output is enabled, we output comments
    114 /// describing the encoding.  Desc is an optional string saying what the
    115 /// encoding is specifying (e.g. "LSDA").
    116 void AsmPrinter::emitEncodingByte(unsigned Val, const char *Desc) const {
    117   if (isVerbose()) {
    118     if (Desc)
    119       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
    120                               Twine(DecodeDWARFEncoding(Val)));
    121     else
    122       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
    123   }
    124 
    125   OutStreamer->emitIntValue(Val, 1);
    126 }
    127 
    128 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
    129 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
    130   if (Encoding == dwarf::DW_EH_PE_omit)
    131     return 0;
    132 
    133   switch (Encoding & 0x07) {
    134   default:
    135     llvm_unreachable("Invalid encoded value.");
    136   case dwarf::DW_EH_PE_absptr:
    137     return MF->getDataLayout().getPointerSize();
    138   case dwarf::DW_EH_PE_udata2:
    139     return 2;
    140   case dwarf::DW_EH_PE_udata4:
    141     return 4;
    142   case dwarf::DW_EH_PE_udata8:
    143     return 8;
    144   }
    145 }
    146 
    147 void AsmPrinter::emitTTypeReference(const GlobalValue *GV, unsigned Encoding) {
    148   if (GV) {
    149     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
    150 
    151     const MCExpr *Exp =
    152         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
    153     OutStreamer->emitValue(Exp, GetSizeOfEncodedValue(Encoding));
    154   } else
    155     OutStreamer->emitIntValue(0, GetSizeOfEncodedValue(Encoding));
    156 }
    157 
    158 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
    159                                           bool ForceOffset) const {
    160   if (!ForceOffset) {
    161     // On COFF targets, we have to emit the special .secrel32 directive.
    162     if (MAI->needsDwarfSectionOffsetDirective()) {
    163       assert(!isDwarf64() &&
    164              "emitting DWARF64 is not implemented for COFF targets");
    165       OutStreamer->EmitCOFFSecRel32(Label, /*Offset=*/0);
    166       return;
    167     }
    168 
    169     // If the format uses relocations with dwarf, refer to the symbol directly.
    170     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
    171       OutStreamer->emitSymbolValue(Label, getDwarfOffsetByteSize());
    172       return;
    173     }
    174   }
    175 
    176   // Otherwise, emit it as a label difference from the start of the section.
    177   emitLabelDifference(Label, Label->getSection().getBeginSymbol(),
    178                       getDwarfOffsetByteSize());
    179 }
    180 
    181 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntry S) const {
    182   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
    183     assert(S.Symbol && "No symbol available");
    184     emitDwarfSymbolReference(S.Symbol);
    185     return;
    186   }
    187 
    188   // Just emit the offset directly; no need for symbol math.
    189   OutStreamer->emitIntValue(S.Offset, getDwarfOffsetByteSize());
    190 }
    191 
    192 void AsmPrinter::emitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
    193   emitLabelPlusOffset(Label, Offset, getDwarfOffsetByteSize());
    194 }
    195 
    196 void AsmPrinter::emitDwarfLengthOrOffset(uint64_t Value) const {
    197   assert(isDwarf64() || Value <= UINT32_MAX);
    198   OutStreamer->emitIntValue(Value, getDwarfOffsetByteSize());
    199 }
    200 
    201 void AsmPrinter::emitDwarfUnitLength(uint64_t Length,
    202                                      const Twine &Comment) const {
    203   OutStreamer->emitDwarfUnitLength(Length, Comment);
    204 }
    205 
    206 MCSymbol *AsmPrinter::emitDwarfUnitLength(const Twine &Prefix,
    207                                           const Twine &Comment) const {
    208   return OutStreamer->emitDwarfUnitLength(Prefix, Comment);
    209 }
    210 
    211 void AsmPrinter::emitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
    212                                     unsigned Encoding) const {
    213   // The least significant 3 bits specify the width of the encoding
    214   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
    215     emitLabelDifferenceAsULEB128(Hi, Lo);
    216   else
    217     emitLabelDifference(Hi, Lo, GetSizeOfEncodedValue(Encoding));
    218 }
    219 
    220 void AsmPrinter::emitCallSiteValue(uint64_t Value, unsigned Encoding) const {
    221   // The least significant 3 bits specify the width of the encoding
    222   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
    223     emitULEB128(Value);
    224   else
    225     OutStreamer->emitIntValue(Value, GetSizeOfEncodedValue(Encoding));
    226 }
    227 
    228 //===----------------------------------------------------------------------===//
    229 // Dwarf Lowering Routines
    230 //===----------------------------------------------------------------------===//
    231 
    232 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
    233   switch (Inst.getOperation()) {
    234   default:
    235     llvm_unreachable("Unexpected instruction");
    236   case MCCFIInstruction::OpDefCfaOffset:
    237     OutStreamer->emitCFIDefCfaOffset(Inst.getOffset());
    238     break;
    239   case MCCFIInstruction::OpAdjustCfaOffset:
    240     OutStreamer->emitCFIAdjustCfaOffset(Inst.getOffset());
    241     break;
    242   case MCCFIInstruction::OpDefCfa:
    243     OutStreamer->emitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
    244     break;
    245   case MCCFIInstruction::OpDefCfaRegister:
    246     OutStreamer->emitCFIDefCfaRegister(Inst.getRegister());
    247     break;
    248   case MCCFIInstruction::OpOffset:
    249     OutStreamer->emitCFIOffset(Inst.getRegister(), Inst.getOffset());
    250     break;
    251   case MCCFIInstruction::OpRegister:
    252     OutStreamer->emitCFIRegister(Inst.getRegister(), Inst.getRegister2());
    253     break;
    254   case MCCFIInstruction::OpWindowSave:
    255     OutStreamer->emitCFIWindowSave();
    256     break;
    257   case MCCFIInstruction::OpNegateRAState:
    258     OutStreamer->emitCFINegateRAState();
    259     break;
    260   case MCCFIInstruction::OpSameValue:
    261     OutStreamer->emitCFISameValue(Inst.getRegister());
    262     break;
    263   case MCCFIInstruction::OpGnuArgsSize:
    264     OutStreamer->emitCFIGnuArgsSize(Inst.getOffset());
    265     break;
    266   case MCCFIInstruction::OpEscape:
    267     OutStreamer->AddComment(Inst.getComment());
    268     OutStreamer->emitCFIEscape(Inst.getValues());
    269     break;
    270   case MCCFIInstruction::OpRestore:
    271     OutStreamer->emitCFIRestore(Inst.getRegister());
    272     break;
    273   case MCCFIInstruction::OpUndefined:
    274     OutStreamer->emitCFIUndefined(Inst.getRegister());
    275     break;
    276   }
    277 }
    278 
    279 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
    280   // Emit the code (index) for the abbreviation.
    281   if (isVerbose())
    282     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
    283                             Twine::utohexstr(Die.getOffset()) + ":0x" +
    284                             Twine::utohexstr(Die.getSize()) + " " +
    285                             dwarf::TagString(Die.getTag()));
    286   emitULEB128(Die.getAbbrevNumber());
    287 
    288   // Emit the DIE attribute values.
    289   for (const auto &V : Die.values()) {
    290     dwarf::Attribute Attr = V.getAttribute();
    291     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
    292 
    293     if (isVerbose()) {
    294       OutStreamer->AddComment(dwarf::AttributeString(Attr));
    295       if (Attr == dwarf::DW_AT_accessibility)
    296         OutStreamer->AddComment(
    297             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
    298     }
    299 
    300     // Emit an attribute using the defined form.
    301     V.emitValue(this);
    302   }
    303 
    304   // Emit the DIE children if any.
    305   if (Die.hasChildren()) {
    306     for (auto &Child : Die.children())
    307       emitDwarfDIE(Child);
    308 
    309     OutStreamer->AddComment("End Of Children Mark");
    310     emitInt8(0);
    311   }
    312 }
    313 
    314 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
    315   // Emit the abbreviations code (base 1 index.)
    316   emitULEB128(Abbrev.getNumber(), "Abbreviation Code");
    317 
    318   // Emit the abbreviations data.
    319   Abbrev.Emit(this);
    320 }
    321