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      1 //===-- AsmPrinterDwarf.cpp - AsmPrinter Dwarf Support --------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements the Dwarf emissions parts of AsmPrinter.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "ByteStreamer.h"
     15 #include "DwarfDebug.h"
     16 #include "DwarfExpression.h"
     17 #include "llvm/ADT/Twine.h"
     18 #include "llvm/CodeGen/AsmPrinter.h"
     19 #include "llvm/CodeGen/DIE.h"
     20 #include "llvm/CodeGen/MachineFunction.h"
     21 #include "llvm/CodeGen/MachineModuleInfo.h"
     22 #include "llvm/IR/DataLayout.h"
     23 #include "llvm/MC/MCAsmInfo.h"
     24 #include "llvm/MC/MCRegisterInfo.h"
     25 #include "llvm/MC/MCSection.h"
     26 #include "llvm/MC/MCStreamer.h"
     27 #include "llvm/MC/MCSymbol.h"
     28 #include "llvm/MC/MachineLocation.h"
     29 #include "llvm/Support/Dwarf.h"
     30 #include "llvm/Support/ErrorHandling.h"
     31 #include "llvm/Target/TargetLoweringObjectFile.h"
     32 #include "llvm/Target/TargetMachine.h"
     33 #include "llvm/Target/TargetSubtargetInfo.h"
     34 using namespace llvm;
     35 
     36 #define DEBUG_TYPE "asm-printer"
     37 
     38 //===----------------------------------------------------------------------===//
     39 // Dwarf Emission Helper Routines
     40 //===----------------------------------------------------------------------===//
     41 
     42 /// EmitSLEB128 - emit the specified signed leb128 value.
     43 void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
     44   if (isVerbose() && Desc)
     45     OutStreamer.AddComment(Desc);
     46 
     47   OutStreamer.EmitSLEB128IntValue(Value);
     48 }
     49 
     50 /// EmitULEB128 - emit the specified signed leb128 value.
     51 void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc,
     52                              unsigned PadTo) const {
     53   if (isVerbose() && Desc)
     54     OutStreamer.AddComment(Desc);
     55 
     56   OutStreamer.EmitULEB128IntValue(Value, PadTo);
     57 }
     58 
     59 /// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
     60 void AsmPrinter::EmitCFAByte(unsigned Val) const {
     61   if (isVerbose()) {
     62     if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset + 64)
     63       OutStreamer.AddComment("DW_CFA_offset + Reg (" +
     64                              Twine(Val - dwarf::DW_CFA_offset) + ")");
     65     else
     66       OutStreamer.AddComment(dwarf::CallFrameString(Val));
     67   }
     68   OutStreamer.EmitIntValue(Val, 1);
     69 }
     70 
     71 static const char *DecodeDWARFEncoding(unsigned Encoding) {
     72   switch (Encoding) {
     73   case dwarf::DW_EH_PE_absptr:
     74     return "absptr";
     75   case dwarf::DW_EH_PE_omit:
     76     return "omit";
     77   case dwarf::DW_EH_PE_pcrel:
     78     return "pcrel";
     79   case dwarf::DW_EH_PE_udata4:
     80     return "udata4";
     81   case dwarf::DW_EH_PE_udata8:
     82     return "udata8";
     83   case dwarf::DW_EH_PE_sdata4:
     84     return "sdata4";
     85   case dwarf::DW_EH_PE_sdata8:
     86     return "sdata8";
     87   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
     88     return "pcrel udata4";
     89   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
     90     return "pcrel sdata4";
     91   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
     92     return "pcrel udata8";
     93   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
     94     return "pcrel sdata8";
     95   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
     96       :
     97     return "indirect pcrel udata4";
     98   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
     99       :
    100     return "indirect pcrel sdata4";
    101   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
    102       :
    103     return "indirect pcrel udata8";
    104   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
    105       :
    106     return "indirect pcrel 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 TM.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,
    148                                     unsigned Encoding) const {
    149   if (GV) {
    150     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
    151 
    152     const MCExpr *Exp =
    153         TLOF.getTTypeGlobalReference(GV, Encoding, *Mang, TM, MMI, OutStreamer);
    154     OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
    155   } else
    156     OutStreamer.EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
    157 }
    158 
    159 /// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
    160 /// section.  This can be done with a special directive if the target supports
    161 /// it (e.g. cygwin) or by emitting it as an offset from a label at the start
    162 /// of the section.
    163 ///
    164 /// SectionLabel is a temporary label emitted at the start of the section that
    165 /// Label lives in.
    166 void AsmPrinter::emitSectionOffset(const MCSymbol *Label) const {
    167   // On COFF targets, we have to emit the special .secrel32 directive.
    168   if (MAI->needsDwarfSectionOffsetDirective()) {
    169     OutStreamer.EmitCOFFSecRel32(Label);
    170     return;
    171   }
    172 
    173   // If the format uses relocations with dwarf, refer to the symbol directly.
    174   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
    175     OutStreamer.EmitSymbolValue(Label, 4);
    176     return;
    177   }
    178 
    179   // Otherwise, emit it as a label difference from the start of the section.
    180   EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
    181 }
    182 
    183 /// EmitDwarfRegOp - Emit dwarf register operation.
    184 void AsmPrinter::EmitDwarfRegOp(ByteStreamer &Streamer,
    185                                 const MachineLocation &MLoc) const {
    186   DebugLocDwarfExpression Expr(*MF->getSubtarget().getRegisterInfo(),
    187                                getDwarfDebug()->getDwarfVersion(), Streamer);
    188   const MCRegisterInfo *MRI = MMI->getContext().getRegisterInfo();
    189   int Reg = MRI->getDwarfRegNum(MLoc.getReg(), false);
    190   if (Reg < 0) {
    191     // We assume that pointers are always in an addressable register.
    192     if (MLoc.isIndirect())
    193       // FIXME: We have no reasonable way of handling errors in here. The
    194       // caller might be in the middle of a dwarf expression. We should
    195       // probably assert that Reg >= 0 once debug info generation is more
    196       // mature.
    197       return Expr.EmitOp(dwarf::DW_OP_nop,
    198                          "nop (could not find a dwarf register number)");
    199 
    200     // Attempt to find a valid super- or sub-register.
    201     if (!Expr.AddMachineRegPiece(MLoc.getReg()))
    202       Expr.EmitOp(dwarf::DW_OP_nop,
    203                   "nop (could not find a dwarf register number)");
    204     return;
    205   }
    206 
    207   if (MLoc.isIndirect())
    208     Expr.AddRegIndirect(Reg, MLoc.getOffset());
    209   else
    210     Expr.AddReg(Reg);
    211 }
    212 
    213 //===----------------------------------------------------------------------===//
    214 // Dwarf Lowering Routines
    215 //===----------------------------------------------------------------------===//
    216 
    217 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
    218   switch (Inst.getOperation()) {
    219   default:
    220     llvm_unreachable("Unexpected instruction");
    221   case MCCFIInstruction::OpDefCfaOffset:
    222     OutStreamer.EmitCFIDefCfaOffset(Inst.getOffset());
    223     break;
    224   case MCCFIInstruction::OpDefCfa:
    225     OutStreamer.EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
    226     break;
    227   case MCCFIInstruction::OpDefCfaRegister:
    228     OutStreamer.EmitCFIDefCfaRegister(Inst.getRegister());
    229     break;
    230   case MCCFIInstruction::OpOffset:
    231     OutStreamer.EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
    232     break;
    233   case MCCFIInstruction::OpRegister:
    234     OutStreamer.EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
    235     break;
    236   case MCCFIInstruction::OpWindowSave:
    237     OutStreamer.EmitCFIWindowSave();
    238     break;
    239   case MCCFIInstruction::OpSameValue:
    240     OutStreamer.EmitCFISameValue(Inst.getRegister());
    241     break;
    242   }
    243 }
    244 
    245 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
    246   // Get the abbreviation for this DIE.
    247   const DIEAbbrev &Abbrev = Die.getAbbrev();
    248 
    249   // Emit the code (index) for the abbreviation.
    250   if (isVerbose())
    251     OutStreamer.AddComment("Abbrev [" + Twine(Abbrev.getNumber()) +
    252                            "] 0x" + Twine::utohexstr(Die.getOffset()) +
    253                            ":0x" + Twine::utohexstr(Die.getSize()) + " " +
    254                            dwarf::TagString(Abbrev.getTag()));
    255   EmitULEB128(Abbrev.getNumber());
    256 
    257   const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
    258   const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();
    259 
    260   // Emit the DIE attribute values.
    261   for (unsigned i = 0, N = Values.size(); i < N; ++i) {
    262     dwarf::Attribute Attr = AbbrevData[i].getAttribute();
    263     dwarf::Form Form = AbbrevData[i].getForm();
    264     assert(Form && "Too many attributes for DIE (check abbreviation)");
    265 
    266     if (isVerbose()) {
    267       OutStreamer.AddComment(dwarf::AttributeString(Attr));
    268       if (Attr == dwarf::DW_AT_accessibility)
    269         OutStreamer.AddComment(dwarf::AccessibilityString(
    270             cast<DIEInteger>(Values[i])->getValue()));
    271     }
    272 
    273     // Emit an attribute using the defined form.
    274     Values[i]->EmitValue(this, Form);
    275   }
    276 
    277   // Emit the DIE children if any.
    278   if (Abbrev.hasChildren()) {
    279     for (auto &Child : Die.getChildren())
    280       emitDwarfDIE(*Child);
    281 
    282     OutStreamer.AddComment("End Of Children Mark");
    283     EmitInt8(0);
    284   }
    285 }
    286 
    287 void
    288 AsmPrinter::emitDwarfAbbrevs(const std::vector<DIEAbbrev *>& Abbrevs) const {
    289   // For each abbrevation.
    290   for (const DIEAbbrev *Abbrev : Abbrevs) {
    291     // Emit the abbrevations code (base 1 index.)
    292     EmitULEB128(Abbrev->getNumber(), "Abbreviation Code");
    293 
    294     // Emit the abbreviations data.
    295     Abbrev->Emit(this);
    296   }
    297 
    298   // Mark end of abbreviations.
    299   EmitULEB128(0, "EOM(3)");
    300 }
    301