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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 #define DEBUG_TYPE "asm-printer"
     15 #include "llvm/CodeGen/AsmPrinter.h"
     16 #include "llvm/ADT/Twine.h"
     17 #include "llvm/IR/DataLayout.h"
     18 #include "llvm/MC/MCAsmInfo.h"
     19 #include "llvm/MC/MCSection.h"
     20 #include "llvm/MC/MCStreamer.h"
     21 #include "llvm/MC/MCSymbol.h"
     22 #include "llvm/MC/MachineLocation.h"
     23 #include "llvm/Support/Dwarf.h"
     24 #include "llvm/Support/ErrorHandling.h"
     25 #include "llvm/Target/TargetFrameLowering.h"
     26 #include "llvm/Target/TargetLoweringObjectFile.h"
     27 #include "llvm/Target/TargetMachine.h"
     28 #include "llvm/Target/TargetRegisterInfo.h"
     29 using namespace llvm;
     30 
     31 //===----------------------------------------------------------------------===//
     32 // Dwarf Emission Helper Routines
     33 //===----------------------------------------------------------------------===//
     34 
     35 /// EmitSLEB128 - emit the specified signed leb128 value.
     36 void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
     37   if (isVerbose() && Desc)
     38     OutStreamer.AddComment(Desc);
     39 
     40   OutStreamer.EmitSLEB128IntValue(Value);
     41 }
     42 
     43 /// EmitULEB128 - emit the specified signed leb128 value.
     44 void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc,
     45                              unsigned PadTo) const {
     46   if (isVerbose() && Desc)
     47     OutStreamer.AddComment(Desc);
     48 
     49   OutStreamer.EmitULEB128IntValue(Value, PadTo);
     50 }
     51 
     52 /// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
     53 void AsmPrinter::EmitCFAByte(unsigned Val) const {
     54   if (isVerbose()) {
     55     if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset+64)
     56       OutStreamer.AddComment("DW_CFA_offset + Reg (" +
     57                              Twine(Val-dwarf::DW_CFA_offset) + ")");
     58     else
     59       OutStreamer.AddComment(dwarf::CallFrameString(Val));
     60   }
     61   OutStreamer.EmitIntValue(Val, 1);
     62 }
     63 
     64 static const char *DecodeDWARFEncoding(unsigned Encoding) {
     65   switch (Encoding) {
     66   case dwarf::DW_EH_PE_absptr: return "absptr";
     67   case dwarf::DW_EH_PE_omit:   return "omit";
     68   case dwarf::DW_EH_PE_pcrel:  return "pcrel";
     69   case dwarf::DW_EH_PE_udata4: return "udata4";
     70   case dwarf::DW_EH_PE_udata8: return "udata8";
     71   case dwarf::DW_EH_PE_sdata4: return "sdata4";
     72   case dwarf::DW_EH_PE_sdata8: return "sdata8";
     73   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4: return "pcrel udata4";
     74   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4: return "pcrel sdata4";
     75   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8: return "pcrel udata8";
     76   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8: return "pcrel sdata8";
     77   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
     78     return "indirect pcrel udata4";
     79   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
     80     return "indirect pcrel sdata4";
     81   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
     82     return "indirect pcrel udata8";
     83   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
     84     return "indirect pcrel sdata8";
     85   }
     86 
     87   return "<unknown encoding>";
     88 }
     89 
     90 
     91 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
     92 /// encoding.  If verbose assembly output is enabled, we output comments
     93 /// describing the encoding.  Desc is an optional string saying what the
     94 /// encoding is specifying (e.g. "LSDA").
     95 void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
     96   if (isVerbose()) {
     97     if (Desc != 0)
     98       OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
     99                              Twine(DecodeDWARFEncoding(Val)));
    100     else
    101       OutStreamer.AddComment(Twine("Encoding = ") +
    102                              DecodeDWARFEncoding(Val));
    103   }
    104 
    105   OutStreamer.EmitIntValue(Val, 1);
    106 }
    107 
    108 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
    109 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
    110   if (Encoding == dwarf::DW_EH_PE_omit)
    111     return 0;
    112 
    113   switch (Encoding & 0x07) {
    114   default: llvm_unreachable("Invalid encoded value.");
    115   case dwarf::DW_EH_PE_absptr: return TM.getDataLayout()->getPointerSize();
    116   case dwarf::DW_EH_PE_udata2: return 2;
    117   case dwarf::DW_EH_PE_udata4: return 4;
    118   case dwarf::DW_EH_PE_udata8: return 8;
    119   }
    120 }
    121 
    122 void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
    123                                     unsigned Encoding) const {
    124   if (GV) {
    125     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
    126 
    127     const MCExpr *Exp =
    128       TLOF.getTTypeGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
    129     OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
    130   } else
    131     OutStreamer.EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
    132 }
    133 
    134 /// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
    135 /// section.  This can be done with a special directive if the target supports
    136 /// it (e.g. cygwin) or by emitting it as an offset from a label at the start
    137 /// of the section.
    138 ///
    139 /// SectionLabel is a temporary label emitted at the start of the section that
    140 /// Label lives in.
    141 void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
    142                                    const MCSymbol *SectionLabel) const {
    143   // On COFF targets, we have to emit the special .secrel32 directive.
    144   if (MAI->needsDwarfSectionOffsetDirective()) {
    145     OutStreamer.EmitCOFFSecRel32(Label);
    146     return;
    147   }
    148 
    149   // Get the section that we're referring to, based on SectionLabel.
    150   const MCSection &Section = SectionLabel->getSection();
    151 
    152   // If Label has already been emitted, verify that it is in the same section as
    153   // section label for sanity.
    154   assert((!Label->isInSection() || &Label->getSection() == &Section) &&
    155          "Section offset using wrong section base for label");
    156 
    157   // If the section in question will end up with an address of 0 anyway, we can
    158   // just emit an absolute reference to save a relocation.
    159   if (Section.isBaseAddressKnownZero()) {
    160     OutStreamer.EmitSymbolValue(Label, 4);
    161     return;
    162   }
    163 
    164   // Otherwise, emit it as a label difference from the start of the section.
    165   EmitLabelDifference(Label, SectionLabel, 4);
    166 }
    167 
    168 //===----------------------------------------------------------------------===//
    169 // Dwarf Lowering Routines
    170 //===----------------------------------------------------------------------===//
    171 
    172 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
    173   switch (Inst.getOperation()) {
    174   default:
    175     llvm_unreachable("Unexpected instruction");
    176   case MCCFIInstruction::OpDefCfaOffset:
    177     OutStreamer.EmitCFIDefCfaOffset(Inst.getOffset());
    178     break;
    179   case MCCFIInstruction::OpDefCfa:
    180     OutStreamer.EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
    181     break;
    182   case MCCFIInstruction::OpDefCfaRegister:
    183     OutStreamer.EmitCFIDefCfaRegister(Inst.getRegister());
    184     break;
    185   case MCCFIInstruction::OpOffset:
    186     OutStreamer.EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
    187     break;
    188   }
    189 }
    190