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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/MC/MachineLocation.h"
     17 #include "llvm/MC/MCAsmInfo.h"
     18 #include "llvm/MC/MCSection.h"
     19 #include "llvm/MC/MCStreamer.h"
     20 #include "llvm/MC/MCSymbol.h"
     21 #include "llvm/Target/TargetData.h"
     22 #include "llvm/Target/TargetFrameLowering.h"
     23 #include "llvm/Target/TargetLoweringObjectFile.h"
     24 #include "llvm/Target/TargetMachine.h"
     25 #include "llvm/Target/TargetRegisterInfo.h"
     26 #include "llvm/ADT/Twine.h"
     27 #include "llvm/Support/Dwarf.h"
     28 #include "llvm/Support/ErrorHandling.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(int 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(unsigned Value, const char *Desc,
     45                              unsigned PadTo) const {
     46   if (isVerbose() && Desc)
     47     OutStreamer.AddComment(Desc);
     48 
     49   OutStreamer.EmitULEB128IntValue(Value, 0/*addrspace*/, 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, 0/*addrspace*/);
     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, 0/*addrspace*/);
    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.getTargetData()->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::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
    123   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
    124 
    125   const MCExpr *Exp =
    126     TLOF.getExprForDwarfReference(Sym, Encoding, OutStreamer);
    127   OutStreamer.EmitAbsValue(Exp, GetSizeOfEncodedValue(Encoding));
    128 }
    129 
    130 void AsmPrinter::EmitReference(const GlobalValue *GV, unsigned Encoding)const{
    131   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
    132 
    133   const MCExpr *Exp =
    134     TLOF.getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
    135   OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
    136 }
    137 
    138 /// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
    139 /// section.  This can be done with a special directive if the target supports
    140 /// it (e.g. cygwin) or by emitting it as an offset from a label at the start
    141 /// of the section.
    142 ///
    143 /// SectionLabel is a temporary label emitted at the start of the section that
    144 /// Label lives in.
    145 void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
    146                                    const MCSymbol *SectionLabel) const {
    147   // On COFF targets, we have to emit the special .secrel32 directive.
    148   if (MAI->getDwarfSectionOffsetDirective()) {
    149     OutStreamer.EmitCOFFSecRel32(Label);
    150     return;
    151   }
    152 
    153   // Get the section that we're referring to, based on SectionLabel.
    154   const MCSection &Section = SectionLabel->getSection();
    155 
    156   // If Label has already been emitted, verify that it is in the same section as
    157   // section label for sanity.
    158   assert((!Label->isInSection() || &Label->getSection() == &Section) &&
    159          "Section offset using wrong section base for label");
    160 
    161   // If the section in question will end up with an address of 0 anyway, we can
    162   // just emit an absolute reference to save a relocation.
    163   if (Section.isBaseAddressKnownZero()) {
    164     OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
    165     return;
    166   }
    167 
    168   // Otherwise, emit it as a label difference from the start of the section.
    169   EmitLabelDifference(Label, SectionLabel, 4);
    170 }
    171 
    172 //===----------------------------------------------------------------------===//
    173 // Dwarf Lowering Routines
    174 //===----------------------------------------------------------------------===//
    175 
    176 /// EmitCFIFrameMove - Emit a frame instruction.
    177 void AsmPrinter::EmitCFIFrameMove(const MachineMove &Move) const {
    178   const TargetRegisterInfo *RI = TM.getRegisterInfo();
    179 
    180   const MachineLocation &Dst = Move.getDestination();
    181   const MachineLocation &Src = Move.getSource();
    182 
    183   // If advancing cfa.
    184   if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
    185     if (Src.getReg() == MachineLocation::VirtualFP) {
    186       OutStreamer.EmitCFIDefCfaOffset(-Src.getOffset());
    187     } else {
    188       // Reg + Offset
    189       OutStreamer.EmitCFIDefCfa(RI->getDwarfRegNum(Src.getReg(), true),
    190                                 Src.getOffset());
    191     }
    192   } else if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
    193     assert(Dst.isReg() && "Machine move not supported yet.");
    194     OutStreamer.EmitCFIDefCfaRegister(RI->getDwarfRegNum(Dst.getReg(), true));
    195   } else {
    196     assert(!Dst.isReg() && "Machine move not supported yet.");
    197     OutStreamer.EmitCFIOffset(RI->getDwarfRegNum(Src.getReg(), true),
    198                               Dst.getOffset());
    199   }
    200 }
    201