lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp

   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/CodeGen/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 using namespace llvm;
  29
  30 //===----------------------------------------------------------------------===//
  31 // Dwarf Emission Helper Routines
  32 //===----------------------------------------------------------------------===//
  33
  34 /// EmitSLEB128 - emit the specified signed leb128 value.
  35 void AsmPrinter::EmitSLEB128(int Value, const char *Desc) const {
  36   if (isVerbose() && Desc)
  37     OutStreamer.AddComment(Desc);
  38
  39   if (MAI->hasLEB128()) {
  40     OutStreamer.EmitSLEB128IntValue(Value);
  41     return;
  42   }
  43
  44   // If we don't have .sleb128, emit as .bytes.
  45   int Sign = Value >> (8 * sizeof(Value) - 1);
  46   bool IsMore;
  47
  48   do {
  49     unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
  50     Value >>= 7;
  51     IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
  52     if (IsMore) Byte |= 0x80;
  53     OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
  54   } while (IsMore);
  55 }
  56
  57 /// EmitULEB128 - emit the specified signed leb128 value.
  58 void AsmPrinter::EmitULEB128(unsigned Value, const char *Desc,
  59                              unsigned PadTo) const {
  60   if (isVerbose() && Desc)
  61     OutStreamer.AddComment(Desc);
  62
  63   // FIXME: Should we add a PadTo option to the streamer?
  64   if (MAI->hasLEB128() && PadTo == 0) {
  65     OutStreamer.EmitULEB128IntValue(Value);
  66     return;
  67   }
  68
  69   // If we don't have .uleb128 or we want to emit padding, emit as .bytes.
  70   do {
  71     unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
  72     Value >>= 7;
  73     if (Value || PadTo != 0) Byte |= 0x80;
  74     OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
  75   } while (Value);
  76
  77   if (PadTo) {
  78     if (PadTo > 1)
  79       OutStreamer.EmitFill(PadTo - 1, 0x80/*fillval*/, 0/*addrspace*/);
  80     OutStreamer.EmitFill(1, 0/*fillval*/, 0/*addrspace*/);
  81   }
  82 }
  83
  84 /// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
  85 void AsmPrinter::EmitCFAByte(unsigned Val) const {
  86   if (isVerbose()) {
  87     if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset+64)
  88       OutStreamer.AddComment("DW_CFA_offset + Reg (" +
  89                              Twine(Val-dwarf::DW_CFA_offset) + ")");
  90     else
  91       OutStreamer.AddComment(dwarf::CallFrameString(Val));
  92   }
  93   OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
  94 }
  95
  96 static const char *DecodeDWARFEncoding(unsigned Encoding) {
  97   switch (Encoding) {
  98   case dwarf::DW_EH_PE_absptr: return "absptr";
  99   case dwarf::DW_EH_PE_omit:   return "omit";
 100   case dwarf::DW_EH_PE_pcrel:  return "pcrel";
 101   case dwarf::DW_EH_PE_udata4: return "udata4";
 102   case dwarf::DW_EH_PE_udata8: return "udata8";
 103   case dwarf::DW_EH_PE_sdata4: return "sdata4";
 104   case dwarf::DW_EH_PE_sdata8: return "sdata8";
 105   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4: return "pcrel udata4";
 106   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4: return "pcrel sdata4";
 107   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8: return "pcrel udata8";
 108   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8: return "pcrel sdata8";
 109   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
 110     return "indirect pcrel udata4";
 111   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
 112     return "indirect pcrel sdata4";
 113   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
 114     return "indirect pcrel udata8";
 115   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
 116     return "indirect pcrel sdata8";
 117   }
 118
 119   return "<unknown encoding>";
 120 }
 121
 122
 123 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
 124 /// encoding.  If verbose assembly output is enabled, we output comments
 125 /// describing the encoding.  Desc is an optional string saying what the
 126 /// encoding is specifying (e.g. "LSDA").
 127 void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
 128   if (isVerbose()) {
 129     if (Desc != 0)
 130       OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
 131                              Twine(DecodeDWARFEncoding(Val)));
 132     else
 133       OutStreamer.AddComment(Twine("Encoding = ") +
 134                              DecodeDWARFEncoding(Val));
 135   }
 136
 137   OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
 138 }
 139
 140 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
 141 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
 142   if (Encoding == dwarf::DW_EH_PE_omit)
 143     return 0;
 144
 145   switch (Encoding & 0x07) {
 146   default: assert(0 && "Invalid encoded value.");
 147   case dwarf::DW_EH_PE_absptr: return TM.getTargetData()->getPointerSize();
 148   case dwarf::DW_EH_PE_udata2: return 2;
 149   case dwarf::DW_EH_PE_udata4: return 4;
 150   case dwarf::DW_EH_PE_udata8: return 8;
 151   }
 152 }
 153
 154 void AsmPrinter::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
 155   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
 156
 157   const MCExpr *Exp =
 158     TLOF.getExprForDwarfReference(Sym, Mang, MMI, Encoding, OutStreamer);
 159   OutStreamer.EmitAbsValue(Exp, GetSizeOfEncodedValue(Encoding));
 160 }
 161
 162 void AsmPrinter::EmitReference(const GlobalValue *GV, unsigned Encoding)const{
 163   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
 164
 165   const MCExpr *Exp =
 166     TLOF.getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
 167   OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
 168 }
 169
 170 /// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
 171 /// section.  This can be done with a special directive if the target supports
 172 /// it (e.g. cygwin) or by emitting it as an offset from a label at the start
 173 /// of the section.
 174 ///
 175 /// SectionLabel is a temporary label emitted at the start of the section that
 176 /// Label lives in.
 177 void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
 178                                    const MCSymbol *SectionLabel) const {
 179   // On COFF targets, we have to emit the special .secrel32 directive.
 180   if (const char *SecOffDir = MAI->getDwarfSectionOffsetDirective()) {
 181     // FIXME: MCize.
 182     OutStreamer.EmitRawText(SecOffDir + Twine(Label->getName()));
 183     return;
 184   }
 185
 186   // Get the section that we're referring to, based on SectionLabel.
 187   const MCSection &Section = SectionLabel->getSection();
 188
 189   // If Label has already been emitted, verify that it is in the same section as
 190   // section label for sanity.
 191   assert((!Label->isInSection() || &Label->getSection() == &Section) &&
 192          "Section offset using wrong section base for label");
 193
 194   // If the section in question will end up with an address of 0 anyway, we can
 195   // just emit an absolute reference to save a relocation.
 196   if (Section.isBaseAddressKnownZero()) {
 197     OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
 198     return;
 199   }
 200
 201   // Otherwise, emit it as a label difference from the start of the section.
 202   EmitLabelDifference(Label, SectionLabel, 4);
 203 }
 204
 205 //===----------------------------------------------------------------------===//
 206 // Dwarf Lowering Routines
 207 //===----------------------------------------------------------------------===//
 208
 209
 210 /// EmitFrameMoves - Emit frame instructions to describe the layout of the
 211 /// frame.
 212 void AsmPrinter::EmitFrameMoves(const std::vector<MachineMove> &Moves,
 213                                 MCSymbol *BaseLabel, bool isEH) const {
 214   const TargetRegisterInfo *RI = TM.getRegisterInfo();
 215
 216   int stackGrowth = TM.getTargetData()->getPointerSize();
 217   if (TM.getFrameLowering()->getStackGrowthDirection() !=
 218       TargetFrameLowering::StackGrowsUp)
 219     stackGrowth *= -1;
 220
 221   for (unsigned i = 0, N = Moves.size(); i < N; ++i) {
 222     const MachineMove &Move = Moves[i];
 223     MCSymbol *Label = Move.getLabel();
 224     // Throw out move if the label is invalid.
 225     if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
 226
 227     const MachineLocation &Dst = Move.getDestination();
 228     const MachineLocation &Src = Move.getSource();
 229
 230     // Advance row if new location.
 231     if (BaseLabel && Label) {
 232       MCSymbol *ThisSym = Label;
 233       if (ThisSym != BaseLabel) {
 234         EmitCFAByte(dwarf::DW_CFA_advance_loc4);
 235         EmitLabelDifference(ThisSym, BaseLabel, 4);
 236         BaseLabel = ThisSym;
 237       }
 238     }
 239
 240     // If advancing cfa.
 241     if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
 242       assert(!Src.isReg() && "Machine move not supported yet.");
 243
 244       if (Src.getReg() == MachineLocation::VirtualFP) {
 245         EmitCFAByte(dwarf::DW_CFA_def_cfa_offset);
 246       } else {
 247         EmitCFAByte(dwarf::DW_CFA_def_cfa);
 248         EmitULEB128(RI->getDwarfRegNum(Src.getReg(), isEH), "Register");
 249       }
 250
 251       EmitULEB128(-Src.getOffset(), "Offset");
 252       continue;
 253     }
 254
 255     if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
 256       assert(Dst.isReg() && "Machine move not supported yet.");
 257       EmitCFAByte(dwarf::DW_CFA_def_cfa_register);
 258       EmitULEB128(RI->getDwarfRegNum(Dst.getReg(), isEH), "Register");
 259       continue;
 260     }
 261
 262     unsigned Reg = RI->getDwarfRegNum(Src.getReg(), isEH);
 263     int Offset = Dst.getOffset() / stackGrowth;
 264
 265     if (Offset < 0) {
 266       EmitCFAByte(dwarf::DW_CFA_offset_extended_sf);
 267       EmitULEB128(Reg, "Reg");
 268       EmitSLEB128(Offset, "Offset");
 269     } else if (Reg < 64) {
 270       EmitCFAByte(dwarf::DW_CFA_offset + Reg);
 271       EmitULEB128(Offset, "Offset");
 272     } else {
 273       EmitCFAByte(dwarf::DW_CFA_offset_extended);
 274       EmitULEB128(Reg, "Reg");
 275       EmitULEB128(Offset, "Offset");
 276     }
 277   }
 278 }
 279
 280 /// EmitFrameMoves - Emit frame instructions to describe the layout of the
 281 /// frame.
 282 void AsmPrinter::EmitCFIFrameMoves(const std::vector<MachineMove> &Moves) const {
 283   const TargetRegisterInfo *RI = TM.getRegisterInfo();
 284
 285   for (unsigned i = 0, N = Moves.size(); i < N; ++i) {
 286     const MachineMove &Move = Moves[i];
 287     MCSymbol *Label = Move.getLabel();
 288     // Throw out move if the label is invalid.
 289     if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
 290
 291     const MachineLocation &Dst = Move.getDestination();
 292     const MachineLocation &Src = Move.getSource();
 293
 294     // If advancing cfa.
 295     if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
 296       assert(!Src.isReg() && "Machine move not supported yet.");
 297
 298       if (Src.getReg() == MachineLocation::VirtualFP) {
 299         OutStreamer.EmitCFIDefCfaOffset(-Src.getOffset());
 300       } else {
 301         assert("Machine move not supported yet");
 302         // Reg + Offset
 303       }
 304     } else if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
 305       assert(Dst.isReg() && "Machine move not supported yet.");
 306       OutStreamer.EmitCFIDefCfaRegister(RI->getDwarfRegNum(Dst.getReg(), true));
 307     } else {
 308       assert(!Dst.isReg() && "Machine move not supported yet.");
 309       OutStreamer.EmitCFIOffset(RI->getDwarfRegNum(Src.getReg(), true),
 310                                 Dst.getOffset());
 311     }
 312   }
 313 }