lib/CodeGen/AsmPrinter/DwarfException.cpp

   1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
   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 contains support for writing dwarf exception info into asm files.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "DwarfException.h"
  15 #include "llvm/Module.h"
  16 #include "llvm/CodeGen/MachineModuleInfo.h"
  17 #include "llvm/CodeGen/MachineFrameInfo.h"
  18 #include "llvm/CodeGen/MachineLocation.h"
  19 #include "llvm/Support/Dwarf.h"
  20 #include "llvm/Support/Timer.h"
  21 #include "llvm/Support/raw_ostream.h"
  22 #include "llvm/Target/TargetAsmInfo.h"
  23 #include "llvm/Target/TargetData.h"
  24 #include "llvm/Target/TargetFrameInfo.h"
  25 #include "llvm/Target/TargetLoweringObjectFile.h"
  26 #include "llvm/Target/TargetOptions.h"
  27 #include "llvm/Target/TargetRegisterInfo.h"
  28 #include "llvm/ADT/StringExtras.h"
  29 using namespace llvm;
  30
  31 static TimerGroup &getDwarfTimerGroup() {
  32   static TimerGroup DwarfTimerGroup("Dwarf Exception");
  33   return DwarfTimerGroup;
  34 }
  35
  36 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
  37                                const TargetAsmInfo *T)
  38   : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
  39     shouldEmitTableModule(false), shouldEmitMovesModule(false),
  40     ExceptionTimer(0) {
  41   if (TimePassesIsEnabled)
  42     ExceptionTimer = new Timer("Dwarf Exception Writer",
  43                                getDwarfTimerGroup());
  44 }
  45
  46 DwarfException::~DwarfException() {
  47   delete ExceptionTimer;
  48 }
  49
  50 void DwarfException::EmitCommonEHFrame(const Function *Personality,
  51                                        unsigned Index) {
  52   // Size and sign of stack growth.
  53   int stackGrowth =
  54     Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
  55     TargetFrameInfo::StackGrowsUp ?
  56     TD->getPointerSize() : -TD->getPointerSize();
  57
  58   // Begin eh frame section.
  59   Asm->SwitchToSection(Asm->getObjFileLowering().getEHFrameSection());
  60
  61   if (TAI->is_EHSymbolPrivate())
  62     O << TAI->getPrivateGlobalPrefix();
  63
  64   O << "EH_frame" << Index << ":\n";
  65   EmitLabel("section_eh_frame", Index);
  66
  67   // Define base labels.
  68   EmitLabel("eh_frame_common", Index);
  69
  70   // Define the eh frame length.
  71   EmitDifference("eh_frame_common_end", Index,
  72                  "eh_frame_common_begin", Index, true);
  73   Asm->EOL("Length of Common Information Entry");
  74
  75   // EH frame header.
  76   EmitLabel("eh_frame_common_begin", Index);
  77   Asm->EmitInt32((int)0);
  78   Asm->EOL("CIE Identifier Tag");
  79   Asm->EmitInt8(dwarf::DW_CIE_VERSION);
  80   Asm->EOL("CIE Version");
  81
  82   // The personality presence indicates that language specific information will
  83   // show up in the eh frame.
  84   Asm->EmitString(Personality ? "zPLR" : "zR");
  85   Asm->EOL("CIE Augmentation");
  86
  87   // Round out reader.
  88   Asm->EmitULEB128Bytes(1);
  89   Asm->EOL("CIE Code Alignment Factor");
  90   Asm->EmitSLEB128Bytes(stackGrowth);
  91   Asm->EOL("CIE Data Alignment Factor");
  92   Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
  93   Asm->EOL("CIE Return Address Column");
  94
  95   // If there is a personality, we need to indicate the functions location.
  96   if (Personality) {
  97     Asm->EmitULEB128Bytes(7);
  98     Asm->EOL("Augmentation Size");
  99
 100     if (TAI->getNeedsIndirectEncoding()) {
 101       Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4 |
 102                     dwarf::DW_EH_PE_indirect);
 103       Asm->EOL("Personality (pcrel sdata4 indirect)");
 104     } else {
 105       Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
 106       Asm->EOL("Personality (pcrel sdata4)");
 107     }
 108
 109     PrintRelDirective(true);
 110     O << TAI->getPersonalityPrefix();
 111     Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
 112     O << TAI->getPersonalitySuffix();
 113     if (strcmp(TAI->getPersonalitySuffix(), "+4@GOTPCREL"))
 114       O << "-" << TAI->getPCSymbol();
 115     Asm->EOL("Personality");
 116
 117     Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
 118     Asm->EOL("LSDA Encoding (pcrel sdata4)");
 119
 120     Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
 121     Asm->EOL("FDE Encoding (pcrel sdata4)");
 122   } else {
 123     Asm->EmitULEB128Bytes(1);
 124     Asm->EOL("Augmentation Size");
 125
 126     Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
 127     Asm->EOL("FDE Encoding (pcrel sdata4)");
 128   }
 129
 130   // Indicate locations of general callee saved registers in frame.
 131   std::vector<MachineMove> Moves;
 132   RI->getInitialFrameState(Moves);
 133   EmitFrameMoves(NULL, 0, Moves, true);
 134
 135   // On Darwin the linker honors the alignment of eh_frame, which means it must
 136   // be 8-byte on 64-bit targets to match what gcc does.  Otherwise you get
 137   // holes which confuse readers of eh_frame.
 138   Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
 139                      0, 0, false);
 140   EmitLabel("eh_frame_common_end", Index);
 141
 142   Asm->EOL();
 143 }
 144
 145 /// EmitEHFrame - Emit function exception frame information.
 146 ///
 147 void DwarfException::EmitEHFrame(const FunctionEHFrameInfo &EHFrameInfo) {
 148   assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
 149          "Should not emit 'available externally' functions at all");
 150
 151   const Function *TheFunc = EHFrameInfo.function;
 152
 153   Asm->SwitchToSection(Asm->getObjFileLowering().getEHFrameSection());
 154
 155   // Externally visible entry into the functions eh frame info. If the
 156   // corresponding function is static, this should not be externally visible.
 157   if (!TheFunc->hasLocalLinkage())
 158     if (const char *GlobalEHDirective = TAI->getGlobalEHDirective())
 159       O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
 160
 161   // If corresponding function is weak definition, this should be too.
 162   if (TheFunc->isWeakForLinker() && TAI->getWeakDefDirective())
 163     O << TAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
 164
 165   // If there are no calls then you can't unwind.  This may mean we can omit the
 166   // EH Frame, but some environments do not handle weak absolute symbols. If
 167   // UnwindTablesMandatory is set we cannot do this optimization; the unwind
 168   // info is to be available for non-EH uses.
 169   if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
 170       (!TheFunc->isWeakForLinker() ||
 171        !TAI->getWeakDefDirective() ||
 172        TAI->getSupportsWeakOmittedEHFrame())) {
 173     O << EHFrameInfo.FnName << " = 0\n";
 174     // This name has no connection to the function, so it might get
 175     // dead-stripped when the function is not, erroneously.  Prohibit
 176     // dead-stripping unconditionally.
 177     if (const char *UsedDirective = TAI->getUsedDirective())
 178       O << UsedDirective << EHFrameInfo.FnName << "\n\n";
 179   } else {
 180     O << EHFrameInfo.FnName << ":\n";
 181
 182     // EH frame header.
 183     EmitDifference("eh_frame_end", EHFrameInfo.Number,
 184                    "eh_frame_begin", EHFrameInfo.Number, true);
 185     Asm->EOL("Length of Frame Information Entry");
 186
 187     EmitLabel("eh_frame_begin", EHFrameInfo.Number);
 188
 189     EmitSectionOffset("eh_frame_begin", "eh_frame_common",
 190                       EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
 191                       true, true, false);
 192
 193     Asm->EOL("FDE CIE offset");
 194
 195     EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
 196     Asm->EOL("FDE initial location");
 197     EmitDifference("eh_func_end", EHFrameInfo.Number,
 198                    "eh_func_begin", EHFrameInfo.Number, true);
 199     Asm->EOL("FDE address range");
 200
 201     // If there is a personality and landing pads then point to the language
 202     // specific data area in the exception table.
 203     if (EHFrameInfo.PersonalityIndex) {
 204       Asm->EmitULEB128Bytes(4);
 205       Asm->EOL("Augmentation size");
 206
 207       if (EHFrameInfo.hasLandingPads)
 208         EmitReference("exception", EHFrameInfo.Number, true, true);
 209       else
 210         Asm->EmitInt32((int)0);
 211       Asm->EOL("Language Specific Data Area");
 212     } else {
 213       Asm->EmitULEB128Bytes(0);
 214       Asm->EOL("Augmentation size");
 215     }
 216
 217     // Indicate locations of function specific callee saved registers in frame.
 218     EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
 219                    true);
 220
 221     // On Darwin the linker honors the alignment of eh_frame, which means it
 222     // must be 8-byte on 64-bit targets to match what gcc does.  Otherwise you
 223     // get holes which confuse readers of eh_frame.
 224     Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
 225                        0, 0, false);
 226     EmitLabel("eh_frame_end", EHFrameInfo.Number);
 227
 228     // If the function is marked used, this table should be also.  We cannot
 229     // make the mark unconditional in this case, since retaining the table also
 230     // retains the function in this case, and there is code around that depends
 231     // on unused functions (calling undefined externals) being dead-stripped to
 232     // link correctly.  Yes, there really is.
 233     if (MMI->isUsedFunction(EHFrameInfo.function))
 234       if (const char *UsedDirective = TAI->getUsedDirective())
 235         O << UsedDirective << EHFrameInfo.FnName << "\n\n";
 236   }
 237 }
 238
 239 /// SharedTypeIds - How many leading type ids two landing pads have in common.
 240 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
 241                                        const LandingPadInfo *R) {
 242   const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
 243   unsigned LSize = LIds.size(), RSize = RIds.size();
 244   unsigned MinSize = LSize < RSize ? LSize : RSize;
 245   unsigned Count = 0;
 246
 247   for (; Count != MinSize; ++Count)
 248     if (LIds[Count] != RIds[Count])
 249       return Count;
 250
 251   return Count;
 252 }
 253
 254 /// PadLT - Order landing pads lexicographically by type id.
 255 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
 256   const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
 257   unsigned LSize = LIds.size(), RSize = RIds.size();
 258   unsigned MinSize = LSize < RSize ? LSize : RSize;
 259
 260   for (unsigned i = 0; i != MinSize; ++i)
 261     if (LIds[i] != RIds[i])
 262       return LIds[i] < RIds[i];
 263
 264   return LSize < RSize;
 265 }
 266
 267 /// ComputeActionsTable - Compute the actions table and gather the first action
 268 /// index for each landing pad site.
 269 unsigned DwarfException::
 270 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
 271                     SmallVectorImpl<ActionEntry> &Actions,
 272                     SmallVectorImpl<unsigned> &FirstActions) {
 273   // Negative type IDs index into FilterIds. Positive type IDs index into
 274   // TypeInfos.  The value written for a positive type ID is just the type ID
 275   // itself.  For a negative type ID, however, the value written is the
 276   // (negative) byte offset of the corresponding FilterIds entry.  The byte
 277   // offset is usually equal to the type ID (because the FilterIds entries are
 278   // written using a variable width encoding, which outputs one byte per entry
 279   // as long as the value written is not too large) but can differ.  This kind
 280   // of complication does not occur for positive type IDs because type infos are
 281   // output using a fixed width encoding.  FilterOffsets[i] holds the byte
 282   // offset corresponding to FilterIds[i].
 283
 284   const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
 285   SmallVector<int, 16> FilterOffsets;
 286   FilterOffsets.reserve(FilterIds.size());
 287   int Offset = -1;
 288
 289   for (std::vector<unsigned>::const_iterator
 290          I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
 291     FilterOffsets.push_back(Offset);
 292     Offset -= TargetAsmInfo::getULEB128Size(*I);
 293   }
 294
 295   FirstActions.reserve(LandingPads.size());
 296
 297   int FirstAction = 0;
 298   unsigned SizeActions = 0;
 299   const LandingPadInfo *PrevLPI = 0;
 300
 301   for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
 302          I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
 303     const LandingPadInfo *LPI = *I;
 304     const std::vector<int> &TypeIds = LPI->TypeIds;
 305     const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
 306     unsigned SizeSiteActions = 0;
 307
 308     if (NumShared < TypeIds.size()) {
 309       unsigned SizeAction = 0;
 310       ActionEntry *PrevAction = 0;
 311
 312       if (NumShared) {
 313         const unsigned SizePrevIds = PrevLPI->TypeIds.size();
 314         assert(Actions.size());
 315         PrevAction = &Actions.back();
 316         SizeAction = TargetAsmInfo::getSLEB128Size(PrevAction->NextAction) +
 317           TargetAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
 318
 319         for (unsigned j = NumShared; j != SizePrevIds; ++j) {
 320           SizeAction -=
 321             TargetAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
 322           SizeAction += -PrevAction->NextAction;
 323           PrevAction = PrevAction->Previous;
 324         }
 325       }
 326
 327       // Compute the actions.
 328       for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
 329         int TypeID = TypeIds[J];
 330         assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
 331         int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
 332         unsigned SizeTypeID = TargetAsmInfo::getSLEB128Size(ValueForTypeID);
 333
 334         int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
 335         SizeAction = SizeTypeID + TargetAsmInfo::getSLEB128Size(NextAction);
 336         SizeSiteActions += SizeAction;
 337
 338         ActionEntry Action = {ValueForTypeID, NextAction, PrevAction};
 339         Actions.push_back(Action);
 340         PrevAction = &Actions.back();
 341       }
 342
 343       // Record the first action of the landing pad site.
 344       FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
 345     } // else identical - re-use previous FirstAction
 346
 347     FirstActions.push_back(FirstAction);
 348
 349     // Compute this sites contribution to size.
 350     SizeActions += SizeSiteActions;
 351
 352     PrevLPI = LPI;
 353   }
 354
 355   return SizeActions;
 356 }
 357
 358 /// ComputeCallSiteTable - Compute the call-site table.  The entry for an invoke
 359 /// has a try-range containing the call, a non-zero landing pad and an
 360 /// appropriate action.  The entry for an ordinary call has a try-range
 361 /// containing the call and zero for the landing pad and the action.  Calls
 362 /// marked 'nounwind' have no entry and must not be contained in the try-range
 363 /// of any entry - they form gaps in the table.  Entries must be ordered by
 364 /// try-range address.
 365 void DwarfException::
 366 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
 367                      std::map<unsigned,CallSiteEntry*> &CallSiteIndexMap,
 368                      const RangeMapType &PadMap,
 369                      const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
 370                      const SmallVectorImpl<unsigned> &FirstActions) {
 371   // The end label of the previous invoke or nounwind try-range.
 372   unsigned LastLabel = 0;
 373
 374   // Whether there is a potentially throwing instruction (currently this means
 375   // an ordinary call) between the end of the previous try-range and now.
 376   bool SawPotentiallyThrowing = false;
 377
 378   // Whether the last CallSite entry was for an invoke.
 379   bool PreviousIsInvoke = false;
 380
 381   // Visit all instructions in order of address.
 382   for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
 383        I != E; ++I) {
 384     for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
 385          MI != E; ++MI) {
 386       if (!MI->isLabel()) {
 387         SawPotentiallyThrowing |= MI->getDesc().isCall();
 388         continue;
 389       }
 390
 391       unsigned BeginLabel = MI->getOperand(0).getImm();
 392       assert(BeginLabel && "Invalid label!");
 393
 394       // End of the previous try-range?
 395       if (BeginLabel == LastLabel)
 396         SawPotentiallyThrowing = false;
 397
 398       // Beginning of a new try-range?
 399       RangeMapType::iterator L = PadMap.find(BeginLabel);
 400       if (L == PadMap.end())
 401         // Nope, it was just some random label.
 402         continue;
 403
 404       PadRange P = L->second;
 405       const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
 406       assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
 407              "Inconsistent landing pad map!");
 408
 409       // For Dwarf exception handling (SjLj handling doesn't use this)
 410       // If some instruction between the previous try-range and this one may
 411       // throw, create a call-site entry with no landing pad for the region
 412       // between the try-ranges.
 413       if (SawPotentiallyThrowing &&
 414           TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
 415         CallSiteEntry Site = {LastLabel, BeginLabel, 0, 0};
 416         CallSites.push_back(Site);
 417         PreviousIsInvoke = false;
 418       }
 419
 420       LastLabel = LandingPad->EndLabels[P.RangeIndex];
 421       assert(BeginLabel && LastLabel && "Invalid landing pad!");
 422
 423       if (LandingPad->LandingPadLabel) {
 424         // This try-range is for an invoke.
 425         CallSiteEntry Site = {BeginLabel, LastLabel,
 426                               LandingPad->LandingPadLabel,
 427                               FirstActions[P.PadIndex]};
 428
 429         // Try to merge with the previous call-site.
 430         if (PreviousIsInvoke) {
 431           CallSiteEntry &Prev = CallSites.back();
 432           if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
 433             // Extend the range of the previous entry.
 434             Prev.EndLabel = Site.EndLabel;
 435             continue;
 436           }
 437         }
 438
 439         // Otherwise, create a new call-site.
 440         CallSites.push_back(Site);
 441         // For SjLj handling, map the call site entry to its index
 442         if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
 443           unsigned Index =
 444             MF->getLandingPadCallSiteIndex(LandingPad->LandingPadBlock);
 445           CallSiteIndexMap[Index] = &CallSites.back();
 446         }
 447         PreviousIsInvoke = true;
 448       } else {
 449         // Create a gap.
 450         PreviousIsInvoke = false;
 451       }
 452     }
 453   }
 454
 455   // If some instruction between the previous try-range and the end of the
 456   // function may throw, create a call-site entry with no landing pad for the
 457   // region following the try-range.
 458   if (SawPotentiallyThrowing &&
 459       TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
 460     CallSiteEntry Site = {LastLabel, 0, 0, 0};
 461     CallSites.push_back(Site);
 462   }
 463 }
 464
 465 /// EmitExceptionTable - Emit landing pads and actions.
 466 ///
 467 /// The general organization of the table is complex, but the basic concepts are
 468 /// easy.  First there is a header which describes the location and organization
 469 /// of the three components that follow.
 470 ///
 471 ///  1. The landing pad site information describes the range of code covered by
 472 ///     the try.  In our case it's an accumulation of the ranges covered by the
 473 ///     invokes in the try.  There is also a reference to the landing pad that
 474 ///     handles the exception once processed.  Finally an index into the actions
 475 ///     table.
 476 ///  2. The action table, in our case, is composed of pairs of type ids and next
 477 ///     action offset.  Starting with the action index from the landing pad
 478 ///     site, each type Id is checked for a match to the current exception.  If
 479 ///     it matches then the exception and type id are passed on to the landing
 480 ///     pad.  Otherwise the next action is looked up.  This chain is terminated
 481 ///     with a next action of zero.  If no type id is found the the frame is
 482 ///     unwound and handling continues.
 483 ///  3. Type id table contains references to all the C++ typeinfo for all
 484 ///     catches in the function.  This tables is reversed indexed base 1.
 485 void DwarfException::EmitExceptionTable() {
 486   const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
 487   const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
 488   const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
 489   if (PadInfos.empty()) return;
 490
 491   // Sort the landing pads in order of their type ids.  This is used to fold
 492   // duplicate actions.
 493   SmallVector<const LandingPadInfo *, 64> LandingPads;
 494   LandingPads.reserve(PadInfos.size());
 495
 496   for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
 497     LandingPads.push_back(&PadInfos[i]);
 498
 499   std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
 500
 501   // Compute the actions table and gather the first action index for each
 502   // landing pad site.
 503   SmallVector<ActionEntry, 32> Actions;
 504   SmallVector<unsigned, 64> FirstActions;
 505   unsigned SizeActions = ComputeActionsTable(LandingPads, Actions, FirstActions);
 506
 507   // Invokes and nounwind calls have entries in PadMap (due to being bracketed
 508   // by try-range labels when lowered).  Ordinary calls do not, so appropriate
 509   // try-ranges for them need be deduced when using Dwarf exception handling.
 510   RangeMapType PadMap;
 511   for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
 512     const LandingPadInfo *LandingPad = LandingPads[i];
 513     for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
 514       unsigned BeginLabel = LandingPad->BeginLabels[j];
 515       assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
 516       PadRange P = { i, j };
 517       PadMap[BeginLabel] = P;
 518     }
 519   }
 520
 521   // Compute the call-site table.
 522   SmallVector<CallSiteEntry, 64> CallSites;
 523   std::map<unsigned,CallSiteEntry*> CallSiteIndexMap;
 524   ComputeCallSiteTable(CallSites, CallSiteIndexMap, PadMap,
 525                        LandingPads, FirstActions);
 526
 527   // Final tallies.
 528
 529   // Call sites.
 530   const unsigned SiteStartSize  = sizeof(int32_t); // DW_EH_PE_udata4
 531   const unsigned SiteLengthSize = sizeof(int32_t); // DW_EH_PE_udata4
 532   const unsigned LandingPadSize = sizeof(int32_t); // DW_EH_PE_udata4
 533   unsigned SizeSites;
 534
 535   bool HaveTTData = (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
 536     ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
 537
 538
 539   if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
 540     SizeSites = (MF->getMaxCallSiteIndex() - CallSites.size()) *
 541       TargetAsmInfo::getULEB128Size(0) * 2;
 542   } else
 543     SizeSites = CallSites.size() *
 544       (SiteStartSize + SiteLengthSize + LandingPadSize);
 545   for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
 546     SizeSites += TargetAsmInfo::getULEB128Size(CallSites[i].Action);
 547     if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
 548       SizeSites += TargetAsmInfo::getULEB128Size(i);
 549       // FIXME: 'i' above should be the landing pad index
 550   }
 551   // Type infos.
 552   const unsigned TypeInfoSize = TD->getPointerSize(); // DW_EH_PE_absptr
 553   unsigned SizeTypes = TypeInfos.size() * TypeInfoSize;
 554
 555   unsigned TypeOffset = sizeof(int8_t) + // Call site format
 556     TargetAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
 557     SizeSites + SizeActions + SizeTypes;
 558
 559   unsigned TotalSize = sizeof(int8_t) + // LPStart format
 560                        sizeof(int8_t) + // TType format
 561        (HaveTTData ?
 562           TargetAsmInfo::getULEB128Size(TypeOffset) : 0) + // TType base offset
 563                        TypeOffset;
 564
 565   unsigned SizeAlign = (4 - TotalSize) & 3;
 566
 567   // Begin the exception table.
 568   const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
 569   Asm->SwitchToSection(LSDASection);
 570   Asm->EmitAlignment(2, 0, 0, false);
 571   O << "GCC_except_table" << SubprogramCount << ":\n";
 572
 573   for (unsigned i = 0; i != SizeAlign; ++i) {
 574     Asm->EmitInt8(0);
 575     Asm->EOL("Padding");
 576   }
 577
 578   EmitLabel("exception", SubprogramCount);
 579   if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
 580     std::string SjLjName = "_lsda_";
 581     SjLjName += MF->getFunction()->getName().str();
 582     EmitLabel(SjLjName.c_str(), 0);
 583   }
 584
 585   // Emit the header.
 586   Asm->EmitInt8(dwarf::DW_EH_PE_omit);
 587   Asm->EOL("LPStart format (DW_EH_PE_omit)");
 588
 589 #if 0
 590   if (TypeInfos.empty() && FilterIds.empty()) {
 591     // If there are no typeinfos or filters, there is nothing to emit, optimize
 592     // by specifying the "omit" encoding.
 593     Asm->EmitInt8(dwarf::DW_EH_PE_omit);
 594     Asm->EOL("TType format (DW_EH_PE_omit)");
 595   } else {
 596     // Okay, we have actual filters or typeinfos to emit.  As such, we need to
 597     // pick a type encoding for them.  We're about to emit a list of pointers to
 598     // typeinfo objects at the end of the LSDA.  However, unless we're in static
 599     // mode, this reference will require a relocation by the dynamic linker.
 600     //
 601     // Because of this, we have a couple of options:
 602     //   1) If we are in -static mode, we can always use an absolute reference
 603     //      from the LSDA, because the static linker will resolve it.
 604     //   2) Otherwise, if the LSDA section is writable, we can output the direct
 605     //      reference to the typeinfo and allow the dynamic linker to relocate
 606     //      it.  Since it is in a writable section, the dynamic linker won't
 607     //      have a problem.
 608     //   3) Finally, if we're in PIC mode and the LDSA section isn't writable,
 609     //      we need to use some form of indirection.  For example, on Darwin,
 610     //      we can output a statically-relocatable reference to a dyld stub. The
 611     //      offset to the stub is constant, but the contents are in a section
 612     //      that is updated by the dynamic linker.  This is easy enough, but we
 613     //      need to tell the personality function of the unwinder to indirect
 614     //      through the dyld stub.
 615     //
 616     // FIXME: When this is actually implemented, we'll have to emit the stubs
 617     // somewhere.  This predicate should be moved to a shared location that is
 618     // in target-independent code.
 619     //
 620     if (LSDASection->isWritable() ||
 621         Asm->TM.getRelocationModel() == Reloc::Static) {
 622       Asm->EmitInt8(DW_EH_PE_absptr);
 623       Asm->EOL("TType format (DW_EH_PE_absptr)");
 624     } else {
 625       Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
 626       Asm->EOL("TType format (DW_EH_PE_pcrel | DW_EH_PE_indirect"
 627                " | DW_EH_PE_sdata4)");
 628     }
 629     Asm->EmitULEB128Bytes(TypeOffset);
 630     Asm->EOL("TType base offset");
 631   }
 632 #else
 633   // For SjLj exceptions, if there is no TypeInfo, then we just explicitly
 634   // say that we're omitting that bit.
 635   // FIXME: does this apply to Dwarf also? The above #if 0 implies yes?
 636   if (!HaveTTData) {
 637     Asm->EmitInt8(dwarf::DW_EH_PE_omit);
 638     Asm->EOL("TType format (DW_EH_PE_omit)");
 639   } else {
 640     Asm->EmitInt8(dwarf::DW_EH_PE_absptr);
 641     Asm->EOL("TType format (DW_EH_PE_absptr)");
 642     Asm->EmitULEB128Bytes(TypeOffset);
 643     Asm->EOL("TType base offset");
 644   }
 645 #endif
 646
 647   // SjLj Exception handilng
 648   if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
 649     Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
 650     Asm->EOL("Call site format (DW_EH_PE_udata4)");
 651     Asm->EmitULEB128Bytes(SizeSites);
 652     Asm->EOL("Call-site table length");
 653
 654
 655     assert(MF->getCallSiteCount() == CallSites.size());
 656
 657     // Emit the landing pad site information.
 658     // SjLj handling assigned the call site indices in the front end, so
 659     // we need to make sure the table here lines up with that. That's pretty
 660     // horrible, and should be fixed ASAP to do that stuff in the back end
 661     // instead.
 662     std::map<unsigned, CallSiteEntry*>::const_iterator I, E;
 663     I = CallSiteIndexMap.begin();
 664     E = CallSiteIndexMap.end();
 665     for (unsigned CurrIdx = 1; I != E; ++I) {
 666       // paranoia.
 667       assert(CurrIdx <= I->first);
 668       // Fill in any gaps in the table
 669       while (CurrIdx++ < I->first) {
 670         Asm->EmitULEB128Bytes(0);
 671         Asm->EOL("Filler landing pad");
 672         Asm->EmitULEB128Bytes(0);
 673         Asm->EOL("Filler action");
 674       }
 675       const CallSiteEntry &S = *(I->second);
 676       Asm->EmitULEB128Bytes(I->first - 1);
 677       Asm->EOL("Landing pad");
 678       Asm->EmitULEB128Bytes(S.Action);
 679       Asm->EOL("Action");
 680     }
 681   } else {
 682     // DWARF Exception handling
 683     assert(TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
 684
 685     Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
 686     Asm->EOL("Call site format (DW_EH_PE_udata4)");
 687     Asm->EmitULEB128Bytes(SizeSites);
 688     Asm->EOL("Call-site table length");
 689
 690     // Emit the landing pad site information.
 691     for (SmallVectorImpl<CallSiteEntry>::const_iterator
 692          I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
 693       const CallSiteEntry &S = *I;
 694       const char *BeginTag;
 695       unsigned BeginNumber;
 696
 697       if (!S.BeginLabel) {
 698         BeginTag = "eh_func_begin";
 699         BeginNumber = SubprogramCount;
 700       } else {
 701         BeginTag = "label";
 702         BeginNumber = S.BeginLabel;
 703       }
 704
 705       EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
 706                         true, true);
 707       Asm->EOL("Region start");
 708
 709       if (!S.EndLabel)
 710         EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
 711                        true);
 712       else
 713         EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
 714
 715       Asm->EOL("Region length");
 716
 717       if (!S.PadLabel)
 718         Asm->EmitInt32(0);
 719       else
 720         EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
 721                           true, true);
 722
 723       Asm->EOL("Landing pad");
 724
 725       Asm->EmitULEB128Bytes(S.Action);
 726       Asm->EOL("Action");
 727     }
 728   }
 729
 730   // Emit the actions.
 731   for (SmallVectorImpl<ActionEntry>::const_iterator
 732          I = Actions.begin(), E = Actions.end(); I != E; ++I) {
 733     const ActionEntry &Action = *I;
 734     Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
 735     Asm->EOL("TypeInfo index");
 736     Asm->EmitSLEB128Bytes(Action.NextAction);
 737     Asm->EOL("Next action");
 738   }
 739
 740   // Emit the type ids.
 741   for (std::vector<GlobalVariable *>::const_reverse_iterator
 742          I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
 743     GlobalVariable *GV = *I;
 744     PrintRelDirective();
 745
 746     if (GV) {
 747       std::string GLN;
 748       O << Asm->getGlobalLinkName(GV, GLN);
 749     } else {
 750       O << "0";
 751     }
 752
 753     Asm->EOL("TypeInfo");
 754   }
 755
 756   // Emit the filter typeids.
 757   for (std::vector<unsigned>::const_iterator
 758          I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
 759     unsigned TypeID = *I;
 760     Asm->EmitULEB128Bytes(TypeID);
 761     Asm->EOL("Filter TypeInfo index");
 762   }
 763
 764   Asm->EmitAlignment(2, 0, 0, false);
 765 }
 766
 767 /// EndModule - Emit all exception information that should come after the
 768 /// content.
 769 void DwarfException::EndModule() {
 770   if (TAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
 771     return;
 772   if (TimePassesIsEnabled)
 773     ExceptionTimer->startTimer();
 774
 775   if (shouldEmitMovesModule || shouldEmitTableModule) {
 776     const std::vector<Function *> Personalities = MMI->getPersonalities();
 777     for (unsigned i = 0; i < Personalities.size(); ++i)
 778       EmitCommonEHFrame(Personalities[i], i);
 779
 780     for (std::vector<FunctionEHFrameInfo>::iterator I = EHFrames.begin(),
 781            E = EHFrames.end(); I != E; ++I)
 782       EmitEHFrame(*I);
 783   }
 784
 785   if (TimePassesIsEnabled)
 786     ExceptionTimer->stopTimer();
 787 }
 788
 789 /// BeginFunction - Gather pre-function exception information.  Assumes being
 790 /// emitted immediately after the function entry point.
 791 void DwarfException::BeginFunction(MachineFunction *MF) {
 792   if (TimePassesIsEnabled)
 793     ExceptionTimer->startTimer();
 794
 795   this->MF = MF;
 796   shouldEmitTable = shouldEmitMoves = false;
 797
 798   if (MMI && TAI->doesSupportExceptionHandling()) {
 799     // Map all labels and get rid of any dead landing pads.
 800     MMI->TidyLandingPads();
 801
 802     // If any landing pads survive, we need an EH table.
 803     if (MMI->getLandingPads().size())
 804       shouldEmitTable = true;
 805
 806     // See if we need frame move info.
 807     if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
 808       shouldEmitMoves = true;
 809
 810     if (shouldEmitMoves || shouldEmitTable)
 811       // Assumes in correct section after the entry point.
 812       EmitLabel("eh_func_begin", ++SubprogramCount);
 813   }
 814
 815   shouldEmitTableModule |= shouldEmitTable;
 816   shouldEmitMovesModule |= shouldEmitMoves;
 817
 818   if (TimePassesIsEnabled)
 819     ExceptionTimer->stopTimer();
 820 }
 821
 822 /// EndFunction - Gather and emit post-function exception information.
 823 ///
 824 void DwarfException::EndFunction() {
 825   if (TimePassesIsEnabled)
 826     ExceptionTimer->startTimer();
 827
 828   if (shouldEmitMoves || shouldEmitTable) {
 829     EmitLabel("eh_func_end", SubprogramCount);
 830     EmitExceptionTable();
 831
 832     // Save EH frame information
 833     EHFrames.push_back(
 834         FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
 835                             SubprogramCount,
 836                             MMI->getPersonalityIndex(),
 837                             MF->getFrameInfo()->hasCalls(),
 838                             !MMI->getLandingPads().empty(),
 839                             MMI->getFrameMoves(),
 840                             MF->getFunction()));
 841   }
 842
 843   if (TimePassesIsEnabled)
 844     ExceptionTimer->stopTimer();
 845 }