LLVM  3.7.0
EHStreamer.cpp
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1 //===-- CodeGen/AsmPrinter/EHStreamer.cpp - Exception Directive Streamer --===//
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 exception info into assembly files.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "EHStreamer.h"
19 #include "llvm/IR/Function.h"
20 #include "llvm/MC/MCAsmInfo.h"
21 #include "llvm/MC/MCStreamer.h"
22 #include "llvm/MC/MCSymbol.h"
23 #include "llvm/Support/LEB128.h"
25 
26 using namespace llvm;
27 
29 
31 
32 /// How many leading type ids two landing pads have in common.
34  const LandingPadInfo *R) {
35  const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
36  unsigned LSize = LIds.size(), RSize = RIds.size();
37  unsigned MinSize = LSize < RSize ? LSize : RSize;
38  unsigned Count = 0;
39 
40  for (; Count != MinSize; ++Count)
41  if (LIds[Count] != RIds[Count])
42  return Count;
43 
44  return Count;
45 }
46 
47 /// Compute the actions table and gather the first action index for each landing
48 /// pad site.
49 unsigned EHStreamer::
52  SmallVectorImpl<unsigned> &FirstActions) {
53 
54  // The action table follows the call-site table in the LSDA. The individual
55  // records are of two types:
56  //
57  // * Catch clause
58  // * Exception specification
59  //
60  // The two record kinds have the same format, with only small differences.
61  // They are distinguished by the "switch value" field: Catch clauses
62  // (TypeInfos) have strictly positive switch values, and exception
63  // specifications (FilterIds) have strictly negative switch values. Value 0
64  // indicates a catch-all clause.
65  //
66  // Negative type IDs index into FilterIds. Positive type IDs index into
67  // TypeInfos. The value written for a positive type ID is just the type ID
68  // itself. For a negative type ID, however, the value written is the
69  // (negative) byte offset of the corresponding FilterIds entry. The byte
70  // offset is usually equal to the type ID (because the FilterIds entries are
71  // written using a variable width encoding, which outputs one byte per entry
72  // as long as the value written is not too large) but can differ. This kind
73  // of complication does not occur for positive type IDs because type infos are
74  // output using a fixed width encoding. FilterOffsets[i] holds the byte
75  // offset corresponding to FilterIds[i].
76 
77  const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
78  SmallVector<int, 16> FilterOffsets;
79  FilterOffsets.reserve(FilterIds.size());
80  int Offset = -1;
81 
82  for (std::vector<unsigned>::const_iterator
83  I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
84  FilterOffsets.push_back(Offset);
85  Offset -= getULEB128Size(*I);
86  }
87 
88  FirstActions.reserve(LandingPads.size());
89 
90  int FirstAction = 0;
91  unsigned SizeActions = 0;
92  const LandingPadInfo *PrevLPI = nullptr;
93 
95  I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
96  const LandingPadInfo *LPI = *I;
97  const std::vector<int> &TypeIds = LPI->TypeIds;
98  unsigned NumShared = PrevLPI ? sharedTypeIDs(LPI, PrevLPI) : 0;
99  unsigned SizeSiteActions = 0;
100 
101  if (NumShared < TypeIds.size()) {
102  unsigned SizeAction = 0;
103  unsigned PrevAction = (unsigned)-1;
104 
105  if (NumShared) {
106  unsigned SizePrevIds = PrevLPI->TypeIds.size();
107  assert(Actions.size());
108  PrevAction = Actions.size() - 1;
109  SizeAction = getSLEB128Size(Actions[PrevAction].NextAction) +
110  getSLEB128Size(Actions[PrevAction].ValueForTypeID);
111 
112  for (unsigned j = NumShared; j != SizePrevIds; ++j) {
113  assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
114  SizeAction -= getSLEB128Size(Actions[PrevAction].ValueForTypeID);
115  SizeAction += -Actions[PrevAction].NextAction;
116  PrevAction = Actions[PrevAction].Previous;
117  }
118  }
119 
120  // Compute the actions.
121  for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
122  int TypeID = TypeIds[J];
123  assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
124  int ValueForTypeID =
125  isFilterEHSelector(TypeID) ? FilterOffsets[-1 - TypeID] : TypeID;
126  unsigned SizeTypeID = getSLEB128Size(ValueForTypeID);
127 
128  int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
129  SizeAction = SizeTypeID + getSLEB128Size(NextAction);
130  SizeSiteActions += SizeAction;
131 
132  ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
133  Actions.push_back(Action);
134  PrevAction = Actions.size() - 1;
135  }
136 
137  // Record the first action of the landing pad site.
138  FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
139  } // else identical - re-use previous FirstAction
140 
141  // Information used when created the call-site table. The action record
142  // field of the call site record is the offset of the first associated
143  // action record, relative to the start of the actions table. This value is
144  // biased by 1 (1 indicating the start of the actions table), and 0
145  // indicates that there are no actions.
146  FirstActions.push_back(FirstAction);
147 
148  // Compute this sites contribution to size.
149  SizeActions += SizeSiteActions;
150 
151  PrevLPI = LPI;
152  }
153 
154  return SizeActions;
155 }
156 
157 /// Return `true' if this is a call to a function marked `nounwind'. Return
158 /// `false' otherwise.
160  assert(MI->isCall() && "This should be a call instruction!");
161 
162  bool MarkedNoUnwind = false;
163  bool SawFunc = false;
164 
165  for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
166  const MachineOperand &MO = MI->getOperand(I);
167 
168  if (!MO.isGlobal()) continue;
169 
170  const Function *F = dyn_cast<Function>(MO.getGlobal());
171  if (!F) continue;
172 
173  if (SawFunc) {
174  // Be conservative. If we have more than one function operand for this
175  // call, then we can't make the assumption that it's the callee and
176  // not a parameter to the call.
177  //
178  // FIXME: Determine if there's a way to say that `F' is the callee or
179  // parameter.
180  MarkedNoUnwind = false;
181  break;
182  }
183 
184  MarkedNoUnwind = F->doesNotThrow();
185  SawFunc = true;
186  }
187 
188  return MarkedNoUnwind;
189 }
190 
192  const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
193  RangeMapType &PadMap) {
194  // Invokes and nounwind calls have entries in PadMap (due to being bracketed
195  // by try-range labels when lowered). Ordinary calls do not, so appropriate
196  // try-ranges for them need be deduced so we can put them in the LSDA.
197  for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
198  const LandingPadInfo *LandingPad = LandingPads[i];
199  for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
200  MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
201  assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
202  PadRange P = { i, j };
203  PadMap[BeginLabel] = P;
204  }
205  }
206 }
207 
208 /// Compute the call-site table. The entry for an invoke has a try-range
209 /// containing the call, a non-zero landing pad, and an appropriate action. The
210 /// entry for an ordinary call has a try-range containing the call and zero for
211 /// the landing pad and the action. Calls marked 'nounwind' have no entry and
212 /// must not be contained in the try-range of any entry - they form gaps in the
213 /// table. Entries must be ordered by try-range address.
214 void EHStreamer::
216  const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
217  const SmallVectorImpl<unsigned> &FirstActions) {
218  RangeMapType PadMap;
219  computePadMap(LandingPads, PadMap);
220 
221  // The end label of the previous invoke or nounwind try-range.
222  MCSymbol *LastLabel = nullptr;
223 
224  // Whether there is a potentially throwing instruction (currently this means
225  // an ordinary call) between the end of the previous try-range and now.
226  bool SawPotentiallyThrowing = false;
227 
228  // Whether the last CallSite entry was for an invoke.
229  bool PreviousIsInvoke = false;
230 
232 
233  // Visit all instructions in order of address.
234  for (const auto &MBB : *Asm->MF) {
235  for (const auto &MI : MBB) {
236  if (!MI.isEHLabel()) {
237  if (MI.isCall())
238  SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
239  continue;
240  }
241 
242  // End of the previous try-range?
243  MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
244  if (BeginLabel == LastLabel)
245  SawPotentiallyThrowing = false;
246 
247  // Beginning of a new try-range?
248  RangeMapType::const_iterator L = PadMap.find(BeginLabel);
249  if (L == PadMap.end())
250  // Nope, it was just some random label.
251  continue;
252 
253  const PadRange &P = L->second;
254  const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
255  assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
256  "Inconsistent landing pad map!");
257 
258  // For Dwarf exception handling (SjLj handling doesn't use this). If some
259  // instruction between the previous try-range and this one may throw,
260  // create a call-site entry with no landing pad for the region between the
261  // try-ranges.
262  if (SawPotentiallyThrowing && Asm->MAI->usesCFIForEH()) {
263  CallSiteEntry Site = { LastLabel, BeginLabel, nullptr, 0 };
264  CallSites.push_back(Site);
265  PreviousIsInvoke = false;
266  }
267 
268  LastLabel = LandingPad->EndLabels[P.RangeIndex];
269  assert(BeginLabel && LastLabel && "Invalid landing pad!");
270 
271  if (!LandingPad->LandingPadLabel) {
272  // Create a gap.
273  PreviousIsInvoke = false;
274  } else {
275  // This try-range is for an invoke.
276  CallSiteEntry Site = {
277  BeginLabel,
278  LastLabel,
279  LandingPad,
280  FirstActions[P.PadIndex]
281  };
282 
283  // Try to merge with the previous call-site. SJLJ doesn't do this
284  if (PreviousIsInvoke && !IsSJLJ) {
285  CallSiteEntry &Prev = CallSites.back();
286  if (Site.LPad == Prev.LPad && Site.Action == Prev.Action) {
287  // Extend the range of the previous entry.
288  Prev.EndLabel = Site.EndLabel;
289  continue;
290  }
291  }
292 
293  // Otherwise, create a new call-site.
294  if (!IsSJLJ)
295  CallSites.push_back(Site);
296  else {
297  // SjLj EH must maintain the call sites in the order assigned
298  // to them by the SjLjPrepare pass.
299  unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel);
300  if (CallSites.size() < SiteNo)
301  CallSites.resize(SiteNo);
302  CallSites[SiteNo - 1] = Site;
303  }
304  PreviousIsInvoke = true;
305  }
306  }
307  }
308 
309  // If some instruction between the previous try-range and the end of the
310  // function may throw, create a call-site entry with no landing pad for the
311  // region following the try-range.
312  if (SawPotentiallyThrowing && !IsSJLJ && LastLabel != nullptr) {
313  CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
314  CallSites.push_back(Site);
315  }
316 }
317 
318 /// Emit landing pads and actions.
319 ///
320 /// The general organization of the table is complex, but the basic concepts are
321 /// easy. First there is a header which describes the location and organization
322 /// of the three components that follow.
323 ///
324 /// 1. The landing pad site information describes the range of code covered by
325 /// the try. In our case it's an accumulation of the ranges covered by the
326 /// invokes in the try. There is also a reference to the landing pad that
327 /// handles the exception once processed. Finally an index into the actions
328 /// table.
329 /// 2. The action table, in our case, is composed of pairs of type IDs and next
330 /// action offset. Starting with the action index from the landing pad
331 /// site, each type ID is checked for a match to the current exception. If
332 /// it matches then the exception and type id are passed on to the landing
333 /// pad. Otherwise the next action is looked up. This chain is terminated
334 /// with a next action of zero. If no type id is found then the frame is
335 /// unwound and handling continues.
336 /// 3. Type ID table contains references to all the C++ typeinfo for all
337 /// catches in the function. This tables is reverse indexed base 1.
339  const std::vector<const GlobalValue *> &TypeInfos = MMI->getTypeInfos();
340  const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
341  const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
342 
343  // Sort the landing pads in order of their type ids. This is used to fold
344  // duplicate actions.
346  LandingPads.reserve(PadInfos.size());
347 
348  for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
349  LandingPads.push_back(&PadInfos[i]);
350 
351  // Order landing pads lexicographically by type id.
352  std::sort(LandingPads.begin(), LandingPads.end(),
353  [](const LandingPadInfo *L,
354  const LandingPadInfo *R) { return L->TypeIds < R->TypeIds; });
355 
356  // Compute the actions table and gather the first action index for each
357  // landing pad site.
359  SmallVector<unsigned, 64> FirstActions;
360  unsigned SizeActions =
361  computeActionsTable(LandingPads, Actions, FirstActions);
362 
363  // Compute the call-site table.
365  computeCallSiteTable(CallSites, LandingPads, FirstActions);
366 
367  // Final tallies.
368 
369  // Call sites.
371  bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
372 
373  unsigned CallSiteTableLength;
374  if (IsSJLJ)
375  CallSiteTableLength = 0;
376  else {
377  unsigned SiteStartSize = 4; // dwarf::DW_EH_PE_udata4
378  unsigned SiteLengthSize = 4; // dwarf::DW_EH_PE_udata4
379  unsigned LandingPadSize = 4; // dwarf::DW_EH_PE_udata4
380  CallSiteTableLength =
381  CallSites.size() * (SiteStartSize + SiteLengthSize + LandingPadSize);
382  }
383 
384  for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
385  CallSiteTableLength += getULEB128Size(CallSites[i].Action);
386  if (IsSJLJ)
387  CallSiteTableLength += getULEB128Size(i);
388  }
389 
390  // Type infos.
391  MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
392  unsigned TTypeEncoding;
393  unsigned TypeFormatSize;
394 
395  if (!HaveTTData) {
396  // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
397  // that we're omitting that bit.
398  TTypeEncoding = dwarf::DW_EH_PE_omit;
399  // dwarf::DW_EH_PE_absptr
400  TypeFormatSize = Asm->getDataLayout().getPointerSize();
401  } else {
402  // Okay, we have actual filters or typeinfos to emit. As such, we need to
403  // pick a type encoding for them. We're about to emit a list of pointers to
404  // typeinfo objects at the end of the LSDA. However, unless we're in static
405  // mode, this reference will require a relocation by the dynamic linker.
406  //
407  // Because of this, we have a couple of options:
408  //
409  // 1) If we are in -static mode, we can always use an absolute reference
410  // from the LSDA, because the static linker will resolve it.
411  //
412  // 2) Otherwise, if the LSDA section is writable, we can output the direct
413  // reference to the typeinfo and allow the dynamic linker to relocate
414  // it. Since it is in a writable section, the dynamic linker won't
415  // have a problem.
416  //
417  // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
418  // we need to use some form of indirection. For example, on Darwin,
419  // we can output a statically-relocatable reference to a dyld stub. The
420  // offset to the stub is constant, but the contents are in a section
421  // that is updated by the dynamic linker. This is easy enough, but we
422  // need to tell the personality function of the unwinder to indirect
423  // through the dyld stub.
424  //
425  // FIXME: When (3) is actually implemented, we'll have to emit the stubs
426  // somewhere. This predicate should be moved to a shared location that is
427  // in target-independent code.
428  //
429  TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
430  TypeFormatSize = Asm->GetSizeOfEncodedValue(TTypeEncoding);
431  }
432 
433  // Begin the exception table.
434  // Sometimes we want not to emit the data into separate section (e.g. ARM
435  // EHABI). In this case LSDASection will be NULL.
436  if (LSDASection)
437  Asm->OutStreamer->SwitchSection(LSDASection);
438  Asm->EmitAlignment(2);
439 
440  // Emit the LSDA.
441  MCSymbol *GCCETSym =
442  Asm->OutContext.getOrCreateSymbol(Twine("GCC_except_table")+
444  Asm->OutStreamer->EmitLabel(GCCETSym);
445  Asm->OutStreamer->EmitLabel(Asm->getCurExceptionSym());
446 
447  // Emit the LSDA header.
449  Asm->EmitEncodingByte(TTypeEncoding, "@TType");
450 
451  // The type infos need to be aligned. GCC does this by inserting padding just
452  // before the type infos. However, this changes the size of the exception
453  // table, so you need to take this into account when you output the exception
454  // table size. However, the size is output using a variable length encoding.
455  // So by increasing the size by inserting padding, you may increase the number
456  // of bytes used for writing the size. If it increases, say by one byte, then
457  // you now need to output one less byte of padding to get the type infos
458  // aligned. However this decreases the size of the exception table. This
459  // changes the value you have to output for the exception table size. Due to
460  // the variable length encoding, the number of bytes used for writing the
461  // length may decrease. If so, you then have to increase the amount of
462  // padding. And so on. If you look carefully at the GCC code you will see that
463  // it indeed does this in a loop, going on and on until the values stabilize.
464  // We chose another solution: don't output padding inside the table like GCC
465  // does, instead output it before the table.
466  unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
467  unsigned CallSiteTableLengthSize = getULEB128Size(CallSiteTableLength);
468  unsigned TTypeBaseOffset =
469  sizeof(int8_t) + // Call site format
470  CallSiteTableLengthSize + // Call site table length size
471  CallSiteTableLength + // Call site table length
472  SizeActions + // Actions size
473  SizeTypes;
474  unsigned TTypeBaseOffsetSize = getULEB128Size(TTypeBaseOffset);
475  unsigned TotalSize =
476  sizeof(int8_t) + // LPStart format
477  sizeof(int8_t) + // TType format
478  (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size
479  TTypeBaseOffset; // TType base offset
480  unsigned SizeAlign = (4 - TotalSize) & 3;
481 
482  if (HaveTTData) {
483  // Account for any extra padding that will be added to the call site table
484  // length.
485  Asm->EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign);
486  SizeAlign = 0;
487  }
488 
489  bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
490 
491  // SjLj Exception handling
492  if (IsSJLJ) {
494 
495  // Add extra padding if it wasn't added to the TType base offset.
496  Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
497 
498  // Emit the landing pad site information.
499  unsigned idx = 0;
501  I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
502  const CallSiteEntry &S = *I;
503 
504  // Offset of the landing pad, counted in 16-byte bundles relative to the
505  // @LPStart address.
506  if (VerboseAsm) {
507  Asm->OutStreamer->AddComment(">> Call Site " + Twine(idx) + " <<");
508  Asm->OutStreamer->AddComment(" On exception at call site "+Twine(idx));
509  }
510  Asm->EmitULEB128(idx);
511 
512  // Offset of the first associated action record, relative to the start of
513  // the action table. This value is biased by 1 (1 indicates the start of
514  // the action table), and 0 indicates that there are no actions.
515  if (VerboseAsm) {
516  if (S.Action == 0)
517  Asm->OutStreamer->AddComment(" Action: cleanup");
518  else
519  Asm->OutStreamer->AddComment(" Action: " +
520  Twine((S.Action - 1) / 2 + 1));
521  }
522  Asm->EmitULEB128(S.Action);
523  }
524  } else {
525  // Itanium LSDA exception handling
526 
527  // The call-site table is a list of all call sites that may throw an
528  // exception (including C++ 'throw' statements) in the procedure
529  // fragment. It immediately follows the LSDA header. Each entry indicates,
530  // for a given call, the first corresponding action record and corresponding
531  // landing pad.
532  //
533  // The table begins with the number of bytes, stored as an LEB128
534  // compressed, unsigned integer. The records immediately follow the record
535  // count. They are sorted in increasing call-site address. Each record
536  // indicates:
537  //
538  // * The position of the call-site.
539  // * The position of the landing pad.
540  // * The first action record for that call site.
541  //
542  // A missing entry in the call-site table indicates that a call is not
543  // supposed to throw.
544 
545  // Emit the landing pad call site table.
547 
548  // Add extra padding if it wasn't added to the TType base offset.
549  Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
550 
551  unsigned Entry = 0;
553  I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
554  const CallSiteEntry &S = *I;
555 
556  MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
557 
558  MCSymbol *BeginLabel = S.BeginLabel;
559  if (!BeginLabel)
560  BeginLabel = EHFuncBeginSym;
561  MCSymbol *EndLabel = S.EndLabel;
562  if (!EndLabel)
563  EndLabel = Asm->getFunctionEnd();
564 
565  // Offset of the call site relative to the previous call site, counted in
566  // number of 16-byte bundles. The first call site is counted relative to
567  // the start of the procedure fragment.
568  if (VerboseAsm)
569  Asm->OutStreamer->AddComment(">> Call Site " + Twine(++Entry) + " <<");
570  Asm->EmitLabelDifference(BeginLabel, EHFuncBeginSym, 4);
571  if (VerboseAsm)
572  Asm->OutStreamer->AddComment(Twine(" Call between ") +
573  BeginLabel->getName() + " and " +
574  EndLabel->getName());
575  Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
576 
577  // Offset of the landing pad, counted in 16-byte bundles relative to the
578  // @LPStart address.
579  if (!S.LPad) {
580  if (VerboseAsm)
581  Asm->OutStreamer->AddComment(" has no landing pad");
582  Asm->OutStreamer->EmitIntValue(0, 4/*size*/);
583  } else {
584  if (VerboseAsm)
585  Asm->OutStreamer->AddComment(Twine(" jumps to ") +
587  Asm->EmitLabelDifference(S.LPad->LandingPadLabel, EHFuncBeginSym, 4);
588  }
589 
590  // Offset of the first associated action record, relative to the start of
591  // the action table. This value is biased by 1 (1 indicates the start of
592  // the action table), and 0 indicates that there are no actions.
593  if (VerboseAsm) {
594  if (S.Action == 0)
595  Asm->OutStreamer->AddComment(" On action: cleanup");
596  else
597  Asm->OutStreamer->AddComment(" On action: " +
598  Twine((S.Action - 1) / 2 + 1));
599  }
600  Asm->EmitULEB128(S.Action);
601  }
602  }
603 
604  // Emit the Action Table.
605  int Entry = 0;
607  I = Actions.begin(), E = Actions.end(); I != E; ++I) {
608  const ActionEntry &Action = *I;
609 
610  if (VerboseAsm) {
611  // Emit comments that decode the action table.
612  Asm->OutStreamer->AddComment(">> Action Record " + Twine(++Entry) + " <<");
613  }
614 
615  // Type Filter
616  //
617  // Used by the runtime to match the type of the thrown exception to the
618  // type of the catch clauses or the types in the exception specification.
619  if (VerboseAsm) {
620  if (Action.ValueForTypeID > 0)
621  Asm->OutStreamer->AddComment(" Catch TypeInfo " +
622  Twine(Action.ValueForTypeID));
623  else if (Action.ValueForTypeID < 0)
624  Asm->OutStreamer->AddComment(" Filter TypeInfo " +
625  Twine(Action.ValueForTypeID));
626  else
627  Asm->OutStreamer->AddComment(" Cleanup");
628  }
629  Asm->EmitSLEB128(Action.ValueForTypeID);
630 
631  // Action Record
632  //
633  // Self-relative signed displacement in bytes of the next action record,
634  // or 0 if there is no next action record.
635  if (VerboseAsm) {
636  if (Action.NextAction == 0) {
637  Asm->OutStreamer->AddComment(" No further actions");
638  } else {
639  unsigned NextAction = Entry + (Action.NextAction + 1) / 2;
640  Asm->OutStreamer->AddComment(" Continue to action "+Twine(NextAction));
641  }
642  }
643  Asm->EmitSLEB128(Action.NextAction);
644  }
645 
646  emitTypeInfos(TTypeEncoding);
647 
648  Asm->EmitAlignment(2);
649 }
650 
651 void EHStreamer::emitTypeInfos(unsigned TTypeEncoding) {
652  const std::vector<const GlobalValue *> &TypeInfos = MMI->getTypeInfos();
653  const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
654 
655  bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
656 
657  int Entry = 0;
658  // Emit the Catch TypeInfos.
659  if (VerboseAsm && !TypeInfos.empty()) {
660  Asm->OutStreamer->AddComment(">> Catch TypeInfos <<");
661  Asm->OutStreamer->AddBlankLine();
662  Entry = TypeInfos.size();
663  }
664 
665  for (std::vector<const GlobalValue *>::const_reverse_iterator
666  I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
667  const GlobalValue *GV = *I;
668  if (VerboseAsm)
669  Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--));
670  Asm->EmitTTypeReference(GV, TTypeEncoding);
671  }
672 
673  // Emit the Exception Specifications.
674  if (VerboseAsm && !FilterIds.empty()) {
675  Asm->OutStreamer->AddComment(">> Filter TypeInfos <<");
676  Asm->OutStreamer->AddBlankLine();
677  Entry = 0;
678  }
679  for (std::vector<unsigned>::const_iterator
680  I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
681  unsigned TypeID = *I;
682  if (VerboseAsm) {
683  --Entry;
684  if (isFilterEHSelector(TypeID))
685  Asm->OutStreamer->AddComment("FilterInfo " + Twine(Entry));
686  }
687 
688  Asm->EmitULEB128(TypeID);
689  }
690 }
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:48
static unsigned sharedTypeIDs(const LandingPadInfo *L, const LandingPadInfo *R)
How many leading type ids two landing pads have in common.
Definition: EHStreamer.cpp:33
Structure describing an entry in the call-site table.
Definition: EHStreamer.h:63
const GlobalValue * getGlobal() const
std::unique_ptr< MCStreamer > OutStreamer
This is the MCStreamer object for the file we are generating.
Definition: AsmPrinter.h:83
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:39
const DataLayout & getDataLayout() const
Return information about data layout.
Definition: AsmPrinter.cpp:139
MCContext & OutContext
This is the context for the output file that we are streaming.
Definition: AsmPrinter.h:78
Type::TypeID TypeID
DWARF-like instruction based exceptions.
EHStreamer(AsmPrinter *A)
Definition: EHStreamer.cpp:28
void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo, unsigned Size) const
Emit something like ".long Hi-Lo" where the size in bytes of the directive is specified by Size and H...
bool callToNoUnwindFunction(const MachineInstr *MI)
Return `true' if this is a call to a function marked `nounwind'.
Definition: EHStreamer.cpp:159
const MachineFunction * MF
The current machine function.
Definition: AsmPrinter.h:86
unsigned getCallSiteBeginLabel(MCSymbol *BeginLabel)
getCallSiteBeginLabel - Get the call site number for a begin label.
unsigned getFunctionNumber() const
Return a unique ID for the current function.
Definition: AsmPrinter.cpp:130
F(f)
Structure describing an entry in the actions table.
Definition: EHStreamer.h:56
void reserve(size_type N)
Definition: SmallVector.h:401
static bool isFilterEHSelector(int Selector)
Definition: EHStreamer.h:122
const LandingPadInfo * LPad
Definition: EHStreamer.h:69
MachineModuleInfo * MMI
Collected machine module information.
Definition: EHStreamer.h:39
bool doesNotThrow() const
Determine if the function cannot unwind.
Definition: Function.h:316
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:79
SmallVector< MCSymbol *, 1 > EndLabels
const std::vector< unsigned > & getFilterIds() const
getFilterIds - Return a reference to the typeids encoding filters used in the current function...
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APInt.h:33
TypeID
Definitions of all of the base types for the Type system.
Definition: Type.h:54
~EHStreamer() override
Definition: EHStreamer.cpp:30
void EmitEncodingByte(unsigned Val, const char *Desc=nullptr) const
Emit a .byte 42 directive that corresponds to an encoding.
unsigned getNumOperands() const
Access to explicit operands of the instruction.
Definition: MachineInstr.h:271
bool isGlobal() const
isGlobal - Tests if this is a MO_GlobalAddress operand.
unsigned getTTypeEncoding() const
void emitExceptionTable()
Emit landing pads and actions.
Definition: EHStreamer.cpp:338
LandingPadInfo - This structure is used to retain landing pad info for the current function...
const std::vector< const GlobalValue * > & getTypeInfos() const
getTypeInfos - Return a reference to the C++ typeinfo for the current function.
void computeCallSiteTable(SmallVectorImpl< CallSiteEntry > &CallSites, const SmallVectorImpl< const LandingPadInfo * > &LPs, const SmallVectorImpl< unsigned > &FirstActions)
Compute the call-site table.
Definition: EHStreamer.cpp:215
MCSection * getLSDASection() const
#define P(N)
const MCAsmInfo * MAI
Target Asm Printer information.
Definition: AsmPrinter.h:74
unsigned GetSizeOfEncodedValue(unsigned Encoding) const
Return the size of the encoding in bytes.
SmallVector< MCSymbol *, 1 > BeginLabels
void EmitULEB128(uint64_t Value, const char *Desc=nullptr, unsigned PadTo=0) const
Emit the specified unsigned leb128 value.
const MachineOperand & getOperand(unsigned i) const
Definition: MachineInstr.h:273
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:66
std::vector< int > TypeIds
ExceptionHandling getExceptionHandlingType() const
Definition: MCAsmInfo.h:511
unsigned computeActionsTable(const SmallVectorImpl< const LandingPadInfo * > &LPs, SmallVectorImpl< ActionEntry > &Actions, SmallVectorImpl< unsigned > &FirstActions)
Compute the actions table and gather the first action index for each landing pad site.
Definition: EHStreamer.cpp:50
virtual void emitTypeInfos(unsigned TTypeEncoding)
Definition: EHStreamer.cpp:651
AsmPrinter * Asm
Target of directive emission.
Definition: EHStreamer.h:36
unsigned getULEB128Size(uint64_t Value)
Utility function to get the size of the ULEB128-encoded value.
Definition: LEB128.cpp:20
void EmitAlignment(unsigned NumBits, const GlobalObject *GO=nullptr) const
Emit an alignment directive to the specified power of two boundary.
MachineOperand class - Representation of each machine instruction operand.
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const
Emit reference to a ttype global with a specified encoding.
size_type count(const KeyT &Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:119
MCSymbol * getCurExceptionSym()
LLVM_ATTRIBUTE_UNUSED_RESULT std::enable_if< !is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:285
Representation of each machine instruction.
Definition: MachineInstr.h:51
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:205
MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition: MCContext.cpp:111
const std::vector< LandingPadInfo > & getLandingPads() const
getLandingPads - Return a reference to the landing pad info for the current function.
MCSymbol * getFunctionBegin() const
Definition: AsmPrinter.h:158
void computePadMap(const SmallVectorImpl< const LandingPadInfo * > &LandingPads, RangeMapType &PadMap)
Definition: EHStreamer.cpp:191
void EmitSLEB128(int64_t Value, const char *Desc=nullptr) const
Emit the specified signed leb128 value.
#define I(x, y, z)
Definition: MD5.cpp:54
#define N
bool isCall(QueryType Type=AnyInBundle) const
Definition: MachineInstr.h:403
iterator end()
Definition: DenseMap.h:68
iterator find(const KeyT &Val)
Definition: DenseMap.h:124
MCSymbol * getFunctionEnd() const
Definition: AsmPrinter.h:159
unsigned getSLEB128Size(int64_t Value)
Utility function to get the size of the SLEB128-encoded value.
Definition: LEB128.cpp:30
const TargetLoweringObjectFile & getObjFileLowering() const
Return information about object file lowering.
Definition: AsmPrinter.cpp:134
bool usesCFIForEH() const
Returns true if the exception handling method for the platform uses call frame information to unwind...
Definition: MCAsmInfo.h:516
unsigned getPointerSize(unsigned AS=0) const
Layout pointer size FIXME: The defaults need to be removed once all of the backends/clients are updat...
Definition: DataLayout.cpp:593
Structure holding a try-range and the associated landing pad.
Definition: EHStreamer.h:46
void resize(size_type N)
Definition: SmallVector.h:376