LLVM  6.0.0svn
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"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/ADT/Twine.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/Function.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCStreamer.h"
29 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/Support/Casting.h"
32 #include "llvm/Support/LEB128.h"
33 #include <algorithm>
34 #include <cassert>
35 #include <cstdint>
36 #include <vector>
37 
38 using namespace llvm;
39 
40 EHStreamer::EHStreamer(AsmPrinter *A) : Asm(A), MMI(Asm->MMI) {}
41 
42 EHStreamer::~EHStreamer() = default;
43 
44 /// How many leading type ids two landing pads have in common.
46  const LandingPadInfo *R) {
47  const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
48  unsigned LSize = LIds.size(), RSize = RIds.size();
49  unsigned MinSize = LSize < RSize ? LSize : RSize;
50  unsigned Count = 0;
51 
52  for (; Count != MinSize; ++Count)
53  if (LIds[Count] != RIds[Count])
54  return Count;
55 
56  return Count;
57 }
58 
59 /// Compute the actions table and gather the first action index for each landing
60 /// pad site.
61 unsigned EHStreamer::
64  SmallVectorImpl<unsigned> &FirstActions) {
65  // The action table follows the call-site table in the LSDA. The individual
66  // records are of two types:
67  //
68  // * Catch clause
69  // * Exception specification
70  //
71  // The two record kinds have the same format, with only small differences.
72  // They are distinguished by the "switch value" field: Catch clauses
73  // (TypeInfos) have strictly positive switch values, and exception
74  // specifications (FilterIds) have strictly negative switch values. Value 0
75  // indicates a catch-all clause.
76  //
77  // Negative type IDs index into FilterIds. Positive type IDs index into
78  // TypeInfos. The value written for a positive type ID is just the type ID
79  // itself. For a negative type ID, however, the value written is the
80  // (negative) byte offset of the corresponding FilterIds entry. The byte
81  // offset is usually equal to the type ID (because the FilterIds entries are
82  // written using a variable width encoding, which outputs one byte per entry
83  // as long as the value written is not too large) but can differ. This kind
84  // of complication does not occur for positive type IDs because type infos are
85  // output using a fixed width encoding. FilterOffsets[i] holds the byte
86  // offset corresponding to FilterIds[i].
87 
88  const std::vector<unsigned> &FilterIds = Asm->MF->getFilterIds();
89  SmallVector<int, 16> FilterOffsets;
90  FilterOffsets.reserve(FilterIds.size());
91  int Offset = -1;
92 
93  for (std::vector<unsigned>::const_iterator
94  I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
95  FilterOffsets.push_back(Offset);
96  Offset -= getULEB128Size(*I);
97  }
98 
99  FirstActions.reserve(LandingPads.size());
100 
101  int FirstAction = 0;
102  unsigned SizeActions = 0;
103  const LandingPadInfo *PrevLPI = nullptr;
104 
106  I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
107  const LandingPadInfo *LPI = *I;
108  const std::vector<int> &TypeIds = LPI->TypeIds;
109  unsigned NumShared = PrevLPI ? sharedTypeIDs(LPI, PrevLPI) : 0;
110  unsigned SizeSiteActions = 0;
111 
112  if (NumShared < TypeIds.size()) {
113  unsigned SizeAction = 0;
114  unsigned PrevAction = (unsigned)-1;
115 
116  if (NumShared) {
117  unsigned SizePrevIds = PrevLPI->TypeIds.size();
118  assert(Actions.size());
119  PrevAction = Actions.size() - 1;
120  SizeAction = getSLEB128Size(Actions[PrevAction].NextAction) +
121  getSLEB128Size(Actions[PrevAction].ValueForTypeID);
122 
123  for (unsigned j = NumShared; j != SizePrevIds; ++j) {
124  assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
125  SizeAction -= getSLEB128Size(Actions[PrevAction].ValueForTypeID);
126  SizeAction += -Actions[PrevAction].NextAction;
127  PrevAction = Actions[PrevAction].Previous;
128  }
129  }
130 
131  // Compute the actions.
132  for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
133  int TypeID = TypeIds[J];
134  assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
135  int ValueForTypeID =
136  isFilterEHSelector(TypeID) ? FilterOffsets[-1 - TypeID] : TypeID;
137  unsigned SizeTypeID = getSLEB128Size(ValueForTypeID);
138 
139  int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
140  SizeAction = SizeTypeID + getSLEB128Size(NextAction);
141  SizeSiteActions += SizeAction;
142 
143  ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
144  Actions.push_back(Action);
145  PrevAction = Actions.size() - 1;
146  }
147 
148  // Record the first action of the landing pad site.
149  FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
150  } // else identical - re-use previous FirstAction
151 
152  // Information used when created the call-site table. The action record
153  // field of the call site record is the offset of the first associated
154  // action record, relative to the start of the actions table. This value is
155  // biased by 1 (1 indicating the start of the actions table), and 0
156  // indicates that there are no actions.
157  FirstActions.push_back(FirstAction);
158 
159  // Compute this sites contribution to size.
160  SizeActions += SizeSiteActions;
161 
162  PrevLPI = LPI;
163  }
164 
165  return SizeActions;
166 }
167 
168 /// Return `true' if this is a call to a function marked `nounwind'. Return
169 /// `false' otherwise.
171  assert(MI->isCall() && "This should be a call instruction!");
172 
173  bool MarkedNoUnwind = false;
174  bool SawFunc = false;
175 
176  for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
177  const MachineOperand &MO = MI->getOperand(I);
178 
179  if (!MO.isGlobal()) continue;
180 
181  const Function *F = dyn_cast<Function>(MO.getGlobal());
182  if (!F) continue;
183 
184  if (SawFunc) {
185  // Be conservative. If we have more than one function operand for this
186  // call, then we can't make the assumption that it's the callee and
187  // not a parameter to the call.
188  //
189  // FIXME: Determine if there's a way to say that `F' is the callee or
190  // parameter.
191  MarkedNoUnwind = false;
192  break;
193  }
194 
195  MarkedNoUnwind = F->doesNotThrow();
196  SawFunc = true;
197  }
198 
199  return MarkedNoUnwind;
200 }
201 
203  const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
204  RangeMapType &PadMap) {
205  // Invokes and nounwind calls have entries in PadMap (due to being bracketed
206  // by try-range labels when lowered). Ordinary calls do not, so appropriate
207  // try-ranges for them need be deduced so we can put them in the LSDA.
208  for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
209  const LandingPadInfo *LandingPad = LandingPads[i];
210  for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
211  MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
212  assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
213  PadRange P = { i, j };
214  PadMap[BeginLabel] = P;
215  }
216  }
217 }
218 
219 /// Compute the call-site table. The entry for an invoke has a try-range
220 /// containing the call, a non-zero landing pad, and an appropriate action. The
221 /// entry for an ordinary call has a try-range containing the call and zero for
222 /// the landing pad and the action. Calls marked 'nounwind' have no entry and
223 /// must not be contained in the try-range of any entry - they form gaps in the
224 /// table. Entries must be ordered by try-range address.
225 void EHStreamer::
227  const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
228  const SmallVectorImpl<unsigned> &FirstActions) {
229  RangeMapType PadMap;
230  computePadMap(LandingPads, PadMap);
231 
232  // The end label of the previous invoke or nounwind try-range.
233  MCSymbol *LastLabel = nullptr;
234 
235  // Whether there is a potentially throwing instruction (currently this means
236  // an ordinary call) between the end of the previous try-range and now.
237  bool SawPotentiallyThrowing = false;
238 
239  // Whether the last CallSite entry was for an invoke.
240  bool PreviousIsInvoke = false;
241 
243 
244  // Visit all instructions in order of address.
245  for (const auto &MBB : *Asm->MF) {
246  for (const auto &MI : MBB) {
247  if (!MI.isEHLabel()) {
248  if (MI.isCall())
249  SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
250  continue;
251  }
252 
253  // End of the previous try-range?
254  MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
255  if (BeginLabel == LastLabel)
256  SawPotentiallyThrowing = false;
257 
258  // Beginning of a new try-range?
259  RangeMapType::const_iterator L = PadMap.find(BeginLabel);
260  if (L == PadMap.end())
261  // Nope, it was just some random label.
262  continue;
263 
264  const PadRange &P = L->second;
265  const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
266  assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
267  "Inconsistent landing pad map!");
268 
269  // For Dwarf exception handling (SjLj handling doesn't use this). If some
270  // instruction between the previous try-range and this one may throw,
271  // create a call-site entry with no landing pad for the region between the
272  // try-ranges.
273  if (SawPotentiallyThrowing && Asm->MAI->usesCFIForEH()) {
274  CallSiteEntry Site = { LastLabel, BeginLabel, nullptr, 0 };
275  CallSites.push_back(Site);
276  PreviousIsInvoke = false;
277  }
278 
279  LastLabel = LandingPad->EndLabels[P.RangeIndex];
280  assert(BeginLabel && LastLabel && "Invalid landing pad!");
281 
282  if (!LandingPad->LandingPadLabel) {
283  // Create a gap.
284  PreviousIsInvoke = false;
285  } else {
286  // This try-range is for an invoke.
287  CallSiteEntry Site = {
288  BeginLabel,
289  LastLabel,
290  LandingPad,
291  FirstActions[P.PadIndex]
292  };
293 
294  // Try to merge with the previous call-site. SJLJ doesn't do this
295  if (PreviousIsInvoke && !IsSJLJ) {
296  CallSiteEntry &Prev = CallSites.back();
297  if (Site.LPad == Prev.LPad && Site.Action == Prev.Action) {
298  // Extend the range of the previous entry.
299  Prev.EndLabel = Site.EndLabel;
300  continue;
301  }
302  }
303 
304  // Otherwise, create a new call-site.
305  if (!IsSJLJ)
306  CallSites.push_back(Site);
307  else {
308  // SjLj EH must maintain the call sites in the order assigned
309  // to them by the SjLjPrepare pass.
310  unsigned SiteNo = Asm->MF->getCallSiteBeginLabel(BeginLabel);
311  if (CallSites.size() < SiteNo)
312  CallSites.resize(SiteNo);
313  CallSites[SiteNo - 1] = Site;
314  }
315  PreviousIsInvoke = true;
316  }
317  }
318  }
319 
320  // If some instruction between the previous try-range and the end of the
321  // function may throw, create a call-site entry with no landing pad for the
322  // region following the try-range.
323  if (SawPotentiallyThrowing && !IsSJLJ) {
324  CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
325  CallSites.push_back(Site);
326  }
327 }
328 
329 /// Emit landing pads and actions.
330 ///
331 /// The general organization of the table is complex, but the basic concepts are
332 /// easy. First there is a header which describes the location and organization
333 /// of the three components that follow.
334 ///
335 /// 1. The landing pad site information describes the range of code covered by
336 /// the try. In our case it's an accumulation of the ranges covered by the
337 /// invokes in the try. There is also a reference to the landing pad that
338 /// handles the exception once processed. Finally an index into the actions
339 /// table.
340 /// 2. The action table, in our case, is composed of pairs of type IDs and next
341 /// action offset. Starting with the action index from the landing pad
342 /// site, each type ID is checked for a match to the current exception. If
343 /// it matches then the exception and type id are passed on to the landing
344 /// pad. Otherwise the next action is looked up. This chain is terminated
345 /// with a next action of zero. If no type id is found then the frame is
346 /// unwound and handling continues.
347 /// 3. Type ID table contains references to all the C++ typeinfo for all
348 /// catches in the function. This tables is reverse indexed base 1.
350  const MachineFunction *MF = Asm->MF;
351  const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
352  const std::vector<unsigned> &FilterIds = MF->getFilterIds();
353  const std::vector<LandingPadInfo> &PadInfos = MF->getLandingPads();
354 
355  // Sort the landing pads in order of their type ids. This is used to fold
356  // duplicate actions.
358  LandingPads.reserve(PadInfos.size());
359 
360  for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
361  LandingPads.push_back(&PadInfos[i]);
362 
363  // Order landing pads lexicographically by type id.
364  std::sort(LandingPads.begin(), LandingPads.end(),
365  [](const LandingPadInfo *L,
366  const LandingPadInfo *R) { return L->TypeIds < R->TypeIds; });
367 
368  // Compute the actions table and gather the first action index for each
369  // landing pad site.
371  SmallVector<unsigned, 64> FirstActions;
372  unsigned SizeActions =
373  computeActionsTable(LandingPads, Actions, FirstActions);
374 
375  // Compute the call-site table.
377  computeCallSiteTable(CallSites, LandingPads, FirstActions);
378 
379  // Final tallies.
380 
381  // Call sites.
383  bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
384 
385  unsigned CallSiteTableLength;
386  if (IsSJLJ)
387  CallSiteTableLength = 0;
388  else {
389  unsigned SiteStartSize = 4; // dwarf::DW_EH_PE_udata4
390  unsigned SiteLengthSize = 4; // dwarf::DW_EH_PE_udata4
391  unsigned LandingPadSize = 4; // dwarf::DW_EH_PE_udata4
392  CallSiteTableLength =
393  CallSites.size() * (SiteStartSize + SiteLengthSize + LandingPadSize);
394  }
395 
396  for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
397  CallSiteTableLength += getULEB128Size(CallSites[i].Action);
398  if (IsSJLJ)
399  CallSiteTableLength += getULEB128Size(i);
400  }
401 
402  // Type infos.
403  MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
404  unsigned TTypeEncoding;
405  unsigned TypeFormatSize;
406 
407  if (!HaveTTData) {
408  // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
409  // that we're omitting that bit.
410  TTypeEncoding = dwarf::DW_EH_PE_omit;
411  // dwarf::DW_EH_PE_absptr
412  TypeFormatSize = Asm->getDataLayout().getPointerSize();
413  } else {
414  // Okay, we have actual filters or typeinfos to emit. As such, we need to
415  // pick a type encoding for them. We're about to emit a list of pointers to
416  // typeinfo objects at the end of the LSDA. However, unless we're in static
417  // mode, this reference will require a relocation by the dynamic linker.
418  //
419  // Because of this, we have a couple of options:
420  //
421  // 1) If we are in -static mode, we can always use an absolute reference
422  // from the LSDA, because the static linker will resolve it.
423  //
424  // 2) Otherwise, if the LSDA section is writable, we can output the direct
425  // reference to the typeinfo and allow the dynamic linker to relocate
426  // it. Since it is in a writable section, the dynamic linker won't
427  // have a problem.
428  //
429  // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
430  // we need to use some form of indirection. For example, on Darwin,
431  // we can output a statically-relocatable reference to a dyld stub. The
432  // offset to the stub is constant, but the contents are in a section
433  // that is updated by the dynamic linker. This is easy enough, but we
434  // need to tell the personality function of the unwinder to indirect
435  // through the dyld stub.
436  //
437  // FIXME: When (3) is actually implemented, we'll have to emit the stubs
438  // somewhere. This predicate should be moved to a shared location that is
439  // in target-independent code.
440  //
441  TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
442  TypeFormatSize = Asm->GetSizeOfEncodedValue(TTypeEncoding);
443  }
444 
445  // Begin the exception table.
446  // Sometimes we want not to emit the data into separate section (e.g. ARM
447  // EHABI). In this case LSDASection will be NULL.
448  if (LSDASection)
449  Asm->OutStreamer->SwitchSection(LSDASection);
450  Asm->EmitAlignment(2);
451 
452  // Emit the LSDA.
453  MCSymbol *GCCETSym =
454  Asm->OutContext.getOrCreateSymbol(Twine("GCC_except_table")+
456  Asm->OutStreamer->EmitLabel(GCCETSym);
457  Asm->OutStreamer->EmitLabel(Asm->getCurExceptionSym());
458 
459  // Emit the LSDA header.
461  Asm->EmitEncodingByte(TTypeEncoding, "@TType");
462 
463  // The type infos need to be aligned. GCC does this by inserting padding just
464  // before the type infos. However, this changes the size of the exception
465  // table, so you need to take this into account when you output the exception
466  // table size. However, the size is output using a variable length encoding.
467  // So by increasing the size by inserting padding, you may increase the number
468  // of bytes used for writing the size. If it increases, say by one byte, then
469  // you now need to output one less byte of padding to get the type infos
470  // aligned. However this decreases the size of the exception table. This
471  // changes the value you have to output for the exception table size. Due to
472  // the variable length encoding, the number of bytes used for writing the
473  // length may decrease. If so, you then have to increase the amount of
474  // padding. And so on. If you look carefully at the GCC code you will see that
475  // it indeed does this in a loop, going on and on until the values stabilize.
476  // We chose another solution: don't output padding inside the table like GCC
477  // does, instead output it before the table.
478  unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
479  unsigned CallSiteTableLengthSize = getULEB128Size(CallSiteTableLength);
480  unsigned TTypeBaseOffset =
481  sizeof(int8_t) + // Call site format
482  CallSiteTableLengthSize + // Call site table length size
483  CallSiteTableLength + // Call site table length
484  SizeActions + // Actions size
485  SizeTypes;
486  unsigned TTypeBaseOffsetSize = getULEB128Size(TTypeBaseOffset);
487  unsigned TotalSize =
488  sizeof(int8_t) + // LPStart format
489  sizeof(int8_t) + // TType format
490  (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size
491  TTypeBaseOffset; // TType base offset
492  unsigned PadBytes = (4 - TotalSize) & 3;
493 
494  if (HaveTTData) {
495  // Account for any extra padding that will be added to the call site table
496  // length.
497  Asm->EmitPaddedULEB128(TTypeBaseOffset, TTypeBaseOffsetSize + PadBytes,
498  "@TType base offset");
499  PadBytes = 0;
500  }
501 
502  bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
503 
504  // SjLj Exception handling
505  if (IsSJLJ) {
507 
508  // Add extra padding if it wasn't added to the TType base offset.
509  Asm->EmitPaddedULEB128(CallSiteTableLength,
510  CallSiteTableLengthSize + PadBytes,
511  "Call site table length");
512 
513  // Emit the landing pad site information.
514  unsigned idx = 0;
516  I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
517  const CallSiteEntry &S = *I;
518 
519  // Offset of the landing pad, counted in 16-byte bundles relative to the
520  // @LPStart address.
521  if (VerboseAsm) {
522  Asm->OutStreamer->AddComment(">> Call Site " + Twine(idx) + " <<");
523  Asm->OutStreamer->AddComment(" On exception at call site "+Twine(idx));
524  }
525  Asm->EmitULEB128(idx);
526 
527  // Offset of the first associated action record, relative to the start of
528  // the action table. This value is biased by 1 (1 indicates the start of
529  // the action table), and 0 indicates that there are no actions.
530  if (VerboseAsm) {
531  if (S.Action == 0)
532  Asm->OutStreamer->AddComment(" Action: cleanup");
533  else
534  Asm->OutStreamer->AddComment(" Action: " +
535  Twine((S.Action - 1) / 2 + 1));
536  }
537  Asm->EmitULEB128(S.Action);
538  }
539  } else {
540  // Itanium LSDA exception handling
541 
542  // The call-site table is a list of all call sites that may throw an
543  // exception (including C++ 'throw' statements) in the procedure
544  // fragment. It immediately follows the LSDA header. Each entry indicates,
545  // for a given call, the first corresponding action record and corresponding
546  // landing pad.
547  //
548  // The table begins with the number of bytes, stored as an LEB128
549  // compressed, unsigned integer. The records immediately follow the record
550  // count. They are sorted in increasing call-site address. Each record
551  // indicates:
552  //
553  // * The position of the call-site.
554  // * The position of the landing pad.
555  // * The first action record for that call site.
556  //
557  // A missing entry in the call-site table indicates that a call is not
558  // supposed to throw.
559 
560  // Emit the landing pad call site table.
562 
563  // Add extra padding if it wasn't added to the TType base offset.
564  Asm->EmitPaddedULEB128(CallSiteTableLength,
565  CallSiteTableLengthSize + PadBytes,
566  "Call site table length");
567 
568  unsigned Entry = 0;
570  I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
571  const CallSiteEntry &S = *I;
572 
573  MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
574 
575  MCSymbol *BeginLabel = S.BeginLabel;
576  if (!BeginLabel)
577  BeginLabel = EHFuncBeginSym;
578  MCSymbol *EndLabel = S.EndLabel;
579  if (!EndLabel)
580  EndLabel = Asm->getFunctionEnd();
581 
582  // Offset of the call site relative to the previous call site, counted in
583  // number of 16-byte bundles. The first call site is counted relative to
584  // the start of the procedure fragment.
585  if (VerboseAsm)
586  Asm->OutStreamer->AddComment(">> Call Site " + Twine(++Entry) + " <<");
587  Asm->EmitLabelDifference(BeginLabel, EHFuncBeginSym, 4);
588  if (VerboseAsm)
589  Asm->OutStreamer->AddComment(Twine(" Call between ") +
590  BeginLabel->getName() + " and " +
591  EndLabel->getName());
592  Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
593 
594  // Offset of the landing pad, counted in 16-byte bundles relative to the
595  // @LPStart address.
596  if (!S.LPad) {
597  if (VerboseAsm)
598  Asm->OutStreamer->AddComment(" has no landing pad");
599  Asm->OutStreamer->EmitIntValue(0, 4/*size*/);
600  } else {
601  if (VerboseAsm)
602  Asm->OutStreamer->AddComment(Twine(" jumps to ") +
604  Asm->EmitLabelDifference(S.LPad->LandingPadLabel, EHFuncBeginSym, 4);
605  }
606 
607  // Offset of the first associated action record, relative to the start of
608  // the action table. This value is biased by 1 (1 indicates the start of
609  // the action table), and 0 indicates that there are no actions.
610  if (VerboseAsm) {
611  if (S.Action == 0)
612  Asm->OutStreamer->AddComment(" On action: cleanup");
613  else
614  Asm->OutStreamer->AddComment(" On action: " +
615  Twine((S.Action - 1) / 2 + 1));
616  }
617  Asm->EmitULEB128(S.Action);
618  }
619  }
620 
621  // Emit the Action Table.
622  int Entry = 0;
624  I = Actions.begin(), E = Actions.end(); I != E; ++I) {
625  const ActionEntry &Action = *I;
626 
627  if (VerboseAsm) {
628  // Emit comments that decode the action table.
629  Asm->OutStreamer->AddComment(">> Action Record " + Twine(++Entry) + " <<");
630  }
631 
632  // Type Filter
633  //
634  // Used by the runtime to match the type of the thrown exception to the
635  // type of the catch clauses or the types in the exception specification.
636  if (VerboseAsm) {
637  if (Action.ValueForTypeID > 0)
638  Asm->OutStreamer->AddComment(" Catch TypeInfo " +
639  Twine(Action.ValueForTypeID));
640  else if (Action.ValueForTypeID < 0)
641  Asm->OutStreamer->AddComment(" Filter TypeInfo " +
642  Twine(Action.ValueForTypeID));
643  else
644  Asm->OutStreamer->AddComment(" Cleanup");
645  }
646  Asm->EmitSLEB128(Action.ValueForTypeID);
647 
648  // Action Record
649  //
650  // Self-relative signed displacement in bytes of the next action record,
651  // or 0 if there is no next action record.
652  if (VerboseAsm) {
653  if (Action.NextAction == 0) {
654  Asm->OutStreamer->AddComment(" No further actions");
655  } else {
656  unsigned NextAction = Entry + (Action.NextAction + 1) / 2;
657  Asm->OutStreamer->AddComment(" Continue to action "+Twine(NextAction));
658  }
659  }
660  Asm->EmitSLEB128(Action.NextAction);
661  }
662 
663  emitTypeInfos(TTypeEncoding);
664 
665  Asm->EmitAlignment(2);
666 }
667 
668 void EHStreamer::emitTypeInfos(unsigned TTypeEncoding) {
669  const MachineFunction *MF = Asm->MF;
670  const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
671  const std::vector<unsigned> &FilterIds = MF->getFilterIds();
672 
673  bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
674 
675  int Entry = 0;
676  // Emit the Catch TypeInfos.
677  if (VerboseAsm && !TypeInfos.empty()) {
678  Asm->OutStreamer->AddComment(">> Catch TypeInfos <<");
679  Asm->OutStreamer->AddBlankLine();
680  Entry = TypeInfos.size();
681  }
682 
683  for (const GlobalValue *GV : make_range(TypeInfos.rbegin(),
684  TypeInfos.rend())) {
685  if (VerboseAsm)
686  Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--));
687  Asm->EmitTTypeReference(GV, TTypeEncoding);
688  }
689 
690  // Emit the Exception Specifications.
691  if (VerboseAsm && !FilterIds.empty()) {
692  Asm->OutStreamer->AddComment(">> Filter TypeInfos <<");
693  Asm->OutStreamer->AddBlankLine();
694  Entry = 0;
695  }
696  for (std::vector<unsigned>::const_iterator
697  I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
698  unsigned TypeID = *I;
699  if (VerboseAsm) {
700  --Entry;
701  if (isFilterEHSelector(TypeID))
702  Asm->OutStreamer->AddComment("FilterInfo " + Twine(Entry));
703  }
704 
705  Asm->EmitULEB128(TypeID);
706  }
707 }
const TargetLoweringObjectFile & getObjFileLowering() const
Return information about object file lowering.
Definition: AsmPrinter.cpp:205
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
static unsigned sharedTypeIDs(const LandingPadInfo *L, const LandingPadInfo *R)
How many leading type ids two landing pads have in common.
Definition: EHStreamer.cpp:45
Structure describing an entry in the call-site table.
Definition: EHStreamer.h:62
bool isCall(QueryType Type=AnyInBundle) const
Definition: MachineInstr.h:458
typename SuperClass::const_iterator const_iterator
Definition: SmallVector.h:329
std::unique_ptr< MCStreamer > OutStreamer
This is the MCStreamer object for the file we are generating.
Definition: AsmPrinter.h:92
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
MCContext & OutContext
This is the context for the output file that we are streaming.
Definition: AsmPrinter.h:87
DWARF-like instruction based exceptions.
EHStreamer(AsmPrinter *A)
Definition: EHStreamer.cpp:40
This provides a very simple, boring adaptor for a begin and end iterator into a range type...
static bool callToNoUnwindFunction(const MachineInstr *MI)
Return `true&#39; if this is a call to a function marked `nounwind&#39;.
Definition: EHStreamer.cpp:170
const MachineFunction * MF
The current machine function.
Definition: AsmPrinter.h:95
unsigned getCallSiteBeginLabel(MCSymbol *BeginLabel) const
Get the call site number for a begin label.
F(f)
Structure describing an entry in the actions table.
Definition: EHStreamer.h:55
void reserve(size_type N)
Definition: SmallVector.h:380
static bool isFilterEHSelector(int Selector)
Definition: EHStreamer.h:118
const LandingPadInfo * LPad
Definition: EHStreamer.h:68
const std::vector< unsigned > & getFilterIds() const
Return a reference to the typeids encoding filters used in the current function.
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
SmallVector< MCSymbol *, 1 > EndLabels
unsigned getNumOperands() const
Access to explicit operands of the instruction.
Definition: MachineInstr.h:293
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:42
TypeID
Definitions of all of the base types for the Type system.
Definition: Type.h:55
~EHStreamer() override
void EmitAlignment(unsigned NumBits, const GlobalObject *GO=nullptr) const
Emit an alignment directive to the specified power of two boundary.
void emitExceptionTable()
Emit landing pads and actions.
Definition: EHStreamer.cpp:349
This structure is used to retain landing pad info for the current function.
MCSymbol * getFunctionBegin() const
Definition: AsmPrinter.h:194
iterator find(const_arg_type_t< KeyT > Val)
Definition: DenseMap.h:146
#define P(N)
void EmitPaddedULEB128(uint64_t Value, unsigned PadTo, const char *Desc=nullptr) const
Emit the specified unsigned leb128 value padded to a specific number bytes.
const MCAsmInfo * MAI
Target Asm Printer information.
Definition: AsmPrinter.h:83
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
SmallVector< MCSymbol *, 1 > BeginLabels
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:605
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:116
const GlobalValue * getGlobal() const
void EmitEncodingByte(unsigned Val, const char *Desc=nullptr) const
Emit a .byte 42 directive that corresponds to an encoding.
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:77
Type::TypeID TypeID
std::vector< int > TypeIds
virtual void emitTypeInfos(unsigned TTypeEncoding)
Definition: EHStreamer.cpp:668
unsigned GetSizeOfEncodedValue(unsigned Encoding) const
Return the size of the encoding in bytes.
AsmPrinter * Asm
Target of directive emission.
Definition: EHStreamer.h:34
unsigned getULEB128Size(uint64_t Value)
Utility function to get the size of the ULEB128-encoded value.
Definition: LEB128.cpp:20
bool doesNotThrow() const
Determine if the function cannot unwind.
Definition: Function.h:452
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
unsigned getFunctionNumber() const
Return a unique ID for the current function.
Definition: AsmPrinter.cpp:201
const std::vector< LandingPadInfo > & getLandingPads() const
Return a reference to the landing pad info for the current function.
void EmitSLEB128(int64_t Value, const char *Desc=nullptr) const
Emit the specified signed leb128 value.
bool isGlobal() const
isGlobal - Tests if this is a MO_GlobalAddress operand.
MachineOperand class - Representation of each machine instruction operand.
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const
Emit reference to a ttype global with a specified encoding.
MCSymbol * getFunctionEnd() const
Definition: AsmPrinter.h:195
bool usesCFIForEH() const
Returns true if the exception handling method for the platform uses call frame information to unwind...
Definition: MCAsmInfo.h:563
void computeCallSiteTable(SmallVectorImpl< CallSiteEntry > &CallSites, const SmallVectorImpl< const LandingPadInfo *> &LPs, const SmallVectorImpl< unsigned > &FirstActions)
Compute the call-site table.
Definition: EHStreamer.cpp:226
This file contains constants used for implementing Dwarf debug support.
MCSymbol * getCurExceptionSym()
void computePadMap(const SmallVectorImpl< const LandingPadInfo *> &LandingPads, RangeMapType &PadMap)
Definition: EHStreamer.cpp:202
Representation of each machine instruction.
Definition: MachineInstr.h:59
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:120
MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition: MCContext.cpp:121
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
iterator end()
Definition: DenseMap.h:79
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...
LLVM_NODISCARD 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:323
size_type count(const_arg_type_t< KeyT > Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:141
unsigned getSLEB128Size(int64_t Value)
Utility function to get the size of the SLEB128-encoded value.
Definition: LEB128.cpp:30
StringRef getName() const
getName - Get the symbol name.
Definition: MCSymbol.h:203
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
void EmitULEB128(uint64_t Value, const char *Desc=nullptr) const
Emit the specified unsigned leb128 value.
ExceptionHandling getExceptionHandlingType() const
Definition: MCAsmInfo.h:554
MCSection * getLSDASection() const
const DataLayout & getDataLayout() const
Return information about data layout.
Definition: AsmPrinter.cpp:209
IRTranslator LLVM IR MI
void sort(Policy policy, RandomAccessIterator Start, RandomAccessIterator End, const Comparator &Comp=Comparator())
Definition: Parallel.h:199
unsigned getTTypeEncoding() const
const std::vector< const GlobalValue * > & getTypeInfos() const
Return a reference to the C++ typeinfo for the current function.
const MachineOperand & getOperand(unsigned i) const
Definition: MachineInstr.h:295
Structure holding a try-range and the associated landing pad.
Definition: EHStreamer.h:44
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:62
void resize(size_type N)
Definition: SmallVector.h:355