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"
17 #include "llvm/ADT/iterator_range.h"
18 #include "llvm/BinaryFormat/Dwarf.h"
19 #include "llvm/CodeGen/AsmPrinter.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineInstr.h"
22 #include "llvm/CodeGen/MachineOperand.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
29 #include "llvm/MC/MCTargetOptions.h"
30 #include "llvm/Support/Casting.h"
31 #include "llvm/Support/LEB128.h"
32 #include "llvm/Target/TargetLoweringObjectFile.h"
33 #include <algorithm>
34 #include <cassert>
35 #include <cstdint>
36 #include <vector>
37
38 using namespace llvm;
39
EHStreamer(AsmPrinter * A)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.
sharedTypeIDs(const LandingPadInfo * L,const LandingPadInfo * R)45 unsigned EHStreamer::sharedTypeIDs(const LandingPadInfo *L,
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.
computeActionsTable(const SmallVectorImpl<const LandingPadInfo * > & LandingPads,SmallVectorImpl<ActionEntry> & Actions,SmallVectorImpl<unsigned> & FirstActions)61 void EHStreamer::computeActionsTable(
62 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
63 SmallVectorImpl<ActionEntry> &Actions,
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
105 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
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 creating 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
166 /// Return `true' if this is a call to a function marked `nounwind'. Return
167 /// `false' otherwise.
callToNoUnwindFunction(const MachineInstr * MI)168 bool EHStreamer::callToNoUnwindFunction(const MachineInstr *MI) {
169 assert(MI->isCall() && "This should be a call instruction!");
170
171 bool MarkedNoUnwind = false;
172 bool SawFunc = false;
173
174 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
175 const MachineOperand &MO = MI->getOperand(I);
176
177 if (!MO.isGlobal()) continue;
178
179 const Function *F = dyn_cast<Function>(MO.getGlobal());
180 if (!F) continue;
181
182 if (SawFunc) {
183 // Be conservative. If we have more than one function operand for this
184 // call, then we can't make the assumption that it's the callee and
185 // not a parameter to the call.
186 //
187 // FIXME: Determine if there's a way to say that `F' is the callee or
188 // parameter.
189 MarkedNoUnwind = false;
190 break;
191 }
192
193 MarkedNoUnwind = F->doesNotThrow();
194 SawFunc = true;
195 }
196
197 return MarkedNoUnwind;
198 }
199
computePadMap(const SmallVectorImpl<const LandingPadInfo * > & LandingPads,RangeMapType & PadMap)200 void EHStreamer::computePadMap(
201 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
202 RangeMapType &PadMap) {
203 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
204 // by try-range labels when lowered). Ordinary calls do not, so appropriate
205 // try-ranges for them need be deduced so we can put them in the LSDA.
206 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
207 const LandingPadInfo *LandingPad = LandingPads[i];
208 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
209 MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
210 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
211 PadRange P = { i, j };
212 PadMap[BeginLabel] = P;
213 }
214 }
215 }
216
217 /// Compute the call-site table. The entry for an invoke has a try-range
218 /// containing the call, a non-zero landing pad, and an appropriate action. The
219 /// entry for an ordinary call has a try-range containing the call and zero for
220 /// the landing pad and the action. Calls marked 'nounwind' have no entry and
221 /// must not be contained in the try-range of any entry - they form gaps in the
222 /// table. Entries must be ordered by try-range address.
223 void EHStreamer::
computeCallSiteTable(SmallVectorImpl<CallSiteEntry> & CallSites,const SmallVectorImpl<const LandingPadInfo * > & LandingPads,const SmallVectorImpl<unsigned> & FirstActions)224 computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
225 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
226 const SmallVectorImpl<unsigned> &FirstActions) {
227 RangeMapType PadMap;
228 computePadMap(LandingPads, PadMap);
229
230 // The end label of the previous invoke or nounwind try-range.
231 MCSymbol *LastLabel = nullptr;
232
233 // Whether there is a potentially throwing instruction (currently this means
234 // an ordinary call) between the end of the previous try-range and now.
235 bool SawPotentiallyThrowing = false;
236
237 // Whether the last CallSite entry was for an invoke.
238 bool PreviousIsInvoke = false;
239
240 bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
241
242 // Visit all instructions in order of address.
243 for (const auto &MBB : *Asm->MF) {
244 for (const auto &MI : MBB) {
245 if (!MI.isEHLabel()) {
246 if (MI.isCall())
247 SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
248 continue;
249 }
250
251 // End of the previous try-range?
252 MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
253 if (BeginLabel == LastLabel)
254 SawPotentiallyThrowing = false;
255
256 // Beginning of a new try-range?
257 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
258 if (L == PadMap.end())
259 // Nope, it was just some random label.
260 continue;
261
262 const PadRange &P = L->second;
263 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
264 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
265 "Inconsistent landing pad map!");
266
267 // For Dwarf exception handling (SjLj handling doesn't use this). If some
268 // instruction between the previous try-range and this one may throw,
269 // create a call-site entry with no landing pad for the region between the
270 // try-ranges.
271 if (SawPotentiallyThrowing && Asm->MAI->usesCFIForEH()) {
272 CallSiteEntry Site = { LastLabel, BeginLabel, nullptr, 0 };
273 CallSites.push_back(Site);
274 PreviousIsInvoke = false;
275 }
276
277 LastLabel = LandingPad->EndLabels[P.RangeIndex];
278 assert(BeginLabel && LastLabel && "Invalid landing pad!");
279
280 if (!LandingPad->LandingPadLabel) {
281 // Create a gap.
282 PreviousIsInvoke = false;
283 } else {
284 // This try-range is for an invoke.
285 CallSiteEntry Site = {
286 BeginLabel,
287 LastLabel,
288 LandingPad,
289 FirstActions[P.PadIndex]
290 };
291
292 // Try to merge with the previous call-site. SJLJ doesn't do this
293 if (PreviousIsInvoke && !IsSJLJ) {
294 CallSiteEntry &Prev = CallSites.back();
295 if (Site.LPad == Prev.LPad && Site.Action == Prev.Action) {
296 // Extend the range of the previous entry.
297 Prev.EndLabel = Site.EndLabel;
298 continue;
299 }
300 }
301
302 // Otherwise, create a new call-site.
303 if (!IsSJLJ)
304 CallSites.push_back(Site);
305 else {
306 // SjLj EH must maintain the call sites in the order assigned
307 // to them by the SjLjPrepare pass.
308 unsigned SiteNo = Asm->MF->getCallSiteBeginLabel(BeginLabel);
309 if (CallSites.size() < SiteNo)
310 CallSites.resize(SiteNo);
311 CallSites[SiteNo - 1] = Site;
312 }
313 PreviousIsInvoke = true;
314 }
315 }
316 }
317
318 // If some instruction between the previous try-range and the end of the
319 // function may throw, create a call-site entry with no landing pad for the
320 // region following the try-range.
321 if (SawPotentiallyThrowing && !IsSJLJ) {
322 CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
323 CallSites.push_back(Site);
324 }
325 }
326
327 /// Emit landing pads and actions.
328 ///
329 /// The general organization of the table is complex, but the basic concepts are
330 /// easy. First there is a header which describes the location and organization
331 /// of the three components that follow.
332 ///
333 /// 1. The landing pad site information describes the range of code covered by
334 /// the try. In our case it's an accumulation of the ranges covered by the
335 /// invokes in the try. There is also a reference to the landing pad that
336 /// handles the exception once processed. Finally an index into the actions
337 /// table.
338 /// 2. The action table, in our case, is composed of pairs of type IDs and next
339 /// action offset. Starting with the action index from the landing pad
340 /// site, each type ID is checked for a match to the current exception. If
341 /// it matches then the exception and type id are passed on to the landing
342 /// pad. Otherwise the next action is looked up. This chain is terminated
343 /// with a next action of zero. If no type id is found then the frame is
344 /// unwound and handling continues.
345 /// 3. Type ID table contains references to all the C++ typeinfo for all
346 /// catches in the function. This tables is reverse indexed base 1.
emitExceptionTable()347 void EHStreamer::emitExceptionTable() {
348 const MachineFunction *MF = Asm->MF;
349 const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
350 const std::vector<unsigned> &FilterIds = MF->getFilterIds();
351 const std::vector<LandingPadInfo> &PadInfos = MF->getLandingPads();
352
353 // Sort the landing pads in order of their type ids. This is used to fold
354 // duplicate actions.
355 SmallVector<const LandingPadInfo *, 64> LandingPads;
356 LandingPads.reserve(PadInfos.size());
357
358 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
359 LandingPads.push_back(&PadInfos[i]);
360
361 // Order landing pads lexicographically by type id.
362 llvm::sort(LandingPads.begin(), LandingPads.end(),
363 [](const LandingPadInfo *L,
364 const LandingPadInfo *R) { return L->TypeIds < R->TypeIds; });
365
366 // Compute the actions table and gather the first action index for each
367 // landing pad site.
368 SmallVector<ActionEntry, 32> Actions;
369 SmallVector<unsigned, 64> FirstActions;
370 computeActionsTable(LandingPads, Actions, FirstActions);
371
372 // Compute the call-site table.
373 SmallVector<CallSiteEntry, 64> CallSites;
374 computeCallSiteTable(CallSites, LandingPads, FirstActions);
375
376 bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
377 unsigned CallSiteEncoding =
378 IsSJLJ ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_uleb128;
379 bool HaveTTData = !TypeInfos.empty() || !FilterIds.empty();
380
381 // Type infos.
382 MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
383 unsigned TTypeEncoding;
384
385 if (!HaveTTData) {
386 // If there is no TypeInfo, then we just explicitly say that we're omitting
387 // that bit.
388 TTypeEncoding = dwarf::DW_EH_PE_omit;
389 } else {
390 // Okay, we have actual filters or typeinfos to emit. As such, we need to
391 // pick a type encoding for them. We're about to emit a list of pointers to
392 // typeinfo objects at the end of the LSDA. However, unless we're in static
393 // mode, this reference will require a relocation by the dynamic linker.
394 //
395 // Because of this, we have a couple of options:
396 //
397 // 1) If we are in -static mode, we can always use an absolute reference
398 // from the LSDA, because the static linker will resolve it.
399 //
400 // 2) Otherwise, if the LSDA section is writable, we can output the direct
401 // reference to the typeinfo and allow the dynamic linker to relocate
402 // it. Since it is in a writable section, the dynamic linker won't
403 // have a problem.
404 //
405 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
406 // we need to use some form of indirection. For example, on Darwin,
407 // we can output a statically-relocatable reference to a dyld stub. The
408 // offset to the stub is constant, but the contents are in a section
409 // that is updated by the dynamic linker. This is easy enough, but we
410 // need to tell the personality function of the unwinder to indirect
411 // through the dyld stub.
412 //
413 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
414 // somewhere. This predicate should be moved to a shared location that is
415 // in target-independent code.
416 //
417 TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
418 }
419
420 // Begin the exception table.
421 // Sometimes we want not to emit the data into separate section (e.g. ARM
422 // EHABI). In this case LSDASection will be NULL.
423 if (LSDASection)
424 Asm->OutStreamer->SwitchSection(LSDASection);
425 Asm->EmitAlignment(2);
426
427 // Emit the LSDA.
428 MCSymbol *GCCETSym =
429 Asm->OutContext.getOrCreateSymbol(Twine("GCC_except_table")+
430 Twine(Asm->getFunctionNumber()));
431 Asm->OutStreamer->EmitLabel(GCCETSym);
432 Asm->OutStreamer->EmitLabel(Asm->getCurExceptionSym());
433
434 // Emit the LSDA header.
435 Asm->EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
436 Asm->EmitEncodingByte(TTypeEncoding, "@TType");
437
438 MCSymbol *TTBaseLabel = nullptr;
439 if (HaveTTData) {
440 // N.B.: There is a dependency loop between the size of the TTBase uleb128
441 // here and the amount of padding before the aligned type table. The
442 // assembler must sometimes pad this uleb128 or insert extra padding before
443 // the type table. See PR35809 or GNU as bug 4029.
444 MCSymbol *TTBaseRefLabel = Asm->createTempSymbol("ttbaseref");
445 TTBaseLabel = Asm->createTempSymbol("ttbase");
446 Asm->EmitLabelDifferenceAsULEB128(TTBaseLabel, TTBaseRefLabel);
447 Asm->OutStreamer->EmitLabel(TTBaseRefLabel);
448 }
449
450 bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
451
452 // Emit the landing pad call site table.
453 MCSymbol *CstBeginLabel = Asm->createTempSymbol("cst_begin");
454 MCSymbol *CstEndLabel = Asm->createTempSymbol("cst_end");
455 Asm->EmitEncodingByte(CallSiteEncoding, "Call site");
456 Asm->EmitLabelDifferenceAsULEB128(CstEndLabel, CstBeginLabel);
457 Asm->OutStreamer->EmitLabel(CstBeginLabel);
458
459 // SjLj Exception handling
460 if (IsSJLJ) {
461 unsigned idx = 0;
462 for (SmallVectorImpl<CallSiteEntry>::const_iterator
463 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
464 const CallSiteEntry &S = *I;
465
466 // Index of the call site entry.
467 if (VerboseAsm) {
468 Asm->OutStreamer->AddComment(">> Call Site " + Twine(idx) + " <<");
469 Asm->OutStreamer->AddComment(" On exception at call site "+Twine(idx));
470 }
471 Asm->EmitULEB128(idx);
472
473 // Offset of the first associated action record, relative to the start of
474 // the action table. This value is biased by 1 (1 indicates the start of
475 // the action table), and 0 indicates that there are no actions.
476 if (VerboseAsm) {
477 if (S.Action == 0)
478 Asm->OutStreamer->AddComment(" Action: cleanup");
479 else
480 Asm->OutStreamer->AddComment(" Action: " +
481 Twine((S.Action - 1) / 2 + 1));
482 }
483 Asm->EmitULEB128(S.Action);
484 }
485 } else {
486 // Itanium LSDA exception handling
487
488 // The call-site table is a list of all call sites that may throw an
489 // exception (including C++ 'throw' statements) in the procedure
490 // fragment. It immediately follows the LSDA header. Each entry indicates,
491 // for a given call, the first corresponding action record and corresponding
492 // landing pad.
493 //
494 // The table begins with the number of bytes, stored as an LEB128
495 // compressed, unsigned integer. The records immediately follow the record
496 // count. They are sorted in increasing call-site address. Each record
497 // indicates:
498 //
499 // * The position of the call-site.
500 // * The position of the landing pad.
501 // * The first action record for that call site.
502 //
503 // A missing entry in the call-site table indicates that a call is not
504 // supposed to throw.
505
506 unsigned Entry = 0;
507 for (SmallVectorImpl<CallSiteEntry>::const_iterator
508 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
509 const CallSiteEntry &S = *I;
510
511 MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
512
513 MCSymbol *BeginLabel = S.BeginLabel;
514 if (!BeginLabel)
515 BeginLabel = EHFuncBeginSym;
516 MCSymbol *EndLabel = S.EndLabel;
517 if (!EndLabel)
518 EndLabel = Asm->getFunctionEnd();
519
520 // Offset of the call site relative to the start of the procedure.
521 if (VerboseAsm)
522 Asm->OutStreamer->AddComment(">> Call Site " + Twine(++Entry) + " <<");
523 Asm->EmitLabelDifferenceAsULEB128(BeginLabel, EHFuncBeginSym);
524 if (VerboseAsm)
525 Asm->OutStreamer->AddComment(Twine(" Call between ") +
526 BeginLabel->getName() + " and " +
527 EndLabel->getName());
528 Asm->EmitLabelDifferenceAsULEB128(EndLabel, BeginLabel);
529
530 // Offset of the landing pad relative to the start of the procedure.
531 if (!S.LPad) {
532 if (VerboseAsm)
533 Asm->OutStreamer->AddComment(" has no landing pad");
534 Asm->EmitULEB128(0);
535 } else {
536 if (VerboseAsm)
537 Asm->OutStreamer->AddComment(Twine(" jumps to ") +
538 S.LPad->LandingPadLabel->getName());
539 Asm->EmitLabelDifferenceAsULEB128(S.LPad->LandingPadLabel,
540 EHFuncBeginSym);
541 }
542
543 // Offset of the first associated action record, relative to the start of
544 // the action table. This value is biased by 1 (1 indicates the start of
545 // the action table), and 0 indicates that there are no actions.
546 if (VerboseAsm) {
547 if (S.Action == 0)
548 Asm->OutStreamer->AddComment(" On action: cleanup");
549 else
550 Asm->OutStreamer->AddComment(" On action: " +
551 Twine((S.Action - 1) / 2 + 1));
552 }
553 Asm->EmitULEB128(S.Action);
554 }
555 }
556 Asm->OutStreamer->EmitLabel(CstEndLabel);
557
558 // Emit the Action Table.
559 int Entry = 0;
560 for (SmallVectorImpl<ActionEntry>::const_iterator
561 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
562 const ActionEntry &Action = *I;
563
564 if (VerboseAsm) {
565 // Emit comments that decode the action table.
566 Asm->OutStreamer->AddComment(">> Action Record " + Twine(++Entry) + " <<");
567 }
568
569 // Type Filter
570 //
571 // Used by the runtime to match the type of the thrown exception to the
572 // type of the catch clauses or the types in the exception specification.
573 if (VerboseAsm) {
574 if (Action.ValueForTypeID > 0)
575 Asm->OutStreamer->AddComment(" Catch TypeInfo " +
576 Twine(Action.ValueForTypeID));
577 else if (Action.ValueForTypeID < 0)
578 Asm->OutStreamer->AddComment(" Filter TypeInfo " +
579 Twine(Action.ValueForTypeID));
580 else
581 Asm->OutStreamer->AddComment(" Cleanup");
582 }
583 Asm->EmitSLEB128(Action.ValueForTypeID);
584
585 // Action Record
586 //
587 // Self-relative signed displacement in bytes of the next action record,
588 // or 0 if there is no next action record.
589 if (VerboseAsm) {
590 if (Action.NextAction == 0) {
591 Asm->OutStreamer->AddComment(" No further actions");
592 } else {
593 unsigned NextAction = Entry + (Action.NextAction + 1) / 2;
594 Asm->OutStreamer->AddComment(" Continue to action "+Twine(NextAction));
595 }
596 }
597 Asm->EmitSLEB128(Action.NextAction);
598 }
599
600 if (HaveTTData) {
601 Asm->EmitAlignment(2);
602 emitTypeInfos(TTypeEncoding, TTBaseLabel);
603 }
604
605 Asm->EmitAlignment(2);
606 }
607
emitTypeInfos(unsigned TTypeEncoding,MCSymbol * TTBaseLabel)608 void EHStreamer::emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel) {
609 const MachineFunction *MF = Asm->MF;
610 const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
611 const std::vector<unsigned> &FilterIds = MF->getFilterIds();
612
613 bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
614
615 int Entry = 0;
616 // Emit the Catch TypeInfos.
617 if (VerboseAsm && !TypeInfos.empty()) {
618 Asm->OutStreamer->AddComment(">> Catch TypeInfos <<");
619 Asm->OutStreamer->AddBlankLine();
620 Entry = TypeInfos.size();
621 }
622
623 for (const GlobalValue *GV : make_range(TypeInfos.rbegin(),
624 TypeInfos.rend())) {
625 if (VerboseAsm)
626 Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--));
627 Asm->EmitTTypeReference(GV, TTypeEncoding);
628 }
629
630 Asm->OutStreamer->EmitLabel(TTBaseLabel);
631
632 // Emit the Exception Specifications.
633 if (VerboseAsm && !FilterIds.empty()) {
634 Asm->OutStreamer->AddComment(">> Filter TypeInfos <<");
635 Asm->OutStreamer->AddBlankLine();
636 Entry = 0;
637 }
638 for (std::vector<unsigned>::const_iterator
639 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
640 unsigned TypeID = *I;
641 if (VerboseAsm) {
642 --Entry;
643 if (isFilterEHSelector(TypeID))
644 Asm->OutStreamer->AddComment("FilterInfo " + Twine(Entry));
645 }
646
647 Asm->EmitULEB128(TypeID);
648 }
649 }
650