1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains support for writing DWARF exception info into asm files.
12 //===----------------------------------------------------------------------===//
14 #include "DwarfException.h"
15 #include "llvm/ADT/SmallString.h"
16 #include "llvm/ADT/StringExtras.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/IR/Mangler.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/Support/Dwarf.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/FormattedStream.h"
34 #include "llvm/Support/LEB128.h"
35 #include "llvm/Target/TargetFrameLowering.h"
36 #include "llvm/Target/TargetLoweringObjectFile.h"
37 #include "llvm/Target/TargetOptions.h"
38 #include "llvm/Target/TargetRegisterInfo.h"
41 DwarfException::DwarfException(AsmPrinter *A)
42 : Asm(A), MMI(Asm->MMI) {}
44 DwarfException::~DwarfException() {}
46 /// SharedTypeIds - How many leading type ids two landing pads have in common.
47 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
48 const LandingPadInfo *R) {
49 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
50 unsigned LSize = LIds.size(), RSize = RIds.size();
51 unsigned MinSize = LSize < RSize ? LSize : RSize;
54 for (; Count != MinSize; ++Count)
55 if (LIds[Count] != RIds[Count])
61 /// ComputeActionsTable - Compute the actions table and gather the first action
62 /// index for each landing pad site.
63 unsigned DwarfException::
64 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
65 SmallVectorImpl<ActionEntry> &Actions,
66 SmallVectorImpl<unsigned> &FirstActions) {
68 // The action table follows the call-site table in the LSDA. The individual
69 // records are of two types:
72 // * Exception specification
74 // The two record kinds have the same format, with only small differences.
75 // They are distinguished by the "switch value" field: Catch clauses
76 // (TypeInfos) have strictly positive switch values, and exception
77 // specifications (FilterIds) have strictly negative switch values. Value 0
78 // indicates a catch-all clause.
80 // Negative type IDs index into FilterIds. Positive type IDs index into
81 // TypeInfos. The value written for a positive type ID is just the type ID
82 // itself. For a negative type ID, however, the value written is the
83 // (negative) byte offset of the corresponding FilterIds entry. The byte
84 // offset is usually equal to the type ID (because the FilterIds entries are
85 // written using a variable width encoding, which outputs one byte per entry
86 // as long as the value written is not too large) but can differ. This kind
87 // of complication does not occur for positive type IDs because type infos are
88 // output using a fixed width encoding. FilterOffsets[i] holds the byte
89 // offset corresponding to FilterIds[i].
91 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
92 SmallVector<int, 16> FilterOffsets;
93 FilterOffsets.reserve(FilterIds.size());
96 for (std::vector<unsigned>::const_iterator
97 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
98 FilterOffsets.push_back(Offset);
99 Offset -= getULEB128Size(*I);
102 FirstActions.reserve(LandingPads.size());
105 unsigned SizeActions = 0;
106 const LandingPadInfo *PrevLPI = nullptr;
108 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
109 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
110 const LandingPadInfo *LPI = *I;
111 const std::vector<int> &TypeIds = LPI->TypeIds;
112 unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
113 unsigned SizeSiteActions = 0;
115 if (NumShared < TypeIds.size()) {
116 unsigned SizeAction = 0;
117 unsigned PrevAction = (unsigned)-1;
120 unsigned SizePrevIds = PrevLPI->TypeIds.size();
121 assert(Actions.size());
122 PrevAction = Actions.size() - 1;
123 SizeAction = getSLEB128Size(Actions[PrevAction].NextAction) +
124 getSLEB128Size(Actions[PrevAction].ValueForTypeID);
126 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
127 assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
128 SizeAction -= getSLEB128Size(Actions[PrevAction].ValueForTypeID);
129 SizeAction += -Actions[PrevAction].NextAction;
130 PrevAction = Actions[PrevAction].Previous;
134 // Compute the actions.
135 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
136 int TypeID = TypeIds[J];
137 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
138 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
139 unsigned SizeTypeID = getSLEB128Size(ValueForTypeID);
141 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
142 SizeAction = SizeTypeID + getSLEB128Size(NextAction);
143 SizeSiteActions += SizeAction;
145 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
146 Actions.push_back(Action);
147 PrevAction = Actions.size() - 1;
150 // Record the first action of the landing pad site.
151 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
152 } // else identical - re-use previous FirstAction
154 // Information used when created the call-site table. The action record
155 // field of the call site record is the offset of the first associated
156 // action record, relative to the start of the actions table. This value is
157 // biased by 1 (1 indicating the start of the actions table), and 0
158 // indicates that there are no actions.
159 FirstActions.push_back(FirstAction);
161 // Compute this sites contribution to size.
162 SizeActions += SizeSiteActions;
170 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
171 /// marked `nounwind'. Return `false' otherwise.
172 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
173 assert(MI->isCall() && "This should be a call instruction!");
175 bool MarkedNoUnwind = false;
176 bool SawFunc = false;
178 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
179 const MachineOperand &MO = MI->getOperand(I);
181 if (!MO.isGlobal()) continue;
183 const Function *F = dyn_cast<Function>(MO.getGlobal());
187 // Be conservative. If we have more than one function operand for this
188 // call, then we can't make the assumption that it's the callee and
189 // not a parameter to the call.
191 // FIXME: Determine if there's a way to say that `F' is the callee or
193 MarkedNoUnwind = false;
197 MarkedNoUnwind = F->doesNotThrow();
201 return MarkedNoUnwind;
204 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
205 /// has a try-range containing the call, a non-zero landing pad, and an
206 /// appropriate action. The entry for an ordinary call has a try-range
207 /// containing the call and zero for the landing pad and the action. Calls
208 /// marked 'nounwind' have no entry and must not be contained in the try-range
209 /// of any entry - they form gaps in the table. Entries must be ordered by
210 /// try-range address.
211 void DwarfException::
212 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
213 const RangeMapType &PadMap,
214 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
215 const SmallVectorImpl<unsigned> &FirstActions) {
216 // The end label of the previous invoke or nounwind try-range.
217 MCSymbol *LastLabel = nullptr;
219 // Whether there is a potentially throwing instruction (currently this means
220 // an ordinary call) between the end of the previous try-range and now.
221 bool SawPotentiallyThrowing = false;
223 // Whether the last CallSite entry was for an invoke.
224 bool PreviousIsInvoke = false;
226 // Visit all instructions in order of address.
227 for (const auto &MBB : *Asm->MF) {
228 for (MachineBasicBlock::const_iterator MI = MBB.begin(), E = MBB.end();
230 if (!MI->isEHLabel()) {
232 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
236 // End of the previous try-range?
237 MCSymbol *BeginLabel = MI->getOperand(0).getMCSymbol();
238 if (BeginLabel == LastLabel)
239 SawPotentiallyThrowing = false;
241 // Beginning of a new try-range?
242 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
243 if (L == PadMap.end())
244 // Nope, it was just some random label.
247 const PadRange &P = L->second;
248 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
249 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
250 "Inconsistent landing pad map!");
252 // For Dwarf exception handling (SjLj handling doesn't use this). If some
253 // instruction between the previous try-range and this one may throw,
254 // create a call-site entry with no landing pad for the region between the
256 if (SawPotentiallyThrowing && Asm->MAI->isExceptionHandlingDwarf()) {
257 CallSiteEntry Site = { LastLabel, BeginLabel, nullptr, 0 };
258 CallSites.push_back(Site);
259 PreviousIsInvoke = false;
262 LastLabel = LandingPad->EndLabels[P.RangeIndex];
263 assert(BeginLabel && LastLabel && "Invalid landing pad!");
265 if (!LandingPad->LandingPadLabel) {
267 PreviousIsInvoke = false;
269 // This try-range is for an invoke.
270 CallSiteEntry Site = {
273 LandingPad->LandingPadLabel,
274 FirstActions[P.PadIndex]
277 // Try to merge with the previous call-site. SJLJ doesn't do this
278 if (PreviousIsInvoke && Asm->MAI->isExceptionHandlingDwarf()) {
279 CallSiteEntry &Prev = CallSites.back();
280 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
281 // Extend the range of the previous entry.
282 Prev.EndLabel = Site.EndLabel;
287 // Otherwise, create a new call-site.
288 if (Asm->MAI->isExceptionHandlingDwarf())
289 CallSites.push_back(Site);
291 // SjLj EH must maintain the call sites in the order assigned
292 // to them by the SjLjPrepare pass.
293 unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel);
294 if (CallSites.size() < SiteNo)
295 CallSites.resize(SiteNo);
296 CallSites[SiteNo - 1] = Site;
298 PreviousIsInvoke = true;
303 // If some instruction between the previous try-range and the end of the
304 // function may throw, create a call-site entry with no landing pad for the
305 // region following the try-range.
306 if (SawPotentiallyThrowing && Asm->MAI->isExceptionHandlingDwarf()) {
307 CallSiteEntry Site = { LastLabel, nullptr, nullptr, 0 };
308 CallSites.push_back(Site);
312 /// EmitExceptionTable - Emit landing pads and actions.
314 /// The general organization of the table is complex, but the basic concepts are
315 /// easy. First there is a header which describes the location and organization
316 /// of the three components that follow.
318 /// 1. The landing pad site information describes the range of code covered by
319 /// the try. In our case it's an accumulation of the ranges covered by the
320 /// invokes in the try. There is also a reference to the landing pad that
321 /// handles the exception once processed. Finally an index into the actions
323 /// 2. The action table, in our case, is composed of pairs of type IDs and next
324 /// action offset. Starting with the action index from the landing pad
325 /// site, each type ID is checked for a match to the current exception. If
326 /// it matches then the exception and type id are passed on to the landing
327 /// pad. Otherwise the next action is looked up. This chain is terminated
328 /// with a next action of zero. If no type id is found then the frame is
329 /// unwound and handling continues.
330 /// 3. Type ID table contains references to all the C++ typeinfo for all
331 /// catches in the function. This tables is reverse indexed base 1.
332 void DwarfException::EmitExceptionTable() {
333 const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
334 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
335 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
337 // Sort the landing pads in order of their type ids. This is used to fold
338 // duplicate actions.
339 SmallVector<const LandingPadInfo *, 64> LandingPads;
340 LandingPads.reserve(PadInfos.size());
342 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
343 LandingPads.push_back(&PadInfos[i]);
345 // Order landing pads lexicographically by type id.
346 std::sort(LandingPads.begin(), LandingPads.end(),
347 [](const LandingPadInfo *L,
348 const LandingPadInfo *R) { return L->TypeIds < R->TypeIds; });
350 // Compute the actions table and gather the first action index for each
352 SmallVector<ActionEntry, 32> Actions;
353 SmallVector<unsigned, 64> FirstActions;
354 unsigned SizeActions=ComputeActionsTable(LandingPads, Actions, FirstActions);
356 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
357 // by try-range labels when lowered). Ordinary calls do not, so appropriate
358 // try-ranges for them need be deduced when using DWARF exception handling.
360 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
361 const LandingPadInfo *LandingPad = LandingPads[i];
362 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
363 MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
364 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
365 PadRange P = { i, j };
366 PadMap[BeginLabel] = P;
370 // Compute the call-site table.
371 SmallVector<CallSiteEntry, 64> CallSites;
372 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
377 bool IsSJLJ = Asm->MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
378 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
380 unsigned CallSiteTableLength;
382 CallSiteTableLength = 0;
384 unsigned SiteStartSize = 4; // dwarf::DW_EH_PE_udata4
385 unsigned SiteLengthSize = 4; // dwarf::DW_EH_PE_udata4
386 unsigned LandingPadSize = 4; // dwarf::DW_EH_PE_udata4
387 CallSiteTableLength =
388 CallSites.size() * (SiteStartSize + SiteLengthSize + LandingPadSize);
391 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
392 CallSiteTableLength += getULEB128Size(CallSites[i].Action);
394 CallSiteTableLength += getULEB128Size(i);
398 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
399 unsigned TTypeEncoding;
400 unsigned TypeFormatSize;
403 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
404 // that we're omitting that bit.
405 TTypeEncoding = dwarf::DW_EH_PE_omit;
406 // dwarf::DW_EH_PE_absptr
407 TypeFormatSize = Asm->getDataLayout().getPointerSize();
409 // Okay, we have actual filters or typeinfos to emit. As such, we need to
410 // pick a type encoding for them. We're about to emit a list of pointers to
411 // typeinfo objects at the end of the LSDA. However, unless we're in static
412 // mode, this reference will require a relocation by the dynamic linker.
414 // Because of this, we have a couple of options:
416 // 1) If we are in -static mode, we can always use an absolute reference
417 // from the LSDA, because the static linker will resolve it.
419 // 2) Otherwise, if the LSDA section is writable, we can output the direct
420 // reference to the typeinfo and allow the dynamic linker to relocate
421 // it. Since it is in a writable section, the dynamic linker won't
424 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
425 // we need to use some form of indirection. For example, on Darwin,
426 // we can output a statically-relocatable reference to a dyld stub. The
427 // offset to the stub is constant, but the contents are in a section
428 // that is updated by the dynamic linker. This is easy enough, but we
429 // need to tell the personality function of the unwinder to indirect
430 // through the dyld stub.
432 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
433 // somewhere. This predicate should be moved to a shared location that is
434 // in target-independent code.
436 TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
437 TypeFormatSize = Asm->GetSizeOfEncodedValue(TTypeEncoding);
440 // Begin the exception table.
441 // Sometimes we want not to emit the data into separate section (e.g. ARM
442 // EHABI). In this case LSDASection will be NULL.
444 Asm->OutStreamer.SwitchSection(LSDASection);
445 Asm->EmitAlignment(2);
449 Asm->OutContext.GetOrCreateSymbol(Twine("GCC_except_table")+
450 Twine(Asm->getFunctionNumber()));
451 Asm->OutStreamer.EmitLabel(GCCETSym);
452 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("exception",
453 Asm->getFunctionNumber()));
456 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("_LSDA_",
457 Asm->getFunctionNumber()));
459 // Emit the LSDA header.
460 Asm->EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
461 Asm->EmitEncodingByte(TTypeEncoding, "@TType");
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
486 unsigned TTypeBaseOffsetSize = getULEB128Size(TTypeBaseOffset);
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 SizeAlign = (4 - TotalSize) & 3;
495 // Account for any extra padding that will be added to the call site table
497 Asm->EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign);
501 bool VerboseAsm = Asm->OutStreamer.isVerboseAsm();
503 // SjLj Exception handling
505 Asm->EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
507 // Add extra padding if it wasn't added to the TType base offset.
508 Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
510 // Emit the landing pad site information.
512 for (SmallVectorImpl<CallSiteEntry>::const_iterator
513 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
514 const CallSiteEntry &S = *I;
516 // Offset of the landing pad, counted in 16-byte bundles relative to the
519 Asm->OutStreamer.AddComment(">> Call Site " + Twine(idx) + " <<");
520 Asm->OutStreamer.AddComment(" On exception at call site "+Twine(idx));
522 Asm->EmitULEB128(idx);
524 // Offset of the first associated action record, relative to the start of
525 // the action table. This value is biased by 1 (1 indicates the start of
526 // the action table), and 0 indicates that there are no actions.
529 Asm->OutStreamer.AddComment(" Action: cleanup");
531 Asm->OutStreamer.AddComment(" Action: " +
532 Twine((S.Action - 1) / 2 + 1));
534 Asm->EmitULEB128(S.Action);
537 // DWARF Exception handling
538 assert(Asm->MAI->isExceptionHandlingDwarf());
540 // The call-site table is a list of all call sites that may throw an
541 // exception (including C++ 'throw' statements) in the procedure
542 // fragment. It immediately follows the LSDA header. Each entry indicates,
543 // for a given call, the first corresponding action record and corresponding
546 // The table begins with the number of bytes, stored as an LEB128
547 // compressed, unsigned integer. The records immediately follow the record
548 // count. They are sorted in increasing call-site address. Each record
551 // * The position of the call-site.
552 // * The position of the landing pad.
553 // * The first action record for that call site.
555 // A missing entry in the call-site table indicates that a call is not
556 // supposed to throw.
558 // Emit the landing pad call site table.
559 Asm->EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
561 // Add extra padding if it wasn't added to the TType base offset.
562 Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
565 for (SmallVectorImpl<CallSiteEntry>::const_iterator
566 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
567 const CallSiteEntry &S = *I;
569 MCSymbol *EHFuncBeginSym =
570 Asm->GetTempSymbol("eh_func_begin", Asm->getFunctionNumber());
572 MCSymbol *BeginLabel = S.BeginLabel;
574 BeginLabel = EHFuncBeginSym;
575 MCSymbol *EndLabel = S.EndLabel;
577 EndLabel = Asm->GetTempSymbol("eh_func_end", Asm->getFunctionNumber());
580 // Offset of the call site relative to the previous call site, counted in
581 // number of 16-byte bundles. The first call site is counted relative to
582 // the start of the procedure fragment.
584 Asm->OutStreamer.AddComment(">> Call Site " + Twine(++Entry) + " <<");
585 Asm->EmitLabelDifference(BeginLabel, EHFuncBeginSym, 4);
587 Asm->OutStreamer.AddComment(Twine(" Call between ") +
588 BeginLabel->getName() + " and " +
589 EndLabel->getName());
590 Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
592 // Offset of the landing pad, counted in 16-byte bundles relative to the
596 Asm->OutStreamer.AddComment(" has no landing pad");
597 Asm->OutStreamer.EmitIntValue(0, 4/*size*/);
600 Asm->OutStreamer.AddComment(Twine(" jumps to ") +
601 S.PadLabel->getName());
602 Asm->EmitLabelDifference(S.PadLabel, EHFuncBeginSym, 4);
605 // Offset of the first associated action record, relative to the start of
606 // the action table. This value is biased by 1 (1 indicates the start of
607 // the action table), and 0 indicates that there are no actions.
610 Asm->OutStreamer.AddComment(" On action: cleanup");
612 Asm->OutStreamer.AddComment(" On action: " +
613 Twine((S.Action - 1) / 2 + 1));
615 Asm->EmitULEB128(S.Action);
619 // Emit the Action Table.
621 for (SmallVectorImpl<ActionEntry>::const_iterator
622 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
623 const ActionEntry &Action = *I;
626 // Emit comments that decode the action table.
627 Asm->OutStreamer.AddComment(">> Action Record " + Twine(++Entry) + " <<");
632 // Used by the runtime to match the type of the thrown exception to the
633 // type of the catch clauses or the types in the exception specification.
635 if (Action.ValueForTypeID > 0)
636 Asm->OutStreamer.AddComment(" Catch TypeInfo " +
637 Twine(Action.ValueForTypeID));
638 else if (Action.ValueForTypeID < 0)
639 Asm->OutStreamer.AddComment(" Filter TypeInfo " +
640 Twine(Action.ValueForTypeID));
642 Asm->OutStreamer.AddComment(" Cleanup");
644 Asm->EmitSLEB128(Action.ValueForTypeID);
648 // Self-relative signed displacement in bytes of the next action record,
649 // or 0 if there is no next action record.
651 if (Action.NextAction == 0) {
652 Asm->OutStreamer.AddComment(" No further actions");
654 unsigned NextAction = Entry + (Action.NextAction + 1) / 2;
655 Asm->OutStreamer.AddComment(" Continue to action "+Twine(NextAction));
658 Asm->EmitSLEB128(Action.NextAction);
661 EmitTypeInfos(TTypeEncoding);
663 Asm->EmitAlignment(2);
666 void DwarfException::EmitTypeInfos(unsigned TTypeEncoding) {
667 const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
668 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
670 bool VerboseAsm = Asm->OutStreamer.isVerboseAsm();
673 // Emit the Catch TypeInfos.
674 if (VerboseAsm && !TypeInfos.empty()) {
675 Asm->OutStreamer.AddComment(">> Catch TypeInfos <<");
676 Asm->OutStreamer.AddBlankLine();
677 Entry = TypeInfos.size();
680 for (std::vector<const GlobalVariable *>::const_reverse_iterator
681 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
682 const GlobalVariable *GV = *I;
684 Asm->OutStreamer.AddComment("TypeInfo " + Twine(Entry--));
685 Asm->EmitTTypeReference(GV, TTypeEncoding);
688 // Emit the Exception Specifications.
689 if (VerboseAsm && !FilterIds.empty()) {
690 Asm->OutStreamer.AddComment(">> Filter TypeInfos <<");
691 Asm->OutStreamer.AddBlankLine();
694 for (std::vector<unsigned>::const_iterator
695 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
696 unsigned TypeID = *I;
700 Asm->OutStreamer.AddComment("FilterInfo " + Twine(Entry));
703 Asm->EmitULEB128(TypeID);
707 /// endModule - Emit all exception information that should come after the
709 void DwarfException::endModule() {
710 llvm_unreachable("Should be implemented");
713 /// beginFunction - Gather pre-function exception information. Assumes it's
714 /// being emitted immediately after the function entry point.
715 void DwarfException::beginFunction(const MachineFunction *MF) {
716 llvm_unreachable("Should be implemented");
719 /// endFunction - Gather and emit post-function exception information.
720 void DwarfException::endFunction(const MachineFunction *) {
721 llvm_unreachable("Should be implemented");