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/Module.h"
16 #include "llvm/CodeGen/MachineModuleInfo.h"
17 #include "llvm/CodeGen/MachineFrameInfo.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineLocation.h"
20 #include "llvm/MC/MCStreamer.h"
21 #include "llvm/MC/MCAsmInfo.h"
22 #include "llvm/Target/TargetData.h"
23 #include "llvm/Target/TargetFrameInfo.h"
24 #include "llvm/Target/TargetLoweringObjectFile.h"
25 #include "llvm/Target/TargetOptions.h"
26 #include "llvm/Target/TargetRegisterInfo.h"
27 #include "llvm/Support/Dwarf.h"
28 #include "llvm/Support/Timer.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/ADT/StringExtras.h"
33 static TimerGroup &getDwarfTimerGroup() {
34 static TimerGroup DwarfTimerGroup("Dwarf Exception");
35 return DwarfTimerGroup;
38 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
40 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
41 shouldEmitTableModule(false), shouldEmitMovesModule(false),
43 if (TimePassesIsEnabled)
44 ExceptionTimer = new Timer("Dwarf Exception Writer",
45 getDwarfTimerGroup());
48 DwarfException::~DwarfException() {
49 delete ExceptionTimer;
52 /// EmitCommonInformationEntry - Emit a Common Information Entry (CIE). This
53 /// holds information that is shared among many Frame Description Entries.
54 /// There is at least one CIE in every non-empty .debug_frame section.
55 void DwarfException::EmitCommonInformationEntry(const Function *Personality,
57 // Size and sign of stack growth.
59 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
60 TargetFrameInfo::StackGrowsUp ?
61 TD->getPointerSize() : -TD->getPointerSize();
63 // Begin eh frame section.
64 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
66 if (MAI->is_EHSymbolPrivate())
67 O << MAI->getPrivateGlobalPrefix();
69 O << "EH_frame" << Index << ":\n";
70 EmitLabel("section_eh_frame", Index);
72 // Define base labels.
73 EmitLabel("eh_frame_common", Index);
75 // Define the eh frame length.
76 EmitDifference("eh_frame_common_end", Index,
77 "eh_frame_common_begin", Index, true);
78 Asm->EOL("Length of Common Information Entry");
81 EmitLabel("eh_frame_common_begin", Index);
82 Asm->EmitInt32((int)0);
83 Asm->EOL("CIE Identifier Tag");
84 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
85 Asm->EOL("CIE Version");
87 // The personality presence indicates that language specific information will
88 // show up in the eh frame.
89 Asm->EmitString(Personality ? "zPLR" : "zR");
90 Asm->EOL("CIE Augmentation");
93 Asm->EmitULEB128Bytes(1);
94 Asm->EOL("CIE Code Alignment Factor");
95 Asm->EmitSLEB128Bytes(stackGrowth);
96 Asm->EOL("CIE Data Alignment Factor");
97 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
98 Asm->EOL("CIE Return Address Column");
100 // If there is a personality, we need to indicate the function's location.
102 Asm->EmitULEB128Bytes(7);
103 Asm->EOL("Augmentation Size");
105 if (MAI->getNeedsIndirectEncoding()) {
106 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4 |
107 dwarf::DW_EH_PE_indirect);
108 Asm->EOL("Personality (pcrel sdata4 indirect)");
110 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
111 Asm->EOL("Personality (pcrel sdata4)");
114 PrintRelDirective(true);
115 O << MAI->getPersonalityPrefix();
116 Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
117 O << MAI->getPersonalitySuffix();
118 if (strcmp(MAI->getPersonalitySuffix(), "+4@GOTPCREL"))
119 O << "-" << MAI->getPCSymbol();
120 Asm->EOL("Personality");
122 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
123 Asm->EOL("LSDA Encoding (pcrel sdata4)");
125 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
126 Asm->EOL("FDE Encoding (pcrel sdata4)");
128 Asm->EmitULEB128Bytes(1);
129 Asm->EOL("Augmentation Size");
131 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
132 Asm->EOL("FDE Encoding (pcrel sdata4)");
135 // Indicate locations of general callee saved registers in frame.
136 std::vector<MachineMove> Moves;
137 RI->getInitialFrameState(Moves);
138 EmitFrameMoves(NULL, 0, Moves, true);
140 // On Darwin the linker honors the alignment of eh_frame, which means it must
141 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
142 // holes which confuse readers of eh_frame.
143 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
145 EmitLabel("eh_frame_common_end", Index);
150 /// EmitFrameDescriptionEntry - Emit the Frame Description Entry (FDE) for the
152 void DwarfException::
153 EmitFrameDescriptionEntry(const FunctionEHFrameInfo &EHFrameInfo) {
154 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
155 "Should not emit 'available externally' functions at all");
157 const Function *TheFunc = EHFrameInfo.function;
159 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
161 // Externally visible entry into the functions eh frame info. If the
162 // corresponding function is static, this should not be externally visible.
163 if (!TheFunc->hasLocalLinkage())
164 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
165 O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
167 // If corresponding function is weak definition, this should be too.
168 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
169 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
171 // If there are no calls then you can't unwind. This may mean we can omit the
172 // EH Frame, but some environments do not handle weak absolute symbols. If
173 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
174 // info is to be available for non-EH uses.
175 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
176 (!TheFunc->isWeakForLinker() ||
177 !MAI->getWeakDefDirective() ||
178 MAI->getSupportsWeakOmittedEHFrame())) {
179 O << EHFrameInfo.FnName << " = 0\n";
180 // This name has no connection to the function, so it might get
181 // dead-stripped when the function is not, erroneously. Prohibit
182 // dead-stripping unconditionally.
183 if (const char *UsedDirective = MAI->getUsedDirective())
184 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
186 O << EHFrameInfo.FnName << ":\n";
189 EmitDifference("eh_frame_end", EHFrameInfo.Number,
190 "eh_frame_begin", EHFrameInfo.Number, true);
191 Asm->EOL("Length of Frame Information Entry");
193 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
195 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
196 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
199 Asm->EOL("FDE CIE offset");
201 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
202 Asm->EOL("FDE initial location");
203 EmitDifference("eh_func_end", EHFrameInfo.Number,
204 "eh_func_begin", EHFrameInfo.Number, true);
205 Asm->EOL("FDE address range");
207 // If there is a personality and landing pads then point to the language
208 // specific data area in the exception table.
209 if (EHFrameInfo.PersonalityIndex) {
210 Asm->EmitULEB128Bytes(4);
211 Asm->EOL("Augmentation size");
213 if (EHFrameInfo.hasLandingPads)
214 EmitReference("exception", EHFrameInfo.Number, true, true);
216 Asm->EmitInt32((int)0);
217 Asm->EOL("Language Specific Data Area");
219 Asm->EmitULEB128Bytes(0);
220 Asm->EOL("Augmentation size");
223 // Indicate locations of function specific callee saved registers in frame.
224 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
227 // On Darwin the linker honors the alignment of eh_frame, which means it
228 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
229 // get holes which confuse readers of eh_frame.
230 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
232 EmitLabel("eh_frame_end", EHFrameInfo.Number);
234 // If the function is marked used, this table should be also. We cannot
235 // make the mark unconditional in this case, since retaining the table also
236 // retains the function in this case, and there is code around that depends
237 // on unused functions (calling undefined externals) being dead-stripped to
238 // link correctly. Yes, there really is.
239 if (MMI->isUsedFunction(EHFrameInfo.function))
240 if (const char *UsedDirective = MAI->getUsedDirective())
241 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
247 /// SharedTypeIds - How many leading type ids two landing pads have in common.
248 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
249 const LandingPadInfo *R) {
250 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
251 unsigned LSize = LIds.size(), RSize = RIds.size();
252 unsigned MinSize = LSize < RSize ? LSize : RSize;
255 for (; Count != MinSize; ++Count)
256 if (LIds[Count] != RIds[Count])
262 /// PadLT - Order landing pads lexicographically by type id.
263 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
264 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
265 unsigned LSize = LIds.size(), RSize = RIds.size();
266 unsigned MinSize = LSize < RSize ? LSize : RSize;
268 for (unsigned i = 0; i != MinSize; ++i)
269 if (LIds[i] != RIds[i])
270 return LIds[i] < RIds[i];
272 return LSize < RSize;
275 /// ComputeActionsTable - Compute the actions table and gather the first action
276 /// index for each landing pad site.
277 unsigned DwarfException::
278 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
279 SmallVectorImpl<ActionEntry> &Actions,
280 SmallVectorImpl<unsigned> &FirstActions) {
282 // The action table follows the call-site table in the LSDA. The individual
283 // records are of two types:
286 // * Exception specification
288 // The two record kinds have the same format, with only small differences.
289 // They are distinguished by the "switch value" field: Catch clauses
290 // (TypeInfos) have strictly positive switch values, and exception
291 // specifications (FilterIds) have strictly negative switch values. Value 0
292 // indicates a catch-all clause.
294 // Negative type IDs index into FilterIds. Positive type IDs index into
295 // TypeInfos. The value written for a positive type ID is just the type ID
296 // itself. For a negative type ID, however, the value written is the
297 // (negative) byte offset of the corresponding FilterIds entry. The byte
298 // offset is usually equal to the type ID (because the FilterIds entries are
299 // written using a variable width encoding, which outputs one byte per entry
300 // as long as the value written is not too large) but can differ. This kind
301 // of complication does not occur for positive type IDs because type infos are
302 // output using a fixed width encoding. FilterOffsets[i] holds the byte
303 // offset corresponding to FilterIds[i].
305 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
306 SmallVector<int, 16> FilterOffsets;
307 FilterOffsets.reserve(FilterIds.size());
310 for (std::vector<unsigned>::const_iterator
311 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
312 FilterOffsets.push_back(Offset);
313 Offset -= MCAsmInfo::getULEB128Size(*I);
316 FirstActions.reserve(LandingPads.size());
319 unsigned SizeActions = 0;
320 const LandingPadInfo *PrevLPI = 0;
322 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
323 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
324 const LandingPadInfo *LPI = *I;
325 const std::vector<int> &TypeIds = LPI->TypeIds;
326 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
327 unsigned SizeSiteActions = 0;
329 if (NumShared < TypeIds.size()) {
330 unsigned SizeAction = 0;
331 ActionEntry *PrevAction = 0;
334 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
335 assert(Actions.size());
336 PrevAction = &Actions.back();
337 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
338 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
340 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
342 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
343 SizeAction += -PrevAction->NextAction;
344 PrevAction = PrevAction->Previous;
348 // Compute the actions.
349 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
350 int TypeID = TypeIds[J];
351 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
352 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
353 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
355 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
356 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
357 SizeSiteActions += SizeAction;
359 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
360 Actions.push_back(Action);
361 PrevAction = &Actions.back();
364 // Record the first action of the landing pad site.
365 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
366 } // else identical - re-use previous FirstAction
368 // Information used when created the call-site table. The action record
369 // field of the call site record is the offset of the first associated
370 // action record, relative to the start of the actions table. This value is
371 // biased by 1 (1 in dicating the start of the actions table), and 0
372 // indicates that there are no actions.
373 FirstActions.push_back(FirstAction);
375 // Compute this sites contribution to size.
376 SizeActions += SizeSiteActions;
384 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
385 /// has a try-range containing the call, a non-zero landing pad, and an
386 /// appropriate action. The entry for an ordinary call has a try-range
387 /// containing the call and zero for the landing pad and the action. Calls
388 /// marked 'nounwind' have no entry and must not be contained in the try-range
389 /// of any entry - they form gaps in the table. Entries must be ordered by
390 /// try-range address.
391 void DwarfException::
392 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
393 const RangeMapType &PadMap,
394 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
395 const SmallVectorImpl<unsigned> &FirstActions) {
396 // The end label of the previous invoke or nounwind try-range.
397 unsigned LastLabel = 0;
399 // Whether there is a potentially throwing instruction (currently this means
400 // an ordinary call) between the end of the previous try-range and now.
401 bool SawPotentiallyThrowing = false;
403 // Whether the last CallSite entry was for an invoke.
404 bool PreviousIsInvoke = false;
406 // Visit all instructions in order of address.
407 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
409 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
411 if (!MI->isLabel()) {
412 SawPotentiallyThrowing |= MI->getDesc().isCall();
416 unsigned BeginLabel = MI->getOperand(0).getImm();
417 assert(BeginLabel && "Invalid label!");
419 // End of the previous try-range?
420 if (BeginLabel == LastLabel)
421 SawPotentiallyThrowing = false;
423 // Beginning of a new try-range?
424 RangeMapType::iterator L = PadMap.find(BeginLabel);
425 if (L == PadMap.end())
426 // Nope, it was just some random label.
429 const PadRange &P = L->second;
430 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
431 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
432 "Inconsistent landing pad map!");
434 // For Dwarf exception handling (SjLj handling doesn't use this). If some
435 // instruction between the previous try-range and this one may throw,
436 // create a call-site entry with no landing pad for the region between the
438 if (SawPotentiallyThrowing &&
439 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
440 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
441 CallSites.push_back(Site);
442 PreviousIsInvoke = false;
445 LastLabel = LandingPad->EndLabels[P.RangeIndex];
446 assert(BeginLabel && LastLabel && "Invalid landing pad!");
448 if (LandingPad->LandingPadLabel) {
449 // This try-range is for an invoke.
450 CallSiteEntry Site = {
453 LandingPad->LandingPadLabel,
454 FirstActions[P.PadIndex]
457 // Try to merge with the previous call-site.
458 if (PreviousIsInvoke) {
459 CallSiteEntry &Prev = CallSites.back();
460 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
461 // Extend the range of the previous entry.
462 Prev.EndLabel = Site.EndLabel;
467 // Otherwise, create a new call-site.
468 CallSites.push_back(Site);
469 PreviousIsInvoke = true;
472 PreviousIsInvoke = false;
477 // If some instruction between the previous try-range and the end of the
478 // function may throw, create a call-site entry with no landing pad for the
479 // region following the try-range.
480 if (SawPotentiallyThrowing &&
481 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
482 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
483 CallSites.push_back(Site);
487 /// EmitExceptionTable - Emit landing pads and actions.
489 /// The general organization of the table is complex, but the basic concepts are
490 /// easy. First there is a header which describes the location and organization
491 /// of the three components that follow.
493 /// 1. The landing pad site information describes the range of code covered by
494 /// the try. In our case it's an accumulation of the ranges covered by the
495 /// invokes in the try. There is also a reference to the landing pad that
496 /// handles the exception once processed. Finally an index into the actions
498 /// 2. The action table, in our case, is composed of pairs of type IDs and next
499 /// action offset. Starting with the action index from the landing pad
500 /// site, each type ID is checked for a match to the current exception. If
501 /// it matches then the exception and type id are passed on to the landing
502 /// pad. Otherwise the next action is looked up. This chain is terminated
503 /// with a next action of zero. If no type id is found the the frame is
504 /// unwound and handling continues.
505 /// 3. Type ID table contains references to all the C++ typeinfo for all
506 /// catches in the function. This tables is reversed indexed base 1.
507 void DwarfException::EmitExceptionTable() {
508 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
509 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
510 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
511 if (PadInfos.empty()) return;
513 // Sort the landing pads in order of their type ids. This is used to fold
514 // duplicate actions.
515 SmallVector<const LandingPadInfo *, 64> LandingPads;
516 LandingPads.reserve(PadInfos.size());
518 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
519 LandingPads.push_back(&PadInfos[i]);
521 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
523 // Compute the actions table and gather the first action index for each
525 SmallVector<ActionEntry, 32> Actions;
526 SmallVector<unsigned, 64> FirstActions;
527 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions, FirstActions);
529 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
530 // by try-range labels when lowered). Ordinary calls do not, so appropriate
531 // try-ranges for them need be deduced when using Dwarf exception handling.
533 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
534 const LandingPadInfo *LandingPad = LandingPads[i];
535 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
536 unsigned BeginLabel = LandingPad->BeginLabels[j];
537 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
538 PadRange P = { i, j };
539 PadMap[BeginLabel] = P;
543 // Compute the call-site table.
544 SmallVector<CallSiteEntry, 64> CallSites;
545 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
550 const unsigned SiteStartSize = sizeof(int32_t); // DW_EH_PE_udata4
551 const unsigned SiteLengthSize = sizeof(int32_t); // DW_EH_PE_udata4
552 const unsigned LandingPadSize = sizeof(int32_t); // DW_EH_PE_udata4
555 bool HaveTTData = (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
556 ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
559 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
562 SizeSites = CallSites.size() *
563 (SiteStartSize + SiteLengthSize + LandingPadSize);
564 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
565 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
566 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
567 SizeSites += MCAsmInfo::getULEB128Size(i);
570 const unsigned TypeInfoSize = TD->getPointerSize(); // DW_EH_PE_absptr
571 unsigned SizeTypes = TypeInfos.size() * TypeInfoSize;
573 unsigned TypeOffset = sizeof(int8_t) + // Call site format
574 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
575 SizeSites + SizeActions + SizeTypes;
577 unsigned TotalSize = sizeof(int8_t) + // LPStart format
578 sizeof(int8_t) + // TType format
580 MCAsmInfo::getULEB128Size(TypeOffset) : 0) + // TType base offset
583 unsigned SizeAlign = (4 - TotalSize) & 3;
585 // Begin the exception table.
586 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
587 Asm->OutStreamer.SwitchSection(LSDASection);
588 Asm->EmitAlignment(2, 0, 0, false);
589 O << "GCC_except_table" << SubprogramCount << ":\n";
591 for (unsigned i = 0; i != SizeAlign; ++i) {
596 EmitLabel("exception", SubprogramCount);
597 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
598 std::string SjLjName = "_lsda_";
599 SjLjName += MF->getFunction()->getName().str();
600 EmitLabel(SjLjName.c_str(), 0);
604 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
605 Asm->EOL("@LPStart format (DW_EH_PE_omit)");
608 if (TypeInfos.empty() && FilterIds.empty()) {
609 // If there are no typeinfos or filters, there is nothing to emit, optimize
610 // by specifying the "omit" encoding.
611 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
612 Asm->EOL("@TType format (DW_EH_PE_omit)");
614 // Okay, we have actual filters or typeinfos to emit. As such, we need to
615 // pick a type encoding for them. We're about to emit a list of pointers to
616 // typeinfo objects at the end of the LSDA. However, unless we're in static
617 // mode, this reference will require a relocation by the dynamic linker.
619 // Because of this, we have a couple of options:
620 // 1) If we are in -static mode, we can always use an absolute reference
621 // from the LSDA, because the static linker will resolve it.
622 // 2) Otherwise, if the LSDA section is writable, we can output the direct
623 // reference to the typeinfo and allow the dynamic linker to relocate
624 // it. Since it is in a writable section, the dynamic linker won't
626 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
627 // we need to use some form of indirection. For example, on Darwin,
628 // we can output a statically-relocatable reference to a dyld stub. The
629 // offset to the stub is constant, but the contents are in a section
630 // that is updated by the dynamic linker. This is easy enough, but we
631 // need to tell the personality function of the unwinder to indirect
632 // through the dyld stub.
634 // FIXME: When this is actually implemented, we'll have to emit the stubs
635 // somewhere. This predicate should be moved to a shared location that is
636 // in target-independent code.
638 if (LSDASection->isWritable() ||
639 Asm->TM.getRelocationModel() == Reloc::Static) {
640 Asm->EmitInt8(DW_EH_PE_absptr);
641 Asm->EOL("TType format (DW_EH_PE_absptr)");
643 Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
644 Asm->EOL("TType format (DW_EH_PE_pcrel | DW_EH_PE_indirect"
645 " | DW_EH_PE_sdata4)");
647 Asm->EmitULEB128Bytes(TypeOffset);
648 Asm->EOL("TType base offset");
651 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly
652 // say that we're omitting that bit.
653 // FIXME: does this apply to Dwarf also? The above #if 0 implies yes?
655 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
656 Asm->EOL("@TType format (DW_EH_PE_omit)");
658 Asm->EmitInt8(dwarf::DW_EH_PE_absptr);
659 Asm->EOL("@TType format (DW_EH_PE_absptr)");
660 Asm->EmitULEB128Bytes(TypeOffset);
661 Asm->EOL("@TType base offset");
665 // SjLj Exception handilng
666 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
667 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
668 Asm->EOL("Call site format (DW_EH_PE_udata4)");
669 Asm->EmitULEB128Bytes(SizeSites);
670 Asm->EOL("Call site table length");
672 // Emit the landing pad site information.
674 for (SmallVectorImpl<CallSiteEntry>::const_iterator
675 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
676 const CallSiteEntry &S = *I;
678 // Offset of the landing pad, counted in 16-byte bundles relative to the
680 Asm->EmitULEB128Bytes(idx);
681 Asm->EOL("Landing pad");
683 // Offset of the first associated action record, relative to the start of
684 // the action table. This value is biased by 1 (1 indicates the start of
685 // the action table), and 0 indicates that there are no actions.
686 Asm->EmitULEB128Bytes(S.Action);
690 // DWARF Exception handling
691 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
693 // The call-site table is a list of all call sites that may throw an
694 // exception (including C++ 'throw' statements) in the procedure
695 // fragment. It immediately follows the LSDA header. Each entry indicates,
696 // for a given call, the first corresponding action record and corresponding
699 // The table begins with the number of bytes, stored as an LEB128
700 // compressed, unsigned integer. The records immediately follow the record
701 // count. They are sorted in increasing call-site address. Each record
704 // * The position of the call-site.
705 // * The position of the landing pad.
706 // * The first action record for that call site.
708 // A missing entry in the call-site table indicates that a call is not
709 // supposed to throw. Such calls include:
711 // * Calls to destructors within cleanup code. C++ semantics forbids these
713 // * Calls to intrinsic routines in the standard library which are known
714 // not to throw (sin, memcpy, et al).
716 // If the runtime does not find the call-site entry for a given call, it
717 // will call `terminate()'.
719 // Emit the landing pad call site table.
720 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
721 Asm->EOL("Call site format (DW_EH_PE_udata4)");
722 Asm->EmitULEB128Bytes(SizeSites);
723 Asm->EOL("Call site table size");
725 for (SmallVectorImpl<CallSiteEntry>::const_iterator
726 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
727 const CallSiteEntry &S = *I;
728 const char *BeginTag;
729 unsigned BeginNumber;
732 BeginTag = "eh_func_begin";
733 BeginNumber = SubprogramCount;
736 BeginNumber = S.BeginLabel;
739 // Offset of the call site relative to the previous call site, counted in
740 // number of 16-byte bundles. The first call site is counted relative to
741 // the start of the procedure fragment.
742 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
744 Asm->EOL("Region start");
747 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
750 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
752 Asm->EOL("Region length");
754 // Offset of the landing pad, counted in 16-byte bundles relative to the
759 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
762 Asm->EOL("Landing pad");
764 // Offset of the first associated action record, relative to the start of
765 // the action table. This value is biased by 1 (1 indicates the start of
766 // the action table), and 0 indicates that there are no actions.
767 Asm->EmitULEB128Bytes(S.Action);
772 // Emit the Action Table.
773 for (SmallVectorImpl<ActionEntry>::const_iterator
774 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
775 const ActionEntry &Action = *I;
779 // Used by the runtime to match the type of the thrown exception to the
780 // type of the catch clauses or the types in the exception specification.
782 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
783 Asm->EOL("TypeInfo index");
787 // Self-relative signed displacement in bytes of the next action record,
788 // or 0 if there is no next action record.
790 Asm->EmitSLEB128Bytes(Action.NextAction);
791 Asm->EOL("Next action");
794 // Emit the Catch Clauses. The code for the catch clauses following the same
795 // try is similar to a switch statement. The catch clause action record
796 // informs the runtime about the type of a catch clause and about the
797 // associated switch value.
799 // Action Record Fields:
802 // Positive value, starting at 1. Index in the types table of the
803 // __typeinfo for the catch-clause type. 1 is the first word preceding
804 // TTBase, 2 is the second word, and so on. Used by the runtime to check
805 // if the thrown exception type matches the catch-clause type. Back-end
806 // generated switch statements check against this value.
809 // Signed offset, in bytes from the start of this field, to the next
810 // chained action record, or zero if none.
812 // The order of the action records determined by the next field is the order
813 // of the catch clauses as they appear in the source code, and must be kept in
814 // the same order. As a result, changing the order of the catch clause would
815 // change the semantics of the program.
816 for (std::vector<GlobalVariable *>::const_reverse_iterator
817 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
818 const GlobalVariable *GV = *I;
823 O << Asm->getGlobalLinkName(GV, GLN);
828 Asm->EOL("TypeInfo");
831 // Emit the Type Table.
832 for (std::vector<unsigned>::const_iterator
833 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
834 unsigned TypeID = *I;
835 Asm->EmitULEB128Bytes(TypeID);
836 Asm->EOL("Filter TypeInfo index");
839 Asm->EmitAlignment(2, 0, 0, false);
842 /// EndModule - Emit all exception information that should come after the
844 void DwarfException::EndModule() {
845 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
847 if (TimePassesIsEnabled)
848 ExceptionTimer->startTimer();
850 if (shouldEmitMovesModule || shouldEmitTableModule) {
851 const std::vector<Function *> Personalities = MMI->getPersonalities();
852 for (unsigned i = 0; i < Personalities.size(); ++i)
853 EmitCommonInformationEntry(Personalities[i], i);
855 for (std::vector<FunctionEHFrameInfo>::iterator I = EHFrames.begin(),
856 E = EHFrames.end(); I != E; ++I)
857 EmitFrameDescriptionEntry(*I);
860 if (TimePassesIsEnabled)
861 ExceptionTimer->stopTimer();
864 /// BeginFunction - Gather pre-function exception information. Assumes being
865 /// emitted immediately after the function entry point.
866 void DwarfException::BeginFunction(MachineFunction *MF) {
867 if (TimePassesIsEnabled)
868 ExceptionTimer->startTimer();
871 shouldEmitTable = shouldEmitMoves = false;
873 if (MMI && MAI->doesSupportExceptionHandling()) {
874 // Map all labels and get rid of any dead landing pads.
875 MMI->TidyLandingPads();
877 // If any landing pads survive, we need an EH table.
878 if (MMI->getLandingPads().size())
879 shouldEmitTable = true;
881 // See if we need frame move info.
882 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
883 shouldEmitMoves = true;
885 if (shouldEmitMoves || shouldEmitTable)
886 // Assumes in correct section after the entry point.
887 EmitLabel("eh_func_begin", ++SubprogramCount);
890 shouldEmitTableModule |= shouldEmitTable;
891 shouldEmitMovesModule |= shouldEmitMoves;
893 if (TimePassesIsEnabled)
894 ExceptionTimer->stopTimer();
897 /// EndFunction - Gather and emit post-function exception information.
899 void DwarfException::EndFunction() {
900 if (TimePassesIsEnabled)
901 ExceptionTimer->startTimer();
903 if (shouldEmitMoves || shouldEmitTable) {
904 EmitLabel("eh_func_end", SubprogramCount);
905 EmitExceptionTable();
907 // Save EH frame information
909 FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
911 MMI->getPersonalityIndex(),
912 MF->getFrameInfo()->hasCalls(),
913 !MMI->getLandingPads().empty(),
914 MMI->getFrameMoves(),
918 if (TimePassesIsEnabled)
919 ExceptionTimer->stopTimer();