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 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
53 /// is shared among many Frame Description Entries. There is at least one CIE
54 /// in every non-empty .debug_frame section.
55 void DwarfException::EmitCIE(const Function *Personality, unsigned Index) {
56 // Size and sign of stack growth.
58 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
59 TargetFrameInfo::StackGrowsUp ?
60 TD->getPointerSize() : -TD->getPointerSize();
62 // Begin eh frame section.
63 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
65 if (MAI->is_EHSymbolPrivate())
66 O << MAI->getPrivateGlobalPrefix();
68 O << "EH_frame" << Index << ":\n";
69 EmitLabel("section_eh_frame", Index);
71 // Define base labels.
72 EmitLabel("eh_frame_common", Index);
74 // Define the eh frame length.
75 EmitDifference("eh_frame_common_end", Index,
76 "eh_frame_common_begin", Index, true);
77 Asm->EOL("Length of Common Information Entry");
80 EmitLabel("eh_frame_common_begin", Index);
81 Asm->EmitInt32((int)0);
82 Asm->EOL("CIE Identifier Tag");
83 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
84 Asm->EOL("CIE Version");
86 // The personality presence indicates that language specific information will
87 // show up in the eh frame.
88 Asm->EmitString(Personality ? "zPLR" : "zR");
89 Asm->EOL("CIE Augmentation");
92 Asm->EmitULEB128Bytes(1);
93 Asm->EOL("CIE Code Alignment Factor");
94 Asm->EmitSLEB128Bytes(stackGrowth);
95 Asm->EOL("CIE Data Alignment Factor");
96 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
97 Asm->EOL("CIE Return Address Column");
99 // If there is a personality, we need to indicate the function's location.
101 unsigned Encoding = 0;
102 Asm->EmitULEB128Bytes(7);
103 Asm->EOL("Augmentation Size");
105 if (MAI->getNeedsIndirectEncoding()) {
106 Encoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4 |
107 dwarf::DW_EH_PE_indirect;
108 Asm->EmitInt8(Encoding);
109 Asm->EOL("Personality", Encoding);
111 Encoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
112 Asm->EmitInt8(Encoding);
113 Asm->EOL("Personality", Encoding);
116 PrintRelDirective(true);
117 O << MAI->getPersonalityPrefix();
118 Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
119 O << MAI->getPersonalitySuffix();
120 if (strcmp(MAI->getPersonalitySuffix(), "+4@GOTPCREL"))
121 O << "-" << MAI->getPCSymbol();
122 Asm->EOL("Personality");
124 Encoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
125 Asm->EmitInt8(Encoding);
126 Asm->EOL("LSDA Encoding", Encoding);
128 Encoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
129 Asm->EmitInt8(Encoding);
130 Asm->EOL("FDE Encoding", Encoding);
132 Asm->EmitULEB128Bytes(1);
133 Asm->EOL("Augmentation Size");
135 unsigned Encoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
136 Asm->EmitInt8(Encoding);
137 Asm->EOL("FDE Encoding", Encoding);
140 // Indicate locations of general callee saved registers in frame.
141 std::vector<MachineMove> Moves;
142 RI->getInitialFrameState(Moves);
143 EmitFrameMoves(NULL, 0, Moves, true);
145 // On Darwin the linker honors the alignment of eh_frame, which means it must
146 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
147 // holes which confuse readers of eh_frame.
148 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
150 EmitLabel("eh_frame_common_end", Index);
155 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
156 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
157 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
158 "Should not emit 'available externally' functions at all");
160 const Function *TheFunc = EHFrameInfo.function;
162 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
164 // Externally visible entry into the functions eh frame info. If the
165 // corresponding function is static, this should not be externally visible.
166 if (!TheFunc->hasLocalLinkage())
167 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
168 O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
170 // If corresponding function is weak definition, this should be too.
171 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
172 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
174 // If there are no calls then you can't unwind. This may mean we can omit the
175 // EH Frame, but some environments do not handle weak absolute symbols. If
176 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
177 // info is to be available for non-EH uses.
178 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
179 (!TheFunc->isWeakForLinker() ||
180 !MAI->getWeakDefDirective() ||
181 MAI->getSupportsWeakOmittedEHFrame())) {
182 O << EHFrameInfo.FnName << " = 0\n";
183 // This name has no connection to the function, so it might get
184 // dead-stripped when the function is not, erroneously. Prohibit
185 // dead-stripping unconditionally.
186 if (const char *UsedDirective = MAI->getUsedDirective())
187 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
189 O << EHFrameInfo.FnName << ":\n";
192 EmitDifference("eh_frame_end", EHFrameInfo.Number,
193 "eh_frame_begin", EHFrameInfo.Number, true);
194 Asm->EOL("Length of Frame Information Entry");
196 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
198 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
199 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
202 Asm->EOL("FDE CIE offset");
204 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
205 Asm->EOL("FDE initial location");
206 EmitDifference("eh_func_end", EHFrameInfo.Number,
207 "eh_func_begin", EHFrameInfo.Number, true);
208 Asm->EOL("FDE address range");
210 // If there is a personality and landing pads then point to the language
211 // specific data area in the exception table.
212 if (MMI->getPersonalities()[0] != NULL) {
213 Asm->EmitULEB128Bytes(4);
214 Asm->EOL("Augmentation size");
216 if (EHFrameInfo.hasLandingPads)
217 EmitReference("exception", EHFrameInfo.Number, true, true);
219 Asm->EmitInt32((int)0);
220 Asm->EOL("Language Specific Data Area");
222 Asm->EmitULEB128Bytes(0);
223 Asm->EOL("Augmentation size");
226 // Indicate locations of function specific callee saved registers in frame.
227 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
230 // On Darwin the linker honors the alignment of eh_frame, which means it
231 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
232 // get holes which confuse readers of eh_frame.
233 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
235 EmitLabel("eh_frame_end", EHFrameInfo.Number);
237 // If the function is marked used, this table should be also. We cannot
238 // make the mark unconditional in this case, since retaining the table also
239 // retains the function in this case, and there is code around that depends
240 // on unused functions (calling undefined externals) being dead-stripped to
241 // link correctly. Yes, there really is.
242 if (MMI->isUsedFunction(EHFrameInfo.function))
243 if (const char *UsedDirective = MAI->getUsedDirective())
244 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
250 /// SharedTypeIds - How many leading type ids two landing pads have in common.
251 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
252 const LandingPadInfo *R) {
253 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
254 unsigned LSize = LIds.size(), RSize = RIds.size();
255 unsigned MinSize = LSize < RSize ? LSize : RSize;
258 for (; Count != MinSize; ++Count)
259 if (LIds[Count] != RIds[Count])
265 /// PadLT - Order landing pads lexicographically by type id.
266 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
267 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
268 unsigned LSize = LIds.size(), RSize = RIds.size();
269 unsigned MinSize = LSize < RSize ? LSize : RSize;
271 for (unsigned i = 0; i != MinSize; ++i)
272 if (LIds[i] != RIds[i])
273 return LIds[i] < RIds[i];
275 return LSize < RSize;
278 /// ComputeActionsTable - Compute the actions table and gather the first action
279 /// index for each landing pad site.
280 unsigned DwarfException::
281 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
282 SmallVectorImpl<ActionEntry> &Actions,
283 SmallVectorImpl<unsigned> &FirstActions) {
285 // The action table follows the call-site table in the LSDA. The individual
286 // records are of two types:
289 // * Exception specification
291 // The two record kinds have the same format, with only small differences.
292 // They are distinguished by the "switch value" field: Catch clauses
293 // (TypeInfos) have strictly positive switch values, and exception
294 // specifications (FilterIds) have strictly negative switch values. Value 0
295 // indicates a catch-all clause.
297 // Negative type IDs index into FilterIds. Positive type IDs index into
298 // TypeInfos. The value written for a positive type ID is just the type ID
299 // itself. For a negative type ID, however, the value written is the
300 // (negative) byte offset of the corresponding FilterIds entry. The byte
301 // offset is usually equal to the type ID (because the FilterIds entries are
302 // written using a variable width encoding, which outputs one byte per entry
303 // as long as the value written is not too large) but can differ. This kind
304 // of complication does not occur for positive type IDs because type infos are
305 // output using a fixed width encoding. FilterOffsets[i] holds the byte
306 // offset corresponding to FilterIds[i].
308 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
309 SmallVector<int, 16> FilterOffsets;
310 FilterOffsets.reserve(FilterIds.size());
313 for (std::vector<unsigned>::const_iterator
314 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
315 FilterOffsets.push_back(Offset);
316 Offset -= MCAsmInfo::getULEB128Size(*I);
319 FirstActions.reserve(LandingPads.size());
322 unsigned SizeActions = 0;
323 const LandingPadInfo *PrevLPI = 0;
325 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
326 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
327 const LandingPadInfo *LPI = *I;
328 const std::vector<int> &TypeIds = LPI->TypeIds;
329 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
330 unsigned SizeSiteActions = 0;
332 if (NumShared < TypeIds.size()) {
333 unsigned SizeAction = 0;
334 ActionEntry *PrevAction = 0;
337 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
338 assert(Actions.size());
339 PrevAction = &Actions.back();
340 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
341 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
343 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
345 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
346 SizeAction += -PrevAction->NextAction;
347 PrevAction = PrevAction->Previous;
351 // Compute the actions.
352 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
353 int TypeID = TypeIds[J];
354 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
355 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
356 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
358 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
359 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
360 SizeSiteActions += SizeAction;
362 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
363 Actions.push_back(Action);
364 PrevAction = &Actions.back();
367 // Record the first action of the landing pad site.
368 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
369 } // else identical - re-use previous FirstAction
371 // Information used when created the call-site table. The action record
372 // field of the call site record is the offset of the first associated
373 // action record, relative to the start of the actions table. This value is
374 // biased by 1 (1 in dicating the start of the actions table), and 0
375 // indicates that there are no actions.
376 FirstActions.push_back(FirstAction);
378 // Compute this sites contribution to size.
379 SizeActions += SizeSiteActions;
387 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
388 /// has a try-range containing the call, a non-zero landing pad, and an
389 /// appropriate action. The entry for an ordinary call has a try-range
390 /// containing the call and zero for the landing pad and the action. Calls
391 /// marked 'nounwind' have no entry and must not be contained in the try-range
392 /// of any entry - they form gaps in the table. Entries must be ordered by
393 /// try-range address.
394 void DwarfException::
395 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
396 const RangeMapType &PadMap,
397 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
398 const SmallVectorImpl<unsigned> &FirstActions) {
399 // The end label of the previous invoke or nounwind try-range.
400 unsigned LastLabel = 0;
402 // Whether there is a potentially throwing instruction (currently this means
403 // an ordinary call) between the end of the previous try-range and now.
404 bool SawPotentiallyThrowing = false;
406 // Whether the last CallSite entry was for an invoke.
407 bool PreviousIsInvoke = false;
409 // Visit all instructions in order of address.
410 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
412 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
414 if (!MI->isLabel()) {
415 SawPotentiallyThrowing |= MI->getDesc().isCall();
419 unsigned BeginLabel = MI->getOperand(0).getImm();
420 assert(BeginLabel && "Invalid label!");
422 // End of the previous try-range?
423 if (BeginLabel == LastLabel)
424 SawPotentiallyThrowing = false;
426 // Beginning of a new try-range?
427 RangeMapType::iterator L = PadMap.find(BeginLabel);
428 if (L == PadMap.end())
429 // Nope, it was just some random label.
432 const PadRange &P = L->second;
433 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
434 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
435 "Inconsistent landing pad map!");
437 // For Dwarf exception handling (SjLj handling doesn't use this). If some
438 // instruction between the previous try-range and this one may throw,
439 // create a call-site entry with no landing pad for the region between the
441 if (SawPotentiallyThrowing &&
442 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
443 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
444 CallSites.push_back(Site);
445 PreviousIsInvoke = false;
448 LastLabel = LandingPad->EndLabels[P.RangeIndex];
449 assert(BeginLabel && LastLabel && "Invalid landing pad!");
451 if (LandingPad->LandingPadLabel) {
452 // This try-range is for an invoke.
453 CallSiteEntry Site = {
456 LandingPad->LandingPadLabel,
457 FirstActions[P.PadIndex]
460 // Try to merge with the previous call-site.
461 if (PreviousIsInvoke) {
462 CallSiteEntry &Prev = CallSites.back();
463 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
464 // Extend the range of the previous entry.
465 Prev.EndLabel = Site.EndLabel;
470 // Otherwise, create a new call-site.
471 CallSites.push_back(Site);
472 PreviousIsInvoke = true;
475 PreviousIsInvoke = false;
480 // If some instruction between the previous try-range and the end of the
481 // function may throw, create a call-site entry with no landing pad for the
482 // region following the try-range.
483 if (SawPotentiallyThrowing &&
484 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
485 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
486 CallSites.push_back(Site);
490 /// EmitExceptionTable - Emit landing pads and actions.
492 /// The general organization of the table is complex, but the basic concepts are
493 /// easy. First there is a header which describes the location and organization
494 /// of the three components that follow.
496 /// 1. The landing pad site information describes the range of code covered by
497 /// the try. In our case it's an accumulation of the ranges covered by the
498 /// invokes in the try. There is also a reference to the landing pad that
499 /// handles the exception once processed. Finally an index into the actions
501 /// 2. The action table, in our case, is composed of pairs of type IDs and next
502 /// action offset. Starting with the action index from the landing pad
503 /// site, each type ID is checked for a match to the current exception. If
504 /// it matches then the exception and type id are passed on to the landing
505 /// pad. Otherwise the next action is looked up. This chain is terminated
506 /// with a next action of zero. If no type id is found the the frame is
507 /// unwound and handling continues.
508 /// 3. Type ID table contains references to all the C++ typeinfo for all
509 /// catches in the function. This tables is reversed indexed base 1.
510 void DwarfException::EmitExceptionTable() {
511 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
512 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
513 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
514 if (PadInfos.empty()) return;
516 // Sort the landing pads in order of their type ids. This is used to fold
517 // duplicate actions.
518 SmallVector<const LandingPadInfo *, 64> LandingPads;
519 LandingPads.reserve(PadInfos.size());
521 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
522 LandingPads.push_back(&PadInfos[i]);
524 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
526 // Compute the actions table and gather the first action index for each
528 SmallVector<ActionEntry, 32> Actions;
529 SmallVector<unsigned, 64> FirstActions;
530 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions, FirstActions);
532 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
533 // by try-range labels when lowered). Ordinary calls do not, so appropriate
534 // try-ranges for them need be deduced when using Dwarf exception handling.
536 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
537 const LandingPadInfo *LandingPad = LandingPads[i];
538 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
539 unsigned BeginLabel = LandingPad->BeginLabels[j];
540 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
541 PadRange P = { i, j };
542 PadMap[BeginLabel] = P;
546 // Compute the call-site table.
547 SmallVector<CallSiteEntry, 64> CallSites;
548 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
553 const unsigned SiteStartSize = sizeof(int32_t); // DW_EH_PE_udata4
554 const unsigned SiteLengthSize = sizeof(int32_t); // DW_EH_PE_udata4
555 const unsigned LandingPadSize = sizeof(int32_t); // DW_EH_PE_udata4
558 bool HaveTTData = (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
559 ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
562 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
565 SizeSites = CallSites.size() *
566 (SiteStartSize + SiteLengthSize + LandingPadSize);
567 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
568 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
569 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
570 SizeSites += MCAsmInfo::getULEB128Size(i);
573 const unsigned TypeInfoSize = TD->getPointerSize(); // DW_EH_PE_absptr
574 unsigned SizeTypes = TypeInfos.size() * TypeInfoSize;
576 unsigned TypeOffset = sizeof(int8_t) + // Call site format
577 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
578 SizeSites + SizeActions + SizeTypes;
580 unsigned TotalSize = sizeof(int8_t) + // LPStart format
581 sizeof(int8_t) + // TType format
583 MCAsmInfo::getULEB128Size(TypeOffset) : 0) + // TType base offset
586 unsigned SizeAlign = (4 - TotalSize) & 3;
588 // Begin the exception table.
589 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
590 Asm->OutStreamer.SwitchSection(LSDASection);
591 Asm->EmitAlignment(2, 0, 0, false);
592 O << "GCC_except_table" << SubprogramCount << ":\n";
594 for (unsigned i = 0; i != SizeAlign; ++i) {
599 EmitLabel("exception", SubprogramCount);
600 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
601 std::string SjLjName = "_lsda_";
602 SjLjName += MF->getFunction()->getName().str();
603 EmitLabel(SjLjName.c_str(), 0);
607 unsigned Encoding = dwarf::DW_EH_PE_omit;
608 Asm->EmitInt8(Encoding);
609 Asm->EOL("@LPStart format", Encoding);
612 if (TypeInfos.empty() && FilterIds.empty()) {
613 // If there are no typeinfos or filters, there is nothing to emit, optimize
614 // by specifying the "omit" encoding.
615 Encoding = dwarf::DW_EH_PE_omit;
616 Asm->EmitInt8(Encoding);
617 Asm->EOL("@TType format", Encoding);
619 // Okay, we have actual filters or typeinfos to emit. As such, we need to
620 // pick a type encoding for them. We're about to emit a list of pointers to
621 // typeinfo objects at the end of the LSDA. However, unless we're in static
622 // mode, this reference will require a relocation by the dynamic linker.
624 // Because of this, we have a couple of options:
625 // 1) If we are in -static mode, we can always use an absolute reference
626 // from the LSDA, because the static linker will resolve it.
627 // 2) Otherwise, if the LSDA section is writable, we can output the direct
628 // reference to the typeinfo and allow the dynamic linker to relocate
629 // it. Since it is in a writable section, the dynamic linker won't
631 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
632 // we need to use some form of indirection. For example, on Darwin,
633 // we can output a statically-relocatable reference to a dyld stub. The
634 // offset to the stub is constant, but the contents are in a section
635 // that is updated by the dynamic linker. This is easy enough, but we
636 // need to tell the personality function of the unwinder to indirect
637 // through the dyld stub.
639 // FIXME: When this is actually implemented, we'll have to emit the stubs
640 // somewhere. This predicate should be moved to a shared location that is
641 // in target-independent code.
643 if (LSDASection->isWritable() ||
644 Asm->TM.getRelocationModel() == Reloc::Static) {
645 Encoding = DW_EH_PE_absptr;
646 Asm->EmitInt8(Encoding);
647 Asm->EOL("TType format", Encoding);
649 Encoding = DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4;
650 Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
651 Asm->EOL("TType format", Encoding);
653 Asm->EmitULEB128Bytes(TypeOffset);
654 Asm->EOL("TType base offset");
657 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly
658 // say that we're omitting that bit.
659 // FIXME: does this apply to Dwarf also? The above #if 0 implies yes?
661 Encoding = dwarf::DW_EH_PE_omit;
662 Asm->EmitInt8(Encoding);
663 Asm->EOL("@TType format", Encoding);
665 Encoding = dwarf::DW_EH_PE_absptr;
666 Asm->EmitInt8(Encoding);
667 Asm->EOL("@TType format", Encoding);
668 Asm->EmitULEB128Bytes(TypeOffset);
669 Asm->EOL("@TType base offset");
673 // SjLj Exception handilng
674 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
675 Encoding = dwarf::DW_EH_PE_udata4;
676 Asm->EmitInt8(Encoding);
677 Asm->EOL("Call site format", Encoding);
678 Asm->EmitULEB128Bytes(SizeSites);
679 Asm->EOL("Call site table length");
681 // Emit the landing pad site information.
683 for (SmallVectorImpl<CallSiteEntry>::const_iterator
684 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
685 const CallSiteEntry &S = *I;
687 // Offset of the landing pad, counted in 16-byte bundles relative to the
689 Asm->EmitULEB128Bytes(idx);
690 Asm->EOL("Landing pad");
692 // Offset of the first associated action record, relative to the start of
693 // the action table. This value is biased by 1 (1 indicates the start of
694 // the action table), and 0 indicates that there are no actions.
695 Asm->EmitULEB128Bytes(S.Action);
699 // DWARF Exception handling
700 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
702 // The call-site table is a list of all call sites that may throw an
703 // exception (including C++ 'throw' statements) in the procedure
704 // fragment. It immediately follows the LSDA header. Each entry indicates,
705 // for a given call, the first corresponding action record and corresponding
708 // The table begins with the number of bytes, stored as an LEB128
709 // compressed, unsigned integer. The records immediately follow the record
710 // count. They are sorted in increasing call-site address. Each record
713 // * The position of the call-site.
714 // * The position of the landing pad.
715 // * The first action record for that call site.
717 // A missing entry in the call-site table indicates that a call is not
718 // supposed to throw. Such calls include:
720 // * Calls to destructors within cleanup code. C++ semantics forbids these
722 // * Calls to intrinsic routines in the standard library which are known
723 // not to throw (sin, memcpy, et al).
725 // If the runtime does not find the call-site entry for a given call, it
726 // will call `terminate()'.
728 // Emit the landing pad call site table.
729 Encoding = dwarf::DW_EH_PE_udata4;
730 Asm->EmitInt8(Encoding);
731 Asm->EOL("Call site format", Encoding);
732 Asm->EmitULEB128Bytes(SizeSites);
733 Asm->EOL("Call site table size");
735 for (SmallVectorImpl<CallSiteEntry>::const_iterator
736 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
737 const CallSiteEntry &S = *I;
738 const char *BeginTag;
739 unsigned BeginNumber;
742 BeginTag = "eh_func_begin";
743 BeginNumber = SubprogramCount;
746 BeginNumber = S.BeginLabel;
749 // Offset of the call site relative to the previous call site, counted in
750 // number of 16-byte bundles. The first call site is counted relative to
751 // the start of the procedure fragment.
752 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
754 Asm->EOL("Region start");
757 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
760 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
762 Asm->EOL("Region length");
764 // Offset of the landing pad, counted in 16-byte bundles relative to the
769 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
772 Asm->EOL("Landing pad");
774 // Offset of the first associated action record, relative to the start of
775 // the action table. This value is biased by 1 (1 indicates the start of
776 // the action table), and 0 indicates that there are no actions.
777 Asm->EmitULEB128Bytes(S.Action);
782 // Emit the Action Table.
783 for (SmallVectorImpl<ActionEntry>::const_iterator
784 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
785 const ActionEntry &Action = *I;
789 // Used by the runtime to match the type of the thrown exception to the
790 // type of the catch clauses or the types in the exception specification.
792 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
793 Asm->EOL("TypeInfo index");
797 // Self-relative signed displacement in bytes of the next action record,
798 // or 0 if there is no next action record.
800 Asm->EmitSLEB128Bytes(Action.NextAction);
801 Asm->EOL("Next action");
804 // Emit the Catch Clauses. The code for the catch clauses following the same
805 // try is similar to a switch statement. The catch clause action record
806 // informs the runtime about the type of a catch clause and about the
807 // associated switch value.
809 // Action Record Fields:
812 // Positive value, starting at 1. Index in the types table of the
813 // __typeinfo for the catch-clause type. 1 is the first word preceding
814 // TTBase, 2 is the second word, and so on. Used by the runtime to check
815 // if the thrown exception type matches the catch-clause type. Back-end
816 // generated switch statements check against this value.
819 // Signed offset, in bytes from the start of this field, to the next
820 // chained action record, or zero if none.
822 // The order of the action records determined by the next field is the order
823 // of the catch clauses as they appear in the source code, and must be kept in
824 // the same order. As a result, changing the order of the catch clause would
825 // change the semantics of the program.
826 for (std::vector<GlobalVariable *>::const_reverse_iterator
827 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
828 const GlobalVariable *GV = *I;
833 O << Asm->getGlobalLinkName(GV, GLN);
838 Asm->EOL("TypeInfo");
841 // Emit the Type Table.
842 for (std::vector<unsigned>::const_iterator
843 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
844 unsigned TypeID = *I;
845 Asm->EmitULEB128Bytes(TypeID);
846 Asm->EOL("Filter TypeInfo index");
849 Asm->EmitAlignment(2, 0, 0, false);
852 /// EndModule - Emit all exception information that should come after the
854 void DwarfException::EndModule() {
855 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
857 if (TimePassesIsEnabled)
858 ExceptionTimer->startTimer();
860 if (shouldEmitMovesModule || shouldEmitTableModule) {
861 const std::vector<Function *> Personalities = MMI->getPersonalities();
862 for (unsigned i = 0; i < Personalities.size(); ++i)
863 EmitCIE(Personalities[i], i);
865 for (std::vector<FunctionEHFrameInfo>::iterator I = EHFrames.begin(),
866 E = EHFrames.end(); I != E; ++I)
870 if (TimePassesIsEnabled)
871 ExceptionTimer->stopTimer();
874 /// BeginFunction - Gather pre-function exception information. Assumes being
875 /// emitted immediately after the function entry point.
876 void DwarfException::BeginFunction(MachineFunction *MF) {
877 if (TimePassesIsEnabled)
878 ExceptionTimer->startTimer();
881 shouldEmitTable = shouldEmitMoves = false;
883 if (MMI && MAI->doesSupportExceptionHandling()) {
884 // Map all labels and get rid of any dead landing pads.
885 MMI->TidyLandingPads();
887 // If any landing pads survive, we need an EH table.
888 if (MMI->getLandingPads().size())
889 shouldEmitTable = true;
891 // See if we need frame move info.
892 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
893 shouldEmitMoves = true;
895 if (shouldEmitMoves || shouldEmitTable)
896 // Assumes in correct section after the entry point.
897 EmitLabel("eh_func_begin", ++SubprogramCount);
900 shouldEmitTableModule |= shouldEmitTable;
901 shouldEmitMovesModule |= shouldEmitMoves;
903 if (TimePassesIsEnabled)
904 ExceptionTimer->stopTimer();
907 /// EndFunction - Gather and emit post-function exception information.
909 void DwarfException::EndFunction() {
910 if (TimePassesIsEnabled)
911 ExceptionTimer->startTimer();
913 if (shouldEmitMoves || shouldEmitTable) {
914 EmitLabel("eh_func_end", SubprogramCount);
915 EmitExceptionTable();
917 // Save EH frame information
919 FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
921 MMI->getPersonalityIndex(),
922 MF->getFrameInfo()->hasCalls(),
923 !MMI->getLandingPads().empty(),
924 MMI->getFrameMoves(),
928 if (TimePassesIsEnabled)
929 ExceptionTimer->stopTimer();