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/Target/TargetAsmInfo.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,
39 const TargetAsmInfo *T)
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 void DwarfException::EmitCommonEHFrame(const Function *Personality,
54 // Size and sign of stack growth.
56 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
57 TargetFrameInfo::StackGrowsUp ?
58 TD->getPointerSize() : -TD->getPointerSize();
60 // Begin eh frame section.
61 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
63 if (TAI->is_EHSymbolPrivate())
64 O << TAI->getPrivateGlobalPrefix();
66 O << "EH_frame" << Index << ":\n";
67 EmitLabel("section_eh_frame", Index);
69 // Define base labels.
70 EmitLabel("eh_frame_common", Index);
72 // Define the eh frame length.
73 EmitDifference("eh_frame_common_end", Index,
74 "eh_frame_common_begin", Index, true);
75 Asm->EOL("Length of Common Information Entry");
78 EmitLabel("eh_frame_common_begin", Index);
79 Asm->EmitInt32((int)0);
80 Asm->EOL("CIE Identifier Tag");
81 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
82 Asm->EOL("CIE Version");
84 // The personality presence indicates that language specific information will
85 // show up in the eh frame.
86 Asm->EmitString(Personality ? "zPLR" : "zR");
87 Asm->EOL("CIE Augmentation");
90 Asm->EmitULEB128Bytes(1);
91 Asm->EOL("CIE Code Alignment Factor");
92 Asm->EmitSLEB128Bytes(stackGrowth);
93 Asm->EOL("CIE Data Alignment Factor");
94 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
95 Asm->EOL("CIE Return Address Column");
97 // If there is a personality, we need to indicate the functions location.
99 Asm->EmitULEB128Bytes(7);
100 Asm->EOL("Augmentation Size");
102 if (TAI->getNeedsIndirectEncoding()) {
103 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4 |
104 dwarf::DW_EH_PE_indirect);
105 Asm->EOL("Personality (pcrel sdata4 indirect)");
107 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
108 Asm->EOL("Personality (pcrel sdata4)");
111 PrintRelDirective(true);
112 O << TAI->getPersonalityPrefix();
113 Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
114 O << TAI->getPersonalitySuffix();
115 if (strcmp(TAI->getPersonalitySuffix(), "+4@GOTPCREL"))
116 O << "-" << TAI->getPCSymbol();
117 Asm->EOL("Personality");
119 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
120 Asm->EOL("LSDA Encoding (pcrel sdata4)");
122 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
123 Asm->EOL("FDE Encoding (pcrel sdata4)");
125 Asm->EmitULEB128Bytes(1);
126 Asm->EOL("Augmentation Size");
128 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
129 Asm->EOL("FDE Encoding (pcrel sdata4)");
132 // Indicate locations of general callee saved registers in frame.
133 std::vector<MachineMove> Moves;
134 RI->getInitialFrameState(Moves);
135 EmitFrameMoves(NULL, 0, Moves, true);
137 // On Darwin the linker honors the alignment of eh_frame, which means it must
138 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
139 // holes which confuse readers of eh_frame.
140 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
142 EmitLabel("eh_frame_common_end", Index);
147 /// EmitEHFrame - Emit function exception frame information.
149 void DwarfException::EmitEHFrame(const FunctionEHFrameInfo &EHFrameInfo) {
150 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
151 "Should not emit 'available externally' functions at all");
153 const Function *TheFunc = EHFrameInfo.function;
155 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
157 // Externally visible entry into the functions eh frame info. If the
158 // corresponding function is static, this should not be externally visible.
159 if (!TheFunc->hasLocalLinkage())
160 if (const char *GlobalEHDirective = TAI->getGlobalEHDirective())
161 O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
163 // If corresponding function is weak definition, this should be too.
164 if (TheFunc->isWeakForLinker() && TAI->getWeakDefDirective())
165 O << TAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
167 // If there are no calls then you can't unwind. This may mean we can omit the
168 // EH Frame, but some environments do not handle weak absolute symbols. If
169 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
170 // info is to be available for non-EH uses.
171 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
172 (!TheFunc->isWeakForLinker() ||
173 !TAI->getWeakDefDirective() ||
174 TAI->getSupportsWeakOmittedEHFrame())) {
175 O << EHFrameInfo.FnName << " = 0\n";
176 // This name has no connection to the function, so it might get
177 // dead-stripped when the function is not, erroneously. Prohibit
178 // dead-stripping unconditionally.
179 if (const char *UsedDirective = TAI->getUsedDirective())
180 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
182 O << EHFrameInfo.FnName << ":\n";
185 EmitDifference("eh_frame_end", EHFrameInfo.Number,
186 "eh_frame_begin", EHFrameInfo.Number, true);
187 Asm->EOL("Length of Frame Information Entry");
189 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
191 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
192 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
195 Asm->EOL("FDE CIE offset");
197 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
198 Asm->EOL("FDE initial location");
199 EmitDifference("eh_func_end", EHFrameInfo.Number,
200 "eh_func_begin", EHFrameInfo.Number, true);
201 Asm->EOL("FDE address range");
203 // If there is a personality and landing pads then point to the language
204 // specific data area in the exception table.
205 if (EHFrameInfo.PersonalityIndex) {
206 Asm->EmitULEB128Bytes(4);
207 Asm->EOL("Augmentation size");
209 if (EHFrameInfo.hasLandingPads)
210 EmitReference("exception", EHFrameInfo.Number, true, true);
212 Asm->EmitInt32((int)0);
213 Asm->EOL("Language Specific Data Area");
215 Asm->EmitULEB128Bytes(0);
216 Asm->EOL("Augmentation size");
219 // Indicate locations of function specific callee saved registers in frame.
220 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
223 // On Darwin the linker honors the alignment of eh_frame, which means it
224 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
225 // get holes which confuse readers of eh_frame.
226 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
228 EmitLabel("eh_frame_end", EHFrameInfo.Number);
230 // If the function is marked used, this table should be also. We cannot
231 // make the mark unconditional in this case, since retaining the table also
232 // retains the function in this case, and there is code around that depends
233 // on unused functions (calling undefined externals) being dead-stripped to
234 // link correctly. Yes, there really is.
235 if (MMI->isUsedFunction(EHFrameInfo.function))
236 if (const char *UsedDirective = TAI->getUsedDirective())
237 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
241 /// SharedTypeIds - How many leading type ids two landing pads have in common.
242 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
243 const LandingPadInfo *R) {
244 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
245 unsigned LSize = LIds.size(), RSize = RIds.size();
246 unsigned MinSize = LSize < RSize ? LSize : RSize;
249 for (; Count != MinSize; ++Count)
250 if (LIds[Count] != RIds[Count])
256 /// PadLT - Order landing pads lexicographically by type id.
257 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
258 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
259 unsigned LSize = LIds.size(), RSize = RIds.size();
260 unsigned MinSize = LSize < RSize ? LSize : RSize;
262 for (unsigned i = 0; i != MinSize; ++i)
263 if (LIds[i] != RIds[i])
264 return LIds[i] < RIds[i];
266 return LSize < RSize;
269 /// ComputeActionsTable - Compute the actions table and gather the first action
270 /// index for each landing pad site.
271 unsigned DwarfException::
272 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
273 SmallVectorImpl<ActionEntry> &Actions,
274 SmallVectorImpl<unsigned> &FirstActions) {
275 // Negative type IDs index into FilterIds. Positive type IDs index into
276 // TypeInfos. The value written for a positive type ID is just the type ID
277 // itself. For a negative type ID, however, the value written is the
278 // (negative) byte offset of the corresponding FilterIds entry. The byte
279 // offset is usually equal to the type ID (because the FilterIds entries are
280 // written using a variable width encoding, which outputs one byte per entry
281 // as long as the value written is not too large) but can differ. This kind
282 // of complication does not occur for positive type IDs because type infos are
283 // output using a fixed width encoding. FilterOffsets[i] holds the byte
284 // offset corresponding to FilterIds[i].
286 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
287 SmallVector<int, 16> FilterOffsets;
288 FilterOffsets.reserve(FilterIds.size());
291 for (std::vector<unsigned>::const_iterator
292 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
293 FilterOffsets.push_back(Offset);
294 Offset -= TargetAsmInfo::getULEB128Size(*I);
297 FirstActions.reserve(LandingPads.size());
300 unsigned SizeActions = 0;
301 const LandingPadInfo *PrevLPI = 0;
303 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
304 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
305 const LandingPadInfo *LPI = *I;
306 const std::vector<int> &TypeIds = LPI->TypeIds;
307 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
308 unsigned SizeSiteActions = 0;
310 if (NumShared < TypeIds.size()) {
311 unsigned SizeAction = 0;
312 ActionEntry *PrevAction = 0;
315 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
316 assert(Actions.size());
317 PrevAction = &Actions.back();
318 SizeAction = TargetAsmInfo::getSLEB128Size(PrevAction->NextAction) +
319 TargetAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
321 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
323 TargetAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
324 SizeAction += -PrevAction->NextAction;
325 PrevAction = PrevAction->Previous;
329 // Compute the actions.
330 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
331 int TypeID = TypeIds[J];
332 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
333 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
334 unsigned SizeTypeID = TargetAsmInfo::getSLEB128Size(ValueForTypeID);
336 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
337 SizeAction = SizeTypeID + TargetAsmInfo::getSLEB128Size(NextAction);
338 SizeSiteActions += SizeAction;
340 ActionEntry Action = {ValueForTypeID, NextAction, PrevAction};
341 Actions.push_back(Action);
342 PrevAction = &Actions.back();
345 // Record the first action of the landing pad site.
346 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
347 } // else identical - re-use previous FirstAction
349 FirstActions.push_back(FirstAction);
351 // Compute this sites contribution to size.
352 SizeActions += SizeSiteActions;
360 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
361 /// has a try-range containing the call, a non-zero landing pad and an
362 /// appropriate action. The entry for an ordinary call has a try-range
363 /// containing the call and zero for the landing pad and the action. Calls
364 /// marked 'nounwind' have no entry and must not be contained in the try-range
365 /// of any entry - they form gaps in the table. Entries must be ordered by
366 /// try-range address.
367 void DwarfException::
368 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
369 const RangeMapType &PadMap,
370 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
371 const SmallVectorImpl<unsigned> &FirstActions) {
372 // The end label of the previous invoke or nounwind try-range.
373 unsigned LastLabel = 0;
375 // Whether there is a potentially throwing instruction (currently this means
376 // an ordinary call) between the end of the previous try-range and now.
377 bool SawPotentiallyThrowing = false;
379 // Whether the last CallSite entry was for an invoke.
380 bool PreviousIsInvoke = false;
382 // Visit all instructions in order of address.
383 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
385 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
387 if (!MI->isLabel()) {
388 SawPotentiallyThrowing |= MI->getDesc().isCall();
392 unsigned BeginLabel = MI->getOperand(0).getImm();
393 assert(BeginLabel && "Invalid label!");
395 // End of the previous try-range?
396 if (BeginLabel == LastLabel)
397 SawPotentiallyThrowing = false;
399 // Beginning of a new try-range?
400 RangeMapType::iterator L = PadMap.find(BeginLabel);
401 if (L == PadMap.end())
402 // Nope, it was just some random label.
405 PadRange P = L->second;
406 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
407 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
408 "Inconsistent landing pad map!");
410 // For Dwarf exception handling (SjLj handling doesn't use this)
411 // If some instruction between the previous try-range and this one may
412 // throw, create a call-site entry with no landing pad for the region
413 // between the try-ranges.
414 if (SawPotentiallyThrowing &&
415 TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
416 CallSiteEntry Site = {LastLabel, BeginLabel, 0, 0};
417 CallSites.push_back(Site);
418 PreviousIsInvoke = false;
421 LastLabel = LandingPad->EndLabels[P.RangeIndex];
422 assert(BeginLabel && LastLabel && "Invalid landing pad!");
424 if (LandingPad->LandingPadLabel) {
425 // This try-range is for an invoke.
426 CallSiteEntry Site = {BeginLabel, LastLabel,
427 LandingPad->LandingPadLabel,
428 FirstActions[P.PadIndex]};
430 // Try to merge with the previous call-site.
431 if (PreviousIsInvoke) {
432 CallSiteEntry &Prev = CallSites.back();
433 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
434 // Extend the range of the previous entry.
435 Prev.EndLabel = Site.EndLabel;
440 // Otherwise, create a new call-site.
441 CallSites.push_back(Site);
442 PreviousIsInvoke = true;
445 PreviousIsInvoke = false;
450 // If some instruction between the previous try-range and the end of the
451 // function may throw, create a call-site entry with no landing pad for the
452 // region following the try-range.
453 if (SawPotentiallyThrowing &&
454 TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
455 CallSiteEntry Site = {LastLabel, 0, 0, 0};
456 CallSites.push_back(Site);
460 /// EmitExceptionTable - Emit landing pads and actions.
462 /// The general organization of the table is complex, but the basic concepts are
463 /// easy. First there is a header which describes the location and organization
464 /// of the three components that follow.
466 /// 1. The landing pad site information describes the range of code covered by
467 /// the try. In our case it's an accumulation of the ranges covered by the
468 /// invokes in the try. There is also a reference to the landing pad that
469 /// handles the exception once processed. Finally an index into the actions
471 /// 2. The action table, in our case, is composed of pairs of type ids and next
472 /// action offset. Starting with the action index from the landing pad
473 /// site, each type Id is checked for a match to the current exception. If
474 /// it matches then the exception and type id are passed on to the landing
475 /// pad. Otherwise the next action is looked up. This chain is terminated
476 /// with a next action of zero. If no type id is found the the frame is
477 /// unwound and handling continues.
478 /// 3. Type id table contains references to all the C++ typeinfo for all
479 /// catches in the function. This tables is reversed indexed base 1.
480 void DwarfException::EmitExceptionTable() {
481 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
482 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
483 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
484 if (PadInfos.empty()) return;
486 // Sort the landing pads in order of their type ids. This is used to fold
487 // duplicate actions.
488 SmallVector<const LandingPadInfo *, 64> LandingPads;
489 LandingPads.reserve(PadInfos.size());
491 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
492 LandingPads.push_back(&PadInfos[i]);
494 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
496 // Compute the actions table and gather the first action index for each
498 SmallVector<ActionEntry, 32> Actions;
499 SmallVector<unsigned, 64> FirstActions;
500 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions, FirstActions);
502 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
503 // by try-range labels when lowered). Ordinary calls do not, so appropriate
504 // try-ranges for them need be deduced when using Dwarf exception handling.
506 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
507 const LandingPadInfo *LandingPad = LandingPads[i];
508 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
509 unsigned BeginLabel = LandingPad->BeginLabels[j];
510 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
511 PadRange P = { i, j };
512 PadMap[BeginLabel] = P;
516 // Compute the call-site table.
517 SmallVector<CallSiteEntry, 64> CallSites;
518 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
523 const unsigned SiteStartSize = sizeof(int32_t); // DW_EH_PE_udata4
524 const unsigned SiteLengthSize = sizeof(int32_t); // DW_EH_PE_udata4
525 const unsigned LandingPadSize = sizeof(int32_t); // DW_EH_PE_udata4
528 bool HaveTTData = (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
529 ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
532 if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
535 SizeSites = CallSites.size() *
536 (SiteStartSize + SiteLengthSize + LandingPadSize);
537 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
538 SizeSites += TargetAsmInfo::getULEB128Size(CallSites[i].Action);
539 if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
540 SizeSites += TargetAsmInfo::getULEB128Size(i);
543 const unsigned TypeInfoSize = TD->getPointerSize(); // DW_EH_PE_absptr
544 unsigned SizeTypes = TypeInfos.size() * TypeInfoSize;
546 unsigned TypeOffset = sizeof(int8_t) + // Call site format
547 TargetAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
548 SizeSites + SizeActions + SizeTypes;
550 unsigned TotalSize = sizeof(int8_t) + // LPStart format
551 sizeof(int8_t) + // TType format
553 TargetAsmInfo::getULEB128Size(TypeOffset) : 0) + // TType base offset
556 unsigned SizeAlign = (4 - TotalSize) & 3;
558 // Begin the exception table.
559 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
560 Asm->OutStreamer.SwitchSection(LSDASection);
561 Asm->EmitAlignment(2, 0, 0, false);
562 O << "GCC_except_table" << SubprogramCount << ":\n";
564 for (unsigned i = 0; i != SizeAlign; ++i) {
569 EmitLabel("exception", SubprogramCount);
570 if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
571 std::string SjLjName = "_lsda_";
572 SjLjName += MF->getFunction()->getName().str();
573 EmitLabel(SjLjName.c_str(), 0);
577 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
578 Asm->EOL("LPStart format (DW_EH_PE_omit)");
581 if (TypeInfos.empty() && FilterIds.empty()) {
582 // If there are no typeinfos or filters, there is nothing to emit, optimize
583 // by specifying the "omit" encoding.
584 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
585 Asm->EOL("TType format (DW_EH_PE_omit)");
587 // Okay, we have actual filters or typeinfos to emit. As such, we need to
588 // pick a type encoding for them. We're about to emit a list of pointers to
589 // typeinfo objects at the end of the LSDA. However, unless we're in static
590 // mode, this reference will require a relocation by the dynamic linker.
592 // Because of this, we have a couple of options:
593 // 1) If we are in -static mode, we can always use an absolute reference
594 // from the LSDA, because the static linker will resolve it.
595 // 2) Otherwise, if the LSDA section is writable, we can output the direct
596 // reference to the typeinfo and allow the dynamic linker to relocate
597 // it. Since it is in a writable section, the dynamic linker won't
599 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
600 // we need to use some form of indirection. For example, on Darwin,
601 // we can output a statically-relocatable reference to a dyld stub. The
602 // offset to the stub is constant, but the contents are in a section
603 // that is updated by the dynamic linker. This is easy enough, but we
604 // need to tell the personality function of the unwinder to indirect
605 // through the dyld stub.
607 // FIXME: When this is actually implemented, we'll have to emit the stubs
608 // somewhere. This predicate should be moved to a shared location that is
609 // in target-independent code.
611 if (LSDASection->isWritable() ||
612 Asm->TM.getRelocationModel() == Reloc::Static) {
613 Asm->EmitInt8(DW_EH_PE_absptr);
614 Asm->EOL("TType format (DW_EH_PE_absptr)");
616 Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
617 Asm->EOL("TType format (DW_EH_PE_pcrel | DW_EH_PE_indirect"
618 " | DW_EH_PE_sdata4)");
620 Asm->EmitULEB128Bytes(TypeOffset);
621 Asm->EOL("TType base offset");
624 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly
625 // say that we're omitting that bit.
626 // FIXME: does this apply to Dwarf also? The above #if 0 implies yes?
628 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
629 Asm->EOL("TType format (DW_EH_PE_omit)");
631 Asm->EmitInt8(dwarf::DW_EH_PE_absptr);
632 Asm->EOL("TType format (DW_EH_PE_absptr)");
633 Asm->EmitULEB128Bytes(TypeOffset);
634 Asm->EOL("TType base offset");
638 // SjLj Exception handilng
639 if (TAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
640 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
641 Asm->EOL("Call site format (DW_EH_PE_udata4)");
642 Asm->EmitULEB128Bytes(SizeSites);
643 Asm->EOL("Call-site table length");
645 // Emit the landing pad site information.
647 for (SmallVectorImpl<CallSiteEntry>::const_iterator
648 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
649 const CallSiteEntry &S = *I;
650 Asm->EmitULEB128Bytes(idx);
651 Asm->EOL("Landing pad");
652 Asm->EmitULEB128Bytes(S.Action);
656 // DWARF Exception handling
657 assert(TAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
659 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
660 Asm->EOL("Call site format (DW_EH_PE_udata4)");
661 Asm->EmitULEB128Bytes(SizeSites);
662 Asm->EOL("Call-site table length");
664 // Emit the landing pad site information.
665 for (SmallVectorImpl<CallSiteEntry>::const_iterator
666 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
667 const CallSiteEntry &S = *I;
668 const char *BeginTag;
669 unsigned BeginNumber;
672 BeginTag = "eh_func_begin";
673 BeginNumber = SubprogramCount;
676 BeginNumber = S.BeginLabel;
679 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
681 Asm->EOL("Region start");
684 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
687 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
689 Asm->EOL("Region length");
694 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
697 Asm->EOL("Landing pad");
699 Asm->EmitULEB128Bytes(S.Action);
705 for (SmallVectorImpl<ActionEntry>::const_iterator
706 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
707 const ActionEntry &Action = *I;
708 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
709 Asm->EOL("TypeInfo index");
710 Asm->EmitSLEB128Bytes(Action.NextAction);
711 Asm->EOL("Next action");
714 // Emit the type ids.
715 for (std::vector<GlobalVariable *>::const_reverse_iterator
716 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
717 GlobalVariable *GV = *I;
722 O << Asm->getGlobalLinkName(GV, GLN);
727 Asm->EOL("TypeInfo");
730 // Emit the filter typeids.
731 for (std::vector<unsigned>::const_iterator
732 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
733 unsigned TypeID = *I;
734 Asm->EmitULEB128Bytes(TypeID);
735 Asm->EOL("Filter TypeInfo index");
738 Asm->EmitAlignment(2, 0, 0, false);
741 /// EndModule - Emit all exception information that should come after the
743 void DwarfException::EndModule() {
744 if (TAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
746 if (TimePassesIsEnabled)
747 ExceptionTimer->startTimer();
749 if (shouldEmitMovesModule || shouldEmitTableModule) {
750 const std::vector<Function *> Personalities = MMI->getPersonalities();
751 for (unsigned i = 0; i < Personalities.size(); ++i)
752 EmitCommonEHFrame(Personalities[i], i);
754 for (std::vector<FunctionEHFrameInfo>::iterator I = EHFrames.begin(),
755 E = EHFrames.end(); I != E; ++I)
759 if (TimePassesIsEnabled)
760 ExceptionTimer->stopTimer();
763 /// BeginFunction - Gather pre-function exception information. Assumes being
764 /// emitted immediately after the function entry point.
765 void DwarfException::BeginFunction(MachineFunction *MF) {
766 if (TimePassesIsEnabled)
767 ExceptionTimer->startTimer();
770 shouldEmitTable = shouldEmitMoves = false;
772 if (MMI && TAI->doesSupportExceptionHandling()) {
773 // Map all labels and get rid of any dead landing pads.
774 MMI->TidyLandingPads();
776 // If any landing pads survive, we need an EH table.
777 if (MMI->getLandingPads().size())
778 shouldEmitTable = true;
780 // See if we need frame move info.
781 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
782 shouldEmitMoves = true;
784 if (shouldEmitMoves || shouldEmitTable)
785 // Assumes in correct section after the entry point.
786 EmitLabel("eh_func_begin", ++SubprogramCount);
789 shouldEmitTableModule |= shouldEmitTable;
790 shouldEmitMovesModule |= shouldEmitMoves;
792 if (TimePassesIsEnabled)
793 ExceptionTimer->stopTimer();
796 /// EndFunction - Gather and emit post-function exception information.
798 void DwarfException::EndFunction() {
799 if (TimePassesIsEnabled)
800 ExceptionTimer->startTimer();
802 if (shouldEmitMoves || shouldEmitTable) {
803 EmitLabel("eh_func_end", SubprogramCount);
804 EmitExceptionTable();
806 // Save EH frame information
808 FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
810 MMI->getPersonalityIndex(),
811 MF->getFrameInfo()->hasCalls(),
812 !MMI->getLandingPads().empty(),
813 MMI->getFrameMoves(),
817 if (TimePassesIsEnabled)
818 ExceptionTimer->stopTimer();