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/MCSection.h"
21 #include "llvm/MC/MCStreamer.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/Target/TargetData.h"
24 #include "llvm/Target/TargetFrameInfo.h"
25 #include "llvm/Target/TargetLoweringObjectFile.h"
26 #include "llvm/Target/TargetOptions.h"
27 #include "llvm/Target/TargetRegisterInfo.h"
28 #include "llvm/Support/Dwarf.h"
29 #include "llvm/Support/Mangler.h"
30 #include "llvm/Support/Timer.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/ADT/SmallString.h"
33 #include "llvm/ADT/StringExtras.h"
36 static TimerGroup &getDwarfTimerGroup() {
37 static TimerGroup DwarfTimerGroup("Dwarf Exception");
38 return DwarfTimerGroup;
41 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
43 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
44 shouldEmitTableModule(false), shouldEmitMovesModule(false),
46 if (TimePassesIsEnabled)
47 ExceptionTimer = new Timer("Dwarf Exception Writer",
48 getDwarfTimerGroup());
51 DwarfException::~DwarfException() {
52 delete ExceptionTimer;
55 /// SizeOfEncodedValue - Return the size of the encoding in bytes.
56 unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
57 if (Encoding == dwarf::DW_EH_PE_omit)
60 switch (Encoding & 0x07) {
61 case dwarf::DW_EH_PE_absptr:
62 return TD->getPointerSize();
63 case dwarf::DW_EH_PE_udata2:
65 case dwarf::DW_EH_PE_udata4:
67 case dwarf::DW_EH_PE_udata8:
71 llvm_unreachable("Invalid encoded value.");
75 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
76 /// is shared among many Frame Description Entries. There is at least one CIE
77 /// in every non-empty .debug_frame section.
78 void DwarfException::EmitCIE(const Function *Personality, unsigned Index) {
79 // Size and sign of stack growth.
81 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
82 TargetFrameInfo::StackGrowsUp ?
83 TD->getPointerSize() : -TD->getPointerSize();
85 // Begin eh frame section.
86 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
88 if (MAI->is_EHSymbolPrivate())
89 O << MAI->getPrivateGlobalPrefix();
91 O << "EH_frame" << Index << ":\n";
92 EmitLabel("section_eh_frame", Index);
94 // Define base labels.
95 EmitLabel("eh_frame_common", Index);
97 // Define the eh frame length.
98 EmitDifference("eh_frame_common_end", Index,
99 "eh_frame_common_begin", Index, true);
100 Asm->EOL("Length of Common Information Entry");
103 EmitLabel("eh_frame_common_begin", Index);
104 Asm->EmitInt32((int)0);
105 Asm->EOL("CIE Identifier Tag");
106 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
107 Asm->EOL("CIE Version");
109 // The personality presence indicates that language specific information will
110 // show up in the eh frame.
112 // FIXME: Don't hardcode these encodings.
113 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
114 if (Personality && MAI->getNeedsIndirectEncoding())
115 PerEncoding |= dwarf::DW_EH_PE_indirect;
116 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
117 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
119 char Augmentation[5] = { 0 };
120 unsigned AugmentationSize = 0;
121 char *APtr = Augmentation + 1;
124 // There is a personality function.
126 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
129 if (UsesLSDA[Index]) {
130 // An LSDA pointer is in the FDE augmentation.
135 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
136 // A non-default pointer encoding for the FDE.
141 if (APtr != Augmentation + 1)
142 Augmentation[0] = 'z';
144 Asm->EmitString(Augmentation);
145 Asm->EOL("CIE Augmentation");
148 Asm->EmitULEB128Bytes(1);
149 Asm->EOL("CIE Code Alignment Factor");
150 Asm->EmitSLEB128Bytes(stackGrowth);
151 Asm->EOL("CIE Data Alignment Factor");
152 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
153 Asm->EOL("CIE Return Address Column");
155 Asm->EmitULEB128Bytes(AugmentationSize);
156 Asm->EOL("Augmentation Size");
158 Asm->EmitInt8(PerEncoding);
159 Asm->EOL("Personality", PerEncoding);
161 // If there is a personality, we need to indicate the function's location.
163 PrintRelDirective(true);
164 O << MAI->getPersonalityPrefix();
165 Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
166 O << MAI->getPersonalitySuffix();
167 if (strcmp(MAI->getPersonalitySuffix(), "+4@GOTPCREL"))
168 O << "-" << MAI->getPCSymbol();
169 Asm->EOL("Personality");
171 Asm->EmitInt8(LSDAEncoding);
172 Asm->EOL("LSDA Encoding", LSDAEncoding);
174 Asm->EmitInt8(FDEEncoding);
175 Asm->EOL("FDE Encoding", FDEEncoding);
178 // Indicate locations of general callee saved registers in frame.
179 std::vector<MachineMove> Moves;
180 RI->getInitialFrameState(Moves);
181 EmitFrameMoves(NULL, 0, Moves, true);
183 // On Darwin the linker honors the alignment of eh_frame, which means it must
184 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
185 // holes which confuse readers of eh_frame.
186 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
188 EmitLabel("eh_frame_common_end", Index);
193 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
194 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
195 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
196 "Should not emit 'available externally' functions at all");
198 const Function *TheFunc = EHFrameInfo.function;
200 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
202 // Externally visible entry into the functions eh frame info. If the
203 // corresponding function is static, this should not be externally visible.
204 if (!TheFunc->hasLocalLinkage())
205 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
206 O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
208 // If corresponding function is weak definition, this should be too.
209 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
210 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
212 // If there are no calls then you can't unwind. This may mean we can omit the
213 // EH Frame, but some environments do not handle weak absolute symbols. If
214 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
215 // info is to be available for non-EH uses.
216 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
217 (!TheFunc->isWeakForLinker() ||
218 !MAI->getWeakDefDirective() ||
219 MAI->getSupportsWeakOmittedEHFrame())) {
220 O << EHFrameInfo.FnName << " = 0\n";
221 // This name has no connection to the function, so it might get
222 // dead-stripped when the function is not, erroneously. Prohibit
223 // dead-stripping unconditionally.
224 if (const char *UsedDirective = MAI->getUsedDirective())
225 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
227 O << EHFrameInfo.FnName << ":\n";
230 EmitDifference("eh_frame_end", EHFrameInfo.Number,
231 "eh_frame_begin", EHFrameInfo.Number, true);
232 Asm->EOL("Length of Frame Information Entry");
234 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
236 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
237 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
240 Asm->EOL("FDE CIE offset");
242 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
243 Asm->EOL("FDE initial location");
244 EmitDifference("eh_func_end", EHFrameInfo.Number,
245 "eh_func_begin", EHFrameInfo.Number, true);
246 Asm->EOL("FDE address range");
248 // If there is a personality and landing pads then point to the language
249 // specific data area in the exception table.
250 if (MMI->getPersonalities()[0] != NULL) {
251 bool is4Byte = TD->getPointerSize() == sizeof(int32_t);
253 Asm->EmitULEB128Bytes(is4Byte ? 4 : 8);
254 Asm->EOL("Augmentation size");
256 if (EHFrameInfo.hasLandingPads)
257 EmitReference("exception", EHFrameInfo.Number, true, false);
260 Asm->EmitInt32((int)0);
262 Asm->EmitInt64((int)0);
264 Asm->EOL("Language Specific Data Area");
266 Asm->EmitULEB128Bytes(0);
267 Asm->EOL("Augmentation size");
270 // Indicate locations of function specific callee saved registers in frame.
271 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
274 // On Darwin the linker honors the alignment of eh_frame, which means it
275 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
276 // get holes which confuse readers of eh_frame.
277 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
279 EmitLabel("eh_frame_end", EHFrameInfo.Number);
281 // If the function is marked used, this table should be also. We cannot
282 // make the mark unconditional in this case, since retaining the table also
283 // retains the function in this case, and there is code around that depends
284 // on unused functions (calling undefined externals) being dead-stripped to
285 // link correctly. Yes, there really is.
286 if (MMI->isUsedFunction(EHFrameInfo.function))
287 if (const char *UsedDirective = MAI->getUsedDirective())
288 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
294 /// SharedTypeIds - How many leading type ids two landing pads have in common.
295 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
296 const LandingPadInfo *R) {
297 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
298 unsigned LSize = LIds.size(), RSize = RIds.size();
299 unsigned MinSize = LSize < RSize ? LSize : RSize;
302 for (; Count != MinSize; ++Count)
303 if (LIds[Count] != RIds[Count])
309 /// PadLT - Order landing pads lexicographically by type id.
310 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
311 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
312 unsigned LSize = LIds.size(), RSize = RIds.size();
313 unsigned MinSize = LSize < RSize ? LSize : RSize;
315 for (unsigned i = 0; i != MinSize; ++i)
316 if (LIds[i] != RIds[i])
317 return LIds[i] < RIds[i];
319 return LSize < RSize;
322 /// ComputeActionsTable - Compute the actions table and gather the first action
323 /// index for each landing pad site.
324 unsigned DwarfException::
325 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
326 SmallVectorImpl<ActionEntry> &Actions,
327 SmallVectorImpl<unsigned> &FirstActions) {
329 // The action table follows the call-site table in the LSDA. The individual
330 // records are of two types:
333 // * Exception specification
335 // The two record kinds have the same format, with only small differences.
336 // They are distinguished by the "switch value" field: Catch clauses
337 // (TypeInfos) have strictly positive switch values, and exception
338 // specifications (FilterIds) have strictly negative switch values. Value 0
339 // indicates a catch-all clause.
341 // Negative type IDs index into FilterIds. Positive type IDs index into
342 // TypeInfos. The value written for a positive type ID is just the type ID
343 // itself. For a negative type ID, however, the value written is the
344 // (negative) byte offset of the corresponding FilterIds entry. The byte
345 // offset is usually equal to the type ID (because the FilterIds entries are
346 // written using a variable width encoding, which outputs one byte per entry
347 // as long as the value written is not too large) but can differ. This kind
348 // of complication does not occur for positive type IDs because type infos are
349 // output using a fixed width encoding. FilterOffsets[i] holds the byte
350 // offset corresponding to FilterIds[i].
352 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
353 SmallVector<int, 16> FilterOffsets;
354 FilterOffsets.reserve(FilterIds.size());
357 for (std::vector<unsigned>::const_iterator
358 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
359 FilterOffsets.push_back(Offset);
360 Offset -= MCAsmInfo::getULEB128Size(*I);
363 FirstActions.reserve(LandingPads.size());
366 unsigned SizeActions = 0;
367 const LandingPadInfo *PrevLPI = 0;
369 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
370 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
371 const LandingPadInfo *LPI = *I;
372 const std::vector<int> &TypeIds = LPI->TypeIds;
373 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
374 unsigned SizeSiteActions = 0;
376 if (NumShared < TypeIds.size()) {
377 unsigned SizeAction = 0;
378 ActionEntry *PrevAction = 0;
381 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
382 assert(Actions.size());
383 PrevAction = &Actions.back();
384 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
385 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
387 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
389 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
390 SizeAction += -PrevAction->NextAction;
391 PrevAction = PrevAction->Previous;
395 // Compute the actions.
396 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
397 int TypeID = TypeIds[J];
398 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
399 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
400 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
402 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
403 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
404 SizeSiteActions += SizeAction;
406 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
407 Actions.push_back(Action);
408 PrevAction = &Actions.back();
411 // Record the first action of the landing pad site.
412 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
413 } // else identical - re-use previous FirstAction
415 // Information used when created the call-site table. The action record
416 // field of the call site record is the offset of the first associated
417 // action record, relative to the start of the actions table. This value is
418 // biased by 1 (1 in dicating the start of the actions table), and 0
419 // indicates that there are no actions.
420 FirstActions.push_back(FirstAction);
422 // Compute this sites contribution to size.
423 SizeActions += SizeSiteActions;
431 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
432 /// has a try-range containing the call, a non-zero landing pad, and an
433 /// appropriate action. The entry for an ordinary call has a try-range
434 /// containing the call and zero for the landing pad and the action. Calls
435 /// marked 'nounwind' have no entry and must not be contained in the try-range
436 /// of any entry - they form gaps in the table. Entries must be ordered by
437 /// try-range address.
438 void DwarfException::
439 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
440 const RangeMapType &PadMap,
441 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
442 const SmallVectorImpl<unsigned> &FirstActions) {
443 // The end label of the previous invoke or nounwind try-range.
444 unsigned LastLabel = 0;
446 // Whether there is a potentially throwing instruction (currently this means
447 // an ordinary call) between the end of the previous try-range and now.
448 bool SawPotentiallyThrowing = false;
450 // Whether the last CallSite entry was for an invoke.
451 bool PreviousIsInvoke = false;
453 // Visit all instructions in order of address.
454 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
456 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
458 if (!MI->isLabel()) {
459 SawPotentiallyThrowing |= MI->getDesc().isCall();
463 unsigned BeginLabel = MI->getOperand(0).getImm();
464 assert(BeginLabel && "Invalid label!");
466 // End of the previous try-range?
467 if (BeginLabel == LastLabel)
468 SawPotentiallyThrowing = false;
470 // Beginning of a new try-range?
471 RangeMapType::iterator L = PadMap.find(BeginLabel);
472 if (L == PadMap.end())
473 // Nope, it was just some random label.
476 const PadRange &P = L->second;
477 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
478 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
479 "Inconsistent landing pad map!");
481 // For Dwarf exception handling (SjLj handling doesn't use this). If some
482 // instruction between the previous try-range and this one may throw,
483 // create a call-site entry with no landing pad for the region between the
485 if (SawPotentiallyThrowing &&
486 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
487 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
488 CallSites.push_back(Site);
489 PreviousIsInvoke = false;
492 LastLabel = LandingPad->EndLabels[P.RangeIndex];
493 assert(BeginLabel && LastLabel && "Invalid landing pad!");
495 if (LandingPad->LandingPadLabel) {
496 // This try-range is for an invoke.
497 CallSiteEntry Site = {
500 LandingPad->LandingPadLabel,
501 FirstActions[P.PadIndex]
504 // Try to merge with the previous call-site. SJLJ doesn't do this
505 if (PreviousIsInvoke &&
506 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
507 CallSiteEntry &Prev = CallSites.back();
508 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
509 // Extend the range of the previous entry.
510 Prev.EndLabel = Site.EndLabel;
515 // Otherwise, create a new call-site.
516 CallSites.push_back(Site);
517 PreviousIsInvoke = true;
520 PreviousIsInvoke = false;
525 // If some instruction between the previous try-range and the end of the
526 // function may throw, create a call-site entry with no landing pad for the
527 // region following the try-range.
528 if (SawPotentiallyThrowing &&
529 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
530 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
531 CallSites.push_back(Site);
535 /// EmitExceptionTable - Emit landing pads and actions.
537 /// The general organization of the table is complex, but the basic concepts are
538 /// easy. First there is a header which describes the location and organization
539 /// of the three components that follow.
541 /// 1. The landing pad site information describes the range of code covered by
542 /// the try. In our case it's an accumulation of the ranges covered by the
543 /// invokes in the try. There is also a reference to the landing pad that
544 /// handles the exception once processed. Finally an index into the actions
546 /// 2. The action table, in our case, is composed of pairs of type IDs and next
547 /// action offset. Starting with the action index from the landing pad
548 /// site, each type ID is checked for a match to the current exception. If
549 /// it matches then the exception and type id are passed on to the landing
550 /// pad. Otherwise the next action is looked up. This chain is terminated
551 /// with a next action of zero. If no type id is found the the frame is
552 /// unwound and handling continues.
553 /// 3. Type ID table contains references to all the C++ typeinfo for all
554 /// catches in the function. This tables is reversed indexed base 1.
555 void DwarfException::EmitExceptionTable() {
556 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
557 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
558 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
559 if (PadInfos.empty()) return;
561 // Sort the landing pads in order of their type ids. This is used to fold
562 // duplicate actions.
563 SmallVector<const LandingPadInfo *, 64> LandingPads;
564 LandingPads.reserve(PadInfos.size());
566 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
567 LandingPads.push_back(&PadInfos[i]);
569 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
571 // Compute the actions table and gather the first action index for each
573 SmallVector<ActionEntry, 32> Actions;
574 SmallVector<unsigned, 64> FirstActions;
575 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions, FirstActions);
577 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
578 // by try-range labels when lowered). Ordinary calls do not, so appropriate
579 // try-ranges for them need be deduced when using Dwarf exception handling.
581 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
582 const LandingPadInfo *LandingPad = LandingPads[i];
583 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
584 unsigned BeginLabel = LandingPad->BeginLabels[j];
585 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
586 PadRange P = { i, j };
587 PadMap[BeginLabel] = P;
591 // Compute the call-site table.
592 SmallVector<CallSiteEntry, 64> CallSites;
593 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
598 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
599 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
600 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
603 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
605 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
610 SizeSites = CallSites.size() *
611 (SiteStartSize + SiteLengthSize + LandingPadSize);
613 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
614 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
616 SizeSites += MCAsmInfo::getULEB128Size(i);
620 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
621 unsigned TTypeFormat;
624 TTypeFormat = dwarf::DW_EH_PE_omit;
626 // Okay, we have actual filters or typeinfos to emit. As such, we need to
627 // pick a type encoding for them. We're about to emit a list of pointers to
628 // typeinfo objects at the end of the LSDA. However, unless we're in static
629 // mode, this reference will require a relocation by the dynamic linker.
631 // Because of this, we have a couple of options:
632 // 1) If we are in -static mode, we can always use an absolute reference
633 // from the LSDA, because the static linker will resolve it.
634 // 2) Otherwise, if the LSDA section is writable, we can output the direct
635 // reference to the typeinfo and allow the dynamic linker to relocate
636 // it. Since it is in a writable section, the dynamic linker won't
638 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
639 // we need to use some form of indirection. For example, on Darwin,
640 // we can output a statically-relocatable reference to a dyld stub. The
641 // offset to the stub is constant, but the contents are in a section
642 // that is updated by the dynamic linker. This is easy enough, but we
643 // need to tell the personality function of the unwinder to indirect
644 // through the dyld stub.
646 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
647 // somewhere. This predicate should be moved to a shared location that is
648 // in target-independent code.
650 if (LSDASection->getKind().isWriteable() ||
651 Asm->TM.getRelocationModel() == Reloc::Static)
652 TTypeFormat = dwarf::DW_EH_PE_absptr;
654 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
655 dwarf::DW_EH_PE_sdata4;
658 // Begin the exception table.
659 Asm->OutStreamer.SwitchSection(LSDASection);
660 Asm->EmitAlignment(2, 0, 0, false);
662 O << "GCC_except_table" << SubprogramCount << ":\n";
663 EmitLabel("exception", SubprogramCount);
666 SmallString<16> LSDAName;
667 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
668 "_LSDA_" << Asm->getFunctionNumber();
669 O << LSDAName.str() << ":\n";
673 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
674 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
676 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly
677 // say that we're omitting that bit.
678 Asm->EmitInt8(TTypeFormat);
679 Asm->EOL("@TType format", TTypeFormat);
682 unsigned TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
683 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
684 unsigned BeforeOffset = 2;
685 unsigned TypeOffset = sizeof(int8_t) + // Call site format
686 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
687 SizeSites + SizeActions + SizeTypes;
688 unsigned Offset = TypeOffset;
689 unsigned LastOffset = 0;
691 while (Offset != LastOffset) {
693 unsigned Size = MCAsmInfo::getULEB128Size(Offset);
694 unsigned Pad = BeforeOffset + Size + TypeOffset;
696 if (Pad % TypeFormatSize)
697 Pad = TypeFormatSize - (Pad % TypeFormatSize);
701 Offset = TypeOffset + Pad;
704 Asm->EmitULEB128Bytes(Offset);
705 Asm->EOL("@TType base offset");
708 // SjLj Exception handilng
710 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
711 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
712 Asm->EmitULEB128Bytes(SizeSites);
713 Asm->EOL("Call site table length");
715 // Emit the landing pad site information.
717 for (SmallVectorImpl<CallSiteEntry>::const_iterator
718 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
719 const CallSiteEntry &S = *I;
721 // Offset of the landing pad, counted in 16-byte bundles relative to the
723 Asm->EmitULEB128Bytes(idx);
724 Asm->EOL("Landing pad");
726 // Offset of the first associated action record, relative to the start of
727 // the action table. This value is biased by 1 (1 indicates the start of
728 // the action table), and 0 indicates that there are no actions.
729 Asm->EmitULEB128Bytes(S.Action);
733 // DWARF Exception handling
734 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
736 // The call-site table is a list of all call sites that may throw an
737 // exception (including C++ 'throw' statements) in the procedure
738 // fragment. It immediately follows the LSDA header. Each entry indicates,
739 // for a given call, the first corresponding action record and corresponding
742 // The table begins with the number of bytes, stored as an LEB128
743 // compressed, unsigned integer. The records immediately follow the record
744 // count. They are sorted in increasing call-site address. Each record
747 // * The position of the call-site.
748 // * The position of the landing pad.
749 // * The first action record for that call site.
751 // A missing entry in the call-site table indicates that a call is not
752 // supposed to throw. Such calls include:
754 // * Calls to destructors within cleanup code. C++ semantics forbids these
756 // * Calls to intrinsic routines in the standard library which are known
757 // not to throw (sin, memcpy, et al).
759 // If the runtime does not find the call-site entry for a given call, it
760 // will call `terminate()'.
762 // Emit the landing pad call site table.
763 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
764 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
765 Asm->EmitULEB128Bytes(SizeSites);
766 Asm->EOL("Call site table size");
768 for (SmallVectorImpl<CallSiteEntry>::const_iterator
769 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
770 const CallSiteEntry &S = *I;
771 const char *BeginTag;
772 unsigned BeginNumber;
775 BeginTag = "eh_func_begin";
776 BeginNumber = SubprogramCount;
779 BeginNumber = S.BeginLabel;
782 // Offset of the call site relative to the previous call site, counted in
783 // number of 16-byte bundles. The first call site is counted relative to
784 // the start of the procedure fragment.
785 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
787 Asm->EOL("Region start");
790 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
793 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
795 Asm->EOL("Region length");
797 // Offset of the landing pad, counted in 16-byte bundles relative to the
802 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
805 Asm->EOL("Landing pad");
807 // Offset of the first associated action record, relative to the start of
808 // the action table. This value is biased by 1 (1 indicates the start of
809 // the action table), and 0 indicates that there are no actions.
810 Asm->EmitULEB128Bytes(S.Action);
815 // Emit the Action Table.
816 for (SmallVectorImpl<ActionEntry>::const_iterator
817 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
818 const ActionEntry &Action = *I;
822 // Used by the runtime to match the type of the thrown exception to the
823 // type of the catch clauses or the types in the exception specification.
825 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
826 Asm->EOL("TypeInfo index");
830 // Self-relative signed displacement in bytes of the next action record,
831 // or 0 if there is no next action record.
833 Asm->EmitSLEB128Bytes(Action.NextAction);
834 Asm->EOL("Next action");
837 // Emit the Catch Clauses. The code for the catch clauses following the same
838 // try is similar to a switch statement. The catch clause action record
839 // informs the runtime about the type of a catch clause and about the
840 // associated switch value.
842 // Action Record Fields:
845 // Positive value, starting at 1. Index in the types table of the
846 // __typeinfo for the catch-clause type. 1 is the first word preceding
847 // TTBase, 2 is the second word, and so on. Used by the runtime to check
848 // if the thrown exception type matches the catch-clause type. Back-end
849 // generated switch statements check against this value.
852 // Signed offset, in bytes from the start of this field, to the next
853 // chained action record, or zero if none.
855 // The order of the action records determined by the next field is the order
856 // of the catch clauses as they appear in the source code, and must be kept in
857 // the same order. As a result, changing the order of the catch clause would
858 // change the semantics of the program.
859 for (std::vector<GlobalVariable *>::const_reverse_iterator
860 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
861 const GlobalVariable *GV = *I;
866 O << Asm->getGlobalLinkName(GV, GLN);
871 Asm->EOL("TypeInfo");
874 // Emit the Type Table.
875 for (std::vector<unsigned>::const_iterator
876 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
877 unsigned TypeID = *I;
878 Asm->EmitULEB128Bytes(TypeID);
879 Asm->EOL("Filter TypeInfo index");
882 Asm->EmitAlignment(2, 0, 0, false);
885 /// EndModule - Emit all exception information that should come after the
887 void DwarfException::EndModule() {
888 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
891 if (!shouldEmitMovesModule && !shouldEmitTableModule)
894 if (TimePassesIsEnabled)
895 ExceptionTimer->startTimer();
897 const std::vector<Function *> Personalities = MMI->getPersonalities();
899 for (unsigned i = 0, e = Personalities.size(); i < e; ++i)
900 EmitCIE(Personalities[i], i);
902 for (std::vector<FunctionEHFrameInfo>::iterator
903 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
906 if (TimePassesIsEnabled)
907 ExceptionTimer->stopTimer();
910 /// BeginFunction - Gather pre-function exception information. Assumes being
911 /// emitted immediately after the function entry point.
912 void DwarfException::BeginFunction(MachineFunction *MF) {
913 if (TimePassesIsEnabled)
914 ExceptionTimer->startTimer();
917 shouldEmitTable = shouldEmitMoves = false;
919 if (MMI && MAI->doesSupportExceptionHandling()) {
920 // Map all labels and get rid of any dead landing pads.
921 MMI->TidyLandingPads();
923 // If any landing pads survive, we need an EH table.
924 if (!MMI->getLandingPads().empty())
925 shouldEmitTable = true;
927 // See if we need frame move info.
928 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
929 shouldEmitMoves = true;
931 if (shouldEmitMoves || shouldEmitTable)
932 // Assumes in correct section after the entry point.
933 EmitLabel("eh_func_begin", ++SubprogramCount);
936 shouldEmitTableModule |= shouldEmitTable;
937 shouldEmitMovesModule |= shouldEmitMoves;
939 if (TimePassesIsEnabled)
940 ExceptionTimer->stopTimer();
943 /// EndFunction - Gather and emit post-function exception information.
945 void DwarfException::EndFunction() {
946 if (!shouldEmitMoves && !shouldEmitTable) return;
948 if (TimePassesIsEnabled)
949 ExceptionTimer->startTimer();
951 EmitLabel("eh_func_end", SubprogramCount);
952 EmitExceptionTable();
954 // Save EH frame information
955 EHFrames.push_back(FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
957 MMI->getPersonalityIndex(),
958 MF->getFrameInfo()->hasCalls(),
959 !MMI->getLandingPads().empty(),
960 MMI->getFrameMoves(),
963 // Record if this personality index uses a landing pad.
964 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
966 if (TimePassesIsEnabled)
967 ExceptionTimer->stopTimer();