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/MCAsmInfo.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCStreamer.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/Target/Mangler.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Target/TargetFrameInfo.h"
29 #include "llvm/Target/TargetLoweringObjectFile.h"
30 #include "llvm/Target/TargetOptions.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
32 #include "llvm/Support/Dwarf.h"
33 #include "llvm/Support/FormattedStream.h"
34 #include "llvm/Support/Timer.h"
35 #include "llvm/ADT/SmallString.h"
36 #include "llvm/ADT/StringExtras.h"
39 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
41 : DwarfPrinter(OS, A, T, "eh"), shouldEmitTable(false),shouldEmitMoves(false),
42 shouldEmitTableModule(false), shouldEmitMovesModule(false),
44 if (TimePassesIsEnabled)
45 ExceptionTimer = new Timer("DWARF Exception Writer");
48 DwarfException::~DwarfException() {
49 delete ExceptionTimer;
52 /// SizeOfEncodedValue - Return the size of the encoding in bytes.
53 unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
54 if (Encoding == dwarf::DW_EH_PE_omit)
57 switch (Encoding & 0x07) {
58 case dwarf::DW_EH_PE_absptr:
59 return TD->getPointerSize();
60 case dwarf::DW_EH_PE_udata2:
62 case dwarf::DW_EH_PE_udata4:
64 case dwarf::DW_EH_PE_udata8:
68 assert(0 && "Invalid encoded value.");
72 /// CreateLabelDiff - Emit a label and subtract it from the expression we
73 /// already have. This is equivalent to emitting "foo - .", but we have to emit
74 /// the label for "." directly.
75 const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
76 const char *LabelName,
79 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
80 << LabelName << Asm->getFunctionNumber()
82 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
83 Asm->OutStreamer.EmitLabel(DotSym);
85 return MCBinaryExpr::CreateSub(ExprRef,
86 MCSymbolRefExpr::Create(DotSym,
91 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
92 /// is shared among many Frame Description Entries. There is at least one CIE
93 /// in every non-empty .debug_frame section.
94 void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
95 // Size and sign of stack growth.
97 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
98 TargetFrameInfo::StackGrowsUp ?
99 TD->getPointerSize() : -TD->getPointerSize();
101 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
103 // Begin eh frame section.
104 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
106 if (MAI->is_EHSymbolPrivate())
107 O << MAI->getPrivateGlobalPrefix();
108 O << "EH_frame" << Index << ":\n";
110 EmitLabel("section_eh_frame", Index);
112 // Define base labels.
113 EmitLabel("eh_frame_common", Index);
115 // Define the eh frame length.
116 EmitDifference("eh_frame_common_end", Index,
117 "eh_frame_common_begin", Index, true);
118 EOL("Length of Common Information Entry");
121 EmitLabel("eh_frame_common_begin", Index);
122 if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("CIE Identifier Tag");
123 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
124 if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("DW_CIE_VERSION");
125 Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
127 // The personality presence indicates that language specific information will
128 // show up in the eh frame. Find out how we are supposed to lower the
129 // personality function reference:
130 const MCExpr *PersonalityRef = 0;
131 bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
133 // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
135 // In non-static mode, ask the object file how to represent this reference.
137 TLOF.getSymbolForDwarfGlobalReference(PersonalityFn, Asm->Mang,
139 IsPersonalityIndirect,
143 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
144 if (IsPersonalityIndirect)
145 PerEncoding |= dwarf::DW_EH_PE_indirect;
146 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
147 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
149 char Augmentation[6] = { 0 };
150 unsigned AugmentationSize = 0;
151 char *APtr = Augmentation + 1;
153 if (PersonalityRef) {
154 // There is a personality function.
156 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
159 if (UsesLSDA[Index]) {
160 // An LSDA pointer is in the FDE augmentation.
165 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
166 // A non-default pointer encoding for the FDE.
171 if (APtr != Augmentation + 1)
172 Augmentation[0] = 'z';
174 Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);
175 EOL("CIE Augmentation");
178 EmitULEB128(1, "CIE Code Alignment Factor");
179 EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
180 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
181 EOL("CIE Return Address Column");
183 EmitULEB128(AugmentationSize, "Augmentation Size");
184 EmitEncodingByte(PerEncoding, "Personality");
186 // If there is a personality, we need to indicate the function's location.
187 if (PersonalityRef) {
188 if (!IsPersonalityPCRel)
189 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
192 O << MAI->getData32bitsDirective() << *PersonalityRef;
195 EmitEncodingByte(LSDAEncoding, "LSDA");
196 EmitEncodingByte(FDEEncoding, "FDE");
199 // Indicate locations of general callee saved registers in frame.
200 std::vector<MachineMove> Moves;
201 RI->getInitialFrameState(Moves);
202 EmitFrameMoves(NULL, 0, Moves, true);
204 // On Darwin the linker honors the alignment of eh_frame, which means it must
205 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
206 // holes which confuse readers of eh_frame.
207 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
208 EmitLabel("eh_frame_common_end", Index);
212 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
213 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
214 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
215 "Should not emit 'available externally' functions at all");
217 const Function *TheFunc = EHFrameInfo.function;
219 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
221 // Externally visible entry into the functions eh frame info. If the
222 // corresponding function is static, this should not be externally visible.
223 if (!TheFunc->hasLocalLinkage())
224 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
225 O << GlobalEHDirective << *EHFrameInfo.FunctionEHSym << '\n';
227 // If corresponding function is weak definition, this should be too.
228 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
229 O << MAI->getWeakDefDirective() << *EHFrameInfo.FunctionEHSym << '\n';
231 // If corresponding function is hidden, this should be too.
232 if (TheFunc->hasHiddenVisibility())
233 if (const char *HiddenDirective = MAI->getHiddenDirective())
234 O << HiddenDirective << *EHFrameInfo.FunctionEHSym << '\n';
236 // If there are no calls then you can't unwind. This may mean we can omit the
237 // EH Frame, but some environments do not handle weak absolute symbols. If
238 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
239 // info is to be available for non-EH uses.
240 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
241 (!TheFunc->isWeakForLinker() ||
242 !MAI->getWeakDefDirective() ||
243 MAI->getSupportsWeakOmittedEHFrame())) {
244 O << *EHFrameInfo.FunctionEHSym << " = 0\n";
245 // This name has no connection to the function, so it might get
246 // dead-stripped when the function is not, erroneously. Prohibit
247 // dead-stripping unconditionally.
248 if (MAI->hasNoDeadStrip())
249 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
250 MCStreamer::NoDeadStrip);
252 O << *EHFrameInfo.FunctionEHSym << ":\n";
255 EmitDifference("eh_frame_end", EHFrameInfo.Number,
256 "eh_frame_begin", EHFrameInfo.Number, true);
257 EOL("Length of Frame Information Entry");
259 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
261 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
262 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
265 EOL("FDE CIE offset");
267 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
268 EOL("FDE initial location");
269 EmitDifference("eh_func_end", EHFrameInfo.Number,
270 "eh_func_begin", EHFrameInfo.Number, true);
271 EOL("FDE address range");
273 // If there is a personality and landing pads then point to the language
274 // specific data area in the exception table.
275 if (MMI->getPersonalities()[0] != NULL) {
277 if (Asm->TM.getLSDAEncoding() != DwarfLSDAEncoding::EightByte) {
278 EmitULEB128(4, "Augmentation size");
280 if (EHFrameInfo.hasLandingPads)
281 EmitReference("exception", EHFrameInfo.Number, true, true);
283 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
285 EmitULEB128(TD->getPointerSize(), "Augmentation size");
287 if (EHFrameInfo.hasLandingPads) {
288 EmitReference("exception", EHFrameInfo.Number, true, false);
290 Asm->OutStreamer.EmitIntValue(0, TD->getPointerSize(),
295 EOL("Language Specific Data Area");
297 EmitULEB128(0, "Augmentation size");
300 // Indicate locations of function specific callee saved registers in frame.
301 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
304 // On Darwin the linker honors the alignment of eh_frame, which means it
305 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
306 // get holes which confuse readers of eh_frame.
307 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
309 EmitLabel("eh_frame_end", EHFrameInfo.Number);
311 // If the function is marked used, this table should be also. We cannot
312 // make the mark unconditional in this case, since retaining the table also
313 // retains the function in this case, and there is code around that depends
314 // on unused functions (calling undefined externals) being dead-stripped to
315 // link correctly. Yes, there really is.
316 if (MMI->isUsedFunction(EHFrameInfo.function))
317 if (MAI->hasNoDeadStrip())
318 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
319 MCStreamer::NoDeadStrip);
324 /// SharedTypeIds - How many leading type ids two landing pads have in common.
325 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
326 const LandingPadInfo *R) {
327 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
328 unsigned LSize = LIds.size(), RSize = RIds.size();
329 unsigned MinSize = LSize < RSize ? LSize : RSize;
332 for (; Count != MinSize; ++Count)
333 if (LIds[Count] != RIds[Count])
339 /// PadLT - Order landing pads lexicographically by type id.
340 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
341 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
342 unsigned LSize = LIds.size(), RSize = RIds.size();
343 unsigned MinSize = LSize < RSize ? LSize : RSize;
345 for (unsigned i = 0; i != MinSize; ++i)
346 if (LIds[i] != RIds[i])
347 return LIds[i] < RIds[i];
349 return LSize < RSize;
352 /// ComputeActionsTable - Compute the actions table and gather the first action
353 /// index for each landing pad site.
354 unsigned DwarfException::
355 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
356 SmallVectorImpl<ActionEntry> &Actions,
357 SmallVectorImpl<unsigned> &FirstActions) {
359 // The action table follows the call-site table in the LSDA. The individual
360 // records are of two types:
363 // * Exception specification
365 // The two record kinds have the same format, with only small differences.
366 // They are distinguished by the "switch value" field: Catch clauses
367 // (TypeInfos) have strictly positive switch values, and exception
368 // specifications (FilterIds) have strictly negative switch values. Value 0
369 // indicates a catch-all clause.
371 // Negative type IDs index into FilterIds. Positive type IDs index into
372 // TypeInfos. The value written for a positive type ID is just the type ID
373 // itself. For a negative type ID, however, the value written is the
374 // (negative) byte offset of the corresponding FilterIds entry. The byte
375 // offset is usually equal to the type ID (because the FilterIds entries are
376 // written using a variable width encoding, which outputs one byte per entry
377 // as long as the value written is not too large) but can differ. This kind
378 // of complication does not occur for positive type IDs because type infos are
379 // output using a fixed width encoding. FilterOffsets[i] holds the byte
380 // offset corresponding to FilterIds[i].
382 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
383 SmallVector<int, 16> FilterOffsets;
384 FilterOffsets.reserve(FilterIds.size());
387 for (std::vector<unsigned>::const_iterator
388 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
389 FilterOffsets.push_back(Offset);
390 Offset -= MCAsmInfo::getULEB128Size(*I);
393 FirstActions.reserve(LandingPads.size());
396 unsigned SizeActions = 0;
397 const LandingPadInfo *PrevLPI = 0;
399 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
400 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
401 const LandingPadInfo *LPI = *I;
402 const std::vector<int> &TypeIds = LPI->TypeIds;
403 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
404 unsigned SizeSiteActions = 0;
406 if (NumShared < TypeIds.size()) {
407 unsigned SizeAction = 0;
408 ActionEntry *PrevAction = 0;
411 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
412 assert(Actions.size());
413 PrevAction = &Actions.back();
414 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
415 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
417 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
419 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
420 SizeAction += -PrevAction->NextAction;
421 PrevAction = PrevAction->Previous;
425 // Compute the actions.
426 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
427 int TypeID = TypeIds[J];
428 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
429 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
430 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
432 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
433 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
434 SizeSiteActions += SizeAction;
436 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
437 Actions.push_back(Action);
438 PrevAction = &Actions.back();
441 // Record the first action of the landing pad site.
442 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
443 } // else identical - re-use previous FirstAction
445 // Information used when created the call-site table. The action record
446 // field of the call site record is the offset of the first associated
447 // action record, relative to the start of the actions table. This value is
448 // biased by 1 (1 in dicating the start of the actions table), and 0
449 // indicates that there are no actions.
450 FirstActions.push_back(FirstAction);
452 // Compute this sites contribution to size.
453 SizeActions += SizeSiteActions;
461 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
462 /// marked `nounwind'. Return `false' otherwise.
463 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
464 assert(MI->getDesc().isCall() && "This should be a call instruction!");
466 bool MarkedNoUnwind = false;
467 bool SawFunc = false;
469 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
470 const MachineOperand &MO = MI->getOperand(I);
473 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
475 // Be conservative. If we have more than one function operand for this
476 // call, then we can't make the assumption that it's the callee and
477 // not a parameter to the call.
479 // FIXME: Determine if there's a way to say that `F' is the callee or
481 MarkedNoUnwind = false;
485 MarkedNoUnwind = F->doesNotThrow();
491 return MarkedNoUnwind;
494 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
495 /// has a try-range containing the call, a non-zero landing pad, and an
496 /// appropriate action. The entry for an ordinary call has a try-range
497 /// containing the call and zero for the landing pad and the action. Calls
498 /// marked 'nounwind' have no entry and must not be contained in the try-range
499 /// of any entry - they form gaps in the table. Entries must be ordered by
500 /// try-range address.
501 void DwarfException::
502 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
503 const RangeMapType &PadMap,
504 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
505 const SmallVectorImpl<unsigned> &FirstActions) {
506 // The end label of the previous invoke or nounwind try-range.
507 unsigned LastLabel = 0;
509 // Whether there is a potentially throwing instruction (currently this means
510 // an ordinary call) between the end of the previous try-range and now.
511 bool SawPotentiallyThrowing = false;
513 // Whether the last CallSite entry was for an invoke.
514 bool PreviousIsInvoke = false;
516 // Visit all instructions in order of address.
517 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
519 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
521 if (!MI->isLabel()) {
522 if (MI->getDesc().isCall())
523 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
528 unsigned BeginLabel = MI->getOperand(0).getImm();
529 assert(BeginLabel && "Invalid label!");
531 // End of the previous try-range?
532 if (BeginLabel == LastLabel)
533 SawPotentiallyThrowing = false;
535 // Beginning of a new try-range?
536 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
537 if (L == PadMap.end())
538 // Nope, it was just some random label.
541 const PadRange &P = L->second;
542 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
543 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
544 "Inconsistent landing pad map!");
546 // For Dwarf exception handling (SjLj handling doesn't use this). If some
547 // instruction between the previous try-range and this one may throw,
548 // create a call-site entry with no landing pad for the region between the
550 if (SawPotentiallyThrowing &&
551 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
552 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
553 CallSites.push_back(Site);
554 PreviousIsInvoke = false;
557 LastLabel = LandingPad->EndLabels[P.RangeIndex];
558 assert(BeginLabel && LastLabel && "Invalid landing pad!");
560 if (LandingPad->LandingPadLabel) {
561 // This try-range is for an invoke.
562 CallSiteEntry Site = {
565 LandingPad->LandingPadLabel,
566 FirstActions[P.PadIndex]
569 // Try to merge with the previous call-site. SJLJ doesn't do this
570 if (PreviousIsInvoke &&
571 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
572 CallSiteEntry &Prev = CallSites.back();
573 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
574 // Extend the range of the previous entry.
575 Prev.EndLabel = Site.EndLabel;
580 // Otherwise, create a new call-site.
581 CallSites.push_back(Site);
582 PreviousIsInvoke = true;
585 PreviousIsInvoke = false;
590 // If some instruction between the previous try-range and the end of the
591 // function may throw, create a call-site entry with no landing pad for the
592 // region following the try-range.
593 if (SawPotentiallyThrowing &&
594 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
595 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
596 CallSites.push_back(Site);
600 /// EmitExceptionTable - Emit landing pads and actions.
602 /// The general organization of the table is complex, but the basic concepts are
603 /// easy. First there is a header which describes the location and organization
604 /// of the three components that follow.
606 /// 1. The landing pad site information describes the range of code covered by
607 /// the try. In our case it's an accumulation of the ranges covered by the
608 /// invokes in the try. There is also a reference to the landing pad that
609 /// handles the exception once processed. Finally an index into the actions
611 /// 2. The action table, in our case, is composed of pairs of type IDs and next
612 /// action offset. Starting with the action index from the landing pad
613 /// site, each type ID is checked for a match to the current exception. If
614 /// it matches then the exception and type id are passed on to the landing
615 /// pad. Otherwise the next action is looked up. This chain is terminated
616 /// with a next action of zero. If no type id is found then the frame is
617 /// unwound and handling continues.
618 /// 3. Type ID table contains references to all the C++ typeinfo for all
619 /// catches in the function. This tables is reverse indexed base 1.
620 void DwarfException::EmitExceptionTable() {
621 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
622 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
623 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
624 if (PadInfos.empty()) return;
626 // Sort the landing pads in order of their type ids. This is used to fold
627 // duplicate actions.
628 SmallVector<const LandingPadInfo *, 64> LandingPads;
629 LandingPads.reserve(PadInfos.size());
631 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
632 LandingPads.push_back(&PadInfos[i]);
634 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
636 // Compute the actions table and gather the first action index for each
638 SmallVector<ActionEntry, 32> Actions;
639 SmallVector<unsigned, 64> FirstActions;
640 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
643 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
644 // by try-range labels when lowered). Ordinary calls do not, so appropriate
645 // try-ranges for them need be deduced when using DWARF exception handling.
647 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
648 const LandingPadInfo *LandingPad = LandingPads[i];
649 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
650 unsigned BeginLabel = LandingPad->BeginLabels[j];
651 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
652 PadRange P = { i, j };
653 PadMap[BeginLabel] = P;
657 // Compute the call-site table.
658 SmallVector<CallSiteEntry, 64> CallSites;
659 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
664 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
665 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
666 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
667 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
668 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
674 SizeSites = CallSites.size() *
675 (SiteStartSize + SiteLengthSize + LandingPadSize);
677 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
678 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
680 SizeSites += MCAsmInfo::getULEB128Size(i);
684 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
685 unsigned TTypeFormat;
686 unsigned TypeFormatSize;
689 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
690 // that we're omitting that bit.
691 TTypeFormat = dwarf::DW_EH_PE_omit;
692 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
694 // Okay, we have actual filters or typeinfos to emit. As such, we need to
695 // pick a type encoding for them. We're about to emit a list of pointers to
696 // typeinfo objects at the end of the LSDA. However, unless we're in static
697 // mode, this reference will require a relocation by the dynamic linker.
699 // Because of this, we have a couple of options:
701 // 1) If we are in -static mode, we can always use an absolute reference
702 // from the LSDA, because the static linker will resolve it.
704 // 2) Otherwise, if the LSDA section is writable, we can output the direct
705 // reference to the typeinfo and allow the dynamic linker to relocate
706 // it. Since it is in a writable section, the dynamic linker won't
709 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
710 // we need to use some form of indirection. For example, on Darwin,
711 // we can output a statically-relocatable reference to a dyld stub. The
712 // offset to the stub is constant, but the contents are in a section
713 // that is updated by the dynamic linker. This is easy enough, but we
714 // need to tell the personality function of the unwinder to indirect
715 // through the dyld stub.
717 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
718 // somewhere. This predicate should be moved to a shared location that is
719 // in target-independent code.
721 if (LSDASection->getKind().isWriteable() ||
722 Asm->TM.getRelocationModel() == Reloc::Static)
723 TTypeFormat = dwarf::DW_EH_PE_absptr;
725 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
726 dwarf::DW_EH_PE_sdata4;
728 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
731 // Begin the exception table.
732 Asm->OutStreamer.SwitchSection(LSDASection);
733 Asm->EmitAlignment(2, 0, 0, false);
735 O << "GCC_except_table" << SubprogramCount << ":\n";
737 // The type infos need to be aligned. GCC does this by inserting padding just
738 // before the type infos. However, this changes the size of the exception
739 // table, so you need to take this into account when you output the exception
740 // table size. However, the size is output using a variable length encoding.
741 // So by increasing the size by inserting padding, you may increase the number
742 // of bytes used for writing the size. If it increases, say by one byte, then
743 // you now need to output one less byte of padding to get the type infos
744 // aligned. However this decreases the size of the exception table. This
745 // changes the value you have to output for the exception table size. Due to
746 // the variable length encoding, the number of bytes used for writing the
747 // length may decrease. If so, you then have to increase the amount of
748 // padding. And so on. If you look carefully at the GCC code you will see that
749 // it indeed does this in a loop, going on and on until the values stabilize.
750 // We chose another solution: don't output padding inside the table like GCC
751 // does, instead output it before the table.
752 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
753 unsigned TyOffset = sizeof(int8_t) + // Call site format
754 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
755 SizeSites + SizeActions + SizeTypes;
756 unsigned TotalSize = sizeof(int8_t) + // LPStart format
757 sizeof(int8_t) + // TType format
759 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
761 unsigned SizeAlign = (4 - TotalSize) & 3;
763 for (unsigned i = 0; i != SizeAlign; ++i) {
768 EmitLabel("exception", SubprogramCount);
771 SmallString<16> LSDAName;
772 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
773 "_LSDA_" << Asm->getFunctionNumber();
774 O << LSDAName.str() << ":\n";
778 EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
779 EmitEncodingByte(TTypeFormat, "@TType");
782 EmitULEB128(TyOffset, "@TType base offset");
784 // SjLj Exception handling
786 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
787 EmitULEB128(SizeSites, "Call site table length");
789 // Emit the landing pad site information.
791 for (SmallVectorImpl<CallSiteEntry>::const_iterator
792 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
793 const CallSiteEntry &S = *I;
795 // Offset of the landing pad, counted in 16-byte bundles relative to the
797 EmitULEB128(idx, "Landing pad");
799 // Offset of the first associated action record, relative to the start of
800 // the action table. This value is biased by 1 (1 indicates the start of
801 // the action table), and 0 indicates that there are no actions.
802 EmitULEB128(S.Action, "Action");
805 // DWARF Exception handling
806 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
808 // The call-site table is a list of all call sites that may throw an
809 // exception (including C++ 'throw' statements) in the procedure
810 // fragment. It immediately follows the LSDA header. Each entry indicates,
811 // for a given call, the first corresponding action record and corresponding
814 // The table begins with the number of bytes, stored as an LEB128
815 // compressed, unsigned integer. The records immediately follow the record
816 // count. They are sorted in increasing call-site address. Each record
819 // * The position of the call-site.
820 // * The position of the landing pad.
821 // * The first action record for that call site.
823 // A missing entry in the call-site table indicates that a call is not
824 // supposed to throw.
826 // Emit the landing pad call site table.
827 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
828 EmitULEB128(SizeSites, "Call site table size");
830 for (SmallVectorImpl<CallSiteEntry>::const_iterator
831 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
832 const CallSiteEntry &S = *I;
833 const char *BeginTag;
834 unsigned BeginNumber;
837 BeginTag = "eh_func_begin";
838 BeginNumber = SubprogramCount;
841 BeginNumber = S.BeginLabel;
844 // Offset of the call site relative to the previous call site, counted in
845 // number of 16-byte bundles. The first call site is counted relative to
846 // the start of the procedure fragment.
847 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
852 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
855 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
857 EOL("Region length");
859 // Offset of the landing pad, counted in 16-byte bundles relative to the
862 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
864 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
869 // Offset of the first associated action record, relative to the start of
870 // the action table. This value is biased by 1 (1 indicates the start of
871 // the action table), and 0 indicates that there are no actions.
872 EmitULEB128(S.Action, "Action");
876 // Emit the Action Table.
877 for (SmallVectorImpl<ActionEntry>::const_iterator
878 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
879 const ActionEntry &Action = *I;
883 // Used by the runtime to match the type of the thrown exception to the
884 // type of the catch clauses or the types in the exception specification.
885 EmitSLEB128(Action.ValueForTypeID, "TypeInfo index");
889 // Self-relative signed displacement in bytes of the next action record,
890 // or 0 if there is no next action record.
891 EmitSLEB128(Action.NextAction, "Next action");
894 // Emit the Catch TypeInfos.
895 for (std::vector<GlobalVariable *>::const_reverse_iterator
896 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
897 const GlobalVariable *GV = *I;
901 O << *Asm->GetGlobalValueSymbol(GV);
908 // Emit the Exception Specifications.
909 for (std::vector<unsigned>::const_iterator
910 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
911 unsigned TypeID = *I;
912 EmitULEB128(TypeID, TypeID != 0 ? "Exception specification" : 0);
915 Asm->EmitAlignment(2, 0, 0, false);
918 /// EndModule - Emit all exception information that should come after the
920 void DwarfException::EndModule() {
921 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
924 if (!shouldEmitMovesModule && !shouldEmitTableModule)
927 if (TimePassesIsEnabled)
928 ExceptionTimer->startTimer();
930 const std::vector<Function *> Personalities = MMI->getPersonalities();
932 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
933 EmitCIE(Personalities[I], I);
935 for (std::vector<FunctionEHFrameInfo>::iterator
936 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
939 if (TimePassesIsEnabled)
940 ExceptionTimer->stopTimer();
943 /// BeginFunction - Gather pre-function exception information. Assumes it's
944 /// being emitted immediately after the function entry point.
945 void DwarfException::BeginFunction(MachineFunction *MF) {
946 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
948 if (TimePassesIsEnabled)
949 ExceptionTimer->startTimer();
952 shouldEmitTable = shouldEmitMoves = false;
954 // Map all labels and get rid of any dead landing pads.
955 MMI->TidyLandingPads();
957 // If any landing pads survive, we need an EH table.
958 if (!MMI->getLandingPads().empty())
959 shouldEmitTable = true;
961 // See if we need frame move info.
962 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
963 shouldEmitMoves = true;
965 if (shouldEmitMoves || shouldEmitTable)
966 // Assumes in correct section after the entry point.
967 EmitLabel("eh_func_begin", ++SubprogramCount);
969 shouldEmitTableModule |= shouldEmitTable;
970 shouldEmitMovesModule |= shouldEmitMoves;
972 if (TimePassesIsEnabled)
973 ExceptionTimer->stopTimer();
976 /// EndFunction - Gather and emit post-function exception information.
978 void DwarfException::EndFunction() {
979 if (!shouldEmitMoves && !shouldEmitTable) return;
981 if (TimePassesIsEnabled)
982 ExceptionTimer->startTimer();
984 EmitLabel("eh_func_end", SubprogramCount);
985 EmitExceptionTable();
987 MCSymbol *FunctionEHSym =
988 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
989 Asm->MAI->is_EHSymbolPrivate());
991 // Save EH frame information
992 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
993 MMI->getPersonalityIndex(),
994 MF->getFrameInfo()->hasCalls(),
995 !MMI->getLandingPads().empty(),
996 MMI->getFrameMoves(),
999 // Record if this personality index uses a landing pad.
1000 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
1002 if (TimePassesIsEnabled)
1003 ExceptionTimer->stopTimer();