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/Timer.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include "llvm/ADT/SmallString.h"
36 #include "llvm/ADT/StringExtras.h"
39 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
41 : Dwarf(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 Asm->EOL("Length of Common Information Entry");
121 EmitLabel("eh_frame_common_begin", Index);
122 Asm->EmitInt32((int)0);
123 Asm->EOL("CIE Identifier Tag");
124 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
125 Asm->EOL("CIE Version");
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[5] = { 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->EmitString(Augmentation);
175 Asm->EOL("CIE Augmentation");
178 Asm->EmitULEB128Bytes(1);
179 Asm->EOL("CIE Code Alignment Factor");
180 Asm->EmitSLEB128Bytes(stackGrowth);
181 Asm->EOL("CIE Data Alignment Factor");
182 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
183 Asm->EOL("CIE Return Address Column");
185 Asm->EmitULEB128Bytes(AugmentationSize);
186 Asm->EOL("Augmentation Size");
188 Asm->EmitInt8(PerEncoding);
189 Asm->EOL("Personality", PerEncoding);
191 // If there is a personality, we need to indicate the function's location.
192 if (PersonalityRef) {
193 if (!IsPersonalityPCRel)
194 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
197 O << MAI->getData32bitsDirective() << *PersonalityRef;
198 Asm->EOL("Personality");
200 Asm->EmitInt8(LSDAEncoding);
201 Asm->EOL("LSDA Encoding", LSDAEncoding);
203 Asm->EmitInt8(FDEEncoding);
204 Asm->EOL("FDE Encoding", FDEEncoding);
207 // Indicate locations of general callee saved registers in frame.
208 std::vector<MachineMove> Moves;
209 RI->getInitialFrameState(Moves);
210 EmitFrameMoves(NULL, 0, Moves, true);
212 // On Darwin the linker honors the alignment of eh_frame, which means it must
213 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
214 // holes which confuse readers of eh_frame.
215 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
216 EmitLabel("eh_frame_common_end", Index);
221 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
222 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
223 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
224 "Should not emit 'available externally' functions at all");
226 const Function *TheFunc = EHFrameInfo.function;
228 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
230 // Externally visible entry into the functions eh frame info. If the
231 // corresponding function is static, this should not be externally visible.
232 if (!TheFunc->hasLocalLinkage())
233 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
234 O << GlobalEHDirective << *EHFrameInfo.FunctionEHSym << '\n';
236 // If corresponding function is weak definition, this should be too.
237 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
238 O << MAI->getWeakDefDirective() << *EHFrameInfo.FunctionEHSym << '\n';
240 // If corresponding function is hidden, this should be too.
241 if (TheFunc->hasHiddenVisibility())
242 if (const char *HiddenDirective = MAI->getHiddenDirective())
243 O << HiddenDirective << *EHFrameInfo.FunctionEHSym << '\n';
245 // If there are no calls then you can't unwind. This may mean we can omit the
246 // EH Frame, but some environments do not handle weak absolute symbols. If
247 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
248 // info is to be available for non-EH uses.
249 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
250 (!TheFunc->isWeakForLinker() ||
251 !MAI->getWeakDefDirective() ||
252 MAI->getSupportsWeakOmittedEHFrame())) {
253 O << *EHFrameInfo.FunctionEHSym << " = 0\n";
254 // This name has no connection to the function, so it might get
255 // dead-stripped when the function is not, erroneously. Prohibit
256 // dead-stripping unconditionally.
257 if (const char *UsedDirective = MAI->getUsedDirective())
258 O << UsedDirective << *EHFrameInfo.FunctionEHSym << "\n\n";
260 O << *EHFrameInfo.FunctionEHSym << ":\n";
263 EmitDifference("eh_frame_end", EHFrameInfo.Number,
264 "eh_frame_begin", EHFrameInfo.Number, true);
265 Asm->EOL("Length of Frame Information Entry");
267 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
269 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
270 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
273 Asm->EOL("FDE CIE offset");
275 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
276 Asm->EOL("FDE initial location");
277 EmitDifference("eh_func_end", EHFrameInfo.Number,
278 "eh_func_begin", EHFrameInfo.Number, true);
279 Asm->EOL("FDE address range");
281 // If there is a personality and landing pads then point to the language
282 // specific data area in the exception table.
283 if (MMI->getPersonalities()[0] != NULL) {
284 bool is4Byte = TD->getPointerSize() == sizeof(int32_t);
286 if (Asm->TM.getLSDAEncoding() != DwarfLSDAEncoding::EightByte) {
287 Asm->EmitULEB128Bytes(4);
288 Asm->EOL("Augmentation size");
290 if (EHFrameInfo.hasLandingPads)
291 EmitReference("exception", EHFrameInfo.Number, true, true);
293 Asm->EmitInt32((int)0);
295 Asm->EmitULEB128Bytes(is4Byte ? 4 : 8);
296 Asm->EOL("Augmentation size");
298 if (EHFrameInfo.hasLandingPads) {
299 EmitReference("exception", EHFrameInfo.Number, true, false);
302 Asm->EmitInt32((int)0);
304 Asm->EmitInt64((int)0);
308 Asm->EOL("Language Specific Data Area");
310 Asm->EmitULEB128Bytes(0);
311 Asm->EOL("Augmentation size");
314 // Indicate locations of function specific callee saved registers in frame.
315 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
318 // On Darwin the linker honors the alignment of eh_frame, which means it
319 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
320 // get holes which confuse readers of eh_frame.
321 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
323 EmitLabel("eh_frame_end", EHFrameInfo.Number);
325 // If the function is marked used, this table should be also. We cannot
326 // make the mark unconditional in this case, since retaining the table also
327 // retains the function in this case, and there is code around that depends
328 // on unused functions (calling undefined externals) being dead-stripped to
329 // link correctly. Yes, there really is.
330 if (MMI->isUsedFunction(EHFrameInfo.function))
331 if (const char *UsedDirective = MAI->getUsedDirective()) {
332 O << UsedDirective << *EHFrameInfo.FunctionEHSym << "\n\n";
339 /// SharedTypeIds - How many leading type ids two landing pads have in common.
340 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
341 const LandingPadInfo *R) {
342 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
343 unsigned LSize = LIds.size(), RSize = RIds.size();
344 unsigned MinSize = LSize < RSize ? LSize : RSize;
347 for (; Count != MinSize; ++Count)
348 if (LIds[Count] != RIds[Count])
354 /// PadLT - Order landing pads lexicographically by type id.
355 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
356 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
357 unsigned LSize = LIds.size(), RSize = RIds.size();
358 unsigned MinSize = LSize < RSize ? LSize : RSize;
360 for (unsigned i = 0; i != MinSize; ++i)
361 if (LIds[i] != RIds[i])
362 return LIds[i] < RIds[i];
364 return LSize < RSize;
367 /// ComputeActionsTable - Compute the actions table and gather the first action
368 /// index for each landing pad site.
369 unsigned DwarfException::
370 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
371 SmallVectorImpl<ActionEntry> &Actions,
372 SmallVectorImpl<unsigned> &FirstActions) {
374 // The action table follows the call-site table in the LSDA. The individual
375 // records are of two types:
378 // * Exception specification
380 // The two record kinds have the same format, with only small differences.
381 // They are distinguished by the "switch value" field: Catch clauses
382 // (TypeInfos) have strictly positive switch values, and exception
383 // specifications (FilterIds) have strictly negative switch values. Value 0
384 // indicates a catch-all clause.
386 // Negative type IDs index into FilterIds. Positive type IDs index into
387 // TypeInfos. The value written for a positive type ID is just the type ID
388 // itself. For a negative type ID, however, the value written is the
389 // (negative) byte offset of the corresponding FilterIds entry. The byte
390 // offset is usually equal to the type ID (because the FilterIds entries are
391 // written using a variable width encoding, which outputs one byte per entry
392 // as long as the value written is not too large) but can differ. This kind
393 // of complication does not occur for positive type IDs because type infos are
394 // output using a fixed width encoding. FilterOffsets[i] holds the byte
395 // offset corresponding to FilterIds[i].
397 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
398 SmallVector<int, 16> FilterOffsets;
399 FilterOffsets.reserve(FilterIds.size());
402 for (std::vector<unsigned>::const_iterator
403 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
404 FilterOffsets.push_back(Offset);
405 Offset -= MCAsmInfo::getULEB128Size(*I);
408 FirstActions.reserve(LandingPads.size());
411 unsigned SizeActions = 0;
412 const LandingPadInfo *PrevLPI = 0;
414 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
415 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
416 const LandingPadInfo *LPI = *I;
417 const std::vector<int> &TypeIds = LPI->TypeIds;
418 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
419 unsigned SizeSiteActions = 0;
421 if (NumShared < TypeIds.size()) {
422 unsigned SizeAction = 0;
423 ActionEntry *PrevAction = 0;
426 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
427 assert(Actions.size());
428 PrevAction = &Actions.back();
429 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
430 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
432 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
434 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
435 SizeAction += -PrevAction->NextAction;
436 PrevAction = PrevAction->Previous;
440 // Compute the actions.
441 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
442 int TypeID = TypeIds[J];
443 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
444 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
445 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
447 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
448 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
449 SizeSiteActions += SizeAction;
451 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
452 Actions.push_back(Action);
453 PrevAction = &Actions.back();
456 // Record the first action of the landing pad site.
457 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
458 } // else identical - re-use previous FirstAction
460 // Information used when created the call-site table. The action record
461 // field of the call site record is the offset of the first associated
462 // action record, relative to the start of the actions table. This value is
463 // biased by 1 (1 in dicating the start of the actions table), and 0
464 // indicates that there are no actions.
465 FirstActions.push_back(FirstAction);
467 // Compute this sites contribution to size.
468 SizeActions += SizeSiteActions;
476 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
477 /// marked `nounwind'. Return `false' otherwise.
478 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
479 assert(MI->getDesc().isCall() && "This should be a call instruction!");
481 bool MarkedNoUnwind = false;
482 bool SawFunc = false;
484 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
485 const MachineOperand &MO = MI->getOperand(I);
488 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
490 // Be conservative. If we have more than one function operand for this
491 // call, then we can't make the assumption that it's the callee and
492 // not a parameter to the call.
494 // FIXME: Determine if there's a way to say that `F' is the callee or
496 MarkedNoUnwind = false;
500 MarkedNoUnwind = F->doesNotThrow();
506 return MarkedNoUnwind;
509 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
510 /// has a try-range containing the call, a non-zero landing pad, and an
511 /// appropriate action. The entry for an ordinary call has a try-range
512 /// containing the call and zero for the landing pad and the action. Calls
513 /// marked 'nounwind' have no entry and must not be contained in the try-range
514 /// of any entry - they form gaps in the table. Entries must be ordered by
515 /// try-range address.
516 void DwarfException::
517 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
518 const RangeMapType &PadMap,
519 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
520 const SmallVectorImpl<unsigned> &FirstActions) {
521 // The end label of the previous invoke or nounwind try-range.
522 unsigned LastLabel = 0;
524 // Whether there is a potentially throwing instruction (currently this means
525 // an ordinary call) between the end of the previous try-range and now.
526 bool SawPotentiallyThrowing = false;
528 // Whether the last CallSite entry was for an invoke.
529 bool PreviousIsInvoke = false;
531 // Visit all instructions in order of address.
532 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
534 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
536 if (!MI->isLabel()) {
537 if (MI->getDesc().isCall())
538 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
543 unsigned BeginLabel = MI->getOperand(0).getImm();
544 assert(BeginLabel && "Invalid label!");
546 // End of the previous try-range?
547 if (BeginLabel == LastLabel)
548 SawPotentiallyThrowing = false;
550 // Beginning of a new try-range?
551 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
552 if (L == PadMap.end())
553 // Nope, it was just some random label.
556 const PadRange &P = L->second;
557 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
558 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
559 "Inconsistent landing pad map!");
561 // For Dwarf exception handling (SjLj handling doesn't use this). If some
562 // instruction between the previous try-range and this one may throw,
563 // create a call-site entry with no landing pad for the region between the
565 if (SawPotentiallyThrowing &&
566 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
567 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
568 CallSites.push_back(Site);
569 PreviousIsInvoke = false;
572 LastLabel = LandingPad->EndLabels[P.RangeIndex];
573 assert(BeginLabel && LastLabel && "Invalid landing pad!");
575 if (LandingPad->LandingPadLabel) {
576 // This try-range is for an invoke.
577 CallSiteEntry Site = {
580 LandingPad->LandingPadLabel,
581 FirstActions[P.PadIndex]
584 // Try to merge with the previous call-site. SJLJ doesn't do this
585 if (PreviousIsInvoke &&
586 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
587 CallSiteEntry &Prev = CallSites.back();
588 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
589 // Extend the range of the previous entry.
590 Prev.EndLabel = Site.EndLabel;
595 // Otherwise, create a new call-site.
596 CallSites.push_back(Site);
597 PreviousIsInvoke = true;
600 PreviousIsInvoke = false;
605 // If some instruction between the previous try-range and the end of the
606 // function may throw, create a call-site entry with no landing pad for the
607 // region following the try-range.
608 if (SawPotentiallyThrowing &&
609 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
610 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
611 CallSites.push_back(Site);
615 /// EmitExceptionTable - Emit landing pads and actions.
617 /// The general organization of the table is complex, but the basic concepts are
618 /// easy. First there is a header which describes the location and organization
619 /// of the three components that follow.
621 /// 1. The landing pad site information describes the range of code covered by
622 /// the try. In our case it's an accumulation of the ranges covered by the
623 /// invokes in the try. There is also a reference to the landing pad that
624 /// handles the exception once processed. Finally an index into the actions
626 /// 2. The action table, in our case, is composed of pairs of type IDs and next
627 /// action offset. Starting with the action index from the landing pad
628 /// site, each type ID is checked for a match to the current exception. If
629 /// it matches then the exception and type id are passed on to the landing
630 /// pad. Otherwise the next action is looked up. This chain is terminated
631 /// with a next action of zero. If no type id is found then the frame is
632 /// unwound and handling continues.
633 /// 3. Type ID table contains references to all the C++ typeinfo for all
634 /// catches in the function. This tables is reverse indexed base 1.
635 void DwarfException::EmitExceptionTable() {
636 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
637 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
638 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
639 if (PadInfos.empty()) return;
641 // Sort the landing pads in order of their type ids. This is used to fold
642 // duplicate actions.
643 SmallVector<const LandingPadInfo *, 64> LandingPads;
644 LandingPads.reserve(PadInfos.size());
646 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
647 LandingPads.push_back(&PadInfos[i]);
649 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
651 // Compute the actions table and gather the first action index for each
653 SmallVector<ActionEntry, 32> Actions;
654 SmallVector<unsigned, 64> FirstActions;
655 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
658 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
659 // by try-range labels when lowered). Ordinary calls do not, so appropriate
660 // try-ranges for them need be deduced when using DWARF exception handling.
662 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
663 const LandingPadInfo *LandingPad = LandingPads[i];
664 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
665 unsigned BeginLabel = LandingPad->BeginLabels[j];
666 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
667 PadRange P = { i, j };
668 PadMap[BeginLabel] = P;
672 // Compute the call-site table.
673 SmallVector<CallSiteEntry, 64> CallSites;
674 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
679 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
680 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
681 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
682 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
683 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
689 SizeSites = CallSites.size() *
690 (SiteStartSize + SiteLengthSize + LandingPadSize);
692 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
693 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
695 SizeSites += MCAsmInfo::getULEB128Size(i);
699 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
700 unsigned TTypeFormat;
701 unsigned TypeFormatSize;
704 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
705 // that we're omitting that bit.
706 TTypeFormat = dwarf::DW_EH_PE_omit;
707 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
709 // Okay, we have actual filters or typeinfos to emit. As such, we need to
710 // pick a type encoding for them. We're about to emit a list of pointers to
711 // typeinfo objects at the end of the LSDA. However, unless we're in static
712 // mode, this reference will require a relocation by the dynamic linker.
714 // Because of this, we have a couple of options:
716 // 1) If we are in -static mode, we can always use an absolute reference
717 // from the LSDA, because the static linker will resolve it.
719 // 2) Otherwise, if the LSDA section is writable, we can output the direct
720 // reference to the typeinfo and allow the dynamic linker to relocate
721 // it. Since it is in a writable section, the dynamic linker won't
724 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
725 // we need to use some form of indirection. For example, on Darwin,
726 // we can output a statically-relocatable reference to a dyld stub. The
727 // offset to the stub is constant, but the contents are in a section
728 // that is updated by the dynamic linker. This is easy enough, but we
729 // need to tell the personality function of the unwinder to indirect
730 // through the dyld stub.
732 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
733 // somewhere. This predicate should be moved to a shared location that is
734 // in target-independent code.
736 if (LSDASection->getKind().isWriteable() ||
737 Asm->TM.getRelocationModel() == Reloc::Static)
738 TTypeFormat = dwarf::DW_EH_PE_absptr;
740 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
741 dwarf::DW_EH_PE_sdata4;
743 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
746 // Begin the exception table.
747 Asm->OutStreamer.SwitchSection(LSDASection);
748 Asm->EmitAlignment(2, 0, 0, false);
750 O << "GCC_except_table" << SubprogramCount << ":\n";
752 // The type infos need to be aligned. GCC does this by inserting padding just
753 // before the type infos. However, this changes the size of the exception
754 // table, so you need to take this into account when you output the exception
755 // table size. However, the size is output using a variable length encoding.
756 // So by increasing the size by inserting padding, you may increase the number
757 // of bytes used for writing the size. If it increases, say by one byte, then
758 // you now need to output one less byte of padding to get the type infos
759 // aligned. However this decreases the size of the exception table. This
760 // changes the value you have to output for the exception table size. Due to
761 // the variable length encoding, the number of bytes used for writing the
762 // length may decrease. If so, you then have to increase the amount of
763 // padding. And so on. If you look carefully at the GCC code you will see that
764 // it indeed does this in a loop, going on and on until the values stabilize.
765 // We chose another solution: don't output padding inside the table like GCC
766 // does, instead output it before the table.
767 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
768 unsigned TyOffset = sizeof(int8_t) + // Call site format
769 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
770 SizeSites + SizeActions + SizeTypes;
771 unsigned TotalSize = sizeof(int8_t) + // LPStart format
772 sizeof(int8_t) + // TType format
774 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
776 unsigned SizeAlign = (4 - TotalSize) & 3;
778 for (unsigned i = 0; i != SizeAlign; ++i) {
783 EmitLabel("exception", SubprogramCount);
786 SmallString<16> LSDAName;
787 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
788 "_LSDA_" << Asm->getFunctionNumber();
789 O << LSDAName.str() << ":\n";
793 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
794 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
796 Asm->EmitInt8(TTypeFormat);
797 Asm->EOL("@TType format", TTypeFormat);
800 Asm->EmitULEB128Bytes(TyOffset);
801 Asm->EOL("@TType base offset");
804 // SjLj Exception handling
806 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
807 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
808 Asm->EmitULEB128Bytes(SizeSites);
809 Asm->EOL("Call site table length");
811 // Emit the landing pad site information.
813 for (SmallVectorImpl<CallSiteEntry>::const_iterator
814 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
815 const CallSiteEntry &S = *I;
817 // Offset of the landing pad, counted in 16-byte bundles relative to the
819 Asm->EmitULEB128Bytes(idx);
820 Asm->EOL("Landing pad");
822 // Offset of the first associated action record, relative to the start of
823 // the action table. This value is biased by 1 (1 indicates the start of
824 // the action table), and 0 indicates that there are no actions.
825 Asm->EmitULEB128Bytes(S.Action);
829 // DWARF Exception handling
830 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
832 // The call-site table is a list of all call sites that may throw an
833 // exception (including C++ 'throw' statements) in the procedure
834 // fragment. It immediately follows the LSDA header. Each entry indicates,
835 // for a given call, the first corresponding action record and corresponding
838 // The table begins with the number of bytes, stored as an LEB128
839 // compressed, unsigned integer. The records immediately follow the record
840 // count. They are sorted in increasing call-site address. Each record
843 // * The position of the call-site.
844 // * The position of the landing pad.
845 // * The first action record for that call site.
847 // A missing entry in the call-site table indicates that a call is not
848 // supposed to throw.
850 // Emit the landing pad call site table.
851 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
852 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
853 Asm->EmitULEB128Bytes(SizeSites);
854 Asm->EOL("Call site table size");
856 for (SmallVectorImpl<CallSiteEntry>::const_iterator
857 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
858 const CallSiteEntry &S = *I;
859 const char *BeginTag;
860 unsigned BeginNumber;
863 BeginTag = "eh_func_begin";
864 BeginNumber = SubprogramCount;
867 BeginNumber = S.BeginLabel;
870 // Offset of the call site relative to the previous call site, counted in
871 // number of 16-byte bundles. The first call site is counted relative to
872 // the start of the procedure fragment.
873 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
875 Asm->EOL("Region start");
878 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
881 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
883 Asm->EOL("Region length");
885 // Offset of the landing pad, counted in 16-byte bundles relative to the
890 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
893 Asm->EOL("Landing pad");
895 // Offset of the first associated action record, relative to the start of
896 // the action table. This value is biased by 1 (1 indicates the start of
897 // the action table), and 0 indicates that there are no actions.
898 Asm->EmitULEB128Bytes(S.Action);
903 // Emit the Action Table.
904 for (SmallVectorImpl<ActionEntry>::const_iterator
905 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
906 const ActionEntry &Action = *I;
910 // Used by the runtime to match the type of the thrown exception to the
911 // type of the catch clauses or the types in the exception specification.
913 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
914 Asm->EOL("TypeInfo index");
918 // Self-relative signed displacement in bytes of the next action record,
919 // or 0 if there is no next action record.
921 Asm->EmitSLEB128Bytes(Action.NextAction);
922 Asm->EOL("Next action");
925 // Emit the Catch TypeInfos.
926 for (std::vector<GlobalVariable *>::const_reverse_iterator
927 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
928 const GlobalVariable *GV = *I;
932 O << *Asm->GetGlobalValueSymbol(GV);
937 Asm->EOL("TypeInfo");
940 // Emit the Exception Specifications.
941 for (std::vector<unsigned>::const_iterator
942 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
943 unsigned TypeID = *I;
944 Asm->EmitULEB128Bytes(TypeID);
946 Asm->EOL("Exception specification");
951 Asm->EmitAlignment(2, 0, 0, false);
954 /// EndModule - Emit all exception information that should come after the
956 void DwarfException::EndModule() {
957 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
960 if (!shouldEmitMovesModule && !shouldEmitTableModule)
963 if (TimePassesIsEnabled)
964 ExceptionTimer->startTimer();
966 const std::vector<Function *> Personalities = MMI->getPersonalities();
968 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
969 EmitCIE(Personalities[I], I);
971 for (std::vector<FunctionEHFrameInfo>::iterator
972 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
975 if (TimePassesIsEnabled)
976 ExceptionTimer->stopTimer();
979 /// BeginFunction - Gather pre-function exception information. Assumes it's
980 /// being emitted immediately after the function entry point.
981 void DwarfException::BeginFunction(MachineFunction *MF) {
982 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
984 if (TimePassesIsEnabled)
985 ExceptionTimer->startTimer();
988 shouldEmitTable = shouldEmitMoves = false;
990 // Map all labels and get rid of any dead landing pads.
991 MMI->TidyLandingPads();
993 // If any landing pads survive, we need an EH table.
994 if (!MMI->getLandingPads().empty())
995 shouldEmitTable = true;
997 // See if we need frame move info.
998 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
999 shouldEmitMoves = true;
1001 if (shouldEmitMoves || shouldEmitTable)
1002 // Assumes in correct section after the entry point.
1003 EmitLabel("eh_func_begin", ++SubprogramCount);
1005 shouldEmitTableModule |= shouldEmitTable;
1006 shouldEmitMovesModule |= shouldEmitMoves;
1008 if (TimePassesIsEnabled)
1009 ExceptionTimer->stopTimer();
1012 /// EndFunction - Gather and emit post-function exception information.
1014 void DwarfException::EndFunction() {
1015 if (!shouldEmitMoves && !shouldEmitTable) return;
1017 if (TimePassesIsEnabled)
1018 ExceptionTimer->startTimer();
1020 EmitLabel("eh_func_end", SubprogramCount);
1021 EmitExceptionTable();
1023 const MCSymbol *FunctionEHSym =
1024 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
1025 Asm->MAI->is_EHSymbolPrivate());
1027 // Save EH frame information
1028 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
1029 MMI->getPersonalityIndex(),
1030 MF->getFrameInfo()->hasCalls(),
1031 !MMI->getLandingPads().empty(),
1032 MMI->getFrameMoves(),
1033 MF->getFunction()));
1035 // Record if this personality index uses a landing pad.
1036 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
1038 if (TimePassesIsEnabled)
1039 ExceptionTimer->stopTimer();