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"
37 #include "llvm/ADT/Twine.h"
40 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
42 : DwarfPrinter(OS, A, T, "eh"), shouldEmitTable(false),shouldEmitMoves(false),
43 shouldEmitTableModule(false), shouldEmitMovesModule(false),
45 if (TimePassesIsEnabled)
46 ExceptionTimer = new Timer("DWARF Exception Writer");
49 DwarfException::~DwarfException() {
50 delete ExceptionTimer;
53 /// CreateLabelDiff - Emit a label and subtract it from the expression we
54 /// already have. This is equivalent to emitting "foo - .", but we have to emit
55 /// the label for "." directly.
56 const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
57 const char *LabelName,
60 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
61 << LabelName << Asm->getFunctionNumber()
63 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
64 Asm->OutStreamer.EmitLabel(DotSym);
66 return MCBinaryExpr::CreateSub(ExprRef,
67 MCSymbolRefExpr::Create(DotSym,
72 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
73 /// is shared among many Frame Description Entries. There is at least one CIE
74 /// in every non-empty .debug_frame section.
75 void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
76 // Size and sign of stack growth.
78 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
79 TargetFrameInfo::StackGrowsUp ?
80 TD->getPointerSize() : -TD->getPointerSize();
82 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
84 // Begin eh frame section.
85 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
87 if (MAI->is_EHSymbolPrivate())
88 O << MAI->getPrivateGlobalPrefix();
89 O << "EH_frame" << Index << ":\n";
91 EmitLabel("section_eh_frame", Index);
93 // Define base labels.
94 EmitLabel("eh_frame_common", Index);
96 // Define the eh frame length.
97 EmitDifference("eh_frame_common_end", Index,
98 "eh_frame_common_begin", Index, true);
99 EOL("Length of Common Information Entry");
102 EmitLabel("eh_frame_common_begin", Index);
103 if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("CIE Identifier Tag");
104 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
105 if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("DW_CIE_VERSION");
106 Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
108 // The personality presence indicates that language specific information will
109 // show up in the eh frame. Find out how we are supposed to lower the
110 // personality function reference:
112 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
113 unsigned FDEEncoding = TLOF.getFDEEncoding();
114 unsigned PerEncoding = TLOF.getPersonalityEncoding();
116 char Augmentation[6] = { 0 };
117 unsigned AugmentationSize = 0;
118 char *APtr = Augmentation + 1;
121 // There is a personality function.
123 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
126 if (UsesLSDA[Index]) {
127 // An LSDA pointer is in the FDE augmentation.
132 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
133 // A non-default pointer encoding for the FDE.
138 if (APtr != Augmentation + 1)
139 Augmentation[0] = 'z';
141 Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);
142 EOL("CIE Augmentation");
145 EmitULEB128(1, "CIE Code Alignment Factor");
146 EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
147 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
148 EOL("CIE Return Address Column");
150 if (Augmentation[0]) {
151 EmitULEB128(AugmentationSize, "Augmentation Size");
153 // If there is a personality, we need to indicate the function's location.
155 EmitEncodingByte(PerEncoding, "Personality");
156 EmitReference(PersonalityFn, PerEncoding);
160 EmitEncodingByte(LSDAEncoding, "LSDA");
161 if (FDEEncoding != dwarf::DW_EH_PE_absptr)
162 EmitEncodingByte(FDEEncoding, "FDE");
165 // Indicate locations of general callee saved registers in frame.
166 std::vector<MachineMove> Moves;
167 RI->getInitialFrameState(Moves);
168 EmitFrameMoves(NULL, 0, Moves, true);
170 // On Darwin the linker honors the alignment of eh_frame, which means it must
171 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
172 // holes which confuse readers of eh_frame.
173 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
174 EmitLabel("eh_frame_common_end", Index);
178 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
179 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
180 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
181 "Should not emit 'available externally' functions at all");
183 const Function *TheFunc = EHFrameInfo.function;
184 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
186 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
187 unsigned FDEEncoding = TLOF.getFDEEncoding();
189 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
191 // Externally visible entry into the functions eh frame info. If the
192 // corresponding function is static, this should not be externally visible.
193 if (!TheFunc->hasLocalLinkage())
194 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
195 O << GlobalEHDirective << *EHFrameInfo.FunctionEHSym << '\n';
197 // If corresponding function is weak definition, this should be too.
198 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
199 O << MAI->getWeakDefDirective() << *EHFrameInfo.FunctionEHSym << '\n';
201 // If corresponding function is hidden, this should be too.
202 if (TheFunc->hasHiddenVisibility())
203 if (MCSymbolAttr HiddenAttr = MAI->getHiddenVisibilityAttr())
204 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
207 // If there are no calls then you can't unwind. This may mean we can omit the
208 // EH Frame, but some environments do not handle weak absolute symbols. If
209 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
210 // info is to be available for non-EH uses.
211 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
212 (!TheFunc->isWeakForLinker() ||
213 !MAI->getWeakDefDirective() ||
214 MAI->getSupportsWeakOmittedEHFrame())) {
215 O << *EHFrameInfo.FunctionEHSym << " = 0\n";
216 // This name has no connection to the function, so it might get
217 // dead-stripped when the function is not, erroneously. Prohibit
218 // dead-stripping unconditionally.
219 if (MAI->hasNoDeadStrip())
220 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
223 O << *EHFrameInfo.FunctionEHSym << ":\n";
226 EmitDifference("eh_frame_end", EHFrameInfo.Number,
227 "eh_frame_begin", EHFrameInfo.Number,
229 EOL("Length of Frame Information Entry");
231 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
233 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
234 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
237 EOL("FDE CIE offset");
239 EmitReference("eh_func_begin", EHFrameInfo.Number, FDEEncoding);
240 EOL("FDE initial location");
241 EmitDifference("eh_func_end", EHFrameInfo.Number,
242 "eh_func_begin", EHFrameInfo.Number,
243 SizeOfEncodedValue(FDEEncoding) == 4);
244 EOL("FDE address range");
246 // If there is a personality and landing pads then point to the language
247 // specific data area in the exception table.
248 if (MMI->getPersonalities()[0] != NULL) {
249 unsigned Size = SizeOfEncodedValue(LSDAEncoding);
251 EmitULEB128(Size, "Augmentation size");
252 if (EHFrameInfo.hasLandingPads)
253 EmitReference("exception", EHFrameInfo.Number, LSDAEncoding);
255 Asm->OutStreamer.EmitIntValue(0, Size/*size*/, 0/*addrspace*/);
257 EOL("Language Specific Data Area");
259 EmitULEB128(0, "Augmentation size");
262 // Indicate locations of function specific callee saved registers in frame.
263 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
266 // On Darwin the linker honors the alignment of eh_frame, which means it
267 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
268 // get holes which confuse readers of eh_frame.
269 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
271 EmitLabel("eh_frame_end", EHFrameInfo.Number);
273 // If the function is marked used, this table should be also. We cannot
274 // make the mark unconditional in this case, since retaining the table also
275 // retains the function in this case, and there is code around that depends
276 // on unused functions (calling undefined externals) being dead-stripped to
277 // link correctly. Yes, there really is.
278 if (MMI->isUsedFunction(EHFrameInfo.function))
279 if (MAI->hasNoDeadStrip())
280 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
286 /// SharedTypeIds - How many leading type ids two landing pads have in common.
287 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
288 const LandingPadInfo *R) {
289 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
290 unsigned LSize = LIds.size(), RSize = RIds.size();
291 unsigned MinSize = LSize < RSize ? LSize : RSize;
294 for (; Count != MinSize; ++Count)
295 if (LIds[Count] != RIds[Count])
301 /// PadLT - Order landing pads lexicographically by type id.
302 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
303 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
304 unsigned LSize = LIds.size(), RSize = RIds.size();
305 unsigned MinSize = LSize < RSize ? LSize : RSize;
307 for (unsigned i = 0; i != MinSize; ++i)
308 if (LIds[i] != RIds[i])
309 return LIds[i] < RIds[i];
311 return LSize < RSize;
314 /// ComputeActionsTable - Compute the actions table and gather the first action
315 /// index for each landing pad site.
316 unsigned DwarfException::
317 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
318 SmallVectorImpl<ActionEntry> &Actions,
319 SmallVectorImpl<unsigned> &FirstActions) {
321 // The action table follows the call-site table in the LSDA. The individual
322 // records are of two types:
325 // * Exception specification
327 // The two record kinds have the same format, with only small differences.
328 // They are distinguished by the "switch value" field: Catch clauses
329 // (TypeInfos) have strictly positive switch values, and exception
330 // specifications (FilterIds) have strictly negative switch values. Value 0
331 // indicates a catch-all clause.
333 // Negative type IDs index into FilterIds. Positive type IDs index into
334 // TypeInfos. The value written for a positive type ID is just the type ID
335 // itself. For a negative type ID, however, the value written is the
336 // (negative) byte offset of the corresponding FilterIds entry. The byte
337 // offset is usually equal to the type ID (because the FilterIds entries are
338 // written using a variable width encoding, which outputs one byte per entry
339 // as long as the value written is not too large) but can differ. This kind
340 // of complication does not occur for positive type IDs because type infos are
341 // output using a fixed width encoding. FilterOffsets[i] holds the byte
342 // offset corresponding to FilterIds[i].
344 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
345 SmallVector<int, 16> FilterOffsets;
346 FilterOffsets.reserve(FilterIds.size());
349 for (std::vector<unsigned>::const_iterator
350 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
351 FilterOffsets.push_back(Offset);
352 Offset -= MCAsmInfo::getULEB128Size(*I);
355 FirstActions.reserve(LandingPads.size());
358 unsigned SizeActions = 0;
359 const LandingPadInfo *PrevLPI = 0;
361 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
362 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
363 const LandingPadInfo *LPI = *I;
364 const std::vector<int> &TypeIds = LPI->TypeIds;
365 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
366 unsigned SizeSiteActions = 0;
368 if (NumShared < TypeIds.size()) {
369 unsigned SizeAction = 0;
370 unsigned PrevAction = (unsigned)-1;
373 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
374 assert(Actions.size());
375 PrevAction = Actions.size() - 1;
377 MCAsmInfo::getSLEB128Size(Actions[PrevAction].NextAction) +
378 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
380 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
381 assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
383 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
384 SizeAction += -Actions[PrevAction].NextAction;
385 PrevAction = Actions[PrevAction].Previous;
389 // Compute the actions.
390 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
391 int TypeID = TypeIds[J];
392 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
393 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
394 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
396 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
397 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
398 SizeSiteActions += SizeAction;
400 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
401 Actions.push_back(Action);
402 PrevAction = Actions.size() - 1;
405 // Record the first action of the landing pad site.
406 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
407 } // else identical - re-use previous FirstAction
409 // Information used when created the call-site table. The action record
410 // field of the call site record is the offset of the first associated
411 // action record, relative to the start of the actions table. This value is
412 // biased by 1 (1 indicating the start of the actions table), and 0
413 // indicates that there are no actions.
414 FirstActions.push_back(FirstAction);
416 // Compute this sites contribution to size.
417 SizeActions += SizeSiteActions;
425 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
426 /// marked `nounwind'. Return `false' otherwise.
427 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
428 assert(MI->getDesc().isCall() && "This should be a call instruction!");
430 bool MarkedNoUnwind = false;
431 bool SawFunc = false;
433 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
434 const MachineOperand &MO = MI->getOperand(I);
437 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
439 // Be conservative. If we have more than one function operand for this
440 // call, then we can't make the assumption that it's the callee and
441 // not a parameter to the call.
443 // FIXME: Determine if there's a way to say that `F' is the callee or
445 MarkedNoUnwind = false;
449 MarkedNoUnwind = F->doesNotThrow();
455 return MarkedNoUnwind;
458 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
459 /// has a try-range containing the call, a non-zero landing pad, and an
460 /// appropriate action. The entry for an ordinary call has a try-range
461 /// containing the call and zero for the landing pad and the action. Calls
462 /// marked 'nounwind' have no entry and must not be contained in the try-range
463 /// of any entry - they form gaps in the table. Entries must be ordered by
464 /// try-range address.
465 void DwarfException::
466 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
467 const RangeMapType &PadMap,
468 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
469 const SmallVectorImpl<unsigned> &FirstActions) {
470 // The end label of the previous invoke or nounwind try-range.
471 unsigned LastLabel = 0;
473 // Whether there is a potentially throwing instruction (currently this means
474 // an ordinary call) between the end of the previous try-range and now.
475 bool SawPotentiallyThrowing = false;
477 // Whether the last CallSite entry was for an invoke.
478 bool PreviousIsInvoke = false;
480 // Visit all instructions in order of address.
481 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
483 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
485 if (!MI->isLabel()) {
486 if (MI->getDesc().isCall())
487 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
492 unsigned BeginLabel = MI->getOperand(0).getImm();
493 assert(BeginLabel && "Invalid label!");
495 // End of the previous try-range?
496 if (BeginLabel == LastLabel)
497 SawPotentiallyThrowing = false;
499 // Beginning of a new try-range?
500 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
501 if (L == PadMap.end())
502 // Nope, it was just some random label.
505 const PadRange &P = L->second;
506 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
507 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
508 "Inconsistent landing pad map!");
510 // For Dwarf exception handling (SjLj handling doesn't use this). If some
511 // instruction between the previous try-range and this one may throw,
512 // create a call-site entry with no landing pad for the region between the
514 if (SawPotentiallyThrowing &&
515 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
516 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
517 CallSites.push_back(Site);
518 PreviousIsInvoke = false;
521 LastLabel = LandingPad->EndLabels[P.RangeIndex];
522 assert(BeginLabel && LastLabel && "Invalid landing pad!");
524 if (LandingPad->LandingPadLabel) {
525 // This try-range is for an invoke.
526 CallSiteEntry Site = {
529 LandingPad->LandingPadLabel,
530 FirstActions[P.PadIndex]
533 // Try to merge with the previous call-site. SJLJ doesn't do this
534 if (PreviousIsInvoke &&
535 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
536 CallSiteEntry &Prev = CallSites.back();
537 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
538 // Extend the range of the previous entry.
539 Prev.EndLabel = Site.EndLabel;
544 // Otherwise, create a new call-site.
545 if (MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf)
546 CallSites.push_back(Site);
548 // SjLj EH must maintain the call sites in the order assigned
549 // to them by the SjLjPrepare pass.
550 unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel);
551 if (CallSites.size() < SiteNo)
552 CallSites.resize(SiteNo);
553 CallSites[SiteNo - 1] = Site;
555 PreviousIsInvoke = true;
558 PreviousIsInvoke = false;
563 // If some instruction between the previous try-range and the end of the
564 // function may throw, create a call-site entry with no landing pad for the
565 // region following the try-range.
566 if (SawPotentiallyThrowing &&
567 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
568 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
569 CallSites.push_back(Site);
573 /// EmitExceptionTable - Emit landing pads and actions.
575 /// The general organization of the table is complex, but the basic concepts are
576 /// easy. First there is a header which describes the location and organization
577 /// of the three components that follow.
579 /// 1. The landing pad site information describes the range of code covered by
580 /// the try. In our case it's an accumulation of the ranges covered by the
581 /// invokes in the try. There is also a reference to the landing pad that
582 /// handles the exception once processed. Finally an index into the actions
584 /// 2. The action table, in our case, is composed of pairs of type IDs and next
585 /// action offset. Starting with the action index from the landing pad
586 /// site, each type ID is checked for a match to the current exception. If
587 /// it matches then the exception and type id are passed on to the landing
588 /// pad. Otherwise the next action is looked up. This chain is terminated
589 /// with a next action of zero. If no type id is found then the frame is
590 /// unwound and handling continues.
591 /// 3. Type ID table contains references to all the C++ typeinfo for all
592 /// catches in the function. This tables is reverse indexed base 1.
593 void DwarfException::EmitExceptionTable() {
594 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
595 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
596 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
597 if (PadInfos.empty()) return;
599 // Sort the landing pads in order of their type ids. This is used to fold
600 // duplicate actions.
601 SmallVector<const LandingPadInfo *, 64> LandingPads;
602 LandingPads.reserve(PadInfos.size());
604 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
605 LandingPads.push_back(&PadInfos[i]);
607 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
609 // Compute the actions table and gather the first action index for each
611 SmallVector<ActionEntry, 32> Actions;
612 SmallVector<unsigned, 64> FirstActions;
613 unsigned SizeActions=ComputeActionsTable(LandingPads, Actions, FirstActions);
615 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
616 // by try-range labels when lowered). Ordinary calls do not, so appropriate
617 // try-ranges for them need be deduced when using DWARF exception handling.
619 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
620 const LandingPadInfo *LandingPad = LandingPads[i];
621 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
622 unsigned BeginLabel = LandingPad->BeginLabels[j];
623 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
624 PadRange P = { i, j };
625 PadMap[BeginLabel] = P;
629 // Compute the call-site table.
630 SmallVector<CallSiteEntry, 64> CallSites;
631 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
636 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
637 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
638 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
639 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
640 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
641 unsigned CallSiteTableLength;
644 CallSiteTableLength = 0;
646 CallSiteTableLength = CallSites.size() *
647 (SiteStartSize + SiteLengthSize + LandingPadSize);
649 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
650 CallSiteTableLength += MCAsmInfo::getULEB128Size(CallSites[i].Action);
652 CallSiteTableLength += MCAsmInfo::getULEB128Size(i);
656 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
657 unsigned TTypeEncoding;
658 unsigned TypeFormatSize;
661 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
662 // that we're omitting that bit.
663 TTypeEncoding = dwarf::DW_EH_PE_omit;
664 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
666 // Okay, we have actual filters or typeinfos to emit. As such, we need to
667 // pick a type encoding for them. We're about to emit a list of pointers to
668 // typeinfo objects at the end of the LSDA. However, unless we're in static
669 // mode, this reference will require a relocation by the dynamic linker.
671 // Because of this, we have a couple of options:
673 // 1) If we are in -static mode, we can always use an absolute reference
674 // from the LSDA, because the static linker will resolve it.
676 // 2) Otherwise, if the LSDA section is writable, we can output the direct
677 // reference to the typeinfo and allow the dynamic linker to relocate
678 // it. Since it is in a writable section, the dynamic linker won't
681 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
682 // we need to use some form of indirection. For example, on Darwin,
683 // we can output a statically-relocatable reference to a dyld stub. The
684 // offset to the stub is constant, but the contents are in a section
685 // that is updated by the dynamic linker. This is easy enough, but we
686 // need to tell the personality function of the unwinder to indirect
687 // through the dyld stub.
689 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
690 // somewhere. This predicate should be moved to a shared location that is
691 // in target-independent code.
693 TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
694 TypeFormatSize = SizeOfEncodedValue(TTypeEncoding);
697 // Begin the exception table.
698 Asm->OutStreamer.SwitchSection(LSDASection);
699 Asm->EmitAlignment(2, 0, 0, false);
702 O << "GCC_except_table" << SubprogramCount << ":\n";
703 EmitLabel("exception", SubprogramCount);
706 SmallString<16> LSDAName;
707 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
708 "_LSDA_" << Asm->getFunctionNumber();
709 O << LSDAName.str() << ":\n";
712 // Emit the LSDA header.
713 EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
714 EmitEncodingByte(TTypeEncoding, "@TType");
716 // The type infos need to be aligned. GCC does this by inserting padding just
717 // before the type infos. However, this changes the size of the exception
718 // table, so you need to take this into account when you output the exception
719 // table size. However, the size is output using a variable length encoding.
720 // So by increasing the size by inserting padding, you may increase the number
721 // of bytes used for writing the size. If it increases, say by one byte, then
722 // you now need to output one less byte of padding to get the type infos
723 // aligned. However this decreases the size of the exception table. This
724 // changes the value you have to output for the exception table size. Due to
725 // the variable length encoding, the number of bytes used for writing the
726 // length may decrease. If so, you then have to increase the amount of
727 // padding. And so on. If you look carefully at the GCC code you will see that
728 // it indeed does this in a loop, going on and on until the values stabilize.
729 // We chose another solution: don't output padding inside the table like GCC
730 // does, instead output it before the table.
731 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
732 unsigned CallSiteTableLengthSize =
733 MCAsmInfo::getULEB128Size(CallSiteTableLength);
734 unsigned TTypeBaseOffset =
735 sizeof(int8_t) + // Call site format
736 CallSiteTableLengthSize + // Call site table length size
737 CallSiteTableLength + // Call site table length
738 SizeActions + // Actions size
740 unsigned TTypeBaseOffsetSize = MCAsmInfo::getULEB128Size(TTypeBaseOffset);
742 sizeof(int8_t) + // LPStart format
743 sizeof(int8_t) + // TType format
744 (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size
745 TTypeBaseOffset; // TType base offset
746 unsigned SizeAlign = (4 - TotalSize) & 3;
749 // Account for any extra padding that will be added to the call site table
751 EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign);
755 // SjLj Exception handling
757 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
759 // Add extra padding if it wasn't added to the TType base offset.
760 EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
762 // Emit the landing pad site information.
764 for (SmallVectorImpl<CallSiteEntry>::const_iterator
765 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
766 const CallSiteEntry &S = *I;
768 // Offset of the landing pad, counted in 16-byte bundles relative to the
770 EmitULEB128(idx, "Landing pad");
772 // Offset of the first associated action record, relative to the start of
773 // the action table. This value is biased by 1 (1 indicates the start of
774 // the action table), and 0 indicates that there are no actions.
775 EmitULEB128(S.Action, "Action");
778 // DWARF Exception handling
779 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
781 // The call-site table is a list of all call sites that may throw an
782 // exception (including C++ 'throw' statements) in the procedure
783 // fragment. It immediately follows the LSDA header. Each entry indicates,
784 // for a given call, the first corresponding action record and corresponding
787 // The table begins with the number of bytes, stored as an LEB128
788 // compressed, unsigned integer. The records immediately follow the record
789 // count. They are sorted in increasing call-site address. Each record
792 // * The position of the call-site.
793 // * The position of the landing pad.
794 // * The first action record for that call site.
796 // A missing entry in the call-site table indicates that a call is not
797 // supposed to throw.
799 // Emit the landing pad call site table.
800 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
802 // Add extra padding if it wasn't added to the TType base offset.
803 EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
805 for (SmallVectorImpl<CallSiteEntry>::const_iterator
806 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
807 const CallSiteEntry &S = *I;
808 const char *BeginTag;
809 unsigned BeginNumber;
812 BeginTag = "eh_func_begin";
813 BeginNumber = SubprogramCount;
816 BeginNumber = S.BeginLabel;
819 // Offset of the call site relative to the previous call site, counted in
820 // number of 16-byte bundles. The first call site is counted relative to
821 // the start of the procedure fragment.
822 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
827 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
830 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
832 EOL("Region length");
834 // Offset of the landing pad, counted in 16-byte bundles relative to the
837 Asm->OutStreamer.AddComment("Landing pad");
838 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
840 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
845 // Offset of the first associated action record, relative to the start of
846 // the action table. This value is biased by 1 (1 indicates the start of
847 // the action table), and 0 indicates that there are no actions.
848 EmitULEB128(S.Action, "Action");
852 // Emit the Action Table.
853 if (Actions.size() != 0) EOL("-- Action Record Table --");
854 for (SmallVectorImpl<ActionEntry>::const_iterator
855 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
856 const ActionEntry &Action = *I;
857 EOL("Action Record:");
861 // Used by the runtime to match the type of the thrown exception to the
862 // type of the catch clauses or the types in the exception specification.
863 EmitSLEB128(Action.ValueForTypeID, " TypeInfo index");
867 // Self-relative signed displacement in bytes of the next action record,
868 // or 0 if there is no next action record.
869 EmitSLEB128(Action.NextAction, " Next action");
872 // Emit the Catch TypeInfos.
873 if (!TypeInfos.empty()) EOL("-- Catch TypeInfos --");
874 for (std::vector<GlobalVariable *>::const_reverse_iterator
875 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
876 const GlobalVariable *GV = *I;
879 EmitReference(GV, TTypeEncoding);
882 PrintRelDirective(TTypeEncoding);
888 // Emit the Exception Specifications.
889 if (!FilterIds.empty()) EOL("-- Filter IDs --");
890 for (std::vector<unsigned>::const_iterator
891 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
892 unsigned TypeID = *I;
893 EmitULEB128(TypeID, TypeID != 0 ? "Exception specification" : 0);
896 Asm->EmitAlignment(2, 0, 0, false);
899 /// EndModule - Emit all exception information that should come after the
901 void DwarfException::EndModule() {
902 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
905 if (!shouldEmitMovesModule && !shouldEmitTableModule)
908 if (TimePassesIsEnabled)
909 ExceptionTimer->startTimer();
911 const std::vector<Function *> Personalities = MMI->getPersonalities();
913 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
914 EmitCIE(Personalities[I], I);
916 for (std::vector<FunctionEHFrameInfo>::iterator
917 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
920 if (TimePassesIsEnabled)
921 ExceptionTimer->stopTimer();
924 /// BeginFunction - Gather pre-function exception information. Assumes it's
925 /// being emitted immediately after the function entry point.
926 void DwarfException::BeginFunction(const MachineFunction *MF) {
927 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
929 if (TimePassesIsEnabled)
930 ExceptionTimer->startTimer();
933 shouldEmitTable = shouldEmitMoves = false;
935 // Map all labels and get rid of any dead landing pads.
936 MMI->TidyLandingPads();
938 // If any landing pads survive, we need an EH table.
939 if (!MMI->getLandingPads().empty())
940 shouldEmitTable = true;
942 // See if we need frame move info.
943 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
944 shouldEmitMoves = true;
946 if (shouldEmitMoves || shouldEmitTable)
947 // Assumes in correct section after the entry point.
948 EmitLabel("eh_func_begin", ++SubprogramCount);
950 shouldEmitTableModule |= shouldEmitTable;
951 shouldEmitMovesModule |= shouldEmitMoves;
953 if (TimePassesIsEnabled)
954 ExceptionTimer->stopTimer();
957 /// EndFunction - Gather and emit post-function exception information.
959 void DwarfException::EndFunction() {
960 if (!shouldEmitMoves && !shouldEmitTable) return;
962 if (TimePassesIsEnabled)
963 ExceptionTimer->startTimer();
965 EmitLabel("eh_func_end", SubprogramCount);
966 EmitExceptionTable();
968 MCSymbol *FunctionEHSym =
969 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
970 Asm->MAI->is_EHSymbolPrivate());
972 // Save EH frame information
973 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
974 MMI->getPersonalityIndex(),
975 MF->getFrameInfo()->hasCalls(),
976 !MMI->getLandingPads().empty(),
977 MMI->getFrameMoves(),
980 // Record if this personality index uses a landing pad.
981 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
983 if (TimePassesIsEnabled)
984 ExceptionTimer->stopTimer();