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), 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.GetOrCreateTemporarySymbol(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());
88 if (MAI->is_EHSymbolPrivate())
89 EHFrameSym = getDWLabel("EH_frame", Index);
91 EHFrameSym = Asm->OutContext.GetOrCreateSymbol(Twine("EH_frame") +
93 Asm->OutStreamer.EmitLabel(EHFrameSym);
95 Asm->OutStreamer.EmitLabel(getDWLabel("section_eh_frame", Index));
97 // Define base labels.
98 Asm->OutStreamer.EmitLabel(getDWLabel("eh_frame_common", Index));
100 // Define the eh frame length.
101 Asm->OutStreamer.AddComment("Length of Common Information Entry");
102 EmitDifference(getDWLabel("eh_frame_common_end", Index),
103 getDWLabel("eh_frame_common_begin", Index), true);
106 Asm->OutStreamer.EmitLabel(getDWLabel("eh_frame_common_begin", Index));
107 Asm->OutStreamer.AddComment("CIE Identifier Tag");
108 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
109 Asm->OutStreamer.AddComment("DW_CIE_VERSION");
110 Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
112 // The personality presence indicates that language specific information will
113 // show up in the eh frame. Find out how we are supposed to lower the
114 // personality function reference:
116 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
117 unsigned FDEEncoding = TLOF.getFDEEncoding();
118 unsigned PerEncoding = TLOF.getPersonalityEncoding();
120 char Augmentation[6] = { 0 };
121 unsigned AugmentationSize = 0;
122 char *APtr = Augmentation + 1;
125 // There is a personality function.
127 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
130 if (UsesLSDA[Index]) {
131 // An LSDA pointer is in the FDE augmentation.
136 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
137 // A non-default pointer encoding for the FDE.
142 if (APtr != Augmentation + 1)
143 Augmentation[0] = 'z';
145 Asm->OutStreamer.AddComment("CIE Augmentation");
146 Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);
149 EmitULEB128(1, "CIE Code Alignment Factor");
150 EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
151 Asm->OutStreamer.AddComment("CIE Return Address Column");
152 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
154 if (Augmentation[0]) {
155 EmitULEB128(AugmentationSize, "Augmentation Size");
157 // If there is a personality, we need to indicate the function's location.
159 EmitEncodingByte(PerEncoding, "Personality");
160 Asm->OutStreamer.AddComment("Personality");
161 EmitReference(PersonalityFn, PerEncoding);
164 EmitEncodingByte(LSDAEncoding, "LSDA");
165 if (FDEEncoding != dwarf::DW_EH_PE_absptr)
166 EmitEncodingByte(FDEEncoding, "FDE");
169 // Indicate locations of general callee saved registers in frame.
170 std::vector<MachineMove> Moves;
171 RI->getInitialFrameState(Moves);
172 EmitFrameMoves(NULL, 0, Moves, true);
174 // On Darwin the linker honors the alignment of eh_frame, which means it must
175 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
176 // holes which confuse readers of eh_frame.
177 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
178 Asm->OutStreamer.EmitLabel(getDWLabel("eh_frame_common_end", Index));
181 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
182 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
183 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
184 "Should not emit 'available externally' functions at all");
186 const Function *TheFunc = EHFrameInfo.function;
187 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
189 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
190 unsigned FDEEncoding = TLOF.getFDEEncoding();
192 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
194 // Externally visible entry into the functions eh frame info. If the
195 // corresponding function is static, this should not be externally visible.
196 if (!TheFunc->hasLocalLinkage())
197 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
198 O << GlobalEHDirective << *EHFrameInfo.FunctionEHSym << '\n';
200 // If corresponding function is weak definition, this should be too.
201 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
202 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
203 MCSA_WeakDefinition);
205 // If corresponding function is hidden, this should be too.
206 if (TheFunc->hasHiddenVisibility())
207 if (MCSymbolAttr HiddenAttr = MAI->getHiddenVisibilityAttr())
208 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
211 // If there are no calls then you can't unwind. This may mean we can omit the
212 // EH Frame, but some environments do not handle weak absolute symbols. If
213 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
214 // info is to be available for non-EH uses.
215 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
216 (!TheFunc->isWeakForLinker() ||
217 !MAI->getWeakDefDirective() ||
218 MAI->getSupportsWeakOmittedEHFrame())) {
219 Asm->OutStreamer.EmitAssignment(EHFrameInfo.FunctionEHSym,
220 MCConstantExpr::Create(0, Asm->OutContext));
221 // This name has no connection to the function, so it might get
222 // dead-stripped when the function is not, erroneously. Prohibit
223 // dead-stripping unconditionally.
224 if (MAI->hasNoDeadStrip())
225 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
228 Asm->OutStreamer.EmitLabel(EHFrameInfo.FunctionEHSym);
231 Asm->OutStreamer.AddComment("Length of Frame Information Entry");
232 EmitDifference(getDWLabel("eh_frame_end", EHFrameInfo.Number),
233 getDWLabel("eh_frame_begin", EHFrameInfo.Number),
236 Asm->OutStreamer.EmitLabel(getDWLabel("eh_frame_begin",EHFrameInfo.Number));
238 Asm->OutStreamer.AddComment("FDE CIE offset");
239 EmitSectionOffset(getDWLabel("eh_frame_begin", EHFrameInfo.Number),
240 getDWLabel("eh_frame_common",
241 EHFrameInfo.PersonalityIndex),
245 Asm->OutStreamer.AddComment("FDE initial location");
246 EmitReference(getDWLabel("eh_func_begin", EHFrameInfo.Number), FDEEncoding);
247 Asm->OutStreamer.AddComment("FDE address range");
248 EmitDifference(getDWLabel("eh_func_end", EHFrameInfo.Number),
249 getDWLabel("eh_func_begin", EHFrameInfo.Number),
250 SizeOfEncodedValue(FDEEncoding) == 4);
252 // If there is a personality and landing pads then point to the language
253 // specific data area in the exception table.
254 if (MMI->getPersonalities()[0] != NULL) {
255 unsigned Size = SizeOfEncodedValue(LSDAEncoding);
257 EmitULEB128(Size, "Augmentation size");
258 Asm->OutStreamer.AddComment("Language Specific Data Area");
259 if (EHFrameInfo.hasLandingPads)
260 EmitReference(getDWLabel("exception", EHFrameInfo.Number),LSDAEncoding);
262 Asm->OutStreamer.EmitIntValue(0, Size/*size*/, 0/*addrspace*/);
265 EmitULEB128(0, "Augmentation size");
268 // Indicate locations of function specific callee saved registers in frame.
269 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
272 // On Darwin the linker honors the alignment of eh_frame, which means it
273 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
274 // get holes which confuse readers of eh_frame.
275 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
277 Asm->OutStreamer.EmitLabel(getDWLabel("eh_frame_end", EHFrameInfo.Number));
279 // If the function is marked used, this table should be also. We cannot
280 // make the mark unconditional in this case, since retaining the table also
281 // retains the function in this case, and there is code around that depends
282 // on unused functions (calling undefined externals) being dead-stripped to
283 // link correctly. Yes, there really is.
284 if (MMI->isUsedFunction(EHFrameInfo.function))
285 if (MAI->hasNoDeadStrip())
286 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
289 Asm->OutStreamer.AddBlankLine();
292 /// SharedTypeIds - How many leading type ids two landing pads have in common.
293 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
294 const LandingPadInfo *R) {
295 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
296 unsigned LSize = LIds.size(), RSize = RIds.size();
297 unsigned MinSize = LSize < RSize ? LSize : RSize;
300 for (; Count != MinSize; ++Count)
301 if (LIds[Count] != RIds[Count])
307 /// PadLT - Order landing pads lexicographically by type id.
308 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
309 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
310 unsigned LSize = LIds.size(), RSize = RIds.size();
311 unsigned MinSize = LSize < RSize ? LSize : RSize;
313 for (unsigned i = 0; i != MinSize; ++i)
314 if (LIds[i] != RIds[i])
315 return LIds[i] < RIds[i];
317 return LSize < RSize;
320 /// ComputeActionsTable - Compute the actions table and gather the first action
321 /// index for each landing pad site.
322 unsigned DwarfException::
323 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
324 SmallVectorImpl<ActionEntry> &Actions,
325 SmallVectorImpl<unsigned> &FirstActions) {
327 // The action table follows the call-site table in the LSDA. The individual
328 // records are of two types:
331 // * Exception specification
333 // The two record kinds have the same format, with only small differences.
334 // They are distinguished by the "switch value" field: Catch clauses
335 // (TypeInfos) have strictly positive switch values, and exception
336 // specifications (FilterIds) have strictly negative switch values. Value 0
337 // indicates a catch-all clause.
339 // Negative type IDs index into FilterIds. Positive type IDs index into
340 // TypeInfos. The value written for a positive type ID is just the type ID
341 // itself. For a negative type ID, however, the value written is the
342 // (negative) byte offset of the corresponding FilterIds entry. The byte
343 // offset is usually equal to the type ID (because the FilterIds entries are
344 // written using a variable width encoding, which outputs one byte per entry
345 // as long as the value written is not too large) but can differ. This kind
346 // of complication does not occur for positive type IDs because type infos are
347 // output using a fixed width encoding. FilterOffsets[i] holds the byte
348 // offset corresponding to FilterIds[i].
350 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
351 SmallVector<int, 16> FilterOffsets;
352 FilterOffsets.reserve(FilterIds.size());
355 for (std::vector<unsigned>::const_iterator
356 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
357 FilterOffsets.push_back(Offset);
358 Offset -= MCAsmInfo::getULEB128Size(*I);
361 FirstActions.reserve(LandingPads.size());
364 unsigned SizeActions = 0;
365 const LandingPadInfo *PrevLPI = 0;
367 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
368 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
369 const LandingPadInfo *LPI = *I;
370 const std::vector<int> &TypeIds = LPI->TypeIds;
371 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
372 unsigned SizeSiteActions = 0;
374 if (NumShared < TypeIds.size()) {
375 unsigned SizeAction = 0;
376 unsigned PrevAction = (unsigned)-1;
379 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
380 assert(Actions.size());
381 PrevAction = Actions.size() - 1;
383 MCAsmInfo::getSLEB128Size(Actions[PrevAction].NextAction) +
384 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
386 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
387 assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
389 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
390 SizeAction += -Actions[PrevAction].NextAction;
391 PrevAction = Actions[PrevAction].Previous;
395 // Compute the actions.
396 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
397 int TypeID = TypeIds[J];
398 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
399 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
400 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
402 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
403 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
404 SizeSiteActions += SizeAction;
406 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
407 Actions.push_back(Action);
408 PrevAction = Actions.size() - 1;
411 // Record the first action of the landing pad site.
412 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
413 } // else identical - re-use previous FirstAction
415 // Information used when created the call-site table. The action record
416 // field of the call site record is the offset of the first associated
417 // action record, relative to the start of the actions table. This value is
418 // biased by 1 (1 indicating the start of the actions table), and 0
419 // indicates that there are no actions.
420 FirstActions.push_back(FirstAction);
422 // Compute this sites contribution to size.
423 SizeActions += SizeSiteActions;
431 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
432 /// marked `nounwind'. Return `false' otherwise.
433 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
434 assert(MI->getDesc().isCall() && "This should be a call instruction!");
436 bool MarkedNoUnwind = false;
437 bool SawFunc = false;
439 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
440 const MachineOperand &MO = MI->getOperand(I);
443 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
445 // Be conservative. If we have more than one function operand for this
446 // call, then we can't make the assumption that it's the callee and
447 // not a parameter to the call.
449 // FIXME: Determine if there's a way to say that `F' is the callee or
451 MarkedNoUnwind = false;
455 MarkedNoUnwind = F->doesNotThrow();
461 return MarkedNoUnwind;
464 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
465 /// has a try-range containing the call, a non-zero landing pad, and an
466 /// appropriate action. The entry for an ordinary call has a try-range
467 /// containing the call and zero for the landing pad and the action. Calls
468 /// marked 'nounwind' have no entry and must not be contained in the try-range
469 /// of any entry - they form gaps in the table. Entries must be ordered by
470 /// try-range address.
471 void DwarfException::
472 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
473 const RangeMapType &PadMap,
474 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
475 const SmallVectorImpl<unsigned> &FirstActions) {
476 // The end label of the previous invoke or nounwind try-range.
477 unsigned LastLabel = 0;
479 // Whether there is a potentially throwing instruction (currently this means
480 // an ordinary call) between the end of the previous try-range and now.
481 bool SawPotentiallyThrowing = false;
483 // Whether the last CallSite entry was for an invoke.
484 bool PreviousIsInvoke = false;
486 // Visit all instructions in order of address.
487 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
489 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
491 if (!MI->isLabel()) {
492 if (MI->getDesc().isCall())
493 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
498 unsigned BeginLabel = MI->getOperand(0).getImm();
499 assert(BeginLabel && "Invalid label!");
501 // End of the previous try-range?
502 if (BeginLabel == LastLabel)
503 SawPotentiallyThrowing = false;
505 // Beginning of a new try-range?
506 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
507 if (L == PadMap.end())
508 // Nope, it was just some random label.
511 const PadRange &P = L->second;
512 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
513 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
514 "Inconsistent landing pad map!");
516 // For Dwarf exception handling (SjLj handling doesn't use this). If some
517 // instruction between the previous try-range and this one may throw,
518 // create a call-site entry with no landing pad for the region between the
520 if (SawPotentiallyThrowing &&
521 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
522 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
523 CallSites.push_back(Site);
524 PreviousIsInvoke = false;
527 LastLabel = LandingPad->EndLabels[P.RangeIndex];
528 assert(BeginLabel && LastLabel && "Invalid landing pad!");
530 if (LandingPad->LandingPadLabel) {
531 // This try-range is for an invoke.
532 CallSiteEntry Site = {
535 LandingPad->LandingPadLabel,
536 FirstActions[P.PadIndex]
539 // Try to merge with the previous call-site. SJLJ doesn't do this
540 if (PreviousIsInvoke &&
541 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
542 CallSiteEntry &Prev = CallSites.back();
543 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
544 // Extend the range of the previous entry.
545 Prev.EndLabel = Site.EndLabel;
550 // Otherwise, create a new call-site.
551 if (MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf)
552 CallSites.push_back(Site);
554 // SjLj EH must maintain the call sites in the order assigned
555 // to them by the SjLjPrepare pass.
556 unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel);
557 if (CallSites.size() < SiteNo)
558 CallSites.resize(SiteNo);
559 CallSites[SiteNo - 1] = Site;
561 PreviousIsInvoke = true;
564 PreviousIsInvoke = false;
569 // If some instruction between the previous try-range and the end of the
570 // function may throw, create a call-site entry with no landing pad for the
571 // region following the try-range.
572 if (SawPotentiallyThrowing &&
573 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
574 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
575 CallSites.push_back(Site);
579 /// EmitExceptionTable - Emit landing pads and actions.
581 /// The general organization of the table is complex, but the basic concepts are
582 /// easy. First there is a header which describes the location and organization
583 /// of the three components that follow.
585 /// 1. The landing pad site information describes the range of code covered by
586 /// the try. In our case it's an accumulation of the ranges covered by the
587 /// invokes in the try. There is also a reference to the landing pad that
588 /// handles the exception once processed. Finally an index into the actions
590 /// 2. The action table, in our case, is composed of pairs of type IDs and next
591 /// action offset. Starting with the action index from the landing pad
592 /// site, each type ID is checked for a match to the current exception. If
593 /// it matches then the exception and type id are passed on to the landing
594 /// pad. Otherwise the next action is looked up. This chain is terminated
595 /// with a next action of zero. If no type id is found then the frame is
596 /// unwound and handling continues.
597 /// 3. Type ID table contains references to all the C++ typeinfo for all
598 /// catches in the function. This tables is reverse indexed base 1.
599 void DwarfException::EmitExceptionTable() {
600 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
601 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
602 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
603 if (PadInfos.empty()) return;
605 // Sort the landing pads in order of their type ids. This is used to fold
606 // duplicate actions.
607 SmallVector<const LandingPadInfo *, 64> LandingPads;
608 LandingPads.reserve(PadInfos.size());
610 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
611 LandingPads.push_back(&PadInfos[i]);
613 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
615 // Compute the actions table and gather the first action index for each
617 SmallVector<ActionEntry, 32> Actions;
618 SmallVector<unsigned, 64> FirstActions;
619 unsigned SizeActions=ComputeActionsTable(LandingPads, Actions, FirstActions);
621 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
622 // by try-range labels when lowered). Ordinary calls do not, so appropriate
623 // try-ranges for them need be deduced when using DWARF exception handling.
625 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
626 const LandingPadInfo *LandingPad = LandingPads[i];
627 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
628 unsigned BeginLabel = LandingPad->BeginLabels[j];
629 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
630 PadRange P = { i, j };
631 PadMap[BeginLabel] = P;
635 // Compute the call-site table.
636 SmallVector<CallSiteEntry, 64> CallSites;
637 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
642 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
643 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
644 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
645 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
646 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
647 unsigned CallSiteTableLength;
650 CallSiteTableLength = 0;
652 CallSiteTableLength = CallSites.size() *
653 (SiteStartSize + SiteLengthSize + LandingPadSize);
655 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
656 CallSiteTableLength += MCAsmInfo::getULEB128Size(CallSites[i].Action);
658 CallSiteTableLength += MCAsmInfo::getULEB128Size(i);
662 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
663 unsigned TTypeEncoding;
664 unsigned TypeFormatSize;
667 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
668 // that we're omitting that bit.
669 TTypeEncoding = dwarf::DW_EH_PE_omit;
670 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
672 // Okay, we have actual filters or typeinfos to emit. As such, we need to
673 // pick a type encoding for them. We're about to emit a list of pointers to
674 // typeinfo objects at the end of the LSDA. However, unless we're in static
675 // mode, this reference will require a relocation by the dynamic linker.
677 // Because of this, we have a couple of options:
679 // 1) If we are in -static mode, we can always use an absolute reference
680 // from the LSDA, because the static linker will resolve it.
682 // 2) Otherwise, if the LSDA section is writable, we can output the direct
683 // reference to the typeinfo and allow the dynamic linker to relocate
684 // it. Since it is in a writable section, the dynamic linker won't
687 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
688 // we need to use some form of indirection. For example, on Darwin,
689 // we can output a statically-relocatable reference to a dyld stub. The
690 // offset to the stub is constant, but the contents are in a section
691 // that is updated by the dynamic linker. This is easy enough, but we
692 // need to tell the personality function of the unwinder to indirect
693 // through the dyld stub.
695 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
696 // somewhere. This predicate should be moved to a shared location that is
697 // in target-independent code.
699 TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
700 TypeFormatSize = SizeOfEncodedValue(TTypeEncoding);
703 // Begin the exception table.
704 Asm->OutStreamer.SwitchSection(LSDASection);
705 Asm->EmitAlignment(2, 0, 0, false);
709 Asm->OutContext.GetOrCreateSymbol(Twine("GCC_except_table")+
710 Twine(SubprogramCount));
711 Asm->OutStreamer.EmitLabel(GCCETSym);
712 Asm->OutStreamer.EmitLabel(getDWLabel("exception", SubprogramCount));
715 Asm->OutStreamer.EmitLabel(getDWLabel("_LSDA_", Asm->getFunctionNumber()));
717 // Emit the LSDA header.
718 EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
719 EmitEncodingByte(TTypeEncoding, "@TType");
721 // The type infos need to be aligned. GCC does this by inserting padding just
722 // before the type infos. However, this changes the size of the exception
723 // table, so you need to take this into account when you output the exception
724 // table size. However, the size is output using a variable length encoding.
725 // So by increasing the size by inserting padding, you may increase the number
726 // of bytes used for writing the size. If it increases, say by one byte, then
727 // you now need to output one less byte of padding to get the type infos
728 // aligned. However this decreases the size of the exception table. This
729 // changes the value you have to output for the exception table size. Due to
730 // the variable length encoding, the number of bytes used for writing the
731 // length may decrease. If so, you then have to increase the amount of
732 // padding. And so on. If you look carefully at the GCC code you will see that
733 // it indeed does this in a loop, going on and on until the values stabilize.
734 // We chose another solution: don't output padding inside the table like GCC
735 // does, instead output it before the table.
736 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
737 unsigned CallSiteTableLengthSize =
738 MCAsmInfo::getULEB128Size(CallSiteTableLength);
739 unsigned TTypeBaseOffset =
740 sizeof(int8_t) + // Call site format
741 CallSiteTableLengthSize + // Call site table length size
742 CallSiteTableLength + // Call site table length
743 SizeActions + // Actions size
745 unsigned TTypeBaseOffsetSize = MCAsmInfo::getULEB128Size(TTypeBaseOffset);
747 sizeof(int8_t) + // LPStart format
748 sizeof(int8_t) + // TType format
749 (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size
750 TTypeBaseOffset; // TType base offset
751 unsigned SizeAlign = (4 - TotalSize) & 3;
754 // Account for any extra padding that will be added to the call site table
756 EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign);
760 // SjLj Exception handling
762 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
764 // Add extra padding if it wasn't added to the TType base offset.
765 EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
767 // Emit the landing pad site information.
769 for (SmallVectorImpl<CallSiteEntry>::const_iterator
770 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
771 const CallSiteEntry &S = *I;
773 // Offset of the landing pad, counted in 16-byte bundles relative to the
775 EmitULEB128(idx, "Landing pad");
777 // Offset of the first associated action record, relative to the start of
778 // the action table. This value is biased by 1 (1 indicates the start of
779 // the action table), and 0 indicates that there are no actions.
780 EmitULEB128(S.Action, "Action");
783 // DWARF Exception handling
784 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
786 // The call-site table is a list of all call sites that may throw an
787 // exception (including C++ 'throw' statements) in the procedure
788 // fragment. It immediately follows the LSDA header. Each entry indicates,
789 // for a given call, the first corresponding action record and corresponding
792 // The table begins with the number of bytes, stored as an LEB128
793 // compressed, unsigned integer. The records immediately follow the record
794 // count. They are sorted in increasing call-site address. Each record
797 // * The position of the call-site.
798 // * The position of the landing pad.
799 // * The first action record for that call site.
801 // A missing entry in the call-site table indicates that a call is not
802 // supposed to throw.
804 // Emit the landing pad call site table.
805 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
807 // Add extra padding if it wasn't added to the TType base offset.
808 EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
810 for (SmallVectorImpl<CallSiteEntry>::const_iterator
811 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
812 const CallSiteEntry &S = *I;
813 const char *BeginTag;
814 unsigned BeginNumber;
817 BeginTag = "eh_func_begin";
818 BeginNumber = SubprogramCount;
821 BeginNumber = S.BeginLabel;
824 // Offset of the call site relative to the previous call site, counted in
825 // number of 16-byte bundles. The first call site is counted relative to
826 // the start of the procedure fragment.
827 Asm->OutStreamer.AddComment("Region start");
828 EmitSectionOffset(getDWLabel(BeginTag, BeginNumber),
829 getDWLabel("eh_func_begin", SubprogramCount),
832 Asm->OutStreamer.AddComment("Region length");
834 EmitDifference(getDWLabel("eh_func_end", SubprogramCount),
835 getDWLabel(BeginTag, BeginNumber),
838 EmitDifference(getDWLabel("label", S.EndLabel),
839 getDWLabel(BeginTag, BeginNumber), true);
842 // Offset of the landing pad, counted in 16-byte bundles relative to the
844 Asm->OutStreamer.AddComment("Landing pad");
846 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
848 EmitSectionOffset(getDWLabel("label", S.PadLabel),
849 getDWLabel("eh_func_begin", SubprogramCount),
853 // Offset of the first associated action record, relative to the start of
854 // the action table. This value is biased by 1 (1 indicates the start of
855 // the action table), and 0 indicates that there are no actions.
856 EmitULEB128(S.Action, "Action");
860 // Emit the Action Table.
861 if (Actions.size() != 0) {
862 Asm->OutStreamer.AddComment("-- Action Record Table --");
863 Asm->OutStreamer.AddBlankLine();
866 for (SmallVectorImpl<ActionEntry>::const_iterator
867 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
868 const ActionEntry &Action = *I;
869 Asm->OutStreamer.AddComment("Action Record");
870 Asm->OutStreamer.AddBlankLine();
874 // Used by the runtime to match the type of the thrown exception to the
875 // type of the catch clauses or the types in the exception specification.
876 EmitSLEB128(Action.ValueForTypeID, " TypeInfo index");
880 // Self-relative signed displacement in bytes of the next action record,
881 // or 0 if there is no next action record.
882 EmitSLEB128(Action.NextAction, " Next action");
885 // Emit the Catch TypeInfos.
886 if (!TypeInfos.empty()) {
887 Asm->OutStreamer.AddComment("-- Catch TypeInfos --");
888 Asm->OutStreamer.AddBlankLine();
890 for (std::vector<GlobalVariable *>::const_reverse_iterator
891 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
892 const GlobalVariable *GV = *I;
894 Asm->OutStreamer.AddComment("TypeInfo");
896 EmitReference(GV, TTypeEncoding);
898 Asm->OutStreamer.EmitIntValue(0, SizeOfEncodedValue(TTypeEncoding), 0);
901 // Emit the Exception Specifications.
902 if (!FilterIds.empty()) {
903 Asm->OutStreamer.AddComment("-- Filter IDs --");
904 Asm->OutStreamer.AddBlankLine();
906 for (std::vector<unsigned>::const_iterator
907 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
908 unsigned TypeID = *I;
909 EmitULEB128(TypeID, TypeID != 0 ? "Exception specification" : 0);
912 Asm->EmitAlignment(2, 0, 0, false);
915 /// EndModule - Emit all exception information that should come after the
917 void DwarfException::EndModule() {
918 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
921 if (!shouldEmitMovesModule && !shouldEmitTableModule)
924 if (TimePassesIsEnabled)
925 ExceptionTimer->startTimer();
927 const std::vector<Function *> Personalities = MMI->getPersonalities();
929 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
930 EmitCIE(Personalities[I], I);
932 for (std::vector<FunctionEHFrameInfo>::iterator
933 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
936 if (TimePassesIsEnabled)
937 ExceptionTimer->stopTimer();
940 /// BeginFunction - Gather pre-function exception information. Assumes it's
941 /// being emitted immediately after the function entry point.
942 void DwarfException::BeginFunction(const MachineFunction *MF) {
943 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
945 if (TimePassesIsEnabled)
946 ExceptionTimer->startTimer();
949 shouldEmitTable = shouldEmitMoves = false;
951 // Map all labels and get rid of any dead landing pads.
952 MMI->TidyLandingPads();
954 // If any landing pads survive, we need an EH table.
955 if (!MMI->getLandingPads().empty())
956 shouldEmitTable = true;
958 // See if we need frame move info.
959 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
960 shouldEmitMoves = true;
962 if (shouldEmitMoves || shouldEmitTable)
963 // Assumes in correct section after the entry point.
964 Asm->OutStreamer.EmitLabel(getDWLabel("eh_func_begin", ++SubprogramCount));
966 shouldEmitTableModule |= shouldEmitTable;
967 shouldEmitMovesModule |= shouldEmitMoves;
969 if (TimePassesIsEnabled)
970 ExceptionTimer->stopTimer();
973 /// EndFunction - Gather and emit post-function exception information.
975 void DwarfException::EndFunction() {
976 if (!shouldEmitMoves && !shouldEmitTable) return;
978 if (TimePassesIsEnabled)
979 ExceptionTimer->startTimer();
981 Asm->OutStreamer.EmitLabel(getDWLabel("eh_func_end", SubprogramCount));
982 EmitExceptionTable();
984 MCSymbol *FunctionEHSym =
985 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
986 Asm->MAI->is_EHSymbolPrivate());
988 // Save EH frame information
989 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
990 MMI->getPersonalityIndex(),
991 MF->getFrameInfo()->hasCalls(),
992 !MMI->getLandingPads().empty(),
993 MMI->getFrameMoves(),
996 // Record if this personality index uses a landing pad.
997 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
999 if (TimePassesIsEnabled)
1000 ExceptionTimer->stopTimer();