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/TargetMachine.h"
31 #include "llvm/Target/TargetOptions.h"
32 #include "llvm/Target/TargetRegisterInfo.h"
33 #include "llvm/Support/Dwarf.h"
34 #include "llvm/Support/FormattedStream.h"
35 #include "llvm/Support/Timer.h"
36 #include "llvm/ADT/SmallString.h"
37 #include "llvm/ADT/StringExtras.h"
38 #include "llvm/ADT/Twine.h"
41 DwarfException::DwarfException(AsmPrinter *A)
42 : DwarfPrinter(A), 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 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
54 /// is shared among many Frame Description Entries. There is at least one CIE
55 /// in every non-empty .debug_frame section.
56 void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
57 // Size and sign of stack growth.
59 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
60 TargetFrameInfo::StackGrowsUp ?
61 TD->getPointerSize() : -TD->getPointerSize();
63 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
65 // Begin eh frame section.
66 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
69 if (TLOF.isFunctionEHFrameSymbolPrivate())
70 EHFrameSym = Asm->GetTempSymbol("EH_frame", Index);
72 EHFrameSym = Asm->OutContext.GetOrCreateSymbol(Twine("EH_frame") +
74 Asm->OutStreamer.EmitLabel(EHFrameSym);
76 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("section_eh_frame", Index));
78 // Define base labels.
79 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common", Index));
81 // Define the eh frame length.
82 Asm->OutStreamer.AddComment("Length of Common Information Entry");
83 Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_frame_common_end", Index),
84 Asm->GetTempSymbol("eh_frame_common_begin", Index),
88 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_begin",Index));
89 Asm->OutStreamer.AddComment("CIE Identifier Tag");
90 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
91 Asm->OutStreamer.AddComment("DW_CIE_VERSION");
92 Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
94 // The personality presence indicates that language specific information will
95 // show up in the eh frame. Find out how we are supposed to lower the
96 // personality function reference:
98 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
99 unsigned FDEEncoding = TLOF.getFDEEncoding();
100 unsigned PerEncoding = TLOF.getPersonalityEncoding();
102 char Augmentation[6] = { 0 };
103 unsigned AugmentationSize = 0;
104 char *APtr = Augmentation + 1;
107 // There is a personality function.
109 AugmentationSize += 1 + Asm->GetSizeOfEncodedValue(PerEncoding);
112 if (UsesLSDA[Index]) {
113 // An LSDA pointer is in the FDE augmentation.
118 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
119 // A non-default pointer encoding for the FDE.
124 if (APtr != Augmentation + 1)
125 Augmentation[0] = 'z';
127 Asm->OutStreamer.AddComment("CIE Augmentation");
128 Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);
131 Asm->EmitULEB128(1, "CIE Code Alignment Factor");
132 Asm->EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
133 Asm->OutStreamer.AddComment("CIE Return Address Column");
134 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
136 if (Augmentation[0]) {
137 Asm->EmitULEB128(AugmentationSize, "Augmentation Size");
139 // If there is a personality, we need to indicate the function's location.
141 Asm->EmitEncodingByte(PerEncoding, "Personality");
142 Asm->OutStreamer.AddComment("Personality");
143 Asm->EmitReference(PersonalityFn, PerEncoding);
146 Asm->EmitEncodingByte(LSDAEncoding, "LSDA");
147 if (FDEEncoding != dwarf::DW_EH_PE_absptr)
148 Asm->EmitEncodingByte(FDEEncoding, "FDE");
151 // Indicate locations of general callee saved registers in frame.
152 std::vector<MachineMove> Moves;
153 RI->getInitialFrameState(Moves);
154 EmitFrameMoves(0, Moves, true);
156 // On Darwin the linker honors the alignment of eh_frame, which means it must
157 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
158 // holes which confuse readers of eh_frame.
159 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
160 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_end", Index));
163 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
164 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
165 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
166 "Should not emit 'available externally' functions at all");
168 const Function *TheFunc = EHFrameInfo.function;
169 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
171 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
172 unsigned FDEEncoding = TLOF.getFDEEncoding();
174 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
176 // Externally visible entry into the functions eh frame info. If the
177 // corresponding function is static, this should not be externally visible.
178 if (!TheFunc->hasLocalLinkage() && TLOF.isFunctionEHSymbolGlobal())
179 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,MCSA_Global);
181 // If corresponding function is weak definition, this should be too.
182 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
183 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
184 MCSA_WeakDefinition);
186 // If corresponding function is hidden, this should be too.
187 if (TheFunc->hasHiddenVisibility())
188 if (MCSymbolAttr HiddenAttr = MAI->getHiddenVisibilityAttr())
189 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
192 // If there are no calls then you can't unwind. This may mean we can omit the
193 // EH Frame, but some environments do not handle weak absolute symbols. If
194 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
195 // info is to be available for non-EH uses.
196 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
197 (!TheFunc->isWeakForLinker() ||
198 !MAI->getWeakDefDirective() ||
199 TLOF.getSupportsWeakOmittedEHFrame())) {
200 Asm->OutStreamer.EmitAssignment(EHFrameInfo.FunctionEHSym,
201 MCConstantExpr::Create(0, Asm->OutContext));
202 // This name has no connection to the function, so it might get
203 // dead-stripped when the function is not, erroneously. Prohibit
204 // dead-stripping unconditionally.
205 if (MAI->hasNoDeadStrip())
206 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
209 Asm->OutStreamer.EmitLabel(EHFrameInfo.FunctionEHSym);
212 Asm->OutStreamer.AddComment("Length of Frame Information Entry");
213 Asm->EmitLabelDifference(
214 Asm->GetTempSymbol("eh_frame_end", EHFrameInfo.Number),
215 Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number), 4);
217 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_begin",
218 EHFrameInfo.Number));
220 Asm->OutStreamer.AddComment("FDE CIE offset");
221 EmitSectionOffset(Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number),
222 Asm->GetTempSymbol("eh_frame_common",
223 EHFrameInfo.PersonalityIndex),
226 MCSymbol *EHFuncBeginSym =
227 Asm->GetTempSymbol("eh_func_begin", EHFrameInfo.Number);
229 Asm->OutStreamer.AddComment("FDE initial location");
230 Asm->EmitReference(EHFuncBeginSym, FDEEncoding);
232 Asm->OutStreamer.AddComment("FDE address range");
233 Asm->EmitLabelDifference(Asm->GetTempSymbol("eh_func_end",
236 Asm->GetSizeOfEncodedValue(FDEEncoding));
238 // If there is a personality and landing pads then point to the language
239 // specific data area in the exception table.
240 if (MMI->getPersonalities()[0] != NULL) {
241 unsigned Size = Asm->GetSizeOfEncodedValue(LSDAEncoding);
243 Asm->EmitULEB128(Size, "Augmentation size");
244 Asm->OutStreamer.AddComment("Language Specific Data Area");
245 if (EHFrameInfo.hasLandingPads)
246 Asm->EmitReference(Asm->GetTempSymbol("exception", EHFrameInfo.Number),
249 Asm->OutStreamer.EmitIntValue(0, Size/*size*/, 0/*addrspace*/);
252 Asm->EmitULEB128(0, "Augmentation size");
255 // Indicate locations of function specific callee saved registers in frame.
256 EmitFrameMoves(EHFuncBeginSym, EHFrameInfo.Moves, true);
258 // On Darwin the linker honors the alignment of eh_frame, which means it
259 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
260 // get holes which confuse readers of eh_frame.
261 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
263 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_end",
264 EHFrameInfo.Number));
266 // If the function is marked used, this table should be also. We cannot
267 // make the mark unconditional in this case, since retaining the table also
268 // retains the function in this case, and there is code around that depends
269 // on unused functions (calling undefined externals) being dead-stripped to
270 // link correctly. Yes, there really is.
271 if (MMI->isUsedFunction(EHFrameInfo.function))
272 if (MAI->hasNoDeadStrip())
273 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
276 Asm->OutStreamer.AddBlankLine();
279 /// SharedTypeIds - How many leading type ids two landing pads have in common.
280 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
281 const LandingPadInfo *R) {
282 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
283 unsigned LSize = LIds.size(), RSize = RIds.size();
284 unsigned MinSize = LSize < RSize ? LSize : RSize;
287 for (; Count != MinSize; ++Count)
288 if (LIds[Count] != RIds[Count])
294 /// PadLT - Order landing pads lexicographically by type id.
295 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
296 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
297 unsigned LSize = LIds.size(), RSize = RIds.size();
298 unsigned MinSize = LSize < RSize ? LSize : RSize;
300 for (unsigned i = 0; i != MinSize; ++i)
301 if (LIds[i] != RIds[i])
302 return LIds[i] < RIds[i];
304 return LSize < RSize;
307 /// ComputeActionsTable - Compute the actions table and gather the first action
308 /// index for each landing pad site.
309 unsigned DwarfException::
310 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
311 SmallVectorImpl<ActionEntry> &Actions,
312 SmallVectorImpl<unsigned> &FirstActions) {
314 // The action table follows the call-site table in the LSDA. The individual
315 // records are of two types:
318 // * Exception specification
320 // The two record kinds have the same format, with only small differences.
321 // They are distinguished by the "switch value" field: Catch clauses
322 // (TypeInfos) have strictly positive switch values, and exception
323 // specifications (FilterIds) have strictly negative switch values. Value 0
324 // indicates a catch-all clause.
326 // Negative type IDs index into FilterIds. Positive type IDs index into
327 // TypeInfos. The value written for a positive type ID is just the type ID
328 // itself. For a negative type ID, however, the value written is the
329 // (negative) byte offset of the corresponding FilterIds entry. The byte
330 // offset is usually equal to the type ID (because the FilterIds entries are
331 // written using a variable width encoding, which outputs one byte per entry
332 // as long as the value written is not too large) but can differ. This kind
333 // of complication does not occur for positive type IDs because type infos are
334 // output using a fixed width encoding. FilterOffsets[i] holds the byte
335 // offset corresponding to FilterIds[i].
337 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
338 SmallVector<int, 16> FilterOffsets;
339 FilterOffsets.reserve(FilterIds.size());
342 for (std::vector<unsigned>::const_iterator
343 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
344 FilterOffsets.push_back(Offset);
345 Offset -= MCAsmInfo::getULEB128Size(*I);
348 FirstActions.reserve(LandingPads.size());
351 unsigned SizeActions = 0;
352 const LandingPadInfo *PrevLPI = 0;
354 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
355 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
356 const LandingPadInfo *LPI = *I;
357 const std::vector<int> &TypeIds = LPI->TypeIds;
358 unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
359 unsigned SizeSiteActions = 0;
361 if (NumShared < TypeIds.size()) {
362 unsigned SizeAction = 0;
363 unsigned PrevAction = (unsigned)-1;
366 unsigned SizePrevIds = PrevLPI->TypeIds.size();
367 assert(Actions.size());
368 PrevAction = Actions.size() - 1;
370 MCAsmInfo::getSLEB128Size(Actions[PrevAction].NextAction) +
371 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
373 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
374 assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
376 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
377 SizeAction += -Actions[PrevAction].NextAction;
378 PrevAction = Actions[PrevAction].Previous;
382 // Compute the actions.
383 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
384 int TypeID = TypeIds[J];
385 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
386 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
387 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
389 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
390 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
391 SizeSiteActions += SizeAction;
393 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
394 Actions.push_back(Action);
395 PrevAction = Actions.size() - 1;
398 // Record the first action of the landing pad site.
399 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
400 } // else identical - re-use previous FirstAction
402 // Information used when created the call-site table. The action record
403 // field of the call site record is the offset of the first associated
404 // action record, relative to the start of the actions table. This value is
405 // biased by 1 (1 indicating the start of the actions table), and 0
406 // indicates that there are no actions.
407 FirstActions.push_back(FirstAction);
409 // Compute this sites contribution to size.
410 SizeActions += SizeSiteActions;
418 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
419 /// marked `nounwind'. Return `false' otherwise.
420 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
421 assert(MI->getDesc().isCall() && "This should be a call instruction!");
423 bool MarkedNoUnwind = false;
424 bool SawFunc = false;
426 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
427 const MachineOperand &MO = MI->getOperand(I);
429 if (!MO.isGlobal()) continue;
431 Function *F = dyn_cast<Function>(MO.getGlobal());
432 if (F == 0) continue;
435 // Be conservative. If we have more than one function operand for this
436 // call, then we can't make the assumption that it's the callee and
437 // not a parameter to the call.
439 // FIXME: Determine if there's a way to say that `F' is the callee or
441 MarkedNoUnwind = false;
445 MarkedNoUnwind = F->doesNotThrow();
449 return MarkedNoUnwind;
452 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
453 /// has a try-range containing the call, a non-zero landing pad, and an
454 /// appropriate action. The entry for an ordinary call has a try-range
455 /// containing the call and zero for the landing pad and the action. Calls
456 /// marked 'nounwind' have no entry and must not be contained in the try-range
457 /// of any entry - they form gaps in the table. Entries must be ordered by
458 /// try-range address.
459 void DwarfException::
460 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
461 const RangeMapType &PadMap,
462 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
463 const SmallVectorImpl<unsigned> &FirstActions) {
464 // The end label of the previous invoke or nounwind try-range.
465 MCSymbol *LastLabel = 0;
467 // Whether there is a potentially throwing instruction (currently this means
468 // an ordinary call) between the end of the previous try-range and now.
469 bool SawPotentiallyThrowing = false;
471 // Whether the last CallSite entry was for an invoke.
472 bool PreviousIsInvoke = false;
474 // Visit all instructions in order of address.
475 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
477 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
479 if (!MI->isLabel()) {
480 if (MI->getDesc().isCall())
481 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
485 // End of the previous try-range?
486 MCSymbol *BeginLabel = MI->getOperand(0).getMCSymbol();
487 if (BeginLabel == LastLabel)
488 SawPotentiallyThrowing = false;
490 // Beginning of a new try-range?
491 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
492 if (L == PadMap.end())
493 // Nope, it was just some random label.
496 const PadRange &P = L->second;
497 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
498 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
499 "Inconsistent landing pad map!");
501 // For Dwarf exception handling (SjLj handling doesn't use this). If some
502 // instruction between the previous try-range and this one may throw,
503 // create a call-site entry with no landing pad for the region between the
505 if (SawPotentiallyThrowing &&
506 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
507 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
508 CallSites.push_back(Site);
509 PreviousIsInvoke = false;
512 LastLabel = LandingPad->EndLabels[P.RangeIndex];
513 assert(BeginLabel && LastLabel && "Invalid landing pad!");
515 if (!LandingPad->LandingPadLabel) {
517 PreviousIsInvoke = false;
519 // This try-range is for an invoke.
520 CallSiteEntry Site = {
523 LandingPad->LandingPadLabel,
524 FirstActions[P.PadIndex]
527 // Try to merge with the previous call-site. SJLJ doesn't do this
528 if (PreviousIsInvoke &&
529 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
530 CallSiteEntry &Prev = CallSites.back();
531 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
532 // Extend the range of the previous entry.
533 Prev.EndLabel = Site.EndLabel;
538 // Otherwise, create a new call-site.
539 if (MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf)
540 CallSites.push_back(Site);
542 // SjLj EH must maintain the call sites in the order assigned
543 // to them by the SjLjPrepare pass.
544 unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel);
545 if (CallSites.size() < SiteNo)
546 CallSites.resize(SiteNo);
547 CallSites[SiteNo - 1] = Site;
549 PreviousIsInvoke = true;
554 // If some instruction between the previous try-range and the end of the
555 // function may throw, create a call-site entry with no landing pad for the
556 // region following the try-range.
557 if (SawPotentiallyThrowing &&
558 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
559 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
560 CallSites.push_back(Site);
564 /// EmitExceptionTable - Emit landing pads and actions.
566 /// The general organization of the table is complex, but the basic concepts are
567 /// easy. First there is a header which describes the location and organization
568 /// of the three components that follow.
570 /// 1. The landing pad site information describes the range of code covered by
571 /// the try. In our case it's an accumulation of the ranges covered by the
572 /// invokes in the try. There is also a reference to the landing pad that
573 /// handles the exception once processed. Finally an index into the actions
575 /// 2. The action table, in our case, is composed of pairs of type IDs and next
576 /// action offset. Starting with the action index from the landing pad
577 /// site, each type ID is checked for a match to the current exception. If
578 /// it matches then the exception and type id are passed on to the landing
579 /// pad. Otherwise the next action is looked up. This chain is terminated
580 /// with a next action of zero. If no type id is found then the frame is
581 /// unwound and handling continues.
582 /// 3. Type ID table contains references to all the C++ typeinfo for all
583 /// catches in the function. This tables is reverse indexed base 1.
584 void DwarfException::EmitExceptionTable() {
585 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
586 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
587 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
589 // Sort the landing pads in order of their type ids. This is used to fold
590 // duplicate actions.
591 SmallVector<const LandingPadInfo *, 64> LandingPads;
592 LandingPads.reserve(PadInfos.size());
594 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
595 LandingPads.push_back(&PadInfos[i]);
597 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
599 // Compute the actions table and gather the first action index for each
601 SmallVector<ActionEntry, 32> Actions;
602 SmallVector<unsigned, 64> FirstActions;
603 unsigned SizeActions=ComputeActionsTable(LandingPads, Actions, FirstActions);
605 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
606 // by try-range labels when lowered). Ordinary calls do not, so appropriate
607 // try-ranges for them need be deduced when using DWARF exception handling.
609 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
610 const LandingPadInfo *LandingPad = LandingPads[i];
611 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
612 MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
613 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
614 PadRange P = { i, j };
615 PadMap[BeginLabel] = P;
619 // Compute the call-site table.
620 SmallVector<CallSiteEntry, 64> CallSites;
621 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
626 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
627 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
629 unsigned CallSiteTableLength;
631 CallSiteTableLength = 0;
633 unsigned SiteStartSize = 4; // dwarf::DW_EH_PE_udata4
634 unsigned SiteLengthSize = 4; // dwarf::DW_EH_PE_udata4
635 unsigned LandingPadSize = 4; // dwarf::DW_EH_PE_udata4
636 CallSiteTableLength =
637 CallSites.size() * (SiteStartSize + SiteLengthSize + LandingPadSize);
640 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
641 CallSiteTableLength += MCAsmInfo::getULEB128Size(CallSites[i].Action);
643 CallSiteTableLength += MCAsmInfo::getULEB128Size(i);
647 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
648 unsigned TTypeEncoding;
649 unsigned TypeFormatSize;
652 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
653 // that we're omitting that bit.
654 TTypeEncoding = dwarf::DW_EH_PE_omit;
655 TypeFormatSize = TD->getPointerSize(); // dwarf::DW_EH_PE_absptr
657 // Okay, we have actual filters or typeinfos to emit. As such, we need to
658 // pick a type encoding for them. We're about to emit a list of pointers to
659 // typeinfo objects at the end of the LSDA. However, unless we're in static
660 // mode, this reference will require a relocation by the dynamic linker.
662 // Because of this, we have a couple of options:
664 // 1) If we are in -static mode, we can always use an absolute reference
665 // from the LSDA, because the static linker will resolve it.
667 // 2) Otherwise, if the LSDA section is writable, we can output the direct
668 // reference to the typeinfo and allow the dynamic linker to relocate
669 // it. Since it is in a writable section, the dynamic linker won't
672 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
673 // we need to use some form of indirection. For example, on Darwin,
674 // we can output a statically-relocatable reference to a dyld stub. The
675 // offset to the stub is constant, but the contents are in a section
676 // that is updated by the dynamic linker. This is easy enough, but we
677 // need to tell the personality function of the unwinder to indirect
678 // through the dyld stub.
680 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
681 // somewhere. This predicate should be moved to a shared location that is
682 // in target-independent code.
684 TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
685 TypeFormatSize = Asm->GetSizeOfEncodedValue(TTypeEncoding);
688 // Begin the exception table.
689 Asm->OutStreamer.SwitchSection(LSDASection);
690 Asm->EmitAlignment(2, 0, 0, false);
694 Asm->OutContext.GetOrCreateSymbol(Twine("GCC_except_table")+
695 Twine(SubprogramCount));
696 Asm->OutStreamer.EmitLabel(GCCETSym);
697 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("exception", SubprogramCount));
700 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("_LSDA_",
701 Asm->getFunctionNumber()));
703 // Emit the LSDA header.
704 Asm->EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
705 Asm->EmitEncodingByte(TTypeEncoding, "@TType");
707 // The type infos need to be aligned. GCC does this by inserting padding just
708 // before the type infos. However, this changes the size of the exception
709 // table, so you need to take this into account when you output the exception
710 // table size. However, the size is output using a variable length encoding.
711 // So by increasing the size by inserting padding, you may increase the number
712 // of bytes used for writing the size. If it increases, say by one byte, then
713 // you now need to output one less byte of padding to get the type infos
714 // aligned. However this decreases the size of the exception table. This
715 // changes the value you have to output for the exception table size. Due to
716 // the variable length encoding, the number of bytes used for writing the
717 // length may decrease. If so, you then have to increase the amount of
718 // padding. And so on. If you look carefully at the GCC code you will see that
719 // it indeed does this in a loop, going on and on until the values stabilize.
720 // We chose another solution: don't output padding inside the table like GCC
721 // does, instead output it before the table.
722 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
723 unsigned CallSiteTableLengthSize =
724 MCAsmInfo::getULEB128Size(CallSiteTableLength);
725 unsigned TTypeBaseOffset =
726 sizeof(int8_t) + // Call site format
727 CallSiteTableLengthSize + // Call site table length size
728 CallSiteTableLength + // Call site table length
729 SizeActions + // Actions size
731 unsigned TTypeBaseOffsetSize = MCAsmInfo::getULEB128Size(TTypeBaseOffset);
733 sizeof(int8_t) + // LPStart format
734 sizeof(int8_t) + // TType format
735 (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size
736 TTypeBaseOffset; // TType base offset
737 unsigned SizeAlign = (4 - TotalSize) & 3;
740 // Account for any extra padding that will be added to the call site table
742 Asm->EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign);
746 // SjLj Exception handling
748 Asm->EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
750 // Add extra padding if it wasn't added to the TType base offset.
751 Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
753 // Emit the landing pad site information.
755 for (SmallVectorImpl<CallSiteEntry>::const_iterator
756 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
757 const CallSiteEntry &S = *I;
759 // Offset of the landing pad, counted in 16-byte bundles relative to the
761 Asm->EmitULEB128(idx, "Landing pad");
763 // Offset of the first associated action record, relative to the start of
764 // the action table. This value is biased by 1 (1 indicates the start of
765 // the action table), and 0 indicates that there are no actions.
766 Asm->EmitULEB128(S.Action, "Action");
769 // DWARF Exception handling
770 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
772 // The call-site table is a list of all call sites that may throw an
773 // exception (including C++ 'throw' statements) in the procedure
774 // fragment. It immediately follows the LSDA header. Each entry indicates,
775 // for a given call, the first corresponding action record and corresponding
778 // The table begins with the number of bytes, stored as an LEB128
779 // compressed, unsigned integer. The records immediately follow the record
780 // count. They are sorted in increasing call-site address. Each record
783 // * The position of the call-site.
784 // * The position of the landing pad.
785 // * The first action record for that call site.
787 // A missing entry in the call-site table indicates that a call is not
788 // supposed to throw.
790 // Emit the landing pad call site table.
791 Asm->EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
793 // Add extra padding if it wasn't added to the TType base offset.
794 Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
796 for (SmallVectorImpl<CallSiteEntry>::const_iterator
797 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
798 const CallSiteEntry &S = *I;
800 MCSymbol *EHFuncBeginSym =
801 Asm->GetTempSymbol("eh_func_begin", SubprogramCount);
803 MCSymbol *BeginLabel = S.BeginLabel;
805 BeginLabel = EHFuncBeginSym;
806 MCSymbol *EndLabel = S.EndLabel;
808 EndLabel = Asm->GetTempSymbol("eh_func_end", SubprogramCount);
810 // Offset of the call site relative to the previous call site, counted in
811 // number of 16-byte bundles. The first call site is counted relative to
812 // the start of the procedure fragment.
813 Asm->OutStreamer.AddComment("Region start");
814 EmitSectionOffset(BeginLabel, EHFuncBeginSym, true, true);
816 Asm->OutStreamer.AddComment("Region length");
817 Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
820 // Offset of the landing pad, counted in 16-byte bundles relative to the
822 Asm->OutStreamer.AddComment("Landing pad");
824 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
826 EmitSectionOffset(S.PadLabel, EHFuncBeginSym, true, true);
828 // Offset of the first associated action record, relative to the start of
829 // the action table. This value is biased by 1 (1 indicates the start of
830 // the action table), and 0 indicates that there are no actions.
831 Asm->EmitULEB128(S.Action, "Action");
835 // Emit the Action Table.
836 if (Actions.size() != 0) {
837 Asm->OutStreamer.AddComment("-- Action Record Table --");
838 Asm->OutStreamer.AddBlankLine();
841 for (SmallVectorImpl<ActionEntry>::const_iterator
842 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
843 const ActionEntry &Action = *I;
844 Asm->OutStreamer.AddComment("Action Record");
845 Asm->OutStreamer.AddBlankLine();
849 // Used by the runtime to match the type of the thrown exception to the
850 // type of the catch clauses or the types in the exception specification.
851 Asm->EmitSLEB128(Action.ValueForTypeID, " TypeInfo index");
855 // Self-relative signed displacement in bytes of the next action record,
856 // or 0 if there is no next action record.
857 Asm->EmitSLEB128(Action.NextAction, " Next action");
860 // Emit the Catch TypeInfos.
861 if (!TypeInfos.empty()) {
862 Asm->OutStreamer.AddComment("-- Catch TypeInfos --");
863 Asm->OutStreamer.AddBlankLine();
865 for (std::vector<GlobalVariable *>::const_reverse_iterator
866 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
867 const GlobalVariable *GV = *I;
869 Asm->OutStreamer.AddComment("TypeInfo");
871 Asm->EmitReference(GV, TTypeEncoding);
873 Asm->OutStreamer.EmitIntValue(0,Asm->GetSizeOfEncodedValue(TTypeEncoding),
877 // Emit the Exception Specifications.
878 if (!FilterIds.empty()) {
879 Asm->OutStreamer.AddComment("-- Filter IDs --");
880 Asm->OutStreamer.AddBlankLine();
882 for (std::vector<unsigned>::const_iterator
883 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
884 unsigned TypeID = *I;
885 Asm->EmitULEB128(TypeID, TypeID != 0 ? "Exception specification" : 0);
888 Asm->EmitAlignment(2, 0, 0, false);
891 /// EndModule - Emit all exception information that should come after the
893 void DwarfException::EndModule() {
894 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
897 if (!shouldEmitMovesModule && !shouldEmitTableModule)
900 TimeRegion Timer(ExceptionTimer);
902 const std::vector<Function *> Personalities = MMI->getPersonalities();
904 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
905 EmitCIE(Personalities[I], I);
907 for (std::vector<FunctionEHFrameInfo>::iterator
908 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
912 /// BeginFunction - Gather pre-function exception information. Assumes it's
913 /// being emitted immediately after the function entry point.
914 void DwarfException::BeginFunction(const MachineFunction *MF) {
915 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
917 TimeRegion Timer(ExceptionTimer);
919 shouldEmitTable = shouldEmitMoves = false;
921 // If any landing pads survive, we need an EH table.
922 shouldEmitTable = !MMI->getLandingPads().empty();
924 // See if we need frame move info.
925 shouldEmitMoves = !MF->getFunction()->doesNotThrow() || UnwindTablesMandatory;
927 if (shouldEmitMoves || shouldEmitTable)
928 // Assumes in correct section after the entry point.
929 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
932 shouldEmitTableModule |= shouldEmitTable;
933 shouldEmitMovesModule |= shouldEmitMoves;
936 /// EndFunction - Gather and emit post-function exception information.
938 void DwarfException::EndFunction() {
939 if (!shouldEmitMoves && !shouldEmitTable) return;
941 TimeRegion Timer(ExceptionTimer);
942 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",SubprogramCount));
944 // Record if this personality index uses a landing pad.
945 bool HasLandingPad = !MMI->getLandingPads().empty();
946 UsesLSDA[MMI->getPersonalityIndex()] |= HasLandingPad;
948 // Map all labels and get rid of any dead landing pads.
949 MMI->TidyLandingPads();
952 EmitExceptionTable();
954 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
955 MCSymbol *FunctionEHSym =
956 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
957 TLOF.isFunctionEHFrameSymbolPrivate());
959 // Save EH frame information
960 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
961 MMI->getPersonalityIndex(),
962 MF->getFrameInfo()->hasCalls(),
963 !MMI->getLandingPads().empty(),
964 MMI->getFrameMoves(),