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 EmitDifference(Asm->GetTempSymbol("eh_frame_common_end", Index),
84 Asm->GetTempSymbol("eh_frame_common_begin", Index), true);
87 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_begin",Index));
88 Asm->OutStreamer.AddComment("CIE Identifier Tag");
89 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
90 Asm->OutStreamer.AddComment("DW_CIE_VERSION");
91 Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
93 // The personality presence indicates that language specific information will
94 // show up in the eh frame. Find out how we are supposed to lower the
95 // personality function reference:
97 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
98 unsigned FDEEncoding = TLOF.getFDEEncoding();
99 unsigned PerEncoding = TLOF.getPersonalityEncoding();
101 char Augmentation[6] = { 0 };
102 unsigned AugmentationSize = 0;
103 char *APtr = Augmentation + 1;
106 // There is a personality function.
108 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
111 if (UsesLSDA[Index]) {
112 // An LSDA pointer is in the FDE augmentation.
117 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
118 // A non-default pointer encoding for the FDE.
123 if (APtr != Augmentation + 1)
124 Augmentation[0] = 'z';
126 Asm->OutStreamer.AddComment("CIE Augmentation");
127 Asm->OutStreamer.EmitBytes(StringRef(Augmentation, strlen(Augmentation)+1),0);
130 Asm->EmitULEB128(1, "CIE Code Alignment Factor");
131 Asm->EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
132 Asm->OutStreamer.AddComment("CIE Return Address Column");
133 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
135 if (Augmentation[0]) {
136 Asm->EmitULEB128(AugmentationSize, "Augmentation Size");
138 // If there is a personality, we need to indicate the function's location.
140 EmitEncodingByte(PerEncoding, "Personality");
141 Asm->OutStreamer.AddComment("Personality");
142 EmitReference(PersonalityFn, PerEncoding);
145 EmitEncodingByte(LSDAEncoding, "LSDA");
146 if (FDEEncoding != dwarf::DW_EH_PE_absptr)
147 EmitEncodingByte(FDEEncoding, "FDE");
150 // Indicate locations of general callee saved registers in frame.
151 std::vector<MachineMove> Moves;
152 RI->getInitialFrameState(Moves);
153 EmitFrameMoves(0, Moves, true);
155 // On Darwin the linker honors the alignment of eh_frame, which means it must
156 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
157 // holes which confuse readers of eh_frame.
158 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
159 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_common_end", Index));
162 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
163 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
164 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
165 "Should not emit 'available externally' functions at all");
167 const Function *TheFunc = EHFrameInfo.function;
168 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
170 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
171 unsigned FDEEncoding = TLOF.getFDEEncoding();
173 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
175 // Externally visible entry into the functions eh frame info. If the
176 // corresponding function is static, this should not be externally visible.
177 if (!TheFunc->hasLocalLinkage() && TLOF.isFunctionEHSymbolGlobal())
178 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,MCSA_Global);
180 // If corresponding function is weak definition, this should be too.
181 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
182 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
183 MCSA_WeakDefinition);
185 // If corresponding function is hidden, this should be too.
186 if (TheFunc->hasHiddenVisibility())
187 if (MCSymbolAttr HiddenAttr = MAI->getHiddenVisibilityAttr())
188 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
191 // If there are no calls then you can't unwind. This may mean we can omit the
192 // EH Frame, but some environments do not handle weak absolute symbols. If
193 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
194 // info is to be available for non-EH uses.
195 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
196 (!TheFunc->isWeakForLinker() ||
197 !MAI->getWeakDefDirective() ||
198 TLOF.getSupportsWeakOmittedEHFrame())) {
199 Asm->OutStreamer.EmitAssignment(EHFrameInfo.FunctionEHSym,
200 MCConstantExpr::Create(0, Asm->OutContext));
201 // This name has no connection to the function, so it might get
202 // dead-stripped when the function is not, erroneously. Prohibit
203 // dead-stripping unconditionally.
204 if (MAI->hasNoDeadStrip())
205 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
208 Asm->OutStreamer.EmitLabel(EHFrameInfo.FunctionEHSym);
211 Asm->OutStreamer.AddComment("Length of Frame Information Entry");
212 EmitDifference(Asm->GetTempSymbol("eh_frame_end", EHFrameInfo.Number),
213 Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number),
216 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_begin",
217 EHFrameInfo.Number));
219 Asm->OutStreamer.AddComment("FDE CIE offset");
220 EmitSectionOffset(Asm->GetTempSymbol("eh_frame_begin", EHFrameInfo.Number),
221 Asm->GetTempSymbol("eh_frame_common",
222 EHFrameInfo.PersonalityIndex),
225 MCSymbol *EHFuncBeginSym =
226 Asm->GetTempSymbol("eh_func_begin", EHFrameInfo.Number);
228 Asm->OutStreamer.AddComment("FDE initial location");
229 EmitReference(EHFuncBeginSym, FDEEncoding);
231 Asm->OutStreamer.AddComment("FDE address range");
232 EmitDifference(Asm->GetTempSymbol("eh_func_end", EHFrameInfo.Number),
233 EHFuncBeginSym, SizeOfEncodedValue(FDEEncoding) == 4);
235 // If there is a personality and landing pads then point to the language
236 // specific data area in the exception table.
237 if (MMI->getPersonalities()[0] != NULL) {
238 unsigned Size = SizeOfEncodedValue(LSDAEncoding);
240 Asm->EmitULEB128(Size, "Augmentation size");
241 Asm->OutStreamer.AddComment("Language Specific Data Area");
242 if (EHFrameInfo.hasLandingPads)
243 EmitReference(Asm->GetTempSymbol("exception", EHFrameInfo.Number),
246 Asm->OutStreamer.EmitIntValue(0, Size/*size*/, 0/*addrspace*/);
249 Asm->EmitULEB128(0, "Augmentation size");
252 // Indicate locations of function specific callee saved registers in frame.
253 EmitFrameMoves(EHFuncBeginSym, EHFrameInfo.Moves, true);
255 // On Darwin the linker honors the alignment of eh_frame, which means it
256 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
257 // get holes which confuse readers of eh_frame.
258 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
260 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_frame_end",
261 EHFrameInfo.Number));
263 // If the function is marked used, this table should be also. We cannot
264 // make the mark unconditional in this case, since retaining the table also
265 // retains the function in this case, and there is code around that depends
266 // on unused functions (calling undefined externals) being dead-stripped to
267 // link correctly. Yes, there really is.
268 if (MMI->isUsedFunction(EHFrameInfo.function))
269 if (MAI->hasNoDeadStrip())
270 Asm->OutStreamer.EmitSymbolAttribute(EHFrameInfo.FunctionEHSym,
273 Asm->OutStreamer.AddBlankLine();
276 /// SharedTypeIds - How many leading type ids two landing pads have in common.
277 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
278 const LandingPadInfo *R) {
279 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
280 unsigned LSize = LIds.size(), RSize = RIds.size();
281 unsigned MinSize = LSize < RSize ? LSize : RSize;
284 for (; Count != MinSize; ++Count)
285 if (LIds[Count] != RIds[Count])
291 /// PadLT - Order landing pads lexicographically by type id.
292 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
293 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
294 unsigned LSize = LIds.size(), RSize = RIds.size();
295 unsigned MinSize = LSize < RSize ? LSize : RSize;
297 for (unsigned i = 0; i != MinSize; ++i)
298 if (LIds[i] != RIds[i])
299 return LIds[i] < RIds[i];
301 return LSize < RSize;
304 /// ComputeActionsTable - Compute the actions table and gather the first action
305 /// index for each landing pad site.
306 unsigned DwarfException::
307 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
308 SmallVectorImpl<ActionEntry> &Actions,
309 SmallVectorImpl<unsigned> &FirstActions) {
311 // The action table follows the call-site table in the LSDA. The individual
312 // records are of two types:
315 // * Exception specification
317 // The two record kinds have the same format, with only small differences.
318 // They are distinguished by the "switch value" field: Catch clauses
319 // (TypeInfos) have strictly positive switch values, and exception
320 // specifications (FilterIds) have strictly negative switch values. Value 0
321 // indicates a catch-all clause.
323 // Negative type IDs index into FilterIds. Positive type IDs index into
324 // TypeInfos. The value written for a positive type ID is just the type ID
325 // itself. For a negative type ID, however, the value written is the
326 // (negative) byte offset of the corresponding FilterIds entry. The byte
327 // offset is usually equal to the type ID (because the FilterIds entries are
328 // written using a variable width encoding, which outputs one byte per entry
329 // as long as the value written is not too large) but can differ. This kind
330 // of complication does not occur for positive type IDs because type infos are
331 // output using a fixed width encoding. FilterOffsets[i] holds the byte
332 // offset corresponding to FilterIds[i].
334 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
335 SmallVector<int, 16> FilterOffsets;
336 FilterOffsets.reserve(FilterIds.size());
339 for (std::vector<unsigned>::const_iterator
340 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
341 FilterOffsets.push_back(Offset);
342 Offset -= MCAsmInfo::getULEB128Size(*I);
345 FirstActions.reserve(LandingPads.size());
348 unsigned SizeActions = 0;
349 const LandingPadInfo *PrevLPI = 0;
351 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
352 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
353 const LandingPadInfo *LPI = *I;
354 const std::vector<int> &TypeIds = LPI->TypeIds;
355 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
356 unsigned SizeSiteActions = 0;
358 if (NumShared < TypeIds.size()) {
359 unsigned SizeAction = 0;
360 unsigned PrevAction = (unsigned)-1;
363 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
364 assert(Actions.size());
365 PrevAction = Actions.size() - 1;
367 MCAsmInfo::getSLEB128Size(Actions[PrevAction].NextAction) +
368 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
370 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
371 assert(PrevAction != (unsigned)-1 && "PrevAction is invalid!");
373 MCAsmInfo::getSLEB128Size(Actions[PrevAction].ValueForTypeID);
374 SizeAction += -Actions[PrevAction].NextAction;
375 PrevAction = Actions[PrevAction].Previous;
379 // Compute the actions.
380 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
381 int TypeID = TypeIds[J];
382 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
383 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
384 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
386 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
387 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
388 SizeSiteActions += SizeAction;
390 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
391 Actions.push_back(Action);
392 PrevAction = Actions.size() - 1;
395 // Record the first action of the landing pad site.
396 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
397 } // else identical - re-use previous FirstAction
399 // Information used when created the call-site table. The action record
400 // field of the call site record is the offset of the first associated
401 // action record, relative to the start of the actions table. This value is
402 // biased by 1 (1 indicating the start of the actions table), and 0
403 // indicates that there are no actions.
404 FirstActions.push_back(FirstAction);
406 // Compute this sites contribution to size.
407 SizeActions += SizeSiteActions;
415 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
416 /// marked `nounwind'. Return `false' otherwise.
417 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
418 assert(MI->getDesc().isCall() && "This should be a call instruction!");
420 bool MarkedNoUnwind = false;
421 bool SawFunc = false;
423 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
424 const MachineOperand &MO = MI->getOperand(I);
426 if (!MO.isGlobal()) continue;
428 Function *F = dyn_cast<Function>(MO.getGlobal());
429 if (F == 0) continue;
432 // Be conservative. If we have more than one function operand for this
433 // call, then we can't make the assumption that it's the callee and
434 // not a parameter to the call.
436 // FIXME: Determine if there's a way to say that `F' is the callee or
438 MarkedNoUnwind = false;
442 MarkedNoUnwind = F->doesNotThrow();
446 return MarkedNoUnwind;
449 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
450 /// has a try-range containing the call, a non-zero landing pad, and an
451 /// appropriate action. The entry for an ordinary call has a try-range
452 /// containing the call and zero for the landing pad and the action. Calls
453 /// marked 'nounwind' have no entry and must not be contained in the try-range
454 /// of any entry - they form gaps in the table. Entries must be ordered by
455 /// try-range address.
456 void DwarfException::
457 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
458 const RangeMapType &PadMap,
459 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
460 const SmallVectorImpl<unsigned> &FirstActions) {
461 // The end label of the previous invoke or nounwind try-range.
462 MCSymbol *LastLabel = 0;
464 // Whether there is a potentially throwing instruction (currently this means
465 // an ordinary call) between the end of the previous try-range and now.
466 bool SawPotentiallyThrowing = false;
468 // Whether the last CallSite entry was for an invoke.
469 bool PreviousIsInvoke = false;
471 // Visit all instructions in order of address.
472 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
474 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
476 if (!MI->isLabel()) {
477 if (MI->getDesc().isCall())
478 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
482 // End of the previous try-range?
483 MCSymbol *BeginLabel = MI->getOperand(0).getMCSymbol();
484 if (BeginLabel == LastLabel)
485 SawPotentiallyThrowing = false;
487 // Beginning of a new try-range?
488 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
489 if (L == PadMap.end())
490 // Nope, it was just some random label.
493 const PadRange &P = L->second;
494 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
495 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
496 "Inconsistent landing pad map!");
498 // For Dwarf exception handling (SjLj handling doesn't use this). If some
499 // instruction between the previous try-range and this one may throw,
500 // create a call-site entry with no landing pad for the region between the
502 if (SawPotentiallyThrowing &&
503 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
504 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
505 CallSites.push_back(Site);
506 PreviousIsInvoke = false;
509 LastLabel = LandingPad->EndLabels[P.RangeIndex];
510 assert(BeginLabel && LastLabel && "Invalid landing pad!");
512 if (!LandingPad->LandingPadLabel) {
514 PreviousIsInvoke = false;
516 // This try-range is for an invoke.
517 CallSiteEntry Site = {
520 LandingPad->LandingPadLabel,
521 FirstActions[P.PadIndex]
524 // Try to merge with the previous call-site. SJLJ doesn't do this
525 if (PreviousIsInvoke &&
526 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
527 CallSiteEntry &Prev = CallSites.back();
528 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
529 // Extend the range of the previous entry.
530 Prev.EndLabel = Site.EndLabel;
535 // Otherwise, create a new call-site.
536 if (MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf)
537 CallSites.push_back(Site);
539 // SjLj EH must maintain the call sites in the order assigned
540 // to them by the SjLjPrepare pass.
541 unsigned SiteNo = MMI->getCallSiteBeginLabel(BeginLabel);
542 if (CallSites.size() < SiteNo)
543 CallSites.resize(SiteNo);
544 CallSites[SiteNo - 1] = Site;
546 PreviousIsInvoke = true;
551 // If some instruction between the previous try-range and the end of the
552 // function may throw, create a call-site entry with no landing pad for the
553 // region following the try-range.
554 if (SawPotentiallyThrowing &&
555 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
556 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
557 CallSites.push_back(Site);
561 /// EmitExceptionTable - Emit landing pads and actions.
563 /// The general organization of the table is complex, but the basic concepts are
564 /// easy. First there is a header which describes the location and organization
565 /// of the three components that follow.
567 /// 1. The landing pad site information describes the range of code covered by
568 /// the try. In our case it's an accumulation of the ranges covered by the
569 /// invokes in the try. There is also a reference to the landing pad that
570 /// handles the exception once processed. Finally an index into the actions
572 /// 2. The action table, in our case, is composed of pairs of type IDs and next
573 /// action offset. Starting with the action index from the landing pad
574 /// site, each type ID is checked for a match to the current exception. If
575 /// it matches then the exception and type id are passed on to the landing
576 /// pad. Otherwise the next action is looked up. This chain is terminated
577 /// with a next action of zero. If no type id is found then the frame is
578 /// unwound and handling continues.
579 /// 3. Type ID table contains references to all the C++ typeinfo for all
580 /// catches in the function. This tables is reverse indexed base 1.
581 void DwarfException::EmitExceptionTable() {
582 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
583 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
584 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
586 // Sort the landing pads in order of their type ids. This is used to fold
587 // duplicate actions.
588 SmallVector<const LandingPadInfo *, 64> LandingPads;
589 LandingPads.reserve(PadInfos.size());
591 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
592 LandingPads.push_back(&PadInfos[i]);
594 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
596 // Compute the actions table and gather the first action index for each
598 SmallVector<ActionEntry, 32> Actions;
599 SmallVector<unsigned, 64> FirstActions;
600 unsigned SizeActions=ComputeActionsTable(LandingPads, Actions, FirstActions);
602 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
603 // by try-range labels when lowered). Ordinary calls do not, so appropriate
604 // try-ranges for them need be deduced when using DWARF exception handling.
606 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
607 const LandingPadInfo *LandingPad = LandingPads[i];
608 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
609 MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
610 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
611 PadRange P = { i, j };
612 PadMap[BeginLabel] = P;
616 // Compute the call-site table.
617 SmallVector<CallSiteEntry, 64> CallSites;
618 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
623 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
624 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
625 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
626 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
627 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
628 unsigned CallSiteTableLength;
631 CallSiteTableLength = 0;
633 CallSiteTableLength = CallSites.size() *
634 (SiteStartSize + SiteLengthSize + LandingPadSize);
636 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
637 CallSiteTableLength += MCAsmInfo::getULEB128Size(CallSites[i].Action);
639 CallSiteTableLength += MCAsmInfo::getULEB128Size(i);
643 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
644 unsigned TTypeEncoding;
645 unsigned TypeFormatSize;
648 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
649 // that we're omitting that bit.
650 TTypeEncoding = dwarf::DW_EH_PE_omit;
651 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
653 // Okay, we have actual filters or typeinfos to emit. As such, we need to
654 // pick a type encoding for them. We're about to emit a list of pointers to
655 // typeinfo objects at the end of the LSDA. However, unless we're in static
656 // mode, this reference will require a relocation by the dynamic linker.
658 // Because of this, we have a couple of options:
660 // 1) If we are in -static mode, we can always use an absolute reference
661 // from the LSDA, because the static linker will resolve it.
663 // 2) Otherwise, if the LSDA section is writable, we can output the direct
664 // reference to the typeinfo and allow the dynamic linker to relocate
665 // it. Since it is in a writable section, the dynamic linker won't
668 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
669 // we need to use some form of indirection. For example, on Darwin,
670 // we can output a statically-relocatable reference to a dyld stub. The
671 // offset to the stub is constant, but the contents are in a section
672 // that is updated by the dynamic linker. This is easy enough, but we
673 // need to tell the personality function of the unwinder to indirect
674 // through the dyld stub.
676 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
677 // somewhere. This predicate should be moved to a shared location that is
678 // in target-independent code.
680 TTypeEncoding = Asm->getObjFileLowering().getTTypeEncoding();
681 TypeFormatSize = SizeOfEncodedValue(TTypeEncoding);
684 // Begin the exception table.
685 Asm->OutStreamer.SwitchSection(LSDASection);
686 Asm->EmitAlignment(2, 0, 0, false);
690 Asm->OutContext.GetOrCreateSymbol(Twine("GCC_except_table")+
691 Twine(SubprogramCount));
692 Asm->OutStreamer.EmitLabel(GCCETSym);
693 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("exception", SubprogramCount));
696 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("_LSDA_",
697 Asm->getFunctionNumber()));
699 // Emit the LSDA header.
700 EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
701 EmitEncodingByte(TTypeEncoding, "@TType");
703 // The type infos need to be aligned. GCC does this by inserting padding just
704 // before the type infos. However, this changes the size of the exception
705 // table, so you need to take this into account when you output the exception
706 // table size. However, the size is output using a variable length encoding.
707 // So by increasing the size by inserting padding, you may increase the number
708 // of bytes used for writing the size. If it increases, say by one byte, then
709 // you now need to output one less byte of padding to get the type infos
710 // aligned. However this decreases the size of the exception table. This
711 // changes the value you have to output for the exception table size. Due to
712 // the variable length encoding, the number of bytes used for writing the
713 // length may decrease. If so, you then have to increase the amount of
714 // padding. And so on. If you look carefully at the GCC code you will see that
715 // it indeed does this in a loop, going on and on until the values stabilize.
716 // We chose another solution: don't output padding inside the table like GCC
717 // does, instead output it before the table.
718 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
719 unsigned CallSiteTableLengthSize =
720 MCAsmInfo::getULEB128Size(CallSiteTableLength);
721 unsigned TTypeBaseOffset =
722 sizeof(int8_t) + // Call site format
723 CallSiteTableLengthSize + // Call site table length size
724 CallSiteTableLength + // Call site table length
725 SizeActions + // Actions size
727 unsigned TTypeBaseOffsetSize = MCAsmInfo::getULEB128Size(TTypeBaseOffset);
729 sizeof(int8_t) + // LPStart format
730 sizeof(int8_t) + // TType format
731 (HaveTTData ? TTypeBaseOffsetSize : 0) + // TType base offset size
732 TTypeBaseOffset; // TType base offset
733 unsigned SizeAlign = (4 - TotalSize) & 3;
736 // Account for any extra padding that will be added to the call site table
738 Asm->EmitULEB128(TTypeBaseOffset, "@TType base offset", SizeAlign);
742 // SjLj Exception handling
744 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
746 // Add extra padding if it wasn't added to the TType base offset.
747 Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
749 // Emit the landing pad site information.
751 for (SmallVectorImpl<CallSiteEntry>::const_iterator
752 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
753 const CallSiteEntry &S = *I;
755 // Offset of the landing pad, counted in 16-byte bundles relative to the
757 Asm->EmitULEB128(idx, "Landing pad");
759 // Offset of the first associated action record, relative to the start of
760 // the action table. This value is biased by 1 (1 indicates the start of
761 // the action table), and 0 indicates that there are no actions.
762 Asm->EmitULEB128(S.Action, "Action");
765 // DWARF Exception handling
766 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
768 // The call-site table is a list of all call sites that may throw an
769 // exception (including C++ 'throw' statements) in the procedure
770 // fragment. It immediately follows the LSDA header. Each entry indicates,
771 // for a given call, the first corresponding action record and corresponding
774 // The table begins with the number of bytes, stored as an LEB128
775 // compressed, unsigned integer. The records immediately follow the record
776 // count. They are sorted in increasing call-site address. Each record
779 // * The position of the call-site.
780 // * The position of the landing pad.
781 // * The first action record for that call site.
783 // A missing entry in the call-site table indicates that a call is not
784 // supposed to throw.
786 // Emit the landing pad call site table.
787 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
789 // Add extra padding if it wasn't added to the TType base offset.
790 Asm->EmitULEB128(CallSiteTableLength, "Call site table length", SizeAlign);
792 for (SmallVectorImpl<CallSiteEntry>::const_iterator
793 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
794 const CallSiteEntry &S = *I;
796 MCSymbol *EHFuncBeginSym =
797 Asm->GetTempSymbol("eh_func_begin", SubprogramCount);
799 MCSymbol *BeginLabel = S.BeginLabel;
801 BeginLabel = EHFuncBeginSym;
802 MCSymbol *EndLabel = S.EndLabel;
804 EndLabel = Asm->GetTempSymbol("eh_func_end", SubprogramCount);
806 // Offset of the call site relative to the previous call site, counted in
807 // number of 16-byte bundles. The first call site is counted relative to
808 // the start of the procedure fragment.
809 Asm->OutStreamer.AddComment("Region start");
810 EmitSectionOffset(BeginLabel, EHFuncBeginSym, true, true);
812 Asm->OutStreamer.AddComment("Region length");
813 EmitDifference(EndLabel, BeginLabel, true);
816 // Offset of the landing pad, counted in 16-byte bundles relative to the
818 Asm->OutStreamer.AddComment("Landing pad");
820 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
822 EmitSectionOffset(S.PadLabel, EHFuncBeginSym, true, true);
824 // Offset of the first associated action record, relative to the start of
825 // the action table. This value is biased by 1 (1 indicates the start of
826 // the action table), and 0 indicates that there are no actions.
827 Asm->EmitULEB128(S.Action, "Action");
831 // Emit the Action Table.
832 if (Actions.size() != 0) {
833 Asm->OutStreamer.AddComment("-- Action Record Table --");
834 Asm->OutStreamer.AddBlankLine();
837 for (SmallVectorImpl<ActionEntry>::const_iterator
838 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
839 const ActionEntry &Action = *I;
840 Asm->OutStreamer.AddComment("Action Record");
841 Asm->OutStreamer.AddBlankLine();
845 // Used by the runtime to match the type of the thrown exception to the
846 // type of the catch clauses or the types in the exception specification.
847 Asm->EmitSLEB128(Action.ValueForTypeID, " TypeInfo index");
851 // Self-relative signed displacement in bytes of the next action record,
852 // or 0 if there is no next action record.
853 Asm->EmitSLEB128(Action.NextAction, " Next action");
856 // Emit the Catch TypeInfos.
857 if (!TypeInfos.empty()) {
858 Asm->OutStreamer.AddComment("-- Catch TypeInfos --");
859 Asm->OutStreamer.AddBlankLine();
861 for (std::vector<GlobalVariable *>::const_reverse_iterator
862 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
863 const GlobalVariable *GV = *I;
865 Asm->OutStreamer.AddComment("TypeInfo");
867 EmitReference(GV, TTypeEncoding);
869 Asm->OutStreamer.EmitIntValue(0, SizeOfEncodedValue(TTypeEncoding), 0);
872 // Emit the Exception Specifications.
873 if (!FilterIds.empty()) {
874 Asm->OutStreamer.AddComment("-- Filter IDs --");
875 Asm->OutStreamer.AddBlankLine();
877 for (std::vector<unsigned>::const_iterator
878 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
879 unsigned TypeID = *I;
880 Asm->EmitULEB128(TypeID, TypeID != 0 ? "Exception specification" : 0);
883 Asm->EmitAlignment(2, 0, 0, false);
886 /// EndModule - Emit all exception information that should come after the
888 void DwarfException::EndModule() {
889 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
892 if (!shouldEmitMovesModule && !shouldEmitTableModule)
895 TimeRegion Timer(ExceptionTimer);
897 const std::vector<Function *> Personalities = MMI->getPersonalities();
899 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
900 EmitCIE(Personalities[I], I);
902 for (std::vector<FunctionEHFrameInfo>::iterator
903 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
907 /// BeginFunction - Gather pre-function exception information. Assumes it's
908 /// being emitted immediately after the function entry point.
909 void DwarfException::BeginFunction(const MachineFunction *MF) {
910 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
912 TimeRegion Timer(ExceptionTimer);
914 shouldEmitTable = shouldEmitMoves = false;
916 // If any landing pads survive, we need an EH table.
917 shouldEmitTable = !MMI->getLandingPads().empty();
919 // See if we need frame move info.
920 shouldEmitMoves = !MF->getFunction()->doesNotThrow() || UnwindTablesMandatory;
922 if (shouldEmitMoves || shouldEmitTable)
923 // Assumes in correct section after the entry point.
924 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
927 shouldEmitTableModule |= shouldEmitTable;
928 shouldEmitMovesModule |= shouldEmitMoves;
931 /// EndFunction - Gather and emit post-function exception information.
933 void DwarfException::EndFunction() {
934 if (!shouldEmitMoves && !shouldEmitTable) return;
936 TimeRegion Timer(ExceptionTimer);
937 Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",SubprogramCount));
939 // Record if this personality index uses a landing pad.
940 bool HasLandingPad = !MMI->getLandingPads().empty();
941 UsesLSDA[MMI->getPersonalityIndex()] |= HasLandingPad;
943 // Map all labels and get rid of any dead landing pads.
944 MMI->TidyLandingPads();
947 EmitExceptionTable();
949 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
950 MCSymbol *FunctionEHSym =
951 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
952 TLOF.isFunctionEHFrameSymbolPrivate());
954 // Save EH frame information
955 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
956 MMI->getPersonalityIndex(),
957 MF->getFrameInfo()->hasCalls(),
958 !MMI->getLandingPads().empty(),
959 MMI->getFrameMoves(),