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/Target/TargetData.h"
26 #include "llvm/Target/TargetFrameInfo.h"
27 #include "llvm/Target/TargetLoweringObjectFile.h"
28 #include "llvm/Target/TargetOptions.h"
29 #include "llvm/Target/TargetRegisterInfo.h"
30 #include "llvm/Support/Dwarf.h"
31 #include "llvm/Support/Mangler.h"
32 #include "llvm/Support/Timer.h"
33 #include "llvm/Support/raw_ostream.h"
34 #include "llvm/ADT/SmallString.h"
35 #include "llvm/ADT/StringExtras.h"
38 static TimerGroup &getDwarfTimerGroup() {
39 static TimerGroup DwarfTimerGroup("DWARF Exception");
40 return DwarfTimerGroup;
43 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
45 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
46 shouldEmitTableModule(false), shouldEmitMovesModule(false),
48 if (TimePassesIsEnabled)
49 ExceptionTimer = new Timer("DWARF Exception Writer",
50 getDwarfTimerGroup());
53 DwarfException::~DwarfException() {
54 delete ExceptionTimer;
57 /// SizeOfEncodedValue - Return the size of the encoding in bytes.
58 unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
59 if (Encoding == dwarf::DW_EH_PE_omit)
62 switch (Encoding & 0x07) {
63 case dwarf::DW_EH_PE_absptr:
64 return TD->getPointerSize();
65 case dwarf::DW_EH_PE_udata2:
67 case dwarf::DW_EH_PE_udata4:
69 case dwarf::DW_EH_PE_udata8:
73 assert(0 && "Invalid encoded value.");
77 /// CreateLabelDiff - Emit a label and subtract it from the expression we
78 /// already have. This is equivalent to emitting "foo - .", but we have to emit
79 /// the label for "." directly.
80 const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
81 const char *LabelName,
84 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
85 << LabelName << Asm->getFunctionNumber()
87 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
88 Asm->OutStreamer.EmitLabel(DotSym);
90 return MCBinaryExpr::CreateSub(ExprRef,
91 MCSymbolRefExpr::Create(DotSym,
96 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
97 /// is shared among many Frame Description Entries. There is at least one CIE
98 /// in every non-empty .debug_frame section.
99 void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
100 // Size and sign of stack growth.
102 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
103 TargetFrameInfo::StackGrowsUp ?
104 TD->getPointerSize() : -TD->getPointerSize();
106 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
108 // Begin eh frame section.
109 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
111 if (MAI->is_EHSymbolPrivate())
112 O << MAI->getPrivateGlobalPrefix();
113 O << "EH_frame" << Index << ":\n";
115 EmitLabel("section_eh_frame", Index);
117 // Define base labels.
118 EmitLabel("eh_frame_common", Index);
120 // Define the eh frame length.
121 EmitDifference("eh_frame_common_end", Index,
122 "eh_frame_common_begin", Index, true);
123 Asm->EOL("Length of Common Information Entry");
126 EmitLabel("eh_frame_common_begin", Index);
127 Asm->EmitInt32((int)0);
128 Asm->EOL("CIE Identifier Tag");
129 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
130 Asm->EOL("CIE Version");
132 // The personality presence indicates that language specific information will
133 // show up in the eh frame. Find out how we are supposed to lower the
134 // personality function reference:
135 const MCExpr *PersonalityRef = 0;
136 bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
138 // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
140 // In non-static mode, ask the object file how to represent this reference.
142 TLOF.getSymbolForDwarfGlobalReference(PersonalityFn, Asm->Mang,
144 IsPersonalityIndirect,
148 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
149 if (IsPersonalityIndirect)
150 PerEncoding |= dwarf::DW_EH_PE_indirect;
151 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
152 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
154 char Augmentation[5] = { 0 };
155 unsigned AugmentationSize = 0;
156 char *APtr = Augmentation + 1;
158 if (PersonalityRef) {
159 // There is a personality function.
161 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
164 if (UsesLSDA[Index]) {
165 // An LSDA pointer is in the FDE augmentation.
170 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
171 // A non-default pointer encoding for the FDE.
176 if (APtr != Augmentation + 1)
177 Augmentation[0] = 'z';
179 Asm->EmitString(Augmentation);
180 Asm->EOL("CIE Augmentation");
183 Asm->EmitULEB128Bytes(1);
184 Asm->EOL("CIE Code Alignment Factor");
185 Asm->EmitSLEB128Bytes(stackGrowth);
186 Asm->EOL("CIE Data Alignment Factor");
187 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
188 Asm->EOL("CIE Return Address Column");
190 Asm->EmitULEB128Bytes(AugmentationSize);
191 Asm->EOL("Augmentation Size");
193 Asm->EmitInt8(PerEncoding);
194 Asm->EOL("Personality", PerEncoding);
196 // If there is a personality, we need to indicate the function's location.
197 if (PersonalityRef) {
198 if (!IsPersonalityPCRel)
199 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
202 O << MAI->getData32bitsDirective();
203 PersonalityRef->print(O, MAI);
204 Asm->EOL("Personality");
206 Asm->EmitInt8(LSDAEncoding);
207 Asm->EOL("LSDA Encoding", LSDAEncoding);
209 Asm->EmitInt8(FDEEncoding);
210 Asm->EOL("FDE Encoding", FDEEncoding);
213 // Indicate locations of general callee saved registers in frame.
214 std::vector<MachineMove> Moves;
215 RI->getInitialFrameState(Moves);
216 EmitFrameMoves(NULL, 0, Moves, true);
218 // On Darwin the linker honors the alignment of eh_frame, which means it must
219 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
220 // holes which confuse readers of eh_frame.
221 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
222 EmitLabel("eh_frame_common_end", Index);
227 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
228 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
229 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
230 "Should not emit 'available externally' functions at all");
232 const Function *TheFunc = EHFrameInfo.function;
234 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
236 // Externally visible entry into the functions eh frame info. If the
237 // corresponding function is static, this should not be externally visible.
238 if (!TheFunc->hasLocalLinkage())
239 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
240 O << GlobalEHDirective << EHFrameInfo.FnName << '\n';
242 // If corresponding function is weak definition, this should be too.
243 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
244 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << '\n';
246 // If corresponding function is hidden, this should be too.
247 if (TheFunc->hasHiddenVisibility())
248 if (const char *HiddenDirective = MAI->getHiddenDirective())
249 O << HiddenDirective << EHFrameInfo.FnName << '\n' ;
251 // If there are no calls then you can't unwind. This may mean we can omit the
252 // EH Frame, but some environments do not handle weak absolute symbols. If
253 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
254 // info is to be available for non-EH uses.
255 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
256 (!TheFunc->isWeakForLinker() ||
257 !MAI->getWeakDefDirective() ||
258 MAI->getSupportsWeakOmittedEHFrame())) {
259 O << EHFrameInfo.FnName << " = 0\n";
260 // This name has no connection to the function, so it might get
261 // dead-stripped when the function is not, erroneously. Prohibit
262 // dead-stripping unconditionally.
263 if (const char *UsedDirective = MAI->getUsedDirective())
264 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
266 O << EHFrameInfo.FnName << ":\n";
269 EmitDifference("eh_frame_end", EHFrameInfo.Number,
270 "eh_frame_begin", EHFrameInfo.Number, true);
271 Asm->EOL("Length of Frame Information Entry");
273 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
275 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
276 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
279 Asm->EOL("FDE CIE offset");
281 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
282 Asm->EOL("FDE initial location");
283 EmitDifference("eh_func_end", EHFrameInfo.Number,
284 "eh_func_begin", EHFrameInfo.Number, true);
285 Asm->EOL("FDE address range");
287 // If there is a personality and landing pads then point to the language
288 // specific data area in the exception table.
289 if (MMI->getPersonalities()[0] != NULL) {
290 bool is4Byte = TD->getPointerSize() == sizeof(int32_t);
292 Asm->EmitULEB128Bytes(is4Byte ? 4 : 8);
293 Asm->EOL("Augmentation size");
295 // We force 32-bits here because we've encoded our LSDA in the CIE with
296 // `dwarf::DW_EH_PE_sdata4'. And the CIE and FDE should agree.
297 if (EHFrameInfo.hasLandingPads)
298 EmitReference("exception", EHFrameInfo.Number, true, true);
300 Asm->EmitInt32((int)0);
302 Asm->EOL("Language Specific Data Area");
304 Asm->EmitULEB128Bytes(0);
305 Asm->EOL("Augmentation size");
308 // Indicate locations of function specific callee saved registers in frame.
309 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
312 // On Darwin the linker honors the alignment of eh_frame, which means it
313 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
314 // get holes which confuse readers of eh_frame.
315 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
317 EmitLabel("eh_frame_end", EHFrameInfo.Number);
319 // If the function is marked used, this table should be also. We cannot
320 // make the mark unconditional in this case, since retaining the table also
321 // retains the function in this case, and there is code around that depends
322 // on unused functions (calling undefined externals) being dead-stripped to
323 // link correctly. Yes, there really is.
324 if (MMI->isUsedFunction(EHFrameInfo.function))
325 if (const char *UsedDirective = MAI->getUsedDirective())
326 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
332 /// SharedTypeIds - How many leading type ids two landing pads have in common.
333 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
334 const LandingPadInfo *R) {
335 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
336 unsigned LSize = LIds.size(), RSize = RIds.size();
337 unsigned MinSize = LSize < RSize ? LSize : RSize;
340 for (; Count != MinSize; ++Count)
341 if (LIds[Count] != RIds[Count])
347 /// PadLT - Order landing pads lexicographically by type id.
348 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
349 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
350 unsigned LSize = LIds.size(), RSize = RIds.size();
351 unsigned MinSize = LSize < RSize ? LSize : RSize;
353 for (unsigned i = 0; i != MinSize; ++i)
354 if (LIds[i] != RIds[i])
355 return LIds[i] < RIds[i];
357 return LSize < RSize;
360 /// ComputeActionsTable - Compute the actions table and gather the first action
361 /// index for each landing pad site.
362 unsigned DwarfException::
363 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
364 SmallVectorImpl<ActionEntry> &Actions,
365 SmallVectorImpl<unsigned> &FirstActions) {
367 // The action table follows the call-site table in the LSDA. The individual
368 // records are of two types:
371 // * Exception specification
373 // The two record kinds have the same format, with only small differences.
374 // They are distinguished by the "switch value" field: Catch clauses
375 // (TypeInfos) have strictly positive switch values, and exception
376 // specifications (FilterIds) have strictly negative switch values. Value 0
377 // indicates a catch-all clause.
379 // Negative type IDs index into FilterIds. Positive type IDs index into
380 // TypeInfos. The value written for a positive type ID is just the type ID
381 // itself. For a negative type ID, however, the value written is the
382 // (negative) byte offset of the corresponding FilterIds entry. The byte
383 // offset is usually equal to the type ID (because the FilterIds entries are
384 // written using a variable width encoding, which outputs one byte per entry
385 // as long as the value written is not too large) but can differ. This kind
386 // of complication does not occur for positive type IDs because type infos are
387 // output using a fixed width encoding. FilterOffsets[i] holds the byte
388 // offset corresponding to FilterIds[i].
390 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
391 SmallVector<int, 16> FilterOffsets;
392 FilterOffsets.reserve(FilterIds.size());
395 for (std::vector<unsigned>::const_iterator
396 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
397 FilterOffsets.push_back(Offset);
398 Offset -= MCAsmInfo::getULEB128Size(*I);
401 FirstActions.reserve(LandingPads.size());
404 unsigned SizeActions = 0;
405 const LandingPadInfo *PrevLPI = 0;
407 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
408 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
409 const LandingPadInfo *LPI = *I;
410 const std::vector<int> &TypeIds = LPI->TypeIds;
411 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
412 unsigned SizeSiteActions = 0;
414 if (NumShared < TypeIds.size()) {
415 unsigned SizeAction = 0;
416 ActionEntry *PrevAction = 0;
419 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
420 assert(Actions.size());
421 PrevAction = &Actions.back();
422 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
423 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
425 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
427 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
428 SizeAction += -PrevAction->NextAction;
429 PrevAction = PrevAction->Previous;
433 // Compute the actions.
434 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
435 int TypeID = TypeIds[J];
436 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
437 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
438 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
440 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
441 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
442 SizeSiteActions += SizeAction;
444 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
445 Actions.push_back(Action);
446 PrevAction = &Actions.back();
449 // Record the first action of the landing pad site.
450 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
451 } // else identical - re-use previous FirstAction
453 // Information used when created the call-site table. The action record
454 // field of the call site record is the offset of the first associated
455 // action record, relative to the start of the actions table. This value is
456 // biased by 1 (1 in dicating the start of the actions table), and 0
457 // indicates that there are no actions.
458 FirstActions.push_back(FirstAction);
460 // Compute this sites contribution to size.
461 SizeActions += SizeSiteActions;
469 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
470 /// marked `nounwind'. Return `false' otherwise.
471 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
472 assert(MI->getDesc().isCall() && "This should be a call instruction!");
474 bool MarkedNoUnwind = false;
475 bool SawFunc = false;
477 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
478 const MachineOperand &MO = MI->getOperand(I);
481 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
483 // Be conservative. If we have more than one function operand for this
484 // call, then we can't make the assumption that it's the callee and
485 // not a parameter to the call.
487 // FIXME: Determine if there's a way to say that `F' is the callee or
489 MarkedNoUnwind = false;
493 MarkedNoUnwind = F->doesNotThrow();
499 return MarkedNoUnwind;
502 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
503 /// has a try-range containing the call, a non-zero landing pad, and an
504 /// appropriate action. The entry for an ordinary call has a try-range
505 /// containing the call and zero for the landing pad and the action. Calls
506 /// marked 'nounwind' have no entry and must not be contained in the try-range
507 /// of any entry - they form gaps in the table. Entries must be ordered by
508 /// try-range address.
509 void DwarfException::
510 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
511 const RangeMapType &PadMap,
512 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
513 const SmallVectorImpl<unsigned> &FirstActions) {
514 // The end label of the previous invoke or nounwind try-range.
515 unsigned LastLabel = 0;
517 // Whether there is a potentially throwing instruction (currently this means
518 // an ordinary call) between the end of the previous try-range and now.
519 bool SawPotentiallyThrowing = false;
521 // Whether the last CallSite entry was for an invoke.
522 bool PreviousIsInvoke = false;
524 // Visit all instructions in order of address.
525 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
527 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
529 if (!MI->isLabel()) {
530 if (MI->getDesc().isCall())
531 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
536 unsigned BeginLabel = MI->getOperand(0).getImm();
537 assert(BeginLabel && "Invalid label!");
539 // End of the previous try-range?
540 if (BeginLabel == LastLabel)
541 SawPotentiallyThrowing = false;
543 // Beginning of a new try-range?
544 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
545 if (L == PadMap.end())
546 // Nope, it was just some random label.
549 const PadRange &P = L->second;
550 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
551 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
552 "Inconsistent landing pad map!");
554 // For Dwarf exception handling (SjLj handling doesn't use this). If some
555 // instruction between the previous try-range and this one may throw,
556 // create a call-site entry with no landing pad for the region between the
558 if (SawPotentiallyThrowing &&
559 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
560 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
561 CallSites.push_back(Site);
562 PreviousIsInvoke = false;
565 LastLabel = LandingPad->EndLabels[P.RangeIndex];
566 assert(BeginLabel && LastLabel && "Invalid landing pad!");
568 if (LandingPad->LandingPadLabel) {
569 // This try-range is for an invoke.
570 CallSiteEntry Site = {
573 LandingPad->LandingPadLabel,
574 FirstActions[P.PadIndex]
577 // Try to merge with the previous call-site. SJLJ doesn't do this
578 if (PreviousIsInvoke &&
579 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
580 CallSiteEntry &Prev = CallSites.back();
581 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
582 // Extend the range of the previous entry.
583 Prev.EndLabel = Site.EndLabel;
588 // Otherwise, create a new call-site.
589 CallSites.push_back(Site);
590 PreviousIsInvoke = true;
593 PreviousIsInvoke = false;
598 // If some instruction between the previous try-range and the end of the
599 // function may throw, create a call-site entry with no landing pad for the
600 // region following the try-range.
601 if (SawPotentiallyThrowing &&
602 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
603 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
604 CallSites.push_back(Site);
608 /// EmitExceptionTable - Emit landing pads and actions.
610 /// The general organization of the table is complex, but the basic concepts are
611 /// easy. First there is a header which describes the location and organization
612 /// of the three components that follow.
614 /// 1. The landing pad site information describes the range of code covered by
615 /// the try. In our case it's an accumulation of the ranges covered by the
616 /// invokes in the try. There is also a reference to the landing pad that
617 /// handles the exception once processed. Finally an index into the actions
619 /// 2. The action table, in our case, is composed of pairs of type IDs and next
620 /// action offset. Starting with the action index from the landing pad
621 /// site, each type ID is checked for a match to the current exception. If
622 /// it matches then the exception and type id are passed on to the landing
623 /// pad. Otherwise the next action is looked up. This chain is terminated
624 /// with a next action of zero. If no type id is found then the frame is
625 /// unwound and handling continues.
626 /// 3. Type ID table contains references to all the C++ typeinfo for all
627 /// catches in the function. This tables is reverse indexed base 1.
628 void DwarfException::EmitExceptionTable() {
629 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
630 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
631 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
632 if (PadInfos.empty()) return;
634 // Sort the landing pads in order of their type ids. This is used to fold
635 // duplicate actions.
636 SmallVector<const LandingPadInfo *, 64> LandingPads;
637 LandingPads.reserve(PadInfos.size());
639 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
640 LandingPads.push_back(&PadInfos[i]);
642 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
644 // Compute the actions table and gather the first action index for each
646 SmallVector<ActionEntry, 32> Actions;
647 SmallVector<unsigned, 64> FirstActions;
648 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
651 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
652 // by try-range labels when lowered). Ordinary calls do not, so appropriate
653 // try-ranges for them need be deduced when using DWARF exception handling.
655 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
656 const LandingPadInfo *LandingPad = LandingPads[i];
657 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
658 unsigned BeginLabel = LandingPad->BeginLabels[j];
659 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
660 PadRange P = { i, j };
661 PadMap[BeginLabel] = P;
665 // Compute the call-site table.
666 SmallVector<CallSiteEntry, 64> CallSites;
667 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
672 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
673 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
674 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
675 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
676 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
682 SizeSites = CallSites.size() *
683 (SiteStartSize + SiteLengthSize + LandingPadSize);
685 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
686 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
688 SizeSites += MCAsmInfo::getULEB128Size(i);
692 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
693 unsigned TTypeFormat;
694 unsigned TypeFormatSize;
697 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
698 // that we're omitting that bit.
699 TTypeFormat = dwarf::DW_EH_PE_omit;
700 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
702 // Okay, we have actual filters or typeinfos to emit. As such, we need to
703 // pick a type encoding for them. We're about to emit a list of pointers to
704 // typeinfo objects at the end of the LSDA. However, unless we're in static
705 // mode, this reference will require a relocation by the dynamic linker.
707 // Because of this, we have a couple of options:
709 // 1) If we are in -static mode, we can always use an absolute reference
710 // from the LSDA, because the static linker will resolve it.
712 // 2) Otherwise, if the LSDA section is writable, we can output the direct
713 // reference to the typeinfo and allow the dynamic linker to relocate
714 // it. Since it is in a writable section, the dynamic linker won't
717 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
718 // we need to use some form of indirection. For example, on Darwin,
719 // we can output a statically-relocatable reference to a dyld stub. The
720 // offset to the stub is constant, but the contents are in a section
721 // that is updated by the dynamic linker. This is easy enough, but we
722 // need to tell the personality function of the unwinder to indirect
723 // through the dyld stub.
725 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
726 // somewhere. This predicate should be moved to a shared location that is
727 // in target-independent code.
729 if (LSDASection->getKind().isWriteable() ||
730 Asm->TM.getRelocationModel() == Reloc::Static)
731 TTypeFormat = dwarf::DW_EH_PE_absptr;
733 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
734 dwarf::DW_EH_PE_sdata4;
736 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
739 // Begin the exception table.
740 Asm->OutStreamer.SwitchSection(LSDASection);
741 Asm->EmitAlignment(2, 0, 0, false);
743 O << "GCC_except_table" << SubprogramCount << ":\n";
745 // The type infos need to be aligned. GCC does this by inserting padding just
746 // before the type infos. However, this changes the size of the exception
747 // table, so you need to take this into account when you output the exception
748 // table size. However, the size is output using a variable length encoding.
749 // So by increasing the size by inserting padding, you may increase the number
750 // of bytes used for writing the size. If it increases, say by one byte, then
751 // you now need to output one less byte of padding to get the type infos
752 // aligned. However this decreases the size of the exception table. This
753 // changes the value you have to output for the exception table size. Due to
754 // the variable length encoding, the number of bytes used for writing the
755 // length may decrease. If so, you then have to increase the amount of
756 // padding. And so on. If you look carefully at the GCC code you will see that
757 // it indeed does this in a loop, going on and on until the values stabilize.
758 // We chose another solution: don't output padding inside the table like GCC
759 // does, instead output it before the table.
760 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
761 unsigned TyOffset = sizeof(int8_t) + // Call site format
762 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
763 SizeSites + SizeActions + SizeTypes;
764 unsigned TotalSize = sizeof(int8_t) + // LPStart format
765 sizeof(int8_t) + // TType format
767 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
769 unsigned SizeAlign = (4 - TotalSize) & 3;
771 for (unsigned i = 0; i != SizeAlign; ++i) {
776 EmitLabel("exception", SubprogramCount);
779 SmallString<16> LSDAName;
780 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
781 "_LSDA_" << Asm->getFunctionNumber();
782 O << LSDAName.str() << ":\n";
786 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
787 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
789 Asm->EmitInt8(TTypeFormat);
790 Asm->EOL("@TType format", TTypeFormat);
793 Asm->EmitULEB128Bytes(TyOffset);
794 Asm->EOL("@TType base offset");
797 // SjLj Exception handling
799 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
800 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
801 Asm->EmitULEB128Bytes(SizeSites);
802 Asm->EOL("Call site table length");
804 // Emit the landing pad site information.
806 for (SmallVectorImpl<CallSiteEntry>::const_iterator
807 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
808 const CallSiteEntry &S = *I;
810 // Offset of the landing pad, counted in 16-byte bundles relative to the
812 Asm->EmitULEB128Bytes(idx);
813 Asm->EOL("Landing pad");
815 // Offset of the first associated action record, relative to the start of
816 // the action table. This value is biased by 1 (1 indicates the start of
817 // the action table), and 0 indicates that there are no actions.
818 Asm->EmitULEB128Bytes(S.Action);
822 // DWARF Exception handling
823 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
825 // The call-site table is a list of all call sites that may throw an
826 // exception (including C++ 'throw' statements) in the procedure
827 // fragment. It immediately follows the LSDA header. Each entry indicates,
828 // for a given call, the first corresponding action record and corresponding
831 // The table begins with the number of bytes, stored as an LEB128
832 // compressed, unsigned integer. The records immediately follow the record
833 // count. They are sorted in increasing call-site address. Each record
836 // * The position of the call-site.
837 // * The position of the landing pad.
838 // * The first action record for that call site.
840 // A missing entry in the call-site table indicates that a call is not
841 // supposed to throw.
843 // Emit the landing pad call site table.
844 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
845 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
846 Asm->EmitULEB128Bytes(SizeSites);
847 Asm->EOL("Call site table size");
849 for (SmallVectorImpl<CallSiteEntry>::const_iterator
850 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
851 const CallSiteEntry &S = *I;
852 const char *BeginTag;
853 unsigned BeginNumber;
856 BeginTag = "eh_func_begin";
857 BeginNumber = SubprogramCount;
860 BeginNumber = S.BeginLabel;
863 // Offset of the call site relative to the previous call site, counted in
864 // number of 16-byte bundles. The first call site is counted relative to
865 // the start of the procedure fragment.
866 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
868 Asm->EOL("Region start");
871 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
874 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
876 Asm->EOL("Region length");
878 // Offset of the landing pad, counted in 16-byte bundles relative to the
883 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
886 Asm->EOL("Landing pad");
888 // Offset of the first associated action record, relative to the start of
889 // the action table. This value is biased by 1 (1 indicates the start of
890 // the action table), and 0 indicates that there are no actions.
891 Asm->EmitULEB128Bytes(S.Action);
896 // Emit the Action Table.
897 for (SmallVectorImpl<ActionEntry>::const_iterator
898 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
899 const ActionEntry &Action = *I;
903 // Used by the runtime to match the type of the thrown exception to the
904 // type of the catch clauses or the types in the exception specification.
906 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
907 Asm->EOL("TypeInfo index");
911 // Self-relative signed displacement in bytes of the next action record,
912 // or 0 if there is no next action record.
914 Asm->EmitSLEB128Bytes(Action.NextAction);
915 Asm->EOL("Next action");
918 // Emit the Catch TypeInfos.
919 for (std::vector<GlobalVariable *>::const_reverse_iterator
920 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
921 const GlobalVariable *GV = *I;
925 O << Asm->Mang->getMangledName(GV);
930 Asm->EOL("TypeInfo");
933 // Emit the Exception Specifications.
934 for (std::vector<unsigned>::const_iterator
935 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
936 unsigned TypeID = *I;
937 Asm->EmitULEB128Bytes(TypeID);
939 Asm->EOL("Exception specification");
944 Asm->EmitAlignment(2, 0, 0, false);
947 /// EndModule - Emit all exception information that should come after the
949 void DwarfException::EndModule() {
950 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
953 if (!shouldEmitMovesModule && !shouldEmitTableModule)
956 if (TimePassesIsEnabled)
957 ExceptionTimer->startTimer();
959 const std::vector<Function *> Personalities = MMI->getPersonalities();
961 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
962 EmitCIE(Personalities[I], I);
964 for (std::vector<FunctionEHFrameInfo>::iterator
965 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
968 if (TimePassesIsEnabled)
969 ExceptionTimer->stopTimer();
972 /// BeginFunction - Gather pre-function exception information. Assumes it's
973 /// being emitted immediately after the function entry point.
974 void DwarfException::BeginFunction(MachineFunction *MF) {
975 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
977 if (TimePassesIsEnabled)
978 ExceptionTimer->startTimer();
981 shouldEmitTable = shouldEmitMoves = false;
983 // Map all labels and get rid of any dead landing pads.
984 MMI->TidyLandingPads();
986 // If any landing pads survive, we need an EH table.
987 if (!MMI->getLandingPads().empty())
988 shouldEmitTable = true;
990 // See if we need frame move info.
991 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
992 shouldEmitMoves = true;
994 if (shouldEmitMoves || shouldEmitTable)
995 // Assumes in correct section after the entry point.
996 EmitLabel("eh_func_begin", ++SubprogramCount);
998 shouldEmitTableModule |= shouldEmitTable;
999 shouldEmitMovesModule |= shouldEmitMoves;
1001 if (TimePassesIsEnabled)
1002 ExceptionTimer->stopTimer();
1005 /// EndFunction - Gather and emit post-function exception information.
1007 void DwarfException::EndFunction() {
1008 if (!shouldEmitMoves && !shouldEmitTable) return;
1010 if (TimePassesIsEnabled)
1011 ExceptionTimer->startTimer();
1013 EmitLabel("eh_func_end", SubprogramCount);
1014 EmitExceptionTable();
1016 std::string FunctionEHName =
1017 Asm->Mang->getMangledName(MF->getFunction(), ".eh",
1018 Asm->MAI->is_EHSymbolPrivate());
1020 // Save EH frame information
1021 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHName, SubprogramCount,
1022 MMI->getPersonalityIndex(),
1023 MF->getFrameInfo()->hasCalls(),
1024 !MMI->getLandingPads().empty(),
1025 MMI->getFrameMoves(),
1026 MF->getFunction()));
1028 // Record if this personality index uses a landing pad.
1029 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
1031 if (TimePassesIsEnabled)
1032 ExceptionTimer->stopTimer();