1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains support for writing DWARF exception info into asm files.
12 //===----------------------------------------------------------------------===//
14 #include "DwarfException.h"
15 #include "llvm/Module.h"
16 #include "llvm/CodeGen/MachineModuleInfo.h"
17 #include "llvm/CodeGen/MachineFrameInfo.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineLocation.h"
20 #include "llvm/MC/MCAsmInfo.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCStreamer.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/Target/Mangler.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Target/TargetFrameInfo.h"
29 #include "llvm/Target/TargetLoweringObjectFile.h"
30 #include "llvm/Target/TargetOptions.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
32 #include "llvm/Support/Dwarf.h"
33 #include "llvm/Support/FormattedStream.h"
34 #include "llvm/Support/Timer.h"
35 #include "llvm/ADT/SmallString.h"
36 #include "llvm/ADT/StringExtras.h"
39 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
41 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
42 shouldEmitTableModule(false), shouldEmitMovesModule(false),
44 if (TimePassesIsEnabled)
45 ExceptionTimer = new Timer("DWARF Exception Writer");
48 DwarfException::~DwarfException() {
49 delete ExceptionTimer;
52 /// SizeOfEncodedValue - Return the size of the encoding in bytes.
53 unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
54 if (Encoding == dwarf::DW_EH_PE_omit)
57 switch (Encoding & 0x07) {
58 case dwarf::DW_EH_PE_absptr:
59 return TD->getPointerSize();
60 case dwarf::DW_EH_PE_udata2:
62 case dwarf::DW_EH_PE_udata4:
64 case dwarf::DW_EH_PE_udata8:
68 assert(0 && "Invalid encoded value.");
72 /// CreateLabelDiff - Emit a label and subtract it from the expression we
73 /// already have. This is equivalent to emitting "foo - .", but we have to emit
74 /// the label for "." directly.
75 const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
76 const char *LabelName,
79 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
80 << LabelName << Asm->getFunctionNumber()
82 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
83 Asm->OutStreamer.EmitLabel(DotSym);
85 return MCBinaryExpr::CreateSub(ExprRef,
86 MCSymbolRefExpr::Create(DotSym,
91 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
92 /// is shared among many Frame Description Entries. There is at least one CIE
93 /// in every non-empty .debug_frame section.
94 void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
95 // Size and sign of stack growth.
97 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
98 TargetFrameInfo::StackGrowsUp ?
99 TD->getPointerSize() : -TD->getPointerSize();
101 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
103 // Begin eh frame section.
104 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
106 if (MAI->is_EHSymbolPrivate())
107 O << MAI->getPrivateGlobalPrefix();
108 O << "EH_frame" << Index << ":\n";
110 EmitLabel("section_eh_frame", Index);
112 // Define base labels.
113 EmitLabel("eh_frame_common", Index);
115 // Define the eh frame length.
116 EmitDifference("eh_frame_common_end", Index,
117 "eh_frame_common_begin", Index, true);
118 Asm->EOL("Length of Common Information Entry");
121 EmitLabel("eh_frame_common_begin", Index);
122 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
123 Asm->EOL("CIE Identifier Tag");
124 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
125 Asm->EOL("CIE Version");
127 // The personality presence indicates that language specific information will
128 // show up in the eh frame. Find out how we are supposed to lower the
129 // personality function reference:
130 const MCExpr *PersonalityRef = 0;
131 bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
133 // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
135 // In non-static mode, ask the object file how to represent this reference.
137 TLOF.getSymbolForDwarfGlobalReference(PersonalityFn, Asm->Mang,
139 IsPersonalityIndirect,
143 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
144 if (IsPersonalityIndirect)
145 PerEncoding |= dwarf::DW_EH_PE_indirect;
146 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
147 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
149 char Augmentation[5] = { 0 };
150 unsigned AugmentationSize = 0;
151 char *APtr = Augmentation + 1;
153 if (PersonalityRef) {
154 // There is a personality function.
156 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
159 if (UsesLSDA[Index]) {
160 // An LSDA pointer is in the FDE augmentation.
165 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
166 // A non-default pointer encoding for the FDE.
171 if (APtr != Augmentation + 1)
172 Augmentation[0] = 'z';
174 Asm->EmitString(Augmentation);
175 Asm->EOL("CIE Augmentation");
178 Asm->EmitULEB128Bytes(1);
179 Asm->EOL("CIE Code Alignment Factor");
180 Asm->EmitSLEB128Bytes(stackGrowth);
181 Asm->EOL("CIE Data Alignment Factor");
182 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
183 Asm->EOL("CIE Return Address Column");
185 Asm->EmitULEB128Bytes(AugmentationSize);
186 Asm->EOL("Augmentation Size");
188 Asm->EmitInt8(PerEncoding);
189 Asm->EOL("Personality", PerEncoding);
191 // If there is a personality, we need to indicate the function's location.
192 if (PersonalityRef) {
193 if (!IsPersonalityPCRel)
194 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
197 O << MAI->getData32bitsDirective() << *PersonalityRef;
198 Asm->EOL("Personality");
200 Asm->EmitInt8(LSDAEncoding);
201 Asm->EOL("LSDA Encoding", LSDAEncoding);
203 Asm->EmitInt8(FDEEncoding);
204 Asm->EOL("FDE Encoding", FDEEncoding);
207 // Indicate locations of general callee saved registers in frame.
208 std::vector<MachineMove> Moves;
209 RI->getInitialFrameState(Moves);
210 EmitFrameMoves(NULL, 0, Moves, true);
212 // On Darwin the linker honors the alignment of eh_frame, which means it must
213 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
214 // holes which confuse readers of eh_frame.
215 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
216 EmitLabel("eh_frame_common_end", Index);
220 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
221 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
222 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
223 "Should not emit 'available externally' functions at all");
225 const Function *TheFunc = EHFrameInfo.function;
227 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
229 // Externally visible entry into the functions eh frame info. If the
230 // corresponding function is static, this should not be externally visible.
231 if (!TheFunc->hasLocalLinkage())
232 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
233 O << GlobalEHDirective << *EHFrameInfo.FunctionEHSym << '\n';
235 // If corresponding function is weak definition, this should be too.
236 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
237 O << MAI->getWeakDefDirective() << *EHFrameInfo.FunctionEHSym << '\n';
239 // If corresponding function is hidden, this should be too.
240 if (TheFunc->hasHiddenVisibility())
241 if (const char *HiddenDirective = MAI->getHiddenDirective())
242 O << HiddenDirective << *EHFrameInfo.FunctionEHSym << '\n';
244 // If there are no calls then you can't unwind. This may mean we can omit the
245 // EH Frame, but some environments do not handle weak absolute symbols. If
246 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
247 // info is to be available for non-EH uses.
248 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
249 (!TheFunc->isWeakForLinker() ||
250 !MAI->getWeakDefDirective() ||
251 MAI->getSupportsWeakOmittedEHFrame())) {
252 O << *EHFrameInfo.FunctionEHSym << " = 0\n";
253 // This name has no connection to the function, so it might get
254 // dead-stripped when the function is not, erroneously. Prohibit
255 // dead-stripping unconditionally.
256 if (const char *UsedDirective = MAI->getUsedDirective())
257 O << UsedDirective << *EHFrameInfo.FunctionEHSym << "\n\n";
259 O << *EHFrameInfo.FunctionEHSym << ":\n";
262 EmitDifference("eh_frame_end", EHFrameInfo.Number,
263 "eh_frame_begin", EHFrameInfo.Number, true);
264 Asm->EOL("Length of Frame Information Entry");
266 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
268 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
269 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
272 Asm->EOL("FDE CIE offset");
274 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
275 Asm->EOL("FDE initial location");
276 EmitDifference("eh_func_end", EHFrameInfo.Number,
277 "eh_func_begin", EHFrameInfo.Number, true);
278 Asm->EOL("FDE address range");
280 // If there is a personality and landing pads then point to the language
281 // specific data area in the exception table.
282 if (MMI->getPersonalities()[0] != NULL) {
284 if (Asm->TM.getLSDAEncoding() != DwarfLSDAEncoding::EightByte) {
285 Asm->EmitULEB128Bytes(4);
286 Asm->EOL("Augmentation size");
288 if (EHFrameInfo.hasLandingPads)
289 EmitReference("exception", EHFrameInfo.Number, true, true);
291 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
293 Asm->EmitULEB128Bytes(TD->getPointerSize());
294 Asm->EOL("Augmentation size");
296 if (EHFrameInfo.hasLandingPads) {
297 EmitReference("exception", EHFrameInfo.Number, true, false);
299 Asm->OutStreamer.EmitIntValue(0, TD->getPointerSize(),
304 Asm->EOL("Language Specific Data Area");
306 Asm->EmitULEB128Bytes(0);
307 Asm->EOL("Augmentation size");
310 // Indicate locations of function specific callee saved registers in frame.
311 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
314 // On Darwin the linker honors the alignment of eh_frame, which means it
315 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
316 // get holes which confuse readers of eh_frame.
317 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
319 EmitLabel("eh_frame_end", EHFrameInfo.Number);
321 // If the function is marked used, this table should be also. We cannot
322 // make the mark unconditional in this case, since retaining the table also
323 // retains the function in this case, and there is code around that depends
324 // on unused functions (calling undefined externals) being dead-stripped to
325 // link correctly. Yes, there really is.
326 if (MMI->isUsedFunction(EHFrameInfo.function))
327 if (const char *UsedDirective = MAI->getUsedDirective())
328 O << UsedDirective << *EHFrameInfo.FunctionEHSym << "\n\n";
333 /// SharedTypeIds - How many leading type ids two landing pads have in common.
334 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
335 const LandingPadInfo *R) {
336 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
337 unsigned LSize = LIds.size(), RSize = RIds.size();
338 unsigned MinSize = LSize < RSize ? LSize : RSize;
341 for (; Count != MinSize; ++Count)
342 if (LIds[Count] != RIds[Count])
348 /// PadLT - Order landing pads lexicographically by type id.
349 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
350 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
351 unsigned LSize = LIds.size(), RSize = RIds.size();
352 unsigned MinSize = LSize < RSize ? LSize : RSize;
354 for (unsigned i = 0; i != MinSize; ++i)
355 if (LIds[i] != RIds[i])
356 return LIds[i] < RIds[i];
358 return LSize < RSize;
361 /// ComputeActionsTable - Compute the actions table and gather the first action
362 /// index for each landing pad site.
363 unsigned DwarfException::
364 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
365 SmallVectorImpl<ActionEntry> &Actions,
366 SmallVectorImpl<unsigned> &FirstActions) {
368 // The action table follows the call-site table in the LSDA. The individual
369 // records are of two types:
372 // * Exception specification
374 // The two record kinds have the same format, with only small differences.
375 // They are distinguished by the "switch value" field: Catch clauses
376 // (TypeInfos) have strictly positive switch values, and exception
377 // specifications (FilterIds) have strictly negative switch values. Value 0
378 // indicates a catch-all clause.
380 // Negative type IDs index into FilterIds. Positive type IDs index into
381 // TypeInfos. The value written for a positive type ID is just the type ID
382 // itself. For a negative type ID, however, the value written is the
383 // (negative) byte offset of the corresponding FilterIds entry. The byte
384 // offset is usually equal to the type ID (because the FilterIds entries are
385 // written using a variable width encoding, which outputs one byte per entry
386 // as long as the value written is not too large) but can differ. This kind
387 // of complication does not occur for positive type IDs because type infos are
388 // output using a fixed width encoding. FilterOffsets[i] holds the byte
389 // offset corresponding to FilterIds[i].
391 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
392 SmallVector<int, 16> FilterOffsets;
393 FilterOffsets.reserve(FilterIds.size());
396 for (std::vector<unsigned>::const_iterator
397 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
398 FilterOffsets.push_back(Offset);
399 Offset -= MCAsmInfo::getULEB128Size(*I);
402 FirstActions.reserve(LandingPads.size());
405 unsigned SizeActions = 0;
406 const LandingPadInfo *PrevLPI = 0;
408 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
409 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
410 const LandingPadInfo *LPI = *I;
411 const std::vector<int> &TypeIds = LPI->TypeIds;
412 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
413 unsigned SizeSiteActions = 0;
415 if (NumShared < TypeIds.size()) {
416 unsigned SizeAction = 0;
417 ActionEntry *PrevAction = 0;
420 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
421 assert(Actions.size());
422 PrevAction = &Actions.back();
423 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
424 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
426 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
428 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
429 SizeAction += -PrevAction->NextAction;
430 PrevAction = PrevAction->Previous;
434 // Compute the actions.
435 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
436 int TypeID = TypeIds[J];
437 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
438 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
439 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
441 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
442 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
443 SizeSiteActions += SizeAction;
445 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
446 Actions.push_back(Action);
447 PrevAction = &Actions.back();
450 // Record the first action of the landing pad site.
451 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
452 } // else identical - re-use previous FirstAction
454 // Information used when created the call-site table. The action record
455 // field of the call site record is the offset of the first associated
456 // action record, relative to the start of the actions table. This value is
457 // biased by 1 (1 in dicating the start of the actions table), and 0
458 // indicates that there are no actions.
459 FirstActions.push_back(FirstAction);
461 // Compute this sites contribution to size.
462 SizeActions += SizeSiteActions;
470 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
471 /// marked `nounwind'. Return `false' otherwise.
472 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
473 assert(MI->getDesc().isCall() && "This should be a call instruction!");
475 bool MarkedNoUnwind = false;
476 bool SawFunc = false;
478 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
479 const MachineOperand &MO = MI->getOperand(I);
482 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
484 // Be conservative. If we have more than one function operand for this
485 // call, then we can't make the assumption that it's the callee and
486 // not a parameter to the call.
488 // FIXME: Determine if there's a way to say that `F' is the callee or
490 MarkedNoUnwind = false;
494 MarkedNoUnwind = F->doesNotThrow();
500 return MarkedNoUnwind;
503 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
504 /// has a try-range containing the call, a non-zero landing pad, and an
505 /// appropriate action. The entry for an ordinary call has a try-range
506 /// containing the call and zero for the landing pad and the action. Calls
507 /// marked 'nounwind' have no entry and must not be contained in the try-range
508 /// of any entry - they form gaps in the table. Entries must be ordered by
509 /// try-range address.
510 void DwarfException::
511 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
512 const RangeMapType &PadMap,
513 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
514 const SmallVectorImpl<unsigned> &FirstActions) {
515 // The end label of the previous invoke or nounwind try-range.
516 unsigned LastLabel = 0;
518 // Whether there is a potentially throwing instruction (currently this means
519 // an ordinary call) between the end of the previous try-range and now.
520 bool SawPotentiallyThrowing = false;
522 // Whether the last CallSite entry was for an invoke.
523 bool PreviousIsInvoke = false;
525 // Visit all instructions in order of address.
526 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
528 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
530 if (!MI->isLabel()) {
531 if (MI->getDesc().isCall())
532 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
537 unsigned BeginLabel = MI->getOperand(0).getImm();
538 assert(BeginLabel && "Invalid label!");
540 // End of the previous try-range?
541 if (BeginLabel == LastLabel)
542 SawPotentiallyThrowing = false;
544 // Beginning of a new try-range?
545 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
546 if (L == PadMap.end())
547 // Nope, it was just some random label.
550 const PadRange &P = L->second;
551 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
552 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
553 "Inconsistent landing pad map!");
555 // For Dwarf exception handling (SjLj handling doesn't use this). If some
556 // instruction between the previous try-range and this one may throw,
557 // create a call-site entry with no landing pad for the region between the
559 if (SawPotentiallyThrowing &&
560 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
561 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
562 CallSites.push_back(Site);
563 PreviousIsInvoke = false;
566 LastLabel = LandingPad->EndLabels[P.RangeIndex];
567 assert(BeginLabel && LastLabel && "Invalid landing pad!");
569 if (LandingPad->LandingPadLabel) {
570 // This try-range is for an invoke.
571 CallSiteEntry Site = {
574 LandingPad->LandingPadLabel,
575 FirstActions[P.PadIndex]
578 // Try to merge with the previous call-site. SJLJ doesn't do this
579 if (PreviousIsInvoke &&
580 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
581 CallSiteEntry &Prev = CallSites.back();
582 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
583 // Extend the range of the previous entry.
584 Prev.EndLabel = Site.EndLabel;
589 // Otherwise, create a new call-site.
590 CallSites.push_back(Site);
591 PreviousIsInvoke = true;
594 PreviousIsInvoke = false;
599 // If some instruction between the previous try-range and the end of the
600 // function may throw, create a call-site entry with no landing pad for the
601 // region following the try-range.
602 if (SawPotentiallyThrowing &&
603 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
604 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
605 CallSites.push_back(Site);
609 /// EmitExceptionTable - Emit landing pads and actions.
611 /// The general organization of the table is complex, but the basic concepts are
612 /// easy. First there is a header which describes the location and organization
613 /// of the three components that follow.
615 /// 1. The landing pad site information describes the range of code covered by
616 /// the try. In our case it's an accumulation of the ranges covered by the
617 /// invokes in the try. There is also a reference to the landing pad that
618 /// handles the exception once processed. Finally an index into the actions
620 /// 2. The action table, in our case, is composed of pairs of type IDs and next
621 /// action offset. Starting with the action index from the landing pad
622 /// site, each type ID is checked for a match to the current exception. If
623 /// it matches then the exception and type id are passed on to the landing
624 /// pad. Otherwise the next action is looked up. This chain is terminated
625 /// with a next action of zero. If no type id is found then the frame is
626 /// unwound and handling continues.
627 /// 3. Type ID table contains references to all the C++ typeinfo for all
628 /// catches in the function. This tables is reverse indexed base 1.
629 void DwarfException::EmitExceptionTable() {
630 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
631 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
632 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
633 if (PadInfos.empty()) return;
635 // Sort the landing pads in order of their type ids. This is used to fold
636 // duplicate actions.
637 SmallVector<const LandingPadInfo *, 64> LandingPads;
638 LandingPads.reserve(PadInfos.size());
640 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
641 LandingPads.push_back(&PadInfos[i]);
643 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
645 // Compute the actions table and gather the first action index for each
647 SmallVector<ActionEntry, 32> Actions;
648 SmallVector<unsigned, 64> FirstActions;
649 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
652 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
653 // by try-range labels when lowered). Ordinary calls do not, so appropriate
654 // try-ranges for them need be deduced when using DWARF exception handling.
656 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
657 const LandingPadInfo *LandingPad = LandingPads[i];
658 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
659 unsigned BeginLabel = LandingPad->BeginLabels[j];
660 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
661 PadRange P = { i, j };
662 PadMap[BeginLabel] = P;
666 // Compute the call-site table.
667 SmallVector<CallSiteEntry, 64> CallSites;
668 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
673 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
674 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
675 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
676 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
677 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
683 SizeSites = CallSites.size() *
684 (SiteStartSize + SiteLengthSize + LandingPadSize);
686 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
687 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
689 SizeSites += MCAsmInfo::getULEB128Size(i);
693 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
694 unsigned TTypeFormat;
695 unsigned TypeFormatSize;
698 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
699 // that we're omitting that bit.
700 TTypeFormat = dwarf::DW_EH_PE_omit;
701 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
703 // Okay, we have actual filters or typeinfos to emit. As such, we need to
704 // pick a type encoding for them. We're about to emit a list of pointers to
705 // typeinfo objects at the end of the LSDA. However, unless we're in static
706 // mode, this reference will require a relocation by the dynamic linker.
708 // Because of this, we have a couple of options:
710 // 1) If we are in -static mode, we can always use an absolute reference
711 // from the LSDA, because the static linker will resolve it.
713 // 2) Otherwise, if the LSDA section is writable, we can output the direct
714 // reference to the typeinfo and allow the dynamic linker to relocate
715 // it. Since it is in a writable section, the dynamic linker won't
718 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
719 // we need to use some form of indirection. For example, on Darwin,
720 // we can output a statically-relocatable reference to a dyld stub. The
721 // offset to the stub is constant, but the contents are in a section
722 // that is updated by the dynamic linker. This is easy enough, but we
723 // need to tell the personality function of the unwinder to indirect
724 // through the dyld stub.
726 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
727 // somewhere. This predicate should be moved to a shared location that is
728 // in target-independent code.
730 if (LSDASection->getKind().isWriteable() ||
731 Asm->TM.getRelocationModel() == Reloc::Static)
732 TTypeFormat = dwarf::DW_EH_PE_absptr;
734 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
735 dwarf::DW_EH_PE_sdata4;
737 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
740 // Begin the exception table.
741 Asm->OutStreamer.SwitchSection(LSDASection);
742 Asm->EmitAlignment(2, 0, 0, false);
744 O << "GCC_except_table" << SubprogramCount << ":\n";
746 // The type infos need to be aligned. GCC does this by inserting padding just
747 // before the type infos. However, this changes the size of the exception
748 // table, so you need to take this into account when you output the exception
749 // table size. However, the size is output using a variable length encoding.
750 // So by increasing the size by inserting padding, you may increase the number
751 // of bytes used for writing the size. If it increases, say by one byte, then
752 // you now need to output one less byte of padding to get the type infos
753 // aligned. However this decreases the size of the exception table. This
754 // changes the value you have to output for the exception table size. Due to
755 // the variable length encoding, the number of bytes used for writing the
756 // length may decrease. If so, you then have to increase the amount of
757 // padding. And so on. If you look carefully at the GCC code you will see that
758 // it indeed does this in a loop, going on and on until the values stabilize.
759 // We chose another solution: don't output padding inside the table like GCC
760 // does, instead output it before the table.
761 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
762 unsigned TyOffset = sizeof(int8_t) + // Call site format
763 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
764 SizeSites + SizeActions + SizeTypes;
765 unsigned TotalSize = sizeof(int8_t) + // LPStart format
766 sizeof(int8_t) + // TType format
768 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
770 unsigned SizeAlign = (4 - TotalSize) & 3;
772 for (unsigned i = 0; i != SizeAlign; ++i) {
777 EmitLabel("exception", SubprogramCount);
780 SmallString<16> LSDAName;
781 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
782 "_LSDA_" << Asm->getFunctionNumber();
783 O << LSDAName.str() << ":\n";
787 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
788 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
790 Asm->EmitInt8(TTypeFormat);
791 Asm->EOL("@TType format", TTypeFormat);
794 Asm->EmitULEB128Bytes(TyOffset);
795 Asm->EOL("@TType base offset");
798 // SjLj Exception handling
800 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
801 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
802 Asm->EmitULEB128Bytes(SizeSites);
803 Asm->EOL("Call site table length");
805 // Emit the landing pad site information.
807 for (SmallVectorImpl<CallSiteEntry>::const_iterator
808 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
809 const CallSiteEntry &S = *I;
811 // Offset of the landing pad, counted in 16-byte bundles relative to the
813 Asm->EmitULEB128Bytes(idx);
814 Asm->EOL("Landing pad");
816 // Offset of the first associated action record, relative to the start of
817 // the action table. This value is biased by 1 (1 indicates the start of
818 // the action table), and 0 indicates that there are no actions.
819 Asm->EmitULEB128Bytes(S.Action);
823 // DWARF Exception handling
824 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
826 // The call-site table is a list of all call sites that may throw an
827 // exception (including C++ 'throw' statements) in the procedure
828 // fragment. It immediately follows the LSDA header. Each entry indicates,
829 // for a given call, the first corresponding action record and corresponding
832 // The table begins with the number of bytes, stored as an LEB128
833 // compressed, unsigned integer. The records immediately follow the record
834 // count. They are sorted in increasing call-site address. Each record
837 // * The position of the call-site.
838 // * The position of the landing pad.
839 // * The first action record for that call site.
841 // A missing entry in the call-site table indicates that a call is not
842 // supposed to throw.
844 // Emit the landing pad call site table.
845 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
846 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
847 Asm->EmitULEB128Bytes(SizeSites);
848 Asm->EOL("Call site table size");
850 for (SmallVectorImpl<CallSiteEntry>::const_iterator
851 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
852 const CallSiteEntry &S = *I;
853 const char *BeginTag;
854 unsigned BeginNumber;
857 BeginTag = "eh_func_begin";
858 BeginNumber = SubprogramCount;
861 BeginNumber = S.BeginLabel;
864 // Offset of the call site relative to the previous call site, counted in
865 // number of 16-byte bundles. The first call site is counted relative to
866 // the start of the procedure fragment.
867 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
869 Asm->EOL("Region start");
872 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
875 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
877 Asm->EOL("Region length");
879 // Offset of the landing pad, counted in 16-byte bundles relative to the
882 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
884 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
887 Asm->EOL("Landing pad");
889 // Offset of the first associated action record, relative to the start of
890 // the action table. This value is biased by 1 (1 indicates the start of
891 // the action table), and 0 indicates that there are no actions.
892 Asm->EmitULEB128Bytes(S.Action);
897 // Emit the Action Table.
898 for (SmallVectorImpl<ActionEntry>::const_iterator
899 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
900 const ActionEntry &Action = *I;
904 // Used by the runtime to match the type of the thrown exception to the
905 // type of the catch clauses or the types in the exception specification.
907 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
908 Asm->EOL("TypeInfo index");
912 // Self-relative signed displacement in bytes of the next action record,
913 // or 0 if there is no next action record.
915 Asm->EmitSLEB128Bytes(Action.NextAction);
916 Asm->EOL("Next action");
919 // Emit the Catch TypeInfos.
920 for (std::vector<GlobalVariable *>::const_reverse_iterator
921 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
922 const GlobalVariable *GV = *I;
926 O << *Asm->GetGlobalValueSymbol(GV);
931 Asm->EOL("TypeInfo");
934 // Emit the Exception Specifications.
935 for (std::vector<unsigned>::const_iterator
936 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
937 unsigned TypeID = *I;
938 Asm->EmitULEB128Bytes(TypeID);
940 Asm->EOL("Exception specification");
945 Asm->EmitAlignment(2, 0, 0, false);
948 /// EndModule - Emit all exception information that should come after the
950 void DwarfException::EndModule() {
951 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
954 if (!shouldEmitMovesModule && !shouldEmitTableModule)
957 if (TimePassesIsEnabled)
958 ExceptionTimer->startTimer();
960 const std::vector<Function *> Personalities = MMI->getPersonalities();
962 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
963 EmitCIE(Personalities[I], I);
965 for (std::vector<FunctionEHFrameInfo>::iterator
966 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
969 if (TimePassesIsEnabled)
970 ExceptionTimer->stopTimer();
973 /// BeginFunction - Gather pre-function exception information. Assumes it's
974 /// being emitted immediately after the function entry point.
975 void DwarfException::BeginFunction(MachineFunction *MF) {
976 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
978 if (TimePassesIsEnabled)
979 ExceptionTimer->startTimer();
982 shouldEmitTable = shouldEmitMoves = false;
984 // Map all labels and get rid of any dead landing pads.
985 MMI->TidyLandingPads();
987 // If any landing pads survive, we need an EH table.
988 if (!MMI->getLandingPads().empty())
989 shouldEmitTable = true;
991 // See if we need frame move info.
992 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
993 shouldEmitMoves = true;
995 if (shouldEmitMoves || shouldEmitTable)
996 // Assumes in correct section after the entry point.
997 EmitLabel("eh_func_begin", ++SubprogramCount);
999 shouldEmitTableModule |= shouldEmitTable;
1000 shouldEmitMovesModule |= shouldEmitMoves;
1002 if (TimePassesIsEnabled)
1003 ExceptionTimer->stopTimer();
1006 /// EndFunction - Gather and emit post-function exception information.
1008 void DwarfException::EndFunction() {
1009 if (!shouldEmitMoves && !shouldEmitTable) return;
1011 if (TimePassesIsEnabled)
1012 ExceptionTimer->startTimer();
1014 EmitLabel("eh_func_end", SubprogramCount);
1015 EmitExceptionTable();
1017 const MCSymbol *FunctionEHSym =
1018 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
1019 Asm->MAI->is_EHSymbolPrivate());
1021 // Save EH frame information
1022 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
1023 MMI->getPersonalityIndex(),
1024 MF->getFrameInfo()->hasCalls(),
1025 !MMI->getLandingPads().empty(),
1026 MMI->getFrameMoves(),
1027 MF->getFunction()));
1029 // Record if this personality index uses a landing pad.
1030 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
1032 if (TimePassesIsEnabled)
1033 ExceptionTimer->stopTimer();