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 : DwarfPrinter(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 if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("CIE Identifier Tag");
123 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
124 if (Asm->VerboseAsm) Asm->OutStreamer.AddComment("DW_CIE_VERSION");
125 Asm->OutStreamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1/*size*/, 0/*addr*/);
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 EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
181 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
182 Asm->EOL("CIE Return Address Column");
184 Asm->EmitULEB128Bytes(AugmentationSize);
185 Asm->EOL("Augmentation Size");
187 EmitEncodingByte(PerEncoding, "Personality");
189 // If there is a personality, we need to indicate the function's location.
190 if (PersonalityRef) {
191 if (!IsPersonalityPCRel)
192 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
195 O << MAI->getData32bitsDirective() << *PersonalityRef;
196 Asm->EOL("Personality");
198 EmitEncodingByte(LSDAEncoding, "LSDA");
199 EmitEncodingByte(FDEEncoding, "FDE");
202 // Indicate locations of general callee saved registers in frame.
203 std::vector<MachineMove> Moves;
204 RI->getInitialFrameState(Moves);
205 EmitFrameMoves(NULL, 0, Moves, true);
207 // On Darwin the linker honors the alignment of eh_frame, which means it must
208 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
209 // holes which confuse readers of eh_frame.
210 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
211 EmitLabel("eh_frame_common_end", Index);
215 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
216 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
217 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
218 "Should not emit 'available externally' functions at all");
220 const Function *TheFunc = EHFrameInfo.function;
222 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
224 // Externally visible entry into the functions eh frame info. If the
225 // corresponding function is static, this should not be externally visible.
226 if (!TheFunc->hasLocalLinkage())
227 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
228 O << GlobalEHDirective << *EHFrameInfo.FunctionEHSym << '\n';
230 // If corresponding function is weak definition, this should be too.
231 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
232 O << MAI->getWeakDefDirective() << *EHFrameInfo.FunctionEHSym << '\n';
234 // If corresponding function is hidden, this should be too.
235 if (TheFunc->hasHiddenVisibility())
236 if (const char *HiddenDirective = MAI->getHiddenDirective())
237 O << HiddenDirective << *EHFrameInfo.FunctionEHSym << '\n';
239 // If there are no calls then you can't unwind. This may mean we can omit the
240 // EH Frame, but some environments do not handle weak absolute symbols. If
241 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
242 // info is to be available for non-EH uses.
243 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
244 (!TheFunc->isWeakForLinker() ||
245 !MAI->getWeakDefDirective() ||
246 MAI->getSupportsWeakOmittedEHFrame())) {
247 O << *EHFrameInfo.FunctionEHSym << " = 0\n";
248 // This name has no connection to the function, so it might get
249 // dead-stripped when the function is not, erroneously. Prohibit
250 // dead-stripping unconditionally.
251 if (const char *UsedDirective = MAI->getUsedDirective())
252 O << UsedDirective << *EHFrameInfo.FunctionEHSym << "\n\n";
254 O << *EHFrameInfo.FunctionEHSym << ":\n";
257 EmitDifference("eh_frame_end", EHFrameInfo.Number,
258 "eh_frame_begin", EHFrameInfo.Number, true);
259 Asm->EOL("Length of Frame Information Entry");
261 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
263 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
264 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
267 Asm->EOL("FDE CIE offset");
269 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
270 Asm->EOL("FDE initial location");
271 EmitDifference("eh_func_end", EHFrameInfo.Number,
272 "eh_func_begin", EHFrameInfo.Number, true);
273 Asm->EOL("FDE address range");
275 // If there is a personality and landing pads then point to the language
276 // specific data area in the exception table.
277 if (MMI->getPersonalities()[0] != NULL) {
279 if (Asm->TM.getLSDAEncoding() != DwarfLSDAEncoding::EightByte) {
280 Asm->EmitULEB128Bytes(4);
281 Asm->EOL("Augmentation size");
283 if (EHFrameInfo.hasLandingPads)
284 EmitReference("exception", EHFrameInfo.Number, true, true);
286 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
288 Asm->EmitULEB128Bytes(TD->getPointerSize());
289 Asm->EOL("Augmentation size");
291 if (EHFrameInfo.hasLandingPads) {
292 EmitReference("exception", EHFrameInfo.Number, true, false);
294 Asm->OutStreamer.EmitIntValue(0, TD->getPointerSize(),
299 Asm->EOL("Language Specific Data Area");
301 Asm->EmitULEB128Bytes(0);
302 Asm->EOL("Augmentation size");
305 // Indicate locations of function specific callee saved registers in frame.
306 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
309 // On Darwin the linker honors the alignment of eh_frame, which means it
310 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
311 // get holes which confuse readers of eh_frame.
312 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
314 EmitLabel("eh_frame_end", EHFrameInfo.Number);
316 // If the function is marked used, this table should be also. We cannot
317 // make the mark unconditional in this case, since retaining the table also
318 // retains the function in this case, and there is code around that depends
319 // on unused functions (calling undefined externals) being dead-stripped to
320 // link correctly. Yes, there really is.
321 if (MMI->isUsedFunction(EHFrameInfo.function))
322 if (const char *UsedDirective = MAI->getUsedDirective())
323 O << UsedDirective << *EHFrameInfo.FunctionEHSym << "\n\n";
328 /// SharedTypeIds - How many leading type ids two landing pads have in common.
329 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
330 const LandingPadInfo *R) {
331 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
332 unsigned LSize = LIds.size(), RSize = RIds.size();
333 unsigned MinSize = LSize < RSize ? LSize : RSize;
336 for (; Count != MinSize; ++Count)
337 if (LIds[Count] != RIds[Count])
343 /// PadLT - Order landing pads lexicographically by type id.
344 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
345 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
346 unsigned LSize = LIds.size(), RSize = RIds.size();
347 unsigned MinSize = LSize < RSize ? LSize : RSize;
349 for (unsigned i = 0; i != MinSize; ++i)
350 if (LIds[i] != RIds[i])
351 return LIds[i] < RIds[i];
353 return LSize < RSize;
356 /// ComputeActionsTable - Compute the actions table and gather the first action
357 /// index for each landing pad site.
358 unsigned DwarfException::
359 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
360 SmallVectorImpl<ActionEntry> &Actions,
361 SmallVectorImpl<unsigned> &FirstActions) {
363 // The action table follows the call-site table in the LSDA. The individual
364 // records are of two types:
367 // * Exception specification
369 // The two record kinds have the same format, with only small differences.
370 // They are distinguished by the "switch value" field: Catch clauses
371 // (TypeInfos) have strictly positive switch values, and exception
372 // specifications (FilterIds) have strictly negative switch values. Value 0
373 // indicates a catch-all clause.
375 // Negative type IDs index into FilterIds. Positive type IDs index into
376 // TypeInfos. The value written for a positive type ID is just the type ID
377 // itself. For a negative type ID, however, the value written is the
378 // (negative) byte offset of the corresponding FilterIds entry. The byte
379 // offset is usually equal to the type ID (because the FilterIds entries are
380 // written using a variable width encoding, which outputs one byte per entry
381 // as long as the value written is not too large) but can differ. This kind
382 // of complication does not occur for positive type IDs because type infos are
383 // output using a fixed width encoding. FilterOffsets[i] holds the byte
384 // offset corresponding to FilterIds[i].
386 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
387 SmallVector<int, 16> FilterOffsets;
388 FilterOffsets.reserve(FilterIds.size());
391 for (std::vector<unsigned>::const_iterator
392 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
393 FilterOffsets.push_back(Offset);
394 Offset -= MCAsmInfo::getULEB128Size(*I);
397 FirstActions.reserve(LandingPads.size());
400 unsigned SizeActions = 0;
401 const LandingPadInfo *PrevLPI = 0;
403 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
404 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
405 const LandingPadInfo *LPI = *I;
406 const std::vector<int> &TypeIds = LPI->TypeIds;
407 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
408 unsigned SizeSiteActions = 0;
410 if (NumShared < TypeIds.size()) {
411 unsigned SizeAction = 0;
412 ActionEntry *PrevAction = 0;
415 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
416 assert(Actions.size());
417 PrevAction = &Actions.back();
418 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
419 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
421 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
423 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
424 SizeAction += -PrevAction->NextAction;
425 PrevAction = PrevAction->Previous;
429 // Compute the actions.
430 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
431 int TypeID = TypeIds[J];
432 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
433 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
434 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
436 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
437 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
438 SizeSiteActions += SizeAction;
440 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
441 Actions.push_back(Action);
442 PrevAction = &Actions.back();
445 // Record the first action of the landing pad site.
446 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
447 } // else identical - re-use previous FirstAction
449 // Information used when created the call-site table. The action record
450 // field of the call site record is the offset of the first associated
451 // action record, relative to the start of the actions table. This value is
452 // biased by 1 (1 in dicating the start of the actions table), and 0
453 // indicates that there are no actions.
454 FirstActions.push_back(FirstAction);
456 // Compute this sites contribution to size.
457 SizeActions += SizeSiteActions;
465 /// CallToNoUnwindFunction - Return `true' if this is a call to a function
466 /// marked `nounwind'. Return `false' otherwise.
467 bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
468 assert(MI->getDesc().isCall() && "This should be a call instruction!");
470 bool MarkedNoUnwind = false;
471 bool SawFunc = false;
473 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
474 const MachineOperand &MO = MI->getOperand(I);
477 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
479 // Be conservative. If we have more than one function operand for this
480 // call, then we can't make the assumption that it's the callee and
481 // not a parameter to the call.
483 // FIXME: Determine if there's a way to say that `F' is the callee or
485 MarkedNoUnwind = false;
489 MarkedNoUnwind = F->doesNotThrow();
495 return MarkedNoUnwind;
498 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
499 /// has a try-range containing the call, a non-zero landing pad, and an
500 /// appropriate action. The entry for an ordinary call has a try-range
501 /// containing the call and zero for the landing pad and the action. Calls
502 /// marked 'nounwind' have no entry and must not be contained in the try-range
503 /// of any entry - they form gaps in the table. Entries must be ordered by
504 /// try-range address.
505 void DwarfException::
506 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
507 const RangeMapType &PadMap,
508 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
509 const SmallVectorImpl<unsigned> &FirstActions) {
510 // The end label of the previous invoke or nounwind try-range.
511 unsigned LastLabel = 0;
513 // Whether there is a potentially throwing instruction (currently this means
514 // an ordinary call) between the end of the previous try-range and now.
515 bool SawPotentiallyThrowing = false;
517 // Whether the last CallSite entry was for an invoke.
518 bool PreviousIsInvoke = false;
520 // Visit all instructions in order of address.
521 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
523 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
525 if (!MI->isLabel()) {
526 if (MI->getDesc().isCall())
527 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
532 unsigned BeginLabel = MI->getOperand(0).getImm();
533 assert(BeginLabel && "Invalid label!");
535 // End of the previous try-range?
536 if (BeginLabel == LastLabel)
537 SawPotentiallyThrowing = false;
539 // Beginning of a new try-range?
540 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
541 if (L == PadMap.end())
542 // Nope, it was just some random label.
545 const PadRange &P = L->second;
546 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
547 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
548 "Inconsistent landing pad map!");
550 // For Dwarf exception handling (SjLj handling doesn't use this). If some
551 // instruction between the previous try-range and this one may throw,
552 // create a call-site entry with no landing pad for the region between the
554 if (SawPotentiallyThrowing &&
555 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
556 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
557 CallSites.push_back(Site);
558 PreviousIsInvoke = false;
561 LastLabel = LandingPad->EndLabels[P.RangeIndex];
562 assert(BeginLabel && LastLabel && "Invalid landing pad!");
564 if (LandingPad->LandingPadLabel) {
565 // This try-range is for an invoke.
566 CallSiteEntry Site = {
569 LandingPad->LandingPadLabel,
570 FirstActions[P.PadIndex]
573 // Try to merge with the previous call-site. SJLJ doesn't do this
574 if (PreviousIsInvoke &&
575 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
576 CallSiteEntry &Prev = CallSites.back();
577 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
578 // Extend the range of the previous entry.
579 Prev.EndLabel = Site.EndLabel;
584 // Otherwise, create a new call-site.
585 CallSites.push_back(Site);
586 PreviousIsInvoke = true;
589 PreviousIsInvoke = false;
594 // If some instruction between the previous try-range and the end of the
595 // function may throw, create a call-site entry with no landing pad for the
596 // region following the try-range.
597 if (SawPotentiallyThrowing &&
598 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
599 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
600 CallSites.push_back(Site);
604 /// EmitExceptionTable - Emit landing pads and actions.
606 /// The general organization of the table is complex, but the basic concepts are
607 /// easy. First there is a header which describes the location and organization
608 /// of the three components that follow.
610 /// 1. The landing pad site information describes the range of code covered by
611 /// the try. In our case it's an accumulation of the ranges covered by the
612 /// invokes in the try. There is also a reference to the landing pad that
613 /// handles the exception once processed. Finally an index into the actions
615 /// 2. The action table, in our case, is composed of pairs of type IDs and next
616 /// action offset. Starting with the action index from the landing pad
617 /// site, each type ID is checked for a match to the current exception. If
618 /// it matches then the exception and type id are passed on to the landing
619 /// pad. Otherwise the next action is looked up. This chain is terminated
620 /// with a next action of zero. If no type id is found then the frame is
621 /// unwound and handling continues.
622 /// 3. Type ID table contains references to all the C++ typeinfo for all
623 /// catches in the function. This tables is reverse indexed base 1.
624 void DwarfException::EmitExceptionTable() {
625 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
626 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
627 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
628 if (PadInfos.empty()) return;
630 // Sort the landing pads in order of their type ids. This is used to fold
631 // duplicate actions.
632 SmallVector<const LandingPadInfo *, 64> LandingPads;
633 LandingPads.reserve(PadInfos.size());
635 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
636 LandingPads.push_back(&PadInfos[i]);
638 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
640 // Compute the actions table and gather the first action index for each
642 SmallVector<ActionEntry, 32> Actions;
643 SmallVector<unsigned, 64> FirstActions;
644 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
647 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
648 // by try-range labels when lowered). Ordinary calls do not, so appropriate
649 // try-ranges for them need be deduced when using DWARF exception handling.
651 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
652 const LandingPadInfo *LandingPad = LandingPads[i];
653 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
654 unsigned BeginLabel = LandingPad->BeginLabels[j];
655 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
656 PadRange P = { i, j };
657 PadMap[BeginLabel] = P;
661 // Compute the call-site table.
662 SmallVector<CallSiteEntry, 64> CallSites;
663 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
668 const unsigned SiteStartSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
669 const unsigned SiteLengthSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
670 const unsigned LandingPadSize = SizeOfEncodedValue(dwarf::DW_EH_PE_udata4);
671 bool IsSJLJ = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
672 bool HaveTTData = IsSJLJ ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
678 SizeSites = CallSites.size() *
679 (SiteStartSize + SiteLengthSize + LandingPadSize);
681 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
682 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
684 SizeSites += MCAsmInfo::getULEB128Size(i);
688 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
689 unsigned TTypeFormat;
690 unsigned TypeFormatSize;
693 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly say
694 // that we're omitting that bit.
695 TTypeFormat = dwarf::DW_EH_PE_omit;
696 TypeFormatSize = SizeOfEncodedValue(dwarf::DW_EH_PE_absptr);
698 // Okay, we have actual filters or typeinfos to emit. As such, we need to
699 // pick a type encoding for them. We're about to emit a list of pointers to
700 // typeinfo objects at the end of the LSDA. However, unless we're in static
701 // mode, this reference will require a relocation by the dynamic linker.
703 // Because of this, we have a couple of options:
705 // 1) If we are in -static mode, we can always use an absolute reference
706 // from the LSDA, because the static linker will resolve it.
708 // 2) Otherwise, if the LSDA section is writable, we can output the direct
709 // reference to the typeinfo and allow the dynamic linker to relocate
710 // it. Since it is in a writable section, the dynamic linker won't
713 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
714 // we need to use some form of indirection. For example, on Darwin,
715 // we can output a statically-relocatable reference to a dyld stub. The
716 // offset to the stub is constant, but the contents are in a section
717 // that is updated by the dynamic linker. This is easy enough, but we
718 // need to tell the personality function of the unwinder to indirect
719 // through the dyld stub.
721 // FIXME: When (3) is actually implemented, we'll have to emit the stubs
722 // somewhere. This predicate should be moved to a shared location that is
723 // in target-independent code.
725 if (LSDASection->getKind().isWriteable() ||
726 Asm->TM.getRelocationModel() == Reloc::Static)
727 TTypeFormat = dwarf::DW_EH_PE_absptr;
729 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
730 dwarf::DW_EH_PE_sdata4;
732 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
735 // Begin the exception table.
736 Asm->OutStreamer.SwitchSection(LSDASection);
737 Asm->EmitAlignment(2, 0, 0, false);
739 O << "GCC_except_table" << SubprogramCount << ":\n";
741 // The type infos need to be aligned. GCC does this by inserting padding just
742 // before the type infos. However, this changes the size of the exception
743 // table, so you need to take this into account when you output the exception
744 // table size. However, the size is output using a variable length encoding.
745 // So by increasing the size by inserting padding, you may increase the number
746 // of bytes used for writing the size. If it increases, say by one byte, then
747 // you now need to output one less byte of padding to get the type infos
748 // aligned. However this decreases the size of the exception table. This
749 // changes the value you have to output for the exception table size. Due to
750 // the variable length encoding, the number of bytes used for writing the
751 // length may decrease. If so, you then have to increase the amount of
752 // padding. And so on. If you look carefully at the GCC code you will see that
753 // it indeed does this in a loop, going on and on until the values stabilize.
754 // We chose another solution: don't output padding inside the table like GCC
755 // does, instead output it before the table.
756 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
757 unsigned TyOffset = sizeof(int8_t) + // Call site format
758 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
759 SizeSites + SizeActions + SizeTypes;
760 unsigned TotalSize = sizeof(int8_t) + // LPStart format
761 sizeof(int8_t) + // TType format
763 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
765 unsigned SizeAlign = (4 - TotalSize) & 3;
767 for (unsigned i = 0; i != SizeAlign; ++i) {
772 EmitLabel("exception", SubprogramCount);
775 SmallString<16> LSDAName;
776 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
777 "_LSDA_" << Asm->getFunctionNumber();
778 O << LSDAName.str() << ":\n";
782 EmitEncodingByte(dwarf::DW_EH_PE_omit, "@LPStart");
783 EmitEncodingByte(TTypeFormat, "@TType");
786 Asm->EmitULEB128Bytes(TyOffset);
787 Asm->EOL("@TType base offset");
790 // SjLj Exception handling
792 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
793 Asm->EmitULEB128Bytes(SizeSites);
794 Asm->EOL("Call site table length");
796 // Emit the landing pad site information.
798 for (SmallVectorImpl<CallSiteEntry>::const_iterator
799 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
800 const CallSiteEntry &S = *I;
802 // Offset of the landing pad, counted in 16-byte bundles relative to the
804 Asm->EmitULEB128Bytes(idx);
805 Asm->EOL("Landing pad");
807 // Offset of the first associated action record, relative to the start of
808 // the action table. This value is biased by 1 (1 indicates the start of
809 // the action table), and 0 indicates that there are no actions.
810 Asm->EmitULEB128Bytes(S.Action);
814 // DWARF Exception handling
815 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
817 // The call-site table is a list of all call sites that may throw an
818 // exception (including C++ 'throw' statements) in the procedure
819 // fragment. It immediately follows the LSDA header. Each entry indicates,
820 // for a given call, the first corresponding action record and corresponding
823 // The table begins with the number of bytes, stored as an LEB128
824 // compressed, unsigned integer. The records immediately follow the record
825 // count. They are sorted in increasing call-site address. Each record
828 // * The position of the call-site.
829 // * The position of the landing pad.
830 // * The first action record for that call site.
832 // A missing entry in the call-site table indicates that a call is not
833 // supposed to throw.
835 // Emit the landing pad call site table.
836 EmitEncodingByte(dwarf::DW_EH_PE_udata4, "Call site");
837 Asm->EmitULEB128Bytes(SizeSites);
838 Asm->EOL("Call site table size");
840 for (SmallVectorImpl<CallSiteEntry>::const_iterator
841 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
842 const CallSiteEntry &S = *I;
843 const char *BeginTag;
844 unsigned BeginNumber;
847 BeginTag = "eh_func_begin";
848 BeginNumber = SubprogramCount;
851 BeginNumber = S.BeginLabel;
854 // Offset of the call site relative to the previous call site, counted in
855 // number of 16-byte bundles. The first call site is counted relative to
856 // the start of the procedure fragment.
857 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
859 Asm->EOL("Region start");
862 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
865 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
867 Asm->EOL("Region length");
869 // Offset of the landing pad, counted in 16-byte bundles relative to the
872 Asm->OutStreamer.EmitIntValue(0, 4/*size*/, 0/*addrspace*/);
874 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
877 Asm->EOL("Landing pad");
879 // Offset of the first associated action record, relative to the start of
880 // the action table. This value is biased by 1 (1 indicates the start of
881 // the action table), and 0 indicates that there are no actions.
882 Asm->EmitULEB128Bytes(S.Action);
887 // Emit the Action Table.
888 for (SmallVectorImpl<ActionEntry>::const_iterator
889 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
890 const ActionEntry &Action = *I;
894 // Used by the runtime to match the type of the thrown exception to the
895 // type of the catch clauses or the types in the exception specification.
896 EmitSLEB128(Action.ValueForTypeID, "TypeInfo index");
900 // Self-relative signed displacement in bytes of the next action record,
901 // or 0 if there is no next action record.
902 EmitSLEB128(Action.NextAction, "Next action");
905 // Emit the Catch TypeInfos.
906 for (std::vector<GlobalVariable *>::const_reverse_iterator
907 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
908 const GlobalVariable *GV = *I;
912 O << *Asm->GetGlobalValueSymbol(GV);
917 Asm->EOL("TypeInfo");
920 // Emit the Exception Specifications.
921 for (std::vector<unsigned>::const_iterator
922 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
923 unsigned TypeID = *I;
924 Asm->EmitULEB128Bytes(TypeID);
926 Asm->EOL("Exception specification");
931 Asm->EmitAlignment(2, 0, 0, false);
934 /// EndModule - Emit all exception information that should come after the
936 void DwarfException::EndModule() {
937 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
940 if (!shouldEmitMovesModule && !shouldEmitTableModule)
943 if (TimePassesIsEnabled)
944 ExceptionTimer->startTimer();
946 const std::vector<Function *> Personalities = MMI->getPersonalities();
948 for (unsigned I = 0, E = Personalities.size(); I < E; ++I)
949 EmitCIE(Personalities[I], I);
951 for (std::vector<FunctionEHFrameInfo>::iterator
952 I = EHFrames.begin(), E = EHFrames.end(); I != E; ++I)
955 if (TimePassesIsEnabled)
956 ExceptionTimer->stopTimer();
959 /// BeginFunction - Gather pre-function exception information. Assumes it's
960 /// being emitted immediately after the function entry point.
961 void DwarfException::BeginFunction(MachineFunction *MF) {
962 if (!MMI || !MAI->doesSupportExceptionHandling()) return;
964 if (TimePassesIsEnabled)
965 ExceptionTimer->startTimer();
968 shouldEmitTable = shouldEmitMoves = false;
970 // Map all labels and get rid of any dead landing pads.
971 MMI->TidyLandingPads();
973 // If any landing pads survive, we need an EH table.
974 if (!MMI->getLandingPads().empty())
975 shouldEmitTable = true;
977 // See if we need frame move info.
978 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
979 shouldEmitMoves = true;
981 if (shouldEmitMoves || shouldEmitTable)
982 // Assumes in correct section after the entry point.
983 EmitLabel("eh_func_begin", ++SubprogramCount);
985 shouldEmitTableModule |= shouldEmitTable;
986 shouldEmitMovesModule |= shouldEmitMoves;
988 if (TimePassesIsEnabled)
989 ExceptionTimer->stopTimer();
992 /// EndFunction - Gather and emit post-function exception information.
994 void DwarfException::EndFunction() {
995 if (!shouldEmitMoves && !shouldEmitTable) return;
997 if (TimePassesIsEnabled)
998 ExceptionTimer->startTimer();
1000 EmitLabel("eh_func_end", SubprogramCount);
1001 EmitExceptionTable();
1003 const MCSymbol *FunctionEHSym =
1004 Asm->GetSymbolWithGlobalValueBase(MF->getFunction(), ".eh",
1005 Asm->MAI->is_EHSymbolPrivate());
1007 // Save EH frame information
1008 EHFrames.push_back(FunctionEHFrameInfo(FunctionEHSym, SubprogramCount,
1009 MMI->getPersonalityIndex(),
1010 MF->getFrameInfo()->hasCalls(),
1011 !MMI->getLandingPads().empty(),
1012 MMI->getFrameMoves(),
1013 MF->getFunction()));
1015 // Record if this personality index uses a landing pad.
1016 UsesLSDA[MMI->getPersonalityIndex()] |= !MMI->getLandingPads().empty();
1018 if (TimePassesIsEnabled)
1019 ExceptionTimer->stopTimer();