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/MCStreamer.h"
21 #include "llvm/MC/MCAsmInfo.h"
22 #include "llvm/Target/TargetData.h"
23 #include "llvm/Target/TargetFrameInfo.h"
24 #include "llvm/Target/TargetLoweringObjectFile.h"
25 #include "llvm/Target/TargetOptions.h"
26 #include "llvm/Target/TargetRegisterInfo.h"
27 #include "llvm/Support/Dwarf.h"
28 #include "llvm/Support/Timer.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/ADT/StringExtras.h"
33 static TimerGroup &getDwarfTimerGroup() {
34 static TimerGroup DwarfTimerGroup("Dwarf Exception");
35 return DwarfTimerGroup;
38 DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
40 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
41 shouldEmitTableModule(false), shouldEmitMovesModule(false),
43 if (TimePassesIsEnabled)
44 ExceptionTimer = new Timer("Dwarf Exception Writer",
45 getDwarfTimerGroup());
48 DwarfException::~DwarfException() {
49 delete ExceptionTimer;
52 /// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
53 /// is shared among many Frame Description Entries. There is at least one CIE
54 /// in every non-empty .debug_frame section.
55 void DwarfException::EmitCIE(const Function *Personality, unsigned Index) {
56 // Size and sign of stack growth.
58 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
59 TargetFrameInfo::StackGrowsUp ?
60 TD->getPointerSize() : -TD->getPointerSize();
62 // Begin eh frame section.
63 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
65 if (MAI->is_EHSymbolPrivate())
66 O << MAI->getPrivateGlobalPrefix();
68 O << "EH_frame" << Index << ":\n";
69 EmitLabel("section_eh_frame", Index);
71 // Define base labels.
72 EmitLabel("eh_frame_common", Index);
74 // Define the eh frame length.
75 EmitDifference("eh_frame_common_end", Index,
76 "eh_frame_common_begin", Index, true);
77 Asm->EOL("Length of Common Information Entry");
80 EmitLabel("eh_frame_common_begin", Index);
81 Asm->EmitInt32((int)0);
82 Asm->EOL("CIE Identifier Tag");
83 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
84 Asm->EOL("CIE Version");
86 // The personality presence indicates that language specific information will
87 // show up in the eh frame.
88 Asm->EmitString(Personality ? "zPLR" : "zR");
89 Asm->EOL("CIE Augmentation");
92 Asm->EmitULEB128Bytes(1);
93 Asm->EOL("CIE Code Alignment Factor");
94 Asm->EmitSLEB128Bytes(stackGrowth);
95 Asm->EOL("CIE Data Alignment Factor");
96 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
97 Asm->EOL("CIE Return Address Column");
99 // If there is a personality, we need to indicate the function's location.
101 Asm->EmitULEB128Bytes(7);
102 Asm->EOL("Augmentation Size");
104 if (MAI->getNeedsIndirectEncoding()) {
105 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4 |
106 dwarf::DW_EH_PE_indirect);
107 Asm->EOL("Personality (pcrel sdata4 indirect)");
109 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
110 Asm->EOL("Personality (pcrel sdata4)");
113 PrintRelDirective(true);
114 O << MAI->getPersonalityPrefix();
115 Asm->EmitExternalGlobal((const GlobalVariable *)(Personality));
116 O << MAI->getPersonalitySuffix();
117 if (strcmp(MAI->getPersonalitySuffix(), "+4@GOTPCREL"))
118 O << "-" << MAI->getPCSymbol();
119 Asm->EOL("Personality");
121 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
122 Asm->EOL("LSDA Encoding (pcrel sdata4)");
124 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
125 Asm->EOL("FDE Encoding (pcrel sdata4)");
127 Asm->EmitULEB128Bytes(1);
128 Asm->EOL("Augmentation Size");
130 Asm->EmitInt8(dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4);
131 Asm->EOL("FDE Encoding (pcrel sdata4)");
134 // Indicate locations of general callee saved registers in frame.
135 std::vector<MachineMove> Moves;
136 RI->getInitialFrameState(Moves);
137 EmitFrameMoves(NULL, 0, Moves, true);
139 // On Darwin the linker honors the alignment of eh_frame, which means it must
140 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
141 // holes which confuse readers of eh_frame.
142 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
144 EmitLabel("eh_frame_common_end", Index);
149 /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
150 void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
151 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
152 "Should not emit 'available externally' functions at all");
154 const Function *TheFunc = EHFrameInfo.function;
156 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
158 // Externally visible entry into the functions eh frame info. If the
159 // corresponding function is static, this should not be externally visible.
160 if (!TheFunc->hasLocalLinkage())
161 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
162 O << GlobalEHDirective << EHFrameInfo.FnName << "\n";
164 // If corresponding function is weak definition, this should be too.
165 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
166 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << "\n";
168 // If there are no calls then you can't unwind. This may mean we can omit the
169 // EH Frame, but some environments do not handle weak absolute symbols. If
170 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
171 // info is to be available for non-EH uses.
172 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
173 (!TheFunc->isWeakForLinker() ||
174 !MAI->getWeakDefDirective() ||
175 MAI->getSupportsWeakOmittedEHFrame())) {
176 O << EHFrameInfo.FnName << " = 0\n";
177 // This name has no connection to the function, so it might get
178 // dead-stripped when the function is not, erroneously. Prohibit
179 // dead-stripping unconditionally.
180 if (const char *UsedDirective = MAI->getUsedDirective())
181 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
183 O << EHFrameInfo.FnName << ":\n";
186 EmitDifference("eh_frame_end", EHFrameInfo.Number,
187 "eh_frame_begin", EHFrameInfo.Number, true);
188 Asm->EOL("Length of Frame Information Entry");
190 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
192 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
193 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
196 Asm->EOL("FDE CIE offset");
198 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
199 Asm->EOL("FDE initial location");
200 EmitDifference("eh_func_end", EHFrameInfo.Number,
201 "eh_func_begin", EHFrameInfo.Number, true);
202 Asm->EOL("FDE address range");
204 // If there is a personality and landing pads then point to the language
205 // specific data area in the exception table.
206 if (MMI->getPersonalities()[0] != NULL) {
207 Asm->EmitULEB128Bytes(4);
208 Asm->EOL("Augmentation size");
210 if (EHFrameInfo.hasLandingPads)
211 EmitReference("exception", EHFrameInfo.Number, true, true);
213 Asm->EmitInt32((int)0);
214 Asm->EOL("Language Specific Data Area");
216 Asm->EmitULEB128Bytes(0);
217 Asm->EOL("Augmentation size");
220 // Indicate locations of function specific callee saved registers in frame.
221 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
224 // On Darwin the linker honors the alignment of eh_frame, which means it
225 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
226 // get holes which confuse readers of eh_frame.
227 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
229 EmitLabel("eh_frame_end", EHFrameInfo.Number);
231 // If the function is marked used, this table should be also. We cannot
232 // make the mark unconditional in this case, since retaining the table also
233 // retains the function in this case, and there is code around that depends
234 // on unused functions (calling undefined externals) being dead-stripped to
235 // link correctly. Yes, there really is.
236 if (MMI->isUsedFunction(EHFrameInfo.function))
237 if (const char *UsedDirective = MAI->getUsedDirective())
238 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
244 /// SharedTypeIds - How many leading type ids two landing pads have in common.
245 unsigned DwarfException::SharedTypeIds(const LandingPadInfo *L,
246 const LandingPadInfo *R) {
247 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
248 unsigned LSize = LIds.size(), RSize = RIds.size();
249 unsigned MinSize = LSize < RSize ? LSize : RSize;
252 for (; Count != MinSize; ++Count)
253 if (LIds[Count] != RIds[Count])
259 /// PadLT - Order landing pads lexicographically by type id.
260 bool DwarfException::PadLT(const LandingPadInfo *L, const LandingPadInfo *R) {
261 const std::vector<int> &LIds = L->TypeIds, &RIds = R->TypeIds;
262 unsigned LSize = LIds.size(), RSize = RIds.size();
263 unsigned MinSize = LSize < RSize ? LSize : RSize;
265 for (unsigned i = 0; i != MinSize; ++i)
266 if (LIds[i] != RIds[i])
267 return LIds[i] < RIds[i];
269 return LSize < RSize;
272 /// ComputeActionsTable - Compute the actions table and gather the first action
273 /// index for each landing pad site.
274 unsigned DwarfException::
275 ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
276 SmallVectorImpl<ActionEntry> &Actions,
277 SmallVectorImpl<unsigned> &FirstActions) {
279 // The action table follows the call-site table in the LSDA. The individual
280 // records are of two types:
283 // * Exception specification
285 // The two record kinds have the same format, with only small differences.
286 // They are distinguished by the "switch value" field: Catch clauses
287 // (TypeInfos) have strictly positive switch values, and exception
288 // specifications (FilterIds) have strictly negative switch values. Value 0
289 // indicates a catch-all clause.
291 // Negative type IDs index into FilterIds. Positive type IDs index into
292 // TypeInfos. The value written for a positive type ID is just the type ID
293 // itself. For a negative type ID, however, the value written is the
294 // (negative) byte offset of the corresponding FilterIds entry. The byte
295 // offset is usually equal to the type ID (because the FilterIds entries are
296 // written using a variable width encoding, which outputs one byte per entry
297 // as long as the value written is not too large) but can differ. This kind
298 // of complication does not occur for positive type IDs because type infos are
299 // output using a fixed width encoding. FilterOffsets[i] holds the byte
300 // offset corresponding to FilterIds[i].
302 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
303 SmallVector<int, 16> FilterOffsets;
304 FilterOffsets.reserve(FilterIds.size());
307 for (std::vector<unsigned>::const_iterator
308 I = FilterIds.begin(), E = FilterIds.end(); I != E; ++I) {
309 FilterOffsets.push_back(Offset);
310 Offset -= MCAsmInfo::getULEB128Size(*I);
313 FirstActions.reserve(LandingPads.size());
316 unsigned SizeActions = 0;
317 const LandingPadInfo *PrevLPI = 0;
319 for (SmallVectorImpl<const LandingPadInfo *>::const_iterator
320 I = LandingPads.begin(), E = LandingPads.end(); I != E; ++I) {
321 const LandingPadInfo *LPI = *I;
322 const std::vector<int> &TypeIds = LPI->TypeIds;
323 const unsigned NumShared = PrevLPI ? SharedTypeIds(LPI, PrevLPI) : 0;
324 unsigned SizeSiteActions = 0;
326 if (NumShared < TypeIds.size()) {
327 unsigned SizeAction = 0;
328 ActionEntry *PrevAction = 0;
331 const unsigned SizePrevIds = PrevLPI->TypeIds.size();
332 assert(Actions.size());
333 PrevAction = &Actions.back();
334 SizeAction = MCAsmInfo::getSLEB128Size(PrevAction->NextAction) +
335 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
337 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
339 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
340 SizeAction += -PrevAction->NextAction;
341 PrevAction = PrevAction->Previous;
345 // Compute the actions.
346 for (unsigned J = NumShared, M = TypeIds.size(); J != M; ++J) {
347 int TypeID = TypeIds[J];
348 assert(-1 - TypeID < (int)FilterOffsets.size() && "Unknown filter id!");
349 int ValueForTypeID = TypeID < 0 ? FilterOffsets[-1 - TypeID] : TypeID;
350 unsigned SizeTypeID = MCAsmInfo::getSLEB128Size(ValueForTypeID);
352 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
353 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
354 SizeSiteActions += SizeAction;
356 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
357 Actions.push_back(Action);
358 PrevAction = &Actions.back();
361 // Record the first action of the landing pad site.
362 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
363 } // else identical - re-use previous FirstAction
365 // Information used when created the call-site table. The action record
366 // field of the call site record is the offset of the first associated
367 // action record, relative to the start of the actions table. This value is
368 // biased by 1 (1 in dicating the start of the actions table), and 0
369 // indicates that there are no actions.
370 FirstActions.push_back(FirstAction);
372 // Compute this sites contribution to size.
373 SizeActions += SizeSiteActions;
381 /// ComputeCallSiteTable - Compute the call-site table. The entry for an invoke
382 /// has a try-range containing the call, a non-zero landing pad, and an
383 /// appropriate action. The entry for an ordinary call has a try-range
384 /// containing the call and zero for the landing pad and the action. Calls
385 /// marked 'nounwind' have no entry and must not be contained in the try-range
386 /// of any entry - they form gaps in the table. Entries must be ordered by
387 /// try-range address.
388 void DwarfException::
389 ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
390 const RangeMapType &PadMap,
391 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
392 const SmallVectorImpl<unsigned> &FirstActions) {
393 // The end label of the previous invoke or nounwind try-range.
394 unsigned LastLabel = 0;
396 // Whether there is a potentially throwing instruction (currently this means
397 // an ordinary call) between the end of the previous try-range and now.
398 bool SawPotentiallyThrowing = false;
400 // Whether the last CallSite entry was for an invoke.
401 bool PreviousIsInvoke = false;
403 // Visit all instructions in order of address.
404 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
406 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
408 if (!MI->isLabel()) {
409 SawPotentiallyThrowing |= MI->getDesc().isCall();
413 unsigned BeginLabel = MI->getOperand(0).getImm();
414 assert(BeginLabel && "Invalid label!");
416 // End of the previous try-range?
417 if (BeginLabel == LastLabel)
418 SawPotentiallyThrowing = false;
420 // Beginning of a new try-range?
421 RangeMapType::iterator L = PadMap.find(BeginLabel);
422 if (L == PadMap.end())
423 // Nope, it was just some random label.
426 const PadRange &P = L->second;
427 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
428 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
429 "Inconsistent landing pad map!");
431 // For Dwarf exception handling (SjLj handling doesn't use this). If some
432 // instruction between the previous try-range and this one may throw,
433 // create a call-site entry with no landing pad for the region between the
435 if (SawPotentiallyThrowing &&
436 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
437 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
438 CallSites.push_back(Site);
439 PreviousIsInvoke = false;
442 LastLabel = LandingPad->EndLabels[P.RangeIndex];
443 assert(BeginLabel && LastLabel && "Invalid landing pad!");
445 if (LandingPad->LandingPadLabel) {
446 // This try-range is for an invoke.
447 CallSiteEntry Site = {
450 LandingPad->LandingPadLabel,
451 FirstActions[P.PadIndex]
454 // Try to merge with the previous call-site.
455 if (PreviousIsInvoke) {
456 CallSiteEntry &Prev = CallSites.back();
457 if (Site.PadLabel == Prev.PadLabel && Site.Action == Prev.Action) {
458 // Extend the range of the previous entry.
459 Prev.EndLabel = Site.EndLabel;
464 // Otherwise, create a new call-site.
465 CallSites.push_back(Site);
466 PreviousIsInvoke = true;
469 PreviousIsInvoke = false;
474 // If some instruction between the previous try-range and the end of the
475 // function may throw, create a call-site entry with no landing pad for the
476 // region following the try-range.
477 if (SawPotentiallyThrowing &&
478 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
479 CallSiteEntry Site = { LastLabel, 0, 0, 0 };
480 CallSites.push_back(Site);
484 /// EmitExceptionTable - Emit landing pads and actions.
486 /// The general organization of the table is complex, but the basic concepts are
487 /// easy. First there is a header which describes the location and organization
488 /// of the three components that follow.
490 /// 1. The landing pad site information describes the range of code covered by
491 /// the try. In our case it's an accumulation of the ranges covered by the
492 /// invokes in the try. There is also a reference to the landing pad that
493 /// handles the exception once processed. Finally an index into the actions
495 /// 2. The action table, in our case, is composed of pairs of type IDs and next
496 /// action offset. Starting with the action index from the landing pad
497 /// site, each type ID is checked for a match to the current exception. If
498 /// it matches then the exception and type id are passed on to the landing
499 /// pad. Otherwise the next action is looked up. This chain is terminated
500 /// with a next action of zero. If no type id is found the the frame is
501 /// unwound and handling continues.
502 /// 3. Type ID table contains references to all the C++ typeinfo for all
503 /// catches in the function. This tables is reversed indexed base 1.
504 void DwarfException::EmitExceptionTable() {
505 const std::vector<GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
506 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
507 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
508 if (PadInfos.empty()) return;
510 // Sort the landing pads in order of their type ids. This is used to fold
511 // duplicate actions.
512 SmallVector<const LandingPadInfo *, 64> LandingPads;
513 LandingPads.reserve(PadInfos.size());
515 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
516 LandingPads.push_back(&PadInfos[i]);
518 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
520 // Compute the actions table and gather the first action index for each
522 SmallVector<ActionEntry, 32> Actions;
523 SmallVector<unsigned, 64> FirstActions;
524 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions, FirstActions);
526 // Invokes and nounwind calls have entries in PadMap (due to being bracketed
527 // by try-range labels when lowered). Ordinary calls do not, so appropriate
528 // try-ranges for them need be deduced when using Dwarf exception handling.
530 for (unsigned i = 0, N = LandingPads.size(); i != N; ++i) {
531 const LandingPadInfo *LandingPad = LandingPads[i];
532 for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
533 unsigned BeginLabel = LandingPad->BeginLabels[j];
534 assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
535 PadRange P = { i, j };
536 PadMap[BeginLabel] = P;
540 // Compute the call-site table.
541 SmallVector<CallSiteEntry, 64> CallSites;
542 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
547 const unsigned SiteStartSize = sizeof(int32_t); // DW_EH_PE_udata4
548 const unsigned SiteLengthSize = sizeof(int32_t); // DW_EH_PE_udata4
549 const unsigned LandingPadSize = sizeof(int32_t); // DW_EH_PE_udata4
552 bool HaveTTData = (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
553 ? (!TypeInfos.empty() || !FilterIds.empty()) : true;
556 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
559 SizeSites = CallSites.size() *
560 (SiteStartSize + SiteLengthSize + LandingPadSize);
561 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
562 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
563 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj)
564 SizeSites += MCAsmInfo::getULEB128Size(i);
567 const unsigned TypeInfoSize = TD->getPointerSize(); // DW_EH_PE_absptr
568 unsigned SizeTypes = TypeInfos.size() * TypeInfoSize;
570 unsigned TypeOffset = sizeof(int8_t) + // Call site format
571 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
572 SizeSites + SizeActions + SizeTypes;
574 unsigned TotalSize = sizeof(int8_t) + // LPStart format
575 sizeof(int8_t) + // TType format
577 MCAsmInfo::getULEB128Size(TypeOffset) : 0) + // TType base offset
580 unsigned SizeAlign = (4 - TotalSize) & 3;
582 // Begin the exception table.
583 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
584 Asm->OutStreamer.SwitchSection(LSDASection);
585 Asm->EmitAlignment(2, 0, 0, false);
586 O << "GCC_except_table" << SubprogramCount << ":\n";
588 for (unsigned i = 0; i != SizeAlign; ++i) {
593 EmitLabel("exception", SubprogramCount);
594 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
595 std::string SjLjName = "_lsda_";
596 SjLjName += MF->getFunction()->getName().str();
597 EmitLabel(SjLjName.c_str(), 0);
601 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
602 Asm->EOL("@LPStart format (DW_EH_PE_omit)");
605 if (TypeInfos.empty() && FilterIds.empty()) {
606 // If there are no typeinfos or filters, there is nothing to emit, optimize
607 // by specifying the "omit" encoding.
608 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
609 Asm->EOL("@TType format (DW_EH_PE_omit)");
611 // Okay, we have actual filters or typeinfos to emit. As such, we need to
612 // pick a type encoding for them. We're about to emit a list of pointers to
613 // typeinfo objects at the end of the LSDA. However, unless we're in static
614 // mode, this reference will require a relocation by the dynamic linker.
616 // Because of this, we have a couple of options:
617 // 1) If we are in -static mode, we can always use an absolute reference
618 // from the LSDA, because the static linker will resolve it.
619 // 2) Otherwise, if the LSDA section is writable, we can output the direct
620 // reference to the typeinfo and allow the dynamic linker to relocate
621 // it. Since it is in a writable section, the dynamic linker won't
623 // 3) Finally, if we're in PIC mode and the LDSA section isn't writable,
624 // we need to use some form of indirection. For example, on Darwin,
625 // we can output a statically-relocatable reference to a dyld stub. The
626 // offset to the stub is constant, but the contents are in a section
627 // that is updated by the dynamic linker. This is easy enough, but we
628 // need to tell the personality function of the unwinder to indirect
629 // through the dyld stub.
631 // FIXME: When this is actually implemented, we'll have to emit the stubs
632 // somewhere. This predicate should be moved to a shared location that is
633 // in target-independent code.
635 if (LSDASection->isWritable() ||
636 Asm->TM.getRelocationModel() == Reloc::Static) {
637 Asm->EmitInt8(DW_EH_PE_absptr);
638 Asm->EOL("TType format (DW_EH_PE_absptr)");
640 Asm->EmitInt8(DW_EH_PE_pcrel | DW_EH_PE_indirect | DW_EH_PE_sdata4);
641 Asm->EOL("TType format (DW_EH_PE_pcrel | DW_EH_PE_indirect"
642 " | DW_EH_PE_sdata4)");
644 Asm->EmitULEB128Bytes(TypeOffset);
645 Asm->EOL("TType base offset");
648 // For SjLj exceptions, if there is no TypeInfo, then we just explicitly
649 // say that we're omitting that bit.
650 // FIXME: does this apply to Dwarf also? The above #if 0 implies yes?
652 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
653 Asm->EOL("@TType format (DW_EH_PE_omit)");
655 Asm->EmitInt8(dwarf::DW_EH_PE_absptr);
656 Asm->EOL("@TType format (DW_EH_PE_absptr)");
657 Asm->EmitULEB128Bytes(TypeOffset);
658 Asm->EOL("@TType base offset");
662 // SjLj Exception handilng
663 if (MAI->getExceptionHandlingType() == ExceptionHandling::SjLj) {
664 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
665 Asm->EOL("Call site format (DW_EH_PE_udata4)");
666 Asm->EmitULEB128Bytes(SizeSites);
667 Asm->EOL("Call site table length");
669 // Emit the landing pad site information.
671 for (SmallVectorImpl<CallSiteEntry>::const_iterator
672 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
673 const CallSiteEntry &S = *I;
675 // Offset of the landing pad, counted in 16-byte bundles relative to the
677 Asm->EmitULEB128Bytes(idx);
678 Asm->EOL("Landing pad");
680 // Offset of the first associated action record, relative to the start of
681 // the action table. This value is biased by 1 (1 indicates the start of
682 // the action table), and 0 indicates that there are no actions.
683 Asm->EmitULEB128Bytes(S.Action);
687 // DWARF Exception handling
688 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
690 // The call-site table is a list of all call sites that may throw an
691 // exception (including C++ 'throw' statements) in the procedure
692 // fragment. It immediately follows the LSDA header. Each entry indicates,
693 // for a given call, the first corresponding action record and corresponding
696 // The table begins with the number of bytes, stored as an LEB128
697 // compressed, unsigned integer. The records immediately follow the record
698 // count. They are sorted in increasing call-site address. Each record
701 // * The position of the call-site.
702 // * The position of the landing pad.
703 // * The first action record for that call site.
705 // A missing entry in the call-site table indicates that a call is not
706 // supposed to throw. Such calls include:
708 // * Calls to destructors within cleanup code. C++ semantics forbids these
710 // * Calls to intrinsic routines in the standard library which are known
711 // not to throw (sin, memcpy, et al).
713 // If the runtime does not find the call-site entry for a given call, it
714 // will call `terminate()'.
716 // Emit the landing pad call site table.
717 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
718 Asm->EOL("Call site format (DW_EH_PE_udata4)");
719 Asm->EmitULEB128Bytes(SizeSites);
720 Asm->EOL("Call site table size");
722 for (SmallVectorImpl<CallSiteEntry>::const_iterator
723 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
724 const CallSiteEntry &S = *I;
725 const char *BeginTag;
726 unsigned BeginNumber;
729 BeginTag = "eh_func_begin";
730 BeginNumber = SubprogramCount;
733 BeginNumber = S.BeginLabel;
736 // Offset of the call site relative to the previous call site, counted in
737 // number of 16-byte bundles. The first call site is counted relative to
738 // the start of the procedure fragment.
739 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
741 Asm->EOL("Region start");
744 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
747 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
749 Asm->EOL("Region length");
751 // Offset of the landing pad, counted in 16-byte bundles relative to the
756 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
759 Asm->EOL("Landing pad");
761 // Offset of the first associated action record, relative to the start of
762 // the action table. This value is biased by 1 (1 indicates the start of
763 // the action table), and 0 indicates that there are no actions.
764 Asm->EmitULEB128Bytes(S.Action);
769 // Emit the Action Table.
770 for (SmallVectorImpl<ActionEntry>::const_iterator
771 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
772 const ActionEntry &Action = *I;
776 // Used by the runtime to match the type of the thrown exception to the
777 // type of the catch clauses or the types in the exception specification.
779 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
780 Asm->EOL("TypeInfo index");
784 // Self-relative signed displacement in bytes of the next action record,
785 // or 0 if there is no next action record.
787 Asm->EmitSLEB128Bytes(Action.NextAction);
788 Asm->EOL("Next action");
791 // Emit the Catch Clauses. The code for the catch clauses following the same
792 // try is similar to a switch statement. The catch clause action record
793 // informs the runtime about the type of a catch clause and about the
794 // associated switch value.
796 // Action Record Fields:
799 // Positive value, starting at 1. Index in the types table of the
800 // __typeinfo for the catch-clause type. 1 is the first word preceding
801 // TTBase, 2 is the second word, and so on. Used by the runtime to check
802 // if the thrown exception type matches the catch-clause type. Back-end
803 // generated switch statements check against this value.
806 // Signed offset, in bytes from the start of this field, to the next
807 // chained action record, or zero if none.
809 // The order of the action records determined by the next field is the order
810 // of the catch clauses as they appear in the source code, and must be kept in
811 // the same order. As a result, changing the order of the catch clause would
812 // change the semantics of the program.
813 for (std::vector<GlobalVariable *>::const_reverse_iterator
814 I = TypeInfos.rbegin(), E = TypeInfos.rend(); I != E; ++I) {
815 const GlobalVariable *GV = *I;
820 O << Asm->getGlobalLinkName(GV, GLN);
825 Asm->EOL("TypeInfo");
828 // Emit the Type Table.
829 for (std::vector<unsigned>::const_iterator
830 I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
831 unsigned TypeID = *I;
832 Asm->EmitULEB128Bytes(TypeID);
833 Asm->EOL("Filter TypeInfo index");
836 Asm->EmitAlignment(2, 0, 0, false);
839 /// EndModule - Emit all exception information that should come after the
841 void DwarfException::EndModule() {
842 if (MAI->getExceptionHandlingType() != ExceptionHandling::Dwarf)
844 if (TimePassesIsEnabled)
845 ExceptionTimer->startTimer();
847 if (shouldEmitMovesModule || shouldEmitTableModule) {
848 const std::vector<Function *> Personalities = MMI->getPersonalities();
849 for (unsigned i = 0; i < Personalities.size(); ++i)
850 EmitCIE(Personalities[i], i);
852 for (std::vector<FunctionEHFrameInfo>::iterator I = EHFrames.begin(),
853 E = EHFrames.end(); I != E; ++I)
857 if (TimePassesIsEnabled)
858 ExceptionTimer->stopTimer();
861 /// BeginFunction - Gather pre-function exception information. Assumes being
862 /// emitted immediately after the function entry point.
863 void DwarfException::BeginFunction(MachineFunction *MF) {
864 if (TimePassesIsEnabled)
865 ExceptionTimer->startTimer();
868 shouldEmitTable = shouldEmitMoves = false;
870 if (MMI && MAI->doesSupportExceptionHandling()) {
871 // Map all labels and get rid of any dead landing pads.
872 MMI->TidyLandingPads();
874 // If any landing pads survive, we need an EH table.
875 if (MMI->getLandingPads().size())
876 shouldEmitTable = true;
878 // See if we need frame move info.
879 if (!MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
880 shouldEmitMoves = true;
882 if (shouldEmitMoves || shouldEmitTable)
883 // Assumes in correct section after the entry point.
884 EmitLabel("eh_func_begin", ++SubprogramCount);
887 shouldEmitTableModule |= shouldEmitTable;
888 shouldEmitMovesModule |= shouldEmitMoves;
890 if (TimePassesIsEnabled)
891 ExceptionTimer->stopTimer();
894 /// EndFunction - Gather and emit post-function exception information.
896 void DwarfException::EndFunction() {
897 if (TimePassesIsEnabled)
898 ExceptionTimer->startTimer();
900 if (shouldEmitMoves || shouldEmitTable) {
901 EmitLabel("eh_func_end", SubprogramCount);
902 EmitExceptionTable();
904 // Save EH frame information
906 FunctionEHFrameInfo(getAsm()->getCurrentFunctionEHName(MF),
908 MMI->getPersonalityIndex(),
909 MF->getFrameInfo()->hasCalls(),
910 !MMI->getLandingPads().empty(),
911 MMI->getFrameMoves(),
915 if (TimePassesIsEnabled)
916 ExceptionTimer->stopTimer();