1//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains support for writing DWARF exception info into asm files.
11//
12//===----------------------------------------------------------------------===//
13
14#include "DwarfException.h"
15#include "llvm/Module.h"
16#include "llvm/CodeGen/MachineModuleInfo.h"
17#include "llvm/CodeGen/MachineFrameInfo.h"
18#include "llvm/CodeGen/MachineFunction.h"
19#include "llvm/CodeGen/MachineLocation.h"
20#include "llvm/MC/MCAsmInfo.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCSection.h"
24#include "llvm/MC/MCStreamer.h"
25#include "llvm/Target/TargetData.h"
26#include "llvm/Target/TargetFrameInfo.h"
27#include "llvm/Target/TargetLoweringObjectFile.h"
28#include "llvm/Target/TargetOptions.h"
29#include "llvm/Target/TargetRegisterInfo.h"
30#include "llvm/Support/Dwarf.h"
31#include "llvm/Support/Mangler.h"
32#include "llvm/Support/Timer.h"
33#include "llvm/Support/raw_ostream.h"
34#include "llvm/ADT/SmallString.h"
35#include "llvm/ADT/StringExtras.h"
36using namespace llvm;
37
38static TimerGroup &getDwarfTimerGroup() {
39 static TimerGroup DwarfTimerGroup("DWARF Exception");
40 return DwarfTimerGroup;
41}
42
43DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
44 const MCAsmInfo *T)
45 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
46 shouldEmitTableModule(false), shouldEmitMovesModule(false),
47 ExceptionTimer(0) {
48 if (TimePassesIsEnabled)
49 ExceptionTimer = new Timer("DWARF Exception Writer",
50 getDwarfTimerGroup());
51}
52
53DwarfException::~DwarfException() {
54 delete ExceptionTimer;
55}
56
57/// SizeOfEncodedValue - Return the size of the encoding in bytes.
58unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
59 if (Encoding == dwarf::DW_EH_PE_omit)
60 return 0;
61
62 switch (Encoding & 0x07) {
63 case dwarf::DW_EH_PE_absptr:
64 return TD->getPointerSize();
65 case dwarf::DW_EH_PE_udata2:
66 return 2;
67 case dwarf::DW_EH_PE_udata4:
68 return 4;
69 case dwarf::DW_EH_PE_udata8:
70 return 8;
71 }
72
73 assert(0 && "Invalid encoded value.");
74 return 0;
75}
76
77/// CreateLabelDiff - Emit a label and subtract it from the expression we
78/// already have. This is equivalent to emitting "foo - .", but we have to emit
79/// the label for "." directly.
80const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
81 const char *LabelName,
82 unsigned Index) {
83 SmallString<64> Name;
84 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
85 << LabelName << Asm->getFunctionNumber()
86 << "_" << Index;
87 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
88 Asm->OutStreamer.EmitLabel(DotSym);
89
90 return MCBinaryExpr::CreateSub(ExprRef,
91 MCSymbolRefExpr::Create(DotSym,
92 Asm->OutContext),
93 Asm->OutContext);
94}
95
96/// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
97/// is shared among many Frame Description Entries. There is at least one CIE
98/// in every non-empty .debug_frame section.
99void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
100 // Size and sign of stack growth.
101 int stackGrowth =
102 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
103 TargetFrameInfo::StackGrowsUp ?
104 TD->getPointerSize() : -TD->getPointerSize();
105
106 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
107
108 // Begin eh frame section.
109 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
110
111 if (MAI->is_EHSymbolPrivate())
112 O << MAI->getPrivateGlobalPrefix();
113 O << "EH_frame" << Index << ":\n";
114
115 EmitLabel("section_eh_frame", Index);
116
117 // Define base labels.
118 EmitLabel("eh_frame_common", Index);
119
120 // Define the eh frame length.
121 EmitDifference("eh_frame_common_end", Index,
122 "eh_frame_common_begin", Index, true);
123 Asm->EOL("Length of Common Information Entry");
124
125 // EH frame header.
126 EmitLabel("eh_frame_common_begin", Index);
127 Asm->EmitInt32((int)0);
128 Asm->EOL("CIE Identifier Tag");
129 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
130 Asm->EOL("CIE Version");
131
132 // The personality presence indicates that language specific information will
133 // show up in the eh frame. Find out how we are supposed to lower the
134 // personality function reference:
135 const MCExpr *PersonalityRef = 0;
136 bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
137 if (PersonalityFn) {
138 // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
139
140 // In non-static mode, ask the object file how to represent this reference.
141 PersonalityRef =
142 TLOF.getSymbolForDwarfGlobalReference(PersonalityFn, Asm->Mang,
143 Asm->MMI,
144 IsPersonalityIndirect,
145 IsPersonalityPCRel);
146 }
147
148 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
149 if (IsPersonalityIndirect)
150 PerEncoding |= dwarf::DW_EH_PE_indirect;
151 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
152 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
153
154 char Augmentation[5] = { 0 };
155 unsigned AugmentationSize = 0;
156 char *APtr = Augmentation + 1;
157
158 if (PersonalityRef) {
159 // There is a personality function.
160 *APtr++ = 'P';
161 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
162 }
163
164 if (UsesLSDA[Index]) {
165 // An LSDA pointer is in the FDE augmentation.
166 *APtr++ = 'L';
167 ++AugmentationSize;
168 }
169
170 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
171 // A non-default pointer encoding for the FDE.
172 *APtr++ = 'R';
173 ++AugmentationSize;
174 }
175
176 if (APtr != Augmentation + 1)
177 Augmentation[0] = 'z';
178
179 Asm->EmitString(Augmentation);
180 Asm->EOL("CIE Augmentation");
181
182 // Round out reader.
183 Asm->EmitULEB128Bytes(1);
184 Asm->EOL("CIE Code Alignment Factor");
185 Asm->EmitSLEB128Bytes(stackGrowth);
186 Asm->EOL("CIE Data Alignment Factor");
187 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
188 Asm->EOL("CIE Return Address Column");
189
190 Asm->EmitULEB128Bytes(AugmentationSize);
191 Asm->EOL("Augmentation Size");
192
193 Asm->EmitInt8(PerEncoding);
194 Asm->EOL("Personality", PerEncoding);
195
196 // If there is a personality, we need to indicate the function's location.
197 if (PersonalityRef) {
198 if (!IsPersonalityPCRel)
199 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
200 Index);
201
202 O << MAI->getData32bitsDirective();
203 PersonalityRef->print(O, MAI);
204 Asm->EOL("Personality");
205
206 Asm->EmitInt8(LSDAEncoding);
207 Asm->EOL("LSDA Encoding", LSDAEncoding);
208
209 Asm->EmitInt8(FDEEncoding);
210 Asm->EOL("FDE Encoding", FDEEncoding);
211 }
212
213 // Indicate locations of general callee saved registers in frame.
214 std::vector<MachineMove> Moves;
215 RI->getInitialFrameState(Moves);
216 EmitFrameMoves(NULL, 0, Moves, true);
217
218 // On Darwin the linker honors the alignment of eh_frame, which means it must
219 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
220 // holes which confuse readers of eh_frame.
221 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
222 EmitLabel("eh_frame_common_end", Index);
223
224 Asm->EOL();
225}
226
227/// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
228void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
229 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
230 "Should not emit 'available externally' functions at all");
231
232 const Function *TheFunc = EHFrameInfo.function;
233
234 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
235
236 // Externally visible entry into the functions eh frame info. If the
237 // corresponding function is static, this should not be externally visible.
238 if (!TheFunc->hasLocalLinkage())
239 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
240 O << GlobalEHDirective << EHFrameInfo.FnName << '\n';
241
242 // If corresponding function is weak definition, this should be too.
243 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
244 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << '\n';
245
246 // If corresponding function is hidden, this should be too.
247 if (TheFunc->hasHiddenVisibility())
248 if (const char *HiddenDirective = MAI->getHiddenDirective())
249 O << HiddenDirective << EHFrameInfo.FnName << '\n' ;
250
251 // If there are no calls then you can't unwind. This may mean we can omit the
252 // EH Frame, but some environments do not handle weak absolute symbols. If
253 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
254 // info is to be available for non-EH uses.
255 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
256 (!TheFunc->isWeakForLinker() ||
257 !MAI->getWeakDefDirective() ||
258 MAI->getSupportsWeakOmittedEHFrame())) {
259 O << EHFrameInfo.FnName << " = 0\n";
260 // This name has no connection to the function, so it might get
261 // dead-stripped when the function is not, erroneously. Prohibit
262 // dead-stripping unconditionally.
263 if (const char *UsedDirective = MAI->getUsedDirective())
264 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
265 } else {
266 O << EHFrameInfo.FnName << ":\n";
267
268 // EH frame header.
269 EmitDifference("eh_frame_end", EHFrameInfo.Number,
270 "eh_frame_begin", EHFrameInfo.Number, true);
271 Asm->EOL("Length of Frame Information Entry");
272
273 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
274
275 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
276 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
277 true, true, false);
278
279 Asm->EOL("FDE CIE offset");
280
281 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
282 Asm->EOL("FDE initial location");
283 EmitDifference("eh_func_end", EHFrameInfo.Number,
284 "eh_func_begin", EHFrameInfo.Number, true);
285 Asm->EOL("FDE address range");
286
287 // If there is a personality and landing pads then point to the language
288 // specific data area in the exception table.
289 if (MMI->getPersonalities()[0] != NULL) {
290 bool is4Byte = TD->getPointerSize() == sizeof(int32_t);
291
292 Asm->EmitULEB128Bytes(is4Byte ? 4 : 8);
293 Asm->EOL("Augmentation size");
294
295 if (EHFrameInfo.hasLandingPads)
296 EmitReference("exception", EHFrameInfo.Number, true, false);
297 else {
298 if (is4Byte)
299 Asm->EmitInt32((int)0);
300 else
301 Asm->EmitInt64((int)0);
302 }
303 Asm->EOL("Language Specific Data Area");
304 } else {
305 Asm->EmitULEB128Bytes(0);
306 Asm->EOL("Augmentation size");
307 }
308
309 // Indicate locations of function specific callee saved registers in frame.
310 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
311 true);
312
313 // On Darwin the linker honors the alignment of eh_frame, which means it
314 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
315 // get holes which confuse readers of eh_frame.
316 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
317 0, 0, false);
318 EmitLabel("eh_frame_end", EHFrameInfo.Number);
319
320 // If the function is marked used, this table should be also. We cannot
321 // make the mark unconditional in this case, since retaining the table also
322 // retains the function in this case, and there is code around that depends
323 // on unused functions (calling undefined externals) being dead-stripped to
324 // link correctly. Yes, there really is.
325 if (MMI->isUsedFunction(EHFrameInfo.function))
326 if (const char *UsedDirective = MAI->getUsedDirective())
327 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
328 }
329
330 Asm->EOL();
331}
332
333/// SharedTypeIds - How many leading type ids two landing pads have in common.
334unsigned 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;
339 unsigned Count = 0;
340
341 for (; Count != MinSize; ++Count)
342 if (LIds[Count] != RIds[Count])
343 return Count;
344
345 return Count;
346}
347
348/// PadLT - Order landing pads lexicographically by type id.
349bool 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;
353
354 for (unsigned i = 0; i != MinSize; ++i)
355 if (LIds[i] != RIds[i])
356 return LIds[i] < RIds[i];
357
358 return LSize < RSize;
359}
360
361/// ComputeActionsTable - Compute the actions table and gather the first action
362/// index for each landing pad site.
363unsigned DwarfException::
364ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
365 SmallVectorImpl<ActionEntry> &Actions,
366 SmallVectorImpl<unsigned> &FirstActions) {
367
368 // The action table follows the call-site table in the LSDA. The individual
369 // records are of two types:
370 //
371 // * Catch clause
372 // * Exception specification
373 //
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.
379 //
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].
390
391 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
392 SmallVector<int, 16> FilterOffsets;
393 FilterOffsets.reserve(FilterIds.size());
394 int Offset = -1;
395
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);
400 }
401
402 FirstActions.reserve(LandingPads.size());
403
404 int FirstAction = 0;
405 unsigned SizeActions = 0;
406 const LandingPadInfo *PrevLPI = 0;
407
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;
414
415 if (NumShared < TypeIds.size()) {
416 unsigned SizeAction = 0;
417 ActionEntry *PrevAction = 0;
418
419 if (NumShared) {
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);
425
426 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
427 SizeAction -=
428 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
429 SizeAction += -PrevAction->NextAction;
430 PrevAction = PrevAction->Previous;
431 }
432 }
433
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);
440
441 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
442 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
443 SizeSiteActions += SizeAction;
444
445 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
446 Actions.push_back(Action);
447 PrevAction = &Actions.back();
448 }
449
450 // Record the first action of the landing pad site.
451 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
452 } // else identical - re-use previous FirstAction
453
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);
460
461 // Compute this sites contribution to size.
462 SizeActions += SizeSiteActions;
463
464 PrevLPI = LPI;
465 }
466
467 return SizeActions;
468}
469
470/// CallToNoUnwindFunction - Return `true' if this is a call to a function
471/// marked `nounwind'. Return `false' otherwise.
472bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
473 assert(MI->getDesc().isCall() && "This should be a call instruction!");
474
475 bool MarkedNoUnwind = false;
476 bool SawFunc = false;
477
478 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
479 const MachineOperand &MO = MI->getOperand(I);
480
481 if (MO.isGlobal()) {
482 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
483 if (SawFunc) {
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.
487 //
488 // FIXME: Determine if there's a way to say that `F' is the callee or
489 // parameter.
490 MarkedNoUnwind = false;
491 break;
492 }
493
494 MarkedNoUnwind = F->doesNotThrow();
495 SawFunc = true;
496 }
497 }
498 }
499
500 return MarkedNoUnwind;
501}
502
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.
510void DwarfException::
511ComputeCallSiteTable(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;
517
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;
521
522 // Whether the last CallSite entry was for an invoke.
523 bool PreviousIsInvoke = false;
524
525 // Visit all instructions in order of address.
526 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
527 I != E; ++I) {
528 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
529 MI != E; ++MI) {
530 if (!MI->isLabel()) {
531 if (MI->getDesc().isCall())
532 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
533
534 continue;
535 }
536
537 unsigned BeginLabel = MI->getOperand(0).getImm();
538 assert(BeginLabel && "Invalid label!");
539
540 // End of the previous try-range?
541 if (BeginLabel == LastLabel)
542 SawPotentiallyThrowing = false;
543
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.
548 continue;
549
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!");
554
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
558 // try-ranges.
559 if (SawPotentiallyThrowing &&
560 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
561 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
562 CallSites.push_back(Site);
563 PreviousIsInvoke = false;
564 }
565
566 LastLabel = LandingPad->EndLabels[P.RangeIndex];
567 assert(BeginLabel && LastLabel && "Invalid landing pad!");
568
569 if (LandingPad->LandingPadLabel) {
570 // This try-range is for an invoke.
571 CallSiteEntry Site = {
572 BeginLabel,
573 LastLabel,
574 LandingPad->LandingPadLabel,
575 FirstActions[P.PadIndex]
576 };
577
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;
585 continue;
586 }
587 }
588
589 // Otherwise, create a new call-site.
590 CallSites.push_back(Site);
591 PreviousIsInvoke = true;
592 } else {
593 // Create a gap.
594 PreviousIsInvoke = false;
595 }
596 }
597 }
598
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);
606 }
607}
608
609/// EmitExceptionTable - Emit landing pads and actions.
610///
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.
614///
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
619/// table.
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.
629void 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;
634
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());
639
640 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
641 LandingPads.push_back(&PadInfos[i]);
642
643 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
644
645 // Compute the actions table and gather the first action index for each
646 // landing pad site.
647 SmallVector<ActionEntry, 32> Actions;
648 SmallVector<unsigned, 64> FirstActions;
649 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
650 FirstActions);
651
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.
655 RangeMapType PadMap;
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;
663 }
664 }
665
666 // Compute the call-site table.
667 SmallVector<CallSiteEntry, 64> CallSites;
668 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
669
670 // Final tallies.
671
672 // Call sites.
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;
678 unsigned SizeSites;
679
680 if (IsSJLJ)
681 SizeSites = 0;
682 else
683 SizeSites = CallSites.size() *
684 (SiteStartSize + SiteLengthSize + LandingPadSize);
685
686 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
687 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
688 if (IsSJLJ)
689 SizeSites += MCAsmInfo::getULEB128Size(i);
690 }
691
692 // Type infos.
693 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
694 unsigned TTypeFormat;
695 unsigned TypeFormatSize;
696
697 if (!HaveTTData) {
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);
702 } else {
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.
707 //
708 // Because of this, we have a couple of options:
709 //
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.
712 //
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
716 // have a problem.
717 //
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.
725 //
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.
729 //
| 1//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains support for writing DWARF exception info into asm files.
11//
12//===----------------------------------------------------------------------===//
13
14#include "DwarfException.h"
15#include "llvm/Module.h"
16#include "llvm/CodeGen/MachineModuleInfo.h"
17#include "llvm/CodeGen/MachineFrameInfo.h"
18#include "llvm/CodeGen/MachineFunction.h"
19#include "llvm/CodeGen/MachineLocation.h"
20#include "llvm/MC/MCAsmInfo.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCSection.h"
24#include "llvm/MC/MCStreamer.h"
25#include "llvm/Target/TargetData.h"
26#include "llvm/Target/TargetFrameInfo.h"
27#include "llvm/Target/TargetLoweringObjectFile.h"
28#include "llvm/Target/TargetOptions.h"
29#include "llvm/Target/TargetRegisterInfo.h"
30#include "llvm/Support/Dwarf.h"
31#include "llvm/Support/Mangler.h"
32#include "llvm/Support/Timer.h"
33#include "llvm/Support/raw_ostream.h"
34#include "llvm/ADT/SmallString.h"
35#include "llvm/ADT/StringExtras.h"
36using namespace llvm;
37
38static TimerGroup &getDwarfTimerGroup() {
39 static TimerGroup DwarfTimerGroup("DWARF Exception");
40 return DwarfTimerGroup;
41}
42
43DwarfException::DwarfException(raw_ostream &OS, AsmPrinter *A,
44 const MCAsmInfo *T)
45 : Dwarf(OS, A, T, "eh"), shouldEmitTable(false), shouldEmitMoves(false),
46 shouldEmitTableModule(false), shouldEmitMovesModule(false),
47 ExceptionTimer(0) {
48 if (TimePassesIsEnabled)
49 ExceptionTimer = new Timer("DWARF Exception Writer",
50 getDwarfTimerGroup());
51}
52
53DwarfException::~DwarfException() {
54 delete ExceptionTimer;
55}
56
57/// SizeOfEncodedValue - Return the size of the encoding in bytes.
58unsigned DwarfException::SizeOfEncodedValue(unsigned Encoding) {
59 if (Encoding == dwarf::DW_EH_PE_omit)
60 return 0;
61
62 switch (Encoding & 0x07) {
63 case dwarf::DW_EH_PE_absptr:
64 return TD->getPointerSize();
65 case dwarf::DW_EH_PE_udata2:
66 return 2;
67 case dwarf::DW_EH_PE_udata4:
68 return 4;
69 case dwarf::DW_EH_PE_udata8:
70 return 8;
71 }
72
73 assert(0 && "Invalid encoded value.");
74 return 0;
75}
76
77/// CreateLabelDiff - Emit a label and subtract it from the expression we
78/// already have. This is equivalent to emitting "foo - .", but we have to emit
79/// the label for "." directly.
80const MCExpr *DwarfException::CreateLabelDiff(const MCExpr *ExprRef,
81 const char *LabelName,
82 unsigned Index) {
83 SmallString<64> Name;
84 raw_svector_ostream(Name) << MAI->getPrivateGlobalPrefix()
85 << LabelName << Asm->getFunctionNumber()
86 << "_" << Index;
87 MCSymbol *DotSym = Asm->OutContext.GetOrCreateSymbol(Name.str());
88 Asm->OutStreamer.EmitLabel(DotSym);
89
90 return MCBinaryExpr::CreateSub(ExprRef,
91 MCSymbolRefExpr::Create(DotSym,
92 Asm->OutContext),
93 Asm->OutContext);
94}
95
96/// EmitCIE - Emit a Common Information Entry (CIE). This holds information that
97/// is shared among many Frame Description Entries. There is at least one CIE
98/// in every non-empty .debug_frame section.
99void DwarfException::EmitCIE(const Function *PersonalityFn, unsigned Index) {
100 // Size and sign of stack growth.
101 int stackGrowth =
102 Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
103 TargetFrameInfo::StackGrowsUp ?
104 TD->getPointerSize() : -TD->getPointerSize();
105
106 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
107
108 // Begin eh frame section.
109 Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
110
111 if (MAI->is_EHSymbolPrivate())
112 O << MAI->getPrivateGlobalPrefix();
113 O << "EH_frame" << Index << ":\n";
114
115 EmitLabel("section_eh_frame", Index);
116
117 // Define base labels.
118 EmitLabel("eh_frame_common", Index);
119
120 // Define the eh frame length.
121 EmitDifference("eh_frame_common_end", Index,
122 "eh_frame_common_begin", Index, true);
123 Asm->EOL("Length of Common Information Entry");
124
125 // EH frame header.
126 EmitLabel("eh_frame_common_begin", Index);
127 Asm->EmitInt32((int)0);
128 Asm->EOL("CIE Identifier Tag");
129 Asm->EmitInt8(dwarf::DW_CIE_VERSION);
130 Asm->EOL("CIE Version");
131
132 // The personality presence indicates that language specific information will
133 // show up in the eh frame. Find out how we are supposed to lower the
134 // personality function reference:
135 const MCExpr *PersonalityRef = 0;
136 bool IsPersonalityIndirect = false, IsPersonalityPCRel = false;
137 if (PersonalityFn) {
138 // FIXME: HANDLE STATIC CODEGEN MODEL HERE.
139
140 // In non-static mode, ask the object file how to represent this reference.
141 PersonalityRef =
142 TLOF.getSymbolForDwarfGlobalReference(PersonalityFn, Asm->Mang,
143 Asm->MMI,
144 IsPersonalityIndirect,
145 IsPersonalityPCRel);
146 }
147
148 unsigned PerEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
149 if (IsPersonalityIndirect)
150 PerEncoding |= dwarf::DW_EH_PE_indirect;
151 unsigned LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
152 unsigned FDEEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
153
154 char Augmentation[5] = { 0 };
155 unsigned AugmentationSize = 0;
156 char *APtr = Augmentation + 1;
157
158 if (PersonalityRef) {
159 // There is a personality function.
160 *APtr++ = 'P';
161 AugmentationSize += 1 + SizeOfEncodedValue(PerEncoding);
162 }
163
164 if (UsesLSDA[Index]) {
165 // An LSDA pointer is in the FDE augmentation.
166 *APtr++ = 'L';
167 ++AugmentationSize;
168 }
169
170 if (FDEEncoding != dwarf::DW_EH_PE_absptr) {
171 // A non-default pointer encoding for the FDE.
172 *APtr++ = 'R';
173 ++AugmentationSize;
174 }
175
176 if (APtr != Augmentation + 1)
177 Augmentation[0] = 'z';
178
179 Asm->EmitString(Augmentation);
180 Asm->EOL("CIE Augmentation");
181
182 // Round out reader.
183 Asm->EmitULEB128Bytes(1);
184 Asm->EOL("CIE Code Alignment Factor");
185 Asm->EmitSLEB128Bytes(stackGrowth);
186 Asm->EOL("CIE Data Alignment Factor");
187 Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), true));
188 Asm->EOL("CIE Return Address Column");
189
190 Asm->EmitULEB128Bytes(AugmentationSize);
191 Asm->EOL("Augmentation Size");
192
193 Asm->EmitInt8(PerEncoding);
194 Asm->EOL("Personality", PerEncoding);
195
196 // If there is a personality, we need to indicate the function's location.
197 if (PersonalityRef) {
198 if (!IsPersonalityPCRel)
199 PersonalityRef = CreateLabelDiff(PersonalityRef, "personalityref_addr",
200 Index);
201
202 O << MAI->getData32bitsDirective();
203 PersonalityRef->print(O, MAI);
204 Asm->EOL("Personality");
205
206 Asm->EmitInt8(LSDAEncoding);
207 Asm->EOL("LSDA Encoding", LSDAEncoding);
208
209 Asm->EmitInt8(FDEEncoding);
210 Asm->EOL("FDE Encoding", FDEEncoding);
211 }
212
213 // Indicate locations of general callee saved registers in frame.
214 std::vector<MachineMove> Moves;
215 RI->getInitialFrameState(Moves);
216 EmitFrameMoves(NULL, 0, Moves, true);
217
218 // On Darwin the linker honors the alignment of eh_frame, which means it must
219 // be 8-byte on 64-bit targets to match what gcc does. Otherwise you get
220 // holes which confuse readers of eh_frame.
221 Asm->EmitAlignment(TD->getPointerSize() == 4 ? 2 : 3, 0, 0, false);
222 EmitLabel("eh_frame_common_end", Index);
223
224 Asm->EOL();
225}
226
227/// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
228void DwarfException::EmitFDE(const FunctionEHFrameInfo &EHFrameInfo) {
229 assert(!EHFrameInfo.function->hasAvailableExternallyLinkage() &&
230 "Should not emit 'available externally' functions at all");
231
232 const Function *TheFunc = EHFrameInfo.function;
233
234 Asm->OutStreamer.SwitchSection(Asm->getObjFileLowering().getEHFrameSection());
235
236 // Externally visible entry into the functions eh frame info. If the
237 // corresponding function is static, this should not be externally visible.
238 if (!TheFunc->hasLocalLinkage())
239 if (const char *GlobalEHDirective = MAI->getGlobalEHDirective())
240 O << GlobalEHDirective << EHFrameInfo.FnName << '\n';
241
242 // If corresponding function is weak definition, this should be too.
243 if (TheFunc->isWeakForLinker() && MAI->getWeakDefDirective())
244 O << MAI->getWeakDefDirective() << EHFrameInfo.FnName << '\n';
245
246 // If corresponding function is hidden, this should be too.
247 if (TheFunc->hasHiddenVisibility())
248 if (const char *HiddenDirective = MAI->getHiddenDirective())
249 O << HiddenDirective << EHFrameInfo.FnName << '\n' ;
250
251 // If there are no calls then you can't unwind. This may mean we can omit the
252 // EH Frame, but some environments do not handle weak absolute symbols. If
253 // UnwindTablesMandatory is set we cannot do this optimization; the unwind
254 // info is to be available for non-EH uses.
255 if (!EHFrameInfo.hasCalls && !UnwindTablesMandatory &&
256 (!TheFunc->isWeakForLinker() ||
257 !MAI->getWeakDefDirective() ||
258 MAI->getSupportsWeakOmittedEHFrame())) {
259 O << EHFrameInfo.FnName << " = 0\n";
260 // This name has no connection to the function, so it might get
261 // dead-stripped when the function is not, erroneously. Prohibit
262 // dead-stripping unconditionally.
263 if (const char *UsedDirective = MAI->getUsedDirective())
264 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
265 } else {
266 O << EHFrameInfo.FnName << ":\n";
267
268 // EH frame header.
269 EmitDifference("eh_frame_end", EHFrameInfo.Number,
270 "eh_frame_begin", EHFrameInfo.Number, true);
271 Asm->EOL("Length of Frame Information Entry");
272
273 EmitLabel("eh_frame_begin", EHFrameInfo.Number);
274
275 EmitSectionOffset("eh_frame_begin", "eh_frame_common",
276 EHFrameInfo.Number, EHFrameInfo.PersonalityIndex,
277 true, true, false);
278
279 Asm->EOL("FDE CIE offset");
280
281 EmitReference("eh_func_begin", EHFrameInfo.Number, true, true);
282 Asm->EOL("FDE initial location");
283 EmitDifference("eh_func_end", EHFrameInfo.Number,
284 "eh_func_begin", EHFrameInfo.Number, true);
285 Asm->EOL("FDE address range");
286
287 // If there is a personality and landing pads then point to the language
288 // specific data area in the exception table.
289 if (MMI->getPersonalities()[0] != NULL) {
290 bool is4Byte = TD->getPointerSize() == sizeof(int32_t);
291
292 Asm->EmitULEB128Bytes(is4Byte ? 4 : 8);
293 Asm->EOL("Augmentation size");
294
295 if (EHFrameInfo.hasLandingPads)
296 EmitReference("exception", EHFrameInfo.Number, true, false);
297 else {
298 if (is4Byte)
299 Asm->EmitInt32((int)0);
300 else
301 Asm->EmitInt64((int)0);
302 }
303 Asm->EOL("Language Specific Data Area");
304 } else {
305 Asm->EmitULEB128Bytes(0);
306 Asm->EOL("Augmentation size");
307 }
308
309 // Indicate locations of function specific callee saved registers in frame.
310 EmitFrameMoves("eh_func_begin", EHFrameInfo.Number, EHFrameInfo.Moves,
311 true);
312
313 // On Darwin the linker honors the alignment of eh_frame, which means it
314 // must be 8-byte on 64-bit targets to match what gcc does. Otherwise you
315 // get holes which confuse readers of eh_frame.
316 Asm->EmitAlignment(TD->getPointerSize() == sizeof(int32_t) ? 2 : 3,
317 0, 0, false);
318 EmitLabel("eh_frame_end", EHFrameInfo.Number);
319
320 // If the function is marked used, this table should be also. We cannot
321 // make the mark unconditional in this case, since retaining the table also
322 // retains the function in this case, and there is code around that depends
323 // on unused functions (calling undefined externals) being dead-stripped to
324 // link correctly. Yes, there really is.
325 if (MMI->isUsedFunction(EHFrameInfo.function))
326 if (const char *UsedDirective = MAI->getUsedDirective())
327 O << UsedDirective << EHFrameInfo.FnName << "\n\n";
328 }
329
330 Asm->EOL();
331}
332
333/// SharedTypeIds - How many leading type ids two landing pads have in common.
334unsigned 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;
339 unsigned Count = 0;
340
341 for (; Count != MinSize; ++Count)
342 if (LIds[Count] != RIds[Count])
343 return Count;
344
345 return Count;
346}
347
348/// PadLT - Order landing pads lexicographically by type id.
349bool 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;
353
354 for (unsigned i = 0; i != MinSize; ++i)
355 if (LIds[i] != RIds[i])
356 return LIds[i] < RIds[i];
357
358 return LSize < RSize;
359}
360
361/// ComputeActionsTable - Compute the actions table and gather the first action
362/// index for each landing pad site.
363unsigned DwarfException::
364ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*> &LandingPads,
365 SmallVectorImpl<ActionEntry> &Actions,
366 SmallVectorImpl<unsigned> &FirstActions) {
367
368 // The action table follows the call-site table in the LSDA. The individual
369 // records are of two types:
370 //
371 // * Catch clause
372 // * Exception specification
373 //
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.
379 //
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].
390
391 const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
392 SmallVector<int, 16> FilterOffsets;
393 FilterOffsets.reserve(FilterIds.size());
394 int Offset = -1;
395
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);
400 }
401
402 FirstActions.reserve(LandingPads.size());
403
404 int FirstAction = 0;
405 unsigned SizeActions = 0;
406 const LandingPadInfo *PrevLPI = 0;
407
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;
414
415 if (NumShared < TypeIds.size()) {
416 unsigned SizeAction = 0;
417 ActionEntry *PrevAction = 0;
418
419 if (NumShared) {
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);
425
426 for (unsigned j = NumShared; j != SizePrevIds; ++j) {
427 SizeAction -=
428 MCAsmInfo::getSLEB128Size(PrevAction->ValueForTypeID);
429 SizeAction += -PrevAction->NextAction;
430 PrevAction = PrevAction->Previous;
431 }
432 }
433
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);
440
441 int NextAction = SizeAction ? -(SizeAction + SizeTypeID) : 0;
442 SizeAction = SizeTypeID + MCAsmInfo::getSLEB128Size(NextAction);
443 SizeSiteActions += SizeAction;
444
445 ActionEntry Action = { ValueForTypeID, NextAction, PrevAction };
446 Actions.push_back(Action);
447 PrevAction = &Actions.back();
448 }
449
450 // Record the first action of the landing pad site.
451 FirstAction = SizeActions + SizeSiteActions - SizeAction + 1;
452 } // else identical - re-use previous FirstAction
453
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);
460
461 // Compute this sites contribution to size.
462 SizeActions += SizeSiteActions;
463
464 PrevLPI = LPI;
465 }
466
467 return SizeActions;
468}
469
470/// CallToNoUnwindFunction - Return `true' if this is a call to a function
471/// marked `nounwind'. Return `false' otherwise.
472bool DwarfException::CallToNoUnwindFunction(const MachineInstr *MI) {
473 assert(MI->getDesc().isCall() && "This should be a call instruction!");
474
475 bool MarkedNoUnwind = false;
476 bool SawFunc = false;
477
478 for (unsigned I = 0, E = MI->getNumOperands(); I != E; ++I) {
479 const MachineOperand &MO = MI->getOperand(I);
480
481 if (MO.isGlobal()) {
482 if (Function *F = dyn_cast<Function>(MO.getGlobal())) {
483 if (SawFunc) {
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.
487 //
488 // FIXME: Determine if there's a way to say that `F' is the callee or
489 // parameter.
490 MarkedNoUnwind = false;
491 break;
492 }
493
494 MarkedNoUnwind = F->doesNotThrow();
495 SawFunc = true;
496 }
497 }
498 }
499
500 return MarkedNoUnwind;
501}
502
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.
510void DwarfException::
511ComputeCallSiteTable(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;
517
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;
521
522 // Whether the last CallSite entry was for an invoke.
523 bool PreviousIsInvoke = false;
524
525 // Visit all instructions in order of address.
526 for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
527 I != E; ++I) {
528 for (MachineBasicBlock::const_iterator MI = I->begin(), E = I->end();
529 MI != E; ++MI) {
530 if (!MI->isLabel()) {
531 if (MI->getDesc().isCall())
532 SawPotentiallyThrowing |= !CallToNoUnwindFunction(MI);
533
534 continue;
535 }
536
537 unsigned BeginLabel = MI->getOperand(0).getImm();
538 assert(BeginLabel && "Invalid label!");
539
540 // End of the previous try-range?
541 if (BeginLabel == LastLabel)
542 SawPotentiallyThrowing = false;
543
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.
548 continue;
549
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!");
554
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
558 // try-ranges.
559 if (SawPotentiallyThrowing &&
560 MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf) {
561 CallSiteEntry Site = { LastLabel, BeginLabel, 0, 0 };
562 CallSites.push_back(Site);
563 PreviousIsInvoke = false;
564 }
565
566 LastLabel = LandingPad->EndLabels[P.RangeIndex];
567 assert(BeginLabel && LastLabel && "Invalid landing pad!");
568
569 if (LandingPad->LandingPadLabel) {
570 // This try-range is for an invoke.
571 CallSiteEntry Site = {
572 BeginLabel,
573 LastLabel,
574 LandingPad->LandingPadLabel,
575 FirstActions[P.PadIndex]
576 };
577
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;
585 continue;
586 }
587 }
588
589 // Otherwise, create a new call-site.
590 CallSites.push_back(Site);
591 PreviousIsInvoke = true;
592 } else {
593 // Create a gap.
594 PreviousIsInvoke = false;
595 }
596 }
597 }
598
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);
606 }
607}
608
609/// EmitExceptionTable - Emit landing pads and actions.
610///
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.
614///
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
619/// table.
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.
629void 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;
634
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());
639
640 for (unsigned i = 0, N = PadInfos.size(); i != N; ++i)
641 LandingPads.push_back(&PadInfos[i]);
642
643 std::sort(LandingPads.begin(), LandingPads.end(), PadLT);
644
645 // Compute the actions table and gather the first action index for each
646 // landing pad site.
647 SmallVector<ActionEntry, 32> Actions;
648 SmallVector<unsigned, 64> FirstActions;
649 unsigned SizeActions = ComputeActionsTable(LandingPads, Actions,
650 FirstActions);
651
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.
655 RangeMapType PadMap;
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;
663 }
664 }
665
666 // Compute the call-site table.
667 SmallVector<CallSiteEntry, 64> CallSites;
668 ComputeCallSiteTable(CallSites, PadMap, LandingPads, FirstActions);
669
670 // Final tallies.
671
672 // Call sites.
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;
678 unsigned SizeSites;
679
680 if (IsSJLJ)
681 SizeSites = 0;
682 else
683 SizeSites = CallSites.size() *
684 (SiteStartSize + SiteLengthSize + LandingPadSize);
685
686 for (unsigned i = 0, e = CallSites.size(); i < e; ++i) {
687 SizeSites += MCAsmInfo::getULEB128Size(CallSites[i].Action);
688 if (IsSJLJ)
689 SizeSites += MCAsmInfo::getULEB128Size(i);
690 }
691
692 // Type infos.
693 const MCSection *LSDASection = Asm->getObjFileLowering().getLSDASection();
694 unsigned TTypeFormat;
695 unsigned TypeFormatSize;
696
697 if (!HaveTTData) {
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);
702 } else {
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.
707 //
708 // Because of this, we have a couple of options:
709 //
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.
712 //
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
716 // have a problem.
717 //
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.
725 //
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.
729 //
|
731 Asm->TM.getRelocationModel() == Reloc::Static)
732 TTypeFormat = dwarf::DW_EH_PE_absptr;
733 else
734 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
735 dwarf::DW_EH_PE_sdata4;
736
737 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
738 }
739
740 // Begin the exception table.
741 Asm->OutStreamer.SwitchSection(LSDASection);
742 Asm->EmitAlignment(2, 0, 0, false);
743
744 O << "GCC_except_table" << SubprogramCount << ":\n";
745
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
767 (HaveTTData ?
768 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
769 TyOffset;
770 unsigned SizeAlign = (4 - TotalSize) & 3;
771
772 for (unsigned i = 0; i != SizeAlign; ++i) {
773 Asm->EmitInt8(0);
774 Asm->EOL("Padding");
775 }
776
777 EmitLabel("exception", SubprogramCount);
778
779 if (IsSJLJ) {
780 SmallString<16> LSDAName;
781 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
782 "_LSDA_" << Asm->getFunctionNumber();
783 O << LSDAName.str() << ":\n";
784 }
785
786 // Emit the header.
787 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
788 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
789
790 Asm->EmitInt8(TTypeFormat);
791 Asm->EOL("@TType format", TTypeFormat);
792
793 if (HaveTTData) {
794 Asm->EmitULEB128Bytes(TyOffset);
795 Asm->EOL("@TType base offset");
796 }
797
798 // SjLj Exception handling
799 if (IsSJLJ) {
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");
804
805 // Emit the landing pad site information.
806 unsigned idx = 0;
807 for (SmallVectorImpl<CallSiteEntry>::const_iterator
808 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
809 const CallSiteEntry &S = *I;
810
811 // Offset of the landing pad, counted in 16-byte bundles relative to the
812 // @LPStart address.
813 Asm->EmitULEB128Bytes(idx);
814 Asm->EOL("Landing pad");
815
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);
820 Asm->EOL("Action");
821 }
822 } else {
823 // DWARF Exception handling
824 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
825
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
830 // landing pad.
831 //
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
835 // indicates:
836 //
837 // * The position of the call-site.
838 // * The position of the landing pad.
839 // * The first action record for that call site.
840 //
841 // A missing entry in the call-site table indicates that a call is not
842 // supposed to throw.
843
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");
849
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;
855
856 if (!S.BeginLabel) {
857 BeginTag = "eh_func_begin";
858 BeginNumber = SubprogramCount;
859 } else {
860 BeginTag = "label";
861 BeginNumber = S.BeginLabel;
862 }
863
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,
868 true, true);
869 Asm->EOL("Region start");
870
871 if (!S.EndLabel)
872 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
873 true);
874 else
875 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
876
877 Asm->EOL("Region length");
878
879 // Offset of the landing pad, counted in 16-byte bundles relative to the
880 // @LPStart address.
881 if (!S.PadLabel)
882 Asm->EmitInt32(0);
883 else
884 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
885 true, true);
886
887 Asm->EOL("Landing pad");
888
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);
893 Asm->EOL("Action");
894 }
895 }
896
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;
901
902 // Type Filter
903 //
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.
906
907 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
908 Asm->EOL("TypeInfo index");
909
910 // Action Record
911 //
912 // Self-relative signed displacement in bytes of the next action record,
913 // or 0 if there is no next action record.
914
915 Asm->EmitSLEB128Bytes(Action.NextAction);
916 Asm->EOL("Next action");
917 }
918
919 // Emit the Catch TypeInfos.
| 732 Asm->TM.getRelocationModel() == Reloc::Static)
733 TTypeFormat = dwarf::DW_EH_PE_absptr;
734 else
735 TTypeFormat = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
736 dwarf::DW_EH_PE_sdata4;
737
738 TypeFormatSize = SizeOfEncodedValue(TTypeFormat);
739 }
740
741 // Begin the exception table.
742 Asm->OutStreamer.SwitchSection(LSDASection);
743 Asm->EmitAlignment(2, 0, 0, false);
744
745 O << "GCC_except_table" << SubprogramCount << ":\n";
746
747 // The type infos need to be aligned. GCC does this by inserting padding just
748 // before the type infos. However, this changes the size of the exception
749 // table, so you need to take this into account when you output the exception
750 // table size. However, the size is output using a variable length encoding.
751 // So by increasing the size by inserting padding, you may increase the number
752 // of bytes used for writing the size. If it increases, say by one byte, then
753 // you now need to output one less byte of padding to get the type infos
754 // aligned. However this decreases the size of the exception table. This
755 // changes the value you have to output for the exception table size. Due to
756 // the variable length encoding, the number of bytes used for writing the
757 // length may decrease. If so, you then have to increase the amount of
758 // padding. And so on. If you look carefully at the GCC code you will see that
759 // it indeed does this in a loop, going on and on until the values stabilize.
760 // We chose another solution: don't output padding inside the table like GCC
761 // does, instead output it before the table.
762 unsigned SizeTypes = TypeInfos.size() * TypeFormatSize;
763 unsigned TyOffset = sizeof(int8_t) + // Call site format
764 MCAsmInfo::getULEB128Size(SizeSites) + // Call-site table length
765 SizeSites + SizeActions + SizeTypes;
766 unsigned TotalSize = sizeof(int8_t) + // LPStart format
767 sizeof(int8_t) + // TType format
768 (HaveTTData ?
769 MCAsmInfo::getULEB128Size(TyOffset) : 0) + // TType base offset
770 TyOffset;
771 unsigned SizeAlign = (4 - TotalSize) & 3;
772
773 for (unsigned i = 0; i != SizeAlign; ++i) {
774 Asm->EmitInt8(0);
775 Asm->EOL("Padding");
776 }
777
778 EmitLabel("exception", SubprogramCount);
779
780 if (IsSJLJ) {
781 SmallString<16> LSDAName;
782 raw_svector_ostream(LSDAName) << MAI->getPrivateGlobalPrefix() <<
783 "_LSDA_" << Asm->getFunctionNumber();
784 O << LSDAName.str() << ":\n";
785 }
786
787 // Emit the header.
788 Asm->EmitInt8(dwarf::DW_EH_PE_omit);
789 Asm->EOL("@LPStart format", dwarf::DW_EH_PE_omit);
790
791 Asm->EmitInt8(TTypeFormat);
792 Asm->EOL("@TType format", TTypeFormat);
793
794 if (HaveTTData) {
795 Asm->EmitULEB128Bytes(TyOffset);
796 Asm->EOL("@TType base offset");
797 }
798
799 // SjLj Exception handling
800 if (IsSJLJ) {
801 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
802 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
803 Asm->EmitULEB128Bytes(SizeSites);
804 Asm->EOL("Call site table length");
805
806 // Emit the landing pad site information.
807 unsigned idx = 0;
808 for (SmallVectorImpl<CallSiteEntry>::const_iterator
809 I = CallSites.begin(), E = CallSites.end(); I != E; ++I, ++idx) {
810 const CallSiteEntry &S = *I;
811
812 // Offset of the landing pad, counted in 16-byte bundles relative to the
813 // @LPStart address.
814 Asm->EmitULEB128Bytes(idx);
815 Asm->EOL("Landing pad");
816
817 // Offset of the first associated action record, relative to the start of
818 // the action table. This value is biased by 1 (1 indicates the start of
819 // the action table), and 0 indicates that there are no actions.
820 Asm->EmitULEB128Bytes(S.Action);
821 Asm->EOL("Action");
822 }
823 } else {
824 // DWARF Exception handling
825 assert(MAI->getExceptionHandlingType() == ExceptionHandling::Dwarf);
826
827 // The call-site table is a list of all call sites that may throw an
828 // exception (including C++ 'throw' statements) in the procedure
829 // fragment. It immediately follows the LSDA header. Each entry indicates,
830 // for a given call, the first corresponding action record and corresponding
831 // landing pad.
832 //
833 // The table begins with the number of bytes, stored as an LEB128
834 // compressed, unsigned integer. The records immediately follow the record
835 // count. They are sorted in increasing call-site address. Each record
836 // indicates:
837 //
838 // * The position of the call-site.
839 // * The position of the landing pad.
840 // * The first action record for that call site.
841 //
842 // A missing entry in the call-site table indicates that a call is not
843 // supposed to throw.
844
845 // Emit the landing pad call site table.
846 Asm->EmitInt8(dwarf::DW_EH_PE_udata4);
847 Asm->EOL("Call site format", dwarf::DW_EH_PE_udata4);
848 Asm->EmitULEB128Bytes(SizeSites);
849 Asm->EOL("Call site table size");
850
851 for (SmallVectorImpl<CallSiteEntry>::const_iterator
852 I = CallSites.begin(), E = CallSites.end(); I != E; ++I) {
853 const CallSiteEntry &S = *I;
854 const char *BeginTag;
855 unsigned BeginNumber;
856
857 if (!S.BeginLabel) {
858 BeginTag = "eh_func_begin";
859 BeginNumber = SubprogramCount;
860 } else {
861 BeginTag = "label";
862 BeginNumber = S.BeginLabel;
863 }
864
865 // Offset of the call site relative to the previous call site, counted in
866 // number of 16-byte bundles. The first call site is counted relative to
867 // the start of the procedure fragment.
868 EmitSectionOffset(BeginTag, "eh_func_begin", BeginNumber, SubprogramCount,
869 true, true);
870 Asm->EOL("Region start");
871
872 if (!S.EndLabel)
873 EmitDifference("eh_func_end", SubprogramCount, BeginTag, BeginNumber,
874 true);
875 else
876 EmitDifference("label", S.EndLabel, BeginTag, BeginNumber, true);
877
878 Asm->EOL("Region length");
879
880 // Offset of the landing pad, counted in 16-byte bundles relative to the
881 // @LPStart address.
882 if (!S.PadLabel)
883 Asm->EmitInt32(0);
884 else
885 EmitSectionOffset("label", "eh_func_begin", S.PadLabel, SubprogramCount,
886 true, true);
887
888 Asm->EOL("Landing pad");
889
890 // Offset of the first associated action record, relative to the start of
891 // the action table. This value is biased by 1 (1 indicates the start of
892 // the action table), and 0 indicates that there are no actions.
893 Asm->EmitULEB128Bytes(S.Action);
894 Asm->EOL("Action");
895 }
896 }
897
898 // Emit the Action Table.
899 for (SmallVectorImpl<ActionEntry>::const_iterator
900 I = Actions.begin(), E = Actions.end(); I != E; ++I) {
901 const ActionEntry &Action = *I;
902
903 // Type Filter
904 //
905 // Used by the runtime to match the type of the thrown exception to the
906 // type of the catch clauses or the types in the exception specification.
907
908 Asm->EmitSLEB128Bytes(Action.ValueForTypeID);
909 Asm->EOL("TypeInfo index");
910
911 // Action Record
912 //
913 // Self-relative signed displacement in bytes of the next action record,
914 // or 0 if there is no next action record.
915
916 Asm->EmitSLEB128Bytes(Action.NextAction);
917 Asm->EOL("Next action");
918 }
919
920 // Emit the Catch TypeInfos.
|