1 //===-- CodeGen/AsmPrinter/WinException.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 Win64 exception info into asm files.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "WinException.h"
15 #include "llvm/ADT/Twine.h"
16 #include "llvm/BinaryFormat/COFF.h"
17 #include "llvm/BinaryFormat/Dwarf.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/CodeGen/TargetFrameLowering.h"
23 #include "llvm/CodeGen/TargetLowering.h"
24 #include "llvm/CodeGen/TargetSubtargetInfo.h"
25 #include "llvm/CodeGen/WinEHFuncInfo.h"
26 #include "llvm/IR/DataLayout.h"
27 #include "llvm/IR/Mangler.h"
28 #include "llvm/IR/Module.h"
29 #include "llvm/MC/MCAsmInfo.h"
30 #include "llvm/MC/MCContext.h"
31 #include "llvm/MC/MCExpr.h"
32 #include "llvm/MC/MCSection.h"
33 #include "llvm/MC/MCStreamer.h"
34 #include "llvm/MC/MCSymbol.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/FormattedStream.h"
37 #include "llvm/Target/TargetLoweringObjectFile.h"
38 #include "llvm/Target/TargetOptions.h"
39 using namespace llvm;
40
WinException(AsmPrinter * A)41 WinException::WinException(AsmPrinter *A) : EHStreamer(A) {
42 // MSVC's EH tables are always composed of 32-bit words. All known 64-bit
43 // platforms use an imagerel32 relocation to refer to symbols.
44 useImageRel32 = (A->getDataLayout().getPointerSizeInBits() == 64);
45 }
46
~WinException()47 WinException::~WinException() {}
48
49 /// endModule - Emit all exception information that should come after the
50 /// content.
endModule()51 void WinException::endModule() {
52 auto &OS = *Asm->OutStreamer;
53 const Module *M = MMI->getModule();
54 for (const Function &F : *M)
55 if (F.hasFnAttribute("safeseh"))
56 OS.EmitCOFFSafeSEH(Asm->getSymbol(&F));
57 }
58
beginFunction(const MachineFunction * MF)59 void WinException::beginFunction(const MachineFunction *MF) {
60 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
61
62 // If any landing pads survive, we need an EH table.
63 bool hasLandingPads = !MF->getLandingPads().empty();
64 bool hasEHFunclets = MF->hasEHFunclets();
65
66 const Function &F = MF->getFunction();
67
68 shouldEmitMoves = Asm->needsSEHMoves() && MF->hasWinCFI();
69
70 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
71 unsigned PerEncoding = TLOF.getPersonalityEncoding();
72
73 EHPersonality Per = EHPersonality::Unknown;
74 const Function *PerFn = nullptr;
75 if (F.hasPersonalityFn()) {
76 PerFn = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
77 Per = classifyEHPersonality(PerFn);
78 }
79
80 bool forceEmitPersonality = F.hasPersonalityFn() &&
81 !isNoOpWithoutInvoke(Per) &&
82 F.needsUnwindTableEntry();
83
84 shouldEmitPersonality =
85 forceEmitPersonality || ((hasLandingPads || hasEHFunclets) &&
86 PerEncoding != dwarf::DW_EH_PE_omit && PerFn);
87
88 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
89 shouldEmitLSDA = shouldEmitPersonality &&
90 LSDAEncoding != dwarf::DW_EH_PE_omit;
91
92 // If we're not using CFI, we don't want the CFI or the personality, but we
93 // might want EH tables if we had EH pads.
94 if (!Asm->MAI->usesWindowsCFI()) {
95 if (Per == EHPersonality::MSVC_X86SEH && !hasEHFunclets) {
96 // If this is 32-bit SEH and we don't have any funclets (really invokes),
97 // make sure we emit the parent offset label. Some unreferenced filter
98 // functions may still refer to it.
99 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
100 StringRef FLinkageName =
101 GlobalValue::dropLLVMManglingEscape(MF->getFunction().getName());
102 emitEHRegistrationOffsetLabel(FuncInfo, FLinkageName);
103 }
104 shouldEmitLSDA = hasEHFunclets;
105 shouldEmitPersonality = false;
106 return;
107 }
108
109 beginFunclet(MF->front(), Asm->CurrentFnSym);
110 }
111
112 /// endFunction - Gather and emit post-function exception information.
113 ///
endFunction(const MachineFunction * MF)114 void WinException::endFunction(const MachineFunction *MF) {
115 if (!shouldEmitPersonality && !shouldEmitMoves && !shouldEmitLSDA)
116 return;
117
118 const Function &F = MF->getFunction();
119 EHPersonality Per = EHPersonality::Unknown;
120 if (F.hasPersonalityFn())
121 Per = classifyEHPersonality(F.getPersonalityFn()->stripPointerCasts());
122
123 // Get rid of any dead landing pads if we're not using funclets. In funclet
124 // schemes, the landing pad is not actually reachable. It only exists so
125 // that we can emit the right table data.
126 if (!isFuncletEHPersonality(Per)) {
127 MachineFunction *NonConstMF = const_cast<MachineFunction*>(MF);
128 NonConstMF->tidyLandingPads();
129 }
130
131 endFunclet();
132
133 // endFunclet will emit the necessary .xdata tables for x64 SEH.
134 if (Per == EHPersonality::MSVC_Win64SEH && MF->hasEHFunclets())
135 return;
136
137 if (shouldEmitPersonality || shouldEmitLSDA) {
138 Asm->OutStreamer->PushSection();
139
140 // Just switch sections to the right xdata section.
141 MCSection *XData = Asm->OutStreamer->getAssociatedXDataSection(
142 Asm->OutStreamer->getCurrentSectionOnly());
143 Asm->OutStreamer->SwitchSection(XData);
144
145 // Emit the tables appropriate to the personality function in use. If we
146 // don't recognize the personality, assume it uses an Itanium-style LSDA.
147 if (Per == EHPersonality::MSVC_Win64SEH)
148 emitCSpecificHandlerTable(MF);
149 else if (Per == EHPersonality::MSVC_X86SEH)
150 emitExceptHandlerTable(MF);
151 else if (Per == EHPersonality::MSVC_CXX)
152 emitCXXFrameHandler3Table(MF);
153 else if (Per == EHPersonality::CoreCLR)
154 emitCLRExceptionTable(MF);
155 else
156 emitExceptionTable();
157
158 Asm->OutStreamer->PopSection();
159 }
160 }
161
162 /// Retrieve the MCSymbol for a GlobalValue or MachineBasicBlock.
getMCSymbolForMBB(AsmPrinter * Asm,const MachineBasicBlock * MBB)163 static MCSymbol *getMCSymbolForMBB(AsmPrinter *Asm,
164 const MachineBasicBlock *MBB) {
165 if (!MBB)
166 return nullptr;
167
168 assert(MBB->isEHFuncletEntry());
169
170 // Give catches and cleanups a name based off of their parent function and
171 // their funclet entry block's number.
172 const MachineFunction *MF = MBB->getParent();
173 const Function &F = MF->getFunction();
174 StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
175 MCContext &Ctx = MF->getContext();
176 StringRef HandlerPrefix = MBB->isCleanupFuncletEntry() ? "dtor" : "catch";
177 return Ctx.getOrCreateSymbol("?" + HandlerPrefix + "$" +
178 Twine(MBB->getNumber()) + "@?0?" +
179 FuncLinkageName + "@4HA");
180 }
181
beginFunclet(const MachineBasicBlock & MBB,MCSymbol * Sym)182 void WinException::beginFunclet(const MachineBasicBlock &MBB,
183 MCSymbol *Sym) {
184 CurrentFuncletEntry = &MBB;
185
186 const Function &F = Asm->MF->getFunction();
187 // If a symbol was not provided for the funclet, invent one.
188 if (!Sym) {
189 Sym = getMCSymbolForMBB(Asm, &MBB);
190
191 // Describe our funclet symbol as a function with internal linkage.
192 Asm->OutStreamer->BeginCOFFSymbolDef(Sym);
193 Asm->OutStreamer->EmitCOFFSymbolStorageClass(COFF::IMAGE_SYM_CLASS_STATIC);
194 Asm->OutStreamer->EmitCOFFSymbolType(COFF::IMAGE_SYM_DTYPE_FUNCTION
195 << COFF::SCT_COMPLEX_TYPE_SHIFT);
196 Asm->OutStreamer->EndCOFFSymbolDef();
197
198 // We want our funclet's entry point to be aligned such that no nops will be
199 // present after the label.
200 Asm->EmitAlignment(std::max(Asm->MF->getAlignment(), MBB.getAlignment()),
201 &F);
202
203 // Now that we've emitted the alignment directive, point at our funclet.
204 Asm->OutStreamer->EmitLabel(Sym);
205 }
206
207 // Mark 'Sym' as starting our funclet.
208 if (shouldEmitMoves || shouldEmitPersonality) {
209 CurrentFuncletTextSection = Asm->OutStreamer->getCurrentSectionOnly();
210 Asm->OutStreamer->EmitWinCFIStartProc(Sym);
211 }
212
213 if (shouldEmitPersonality) {
214 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
215 const Function *PerFn = nullptr;
216
217 // Determine which personality routine we are using for this funclet.
218 if (F.hasPersonalityFn())
219 PerFn = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
220 const MCSymbol *PersHandlerSym =
221 TLOF.getCFIPersonalitySymbol(PerFn, Asm->TM, MMI);
222
223 // Do not emit a .seh_handler directives for cleanup funclets.
224 // FIXME: This means cleanup funclets cannot handle exceptions. Given that
225 // Clang doesn't produce EH constructs inside cleanup funclets and LLVM's
226 // inliner doesn't allow inlining them, this isn't a major problem in
227 // practice.
228 if (!CurrentFuncletEntry->isCleanupFuncletEntry())
229 Asm->OutStreamer->EmitWinEHHandler(PersHandlerSym, true, true);
230 }
231 }
232
endFunclet()233 void WinException::endFunclet() {
234 // No funclet to process? Great, we have nothing to do.
235 if (!CurrentFuncletEntry)
236 return;
237
238 const MachineFunction *MF = Asm->MF;
239 if (shouldEmitMoves || shouldEmitPersonality) {
240 const Function &F = MF->getFunction();
241 EHPersonality Per = EHPersonality::Unknown;
242 if (F.hasPersonalityFn())
243 Per = classifyEHPersonality(F.getPersonalityFn()->stripPointerCasts());
244
245 // Emit an UNWIND_INFO struct describing the prologue.
246 Asm->OutStreamer->EmitWinEHHandlerData();
247
248 if (Per == EHPersonality::MSVC_CXX && shouldEmitPersonality &&
249 !CurrentFuncletEntry->isCleanupFuncletEntry()) {
250 // If this is a C++ catch funclet (or the parent function),
251 // emit a reference to the LSDA for the parent function.
252 StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
253 MCSymbol *FuncInfoXData = Asm->OutContext.getOrCreateSymbol(
254 Twine("$cppxdata$", FuncLinkageName));
255 Asm->OutStreamer->EmitValue(create32bitRef(FuncInfoXData), 4);
256 } else if (Per == EHPersonality::MSVC_Win64SEH && MF->hasEHFunclets() &&
257 !CurrentFuncletEntry->isEHFuncletEntry()) {
258 // If this is the parent function in Win64 SEH, emit the LSDA immediately
259 // following .seh_handlerdata.
260 emitCSpecificHandlerTable(MF);
261 }
262
263 // Switch back to the funclet start .text section now that we are done
264 // writing to .xdata, and emit an .seh_endproc directive to mark the end of
265 // the function.
266 Asm->OutStreamer->SwitchSection(CurrentFuncletTextSection);
267 Asm->OutStreamer->EmitWinCFIEndProc();
268 }
269
270 // Let's make sure we don't try to end the same funclet twice.
271 CurrentFuncletEntry = nullptr;
272 }
273
create32bitRef(const MCSymbol * Value)274 const MCExpr *WinException::create32bitRef(const MCSymbol *Value) {
275 if (!Value)
276 return MCConstantExpr::create(0, Asm->OutContext);
277 return MCSymbolRefExpr::create(Value, useImageRel32
278 ? MCSymbolRefExpr::VK_COFF_IMGREL32
279 : MCSymbolRefExpr::VK_None,
280 Asm->OutContext);
281 }
282
create32bitRef(const GlobalValue * GV)283 const MCExpr *WinException::create32bitRef(const GlobalValue *GV) {
284 if (!GV)
285 return MCConstantExpr::create(0, Asm->OutContext);
286 return create32bitRef(Asm->getSymbol(GV));
287 }
288
getLabelPlusOne(const MCSymbol * Label)289 const MCExpr *WinException::getLabelPlusOne(const MCSymbol *Label) {
290 return MCBinaryExpr::createAdd(create32bitRef(Label),
291 MCConstantExpr::create(1, Asm->OutContext),
292 Asm->OutContext);
293 }
294
getOffset(const MCSymbol * OffsetOf,const MCSymbol * OffsetFrom)295 const MCExpr *WinException::getOffset(const MCSymbol *OffsetOf,
296 const MCSymbol *OffsetFrom) {
297 return MCBinaryExpr::createSub(
298 MCSymbolRefExpr::create(OffsetOf, Asm->OutContext),
299 MCSymbolRefExpr::create(OffsetFrom, Asm->OutContext), Asm->OutContext);
300 }
301
getOffsetPlusOne(const MCSymbol * OffsetOf,const MCSymbol * OffsetFrom)302 const MCExpr *WinException::getOffsetPlusOne(const MCSymbol *OffsetOf,
303 const MCSymbol *OffsetFrom) {
304 return MCBinaryExpr::createAdd(getOffset(OffsetOf, OffsetFrom),
305 MCConstantExpr::create(1, Asm->OutContext),
306 Asm->OutContext);
307 }
308
getFrameIndexOffset(int FrameIndex,const WinEHFuncInfo & FuncInfo)309 int WinException::getFrameIndexOffset(int FrameIndex,
310 const WinEHFuncInfo &FuncInfo) {
311 const TargetFrameLowering &TFI = *Asm->MF->getSubtarget().getFrameLowering();
312 unsigned UnusedReg;
313 if (Asm->MAI->usesWindowsCFI()) {
314 int Offset =
315 TFI.getFrameIndexReferencePreferSP(*Asm->MF, FrameIndex, UnusedReg,
316 /*IgnoreSPUpdates*/ true);
317 assert(UnusedReg ==
318 Asm->MF->getSubtarget()
319 .getTargetLowering()
320 ->getStackPointerRegisterToSaveRestore());
321 return Offset;
322 }
323
324 // For 32-bit, offsets should be relative to the end of the EH registration
325 // node. For 64-bit, it's relative to SP at the end of the prologue.
326 assert(FuncInfo.EHRegNodeEndOffset != INT_MAX);
327 int Offset = TFI.getFrameIndexReference(*Asm->MF, FrameIndex, UnusedReg);
328 Offset += FuncInfo.EHRegNodeEndOffset;
329 return Offset;
330 }
331
332 namespace {
333
334 /// Top-level state used to represent unwind to caller
335 const int NullState = -1;
336
337 struct InvokeStateChange {
338 /// EH Label immediately after the last invoke in the previous state, or
339 /// nullptr if the previous state was the null state.
340 const MCSymbol *PreviousEndLabel;
341
342 /// EH label immediately before the first invoke in the new state, or nullptr
343 /// if the new state is the null state.
344 const MCSymbol *NewStartLabel;
345
346 /// State of the invoke following NewStartLabel, or NullState to indicate
347 /// the presence of calls which may unwind to caller.
348 int NewState;
349 };
350
351 /// Iterator that reports all the invoke state changes in a range of machine
352 /// basic blocks. Changes to the null state are reported whenever a call that
353 /// may unwind to caller is encountered. The MBB range is expected to be an
354 /// entire function or funclet, and the start and end of the range are treated
355 /// as being in the NullState even if there's not an unwind-to-caller call
356 /// before the first invoke or after the last one (i.e., the first state change
357 /// reported is the first change to something other than NullState, and a
358 /// change back to NullState is always reported at the end of iteration).
359 class InvokeStateChangeIterator {
InvokeStateChangeIterator(const WinEHFuncInfo & EHInfo,MachineFunction::const_iterator MFI,MachineFunction::const_iterator MFE,MachineBasicBlock::const_iterator MBBI,int BaseState)360 InvokeStateChangeIterator(const WinEHFuncInfo &EHInfo,
361 MachineFunction::const_iterator MFI,
362 MachineFunction::const_iterator MFE,
363 MachineBasicBlock::const_iterator MBBI,
364 int BaseState)
365 : EHInfo(EHInfo), MFI(MFI), MFE(MFE), MBBI(MBBI), BaseState(BaseState) {
366 LastStateChange.PreviousEndLabel = nullptr;
367 LastStateChange.NewStartLabel = nullptr;
368 LastStateChange.NewState = BaseState;
369 scan();
370 }
371
372 public:
373 static iterator_range<InvokeStateChangeIterator>
range(const WinEHFuncInfo & EHInfo,MachineFunction::const_iterator Begin,MachineFunction::const_iterator End,int BaseState=NullState)374 range(const WinEHFuncInfo &EHInfo, MachineFunction::const_iterator Begin,
375 MachineFunction::const_iterator End, int BaseState = NullState) {
376 // Reject empty ranges to simplify bookkeeping by ensuring that we can get
377 // the end of the last block.
378 assert(Begin != End);
379 auto BlockBegin = Begin->begin();
380 auto BlockEnd = std::prev(End)->end();
381 return make_range(
382 InvokeStateChangeIterator(EHInfo, Begin, End, BlockBegin, BaseState),
383 InvokeStateChangeIterator(EHInfo, End, End, BlockEnd, BaseState));
384 }
385
386 // Iterator methods.
operator ==(const InvokeStateChangeIterator & O) const387 bool operator==(const InvokeStateChangeIterator &O) const {
388 assert(BaseState == O.BaseState);
389 // Must be visiting same block.
390 if (MFI != O.MFI)
391 return false;
392 // Must be visiting same isntr.
393 if (MBBI != O.MBBI)
394 return false;
395 // At end of block/instr iteration, we can still have two distinct states:
396 // one to report the final EndLabel, and another indicating the end of the
397 // state change iteration. Check for CurrentEndLabel equality to
398 // distinguish these.
399 return CurrentEndLabel == O.CurrentEndLabel;
400 }
401
operator !=(const InvokeStateChangeIterator & O) const402 bool operator!=(const InvokeStateChangeIterator &O) const {
403 return !operator==(O);
404 }
operator *()405 InvokeStateChange &operator*() { return LastStateChange; }
operator ->()406 InvokeStateChange *operator->() { return &LastStateChange; }
operator ++()407 InvokeStateChangeIterator &operator++() { return scan(); }
408
409 private:
410 InvokeStateChangeIterator &scan();
411
412 const WinEHFuncInfo &EHInfo;
413 const MCSymbol *CurrentEndLabel = nullptr;
414 MachineFunction::const_iterator MFI;
415 MachineFunction::const_iterator MFE;
416 MachineBasicBlock::const_iterator MBBI;
417 InvokeStateChange LastStateChange;
418 bool VisitingInvoke = false;
419 int BaseState;
420 };
421
422 } // end anonymous namespace
423
scan()424 InvokeStateChangeIterator &InvokeStateChangeIterator::scan() {
425 bool IsNewBlock = false;
426 for (; MFI != MFE; ++MFI, IsNewBlock = true) {
427 if (IsNewBlock)
428 MBBI = MFI->begin();
429 for (auto MBBE = MFI->end(); MBBI != MBBE; ++MBBI) {
430 const MachineInstr &MI = *MBBI;
431 if (!VisitingInvoke && LastStateChange.NewState != BaseState &&
432 MI.isCall() && !EHStreamer::callToNoUnwindFunction(&MI)) {
433 // Indicate a change of state to the null state. We don't have
434 // start/end EH labels handy but the caller won't expect them for
435 // null state regions.
436 LastStateChange.PreviousEndLabel = CurrentEndLabel;
437 LastStateChange.NewStartLabel = nullptr;
438 LastStateChange.NewState = BaseState;
439 CurrentEndLabel = nullptr;
440 // Don't re-visit this instr on the next scan
441 ++MBBI;
442 return *this;
443 }
444
445 // All other state changes are at EH labels before/after invokes.
446 if (!MI.isEHLabel())
447 continue;
448 MCSymbol *Label = MI.getOperand(0).getMCSymbol();
449 if (Label == CurrentEndLabel) {
450 VisitingInvoke = false;
451 continue;
452 }
453 auto InvokeMapIter = EHInfo.LabelToStateMap.find(Label);
454 // Ignore EH labels that aren't the ones inserted before an invoke
455 if (InvokeMapIter == EHInfo.LabelToStateMap.end())
456 continue;
457 auto &StateAndEnd = InvokeMapIter->second;
458 int NewState = StateAndEnd.first;
459 // Keep track of the fact that we're between EH start/end labels so
460 // we know not to treat the inoke we'll see as unwinding to caller.
461 VisitingInvoke = true;
462 if (NewState == LastStateChange.NewState) {
463 // The state isn't actually changing here. Record the new end and
464 // keep going.
465 CurrentEndLabel = StateAndEnd.second;
466 continue;
467 }
468 // Found a state change to report
469 LastStateChange.PreviousEndLabel = CurrentEndLabel;
470 LastStateChange.NewStartLabel = Label;
471 LastStateChange.NewState = NewState;
472 // Start keeping track of the new current end
473 CurrentEndLabel = StateAndEnd.second;
474 // Don't re-visit this instr on the next scan
475 ++MBBI;
476 return *this;
477 }
478 }
479 // Iteration hit the end of the block range.
480 if (LastStateChange.NewState != BaseState) {
481 // Report the end of the last new state
482 LastStateChange.PreviousEndLabel = CurrentEndLabel;
483 LastStateChange.NewStartLabel = nullptr;
484 LastStateChange.NewState = BaseState;
485 // Leave CurrentEndLabel non-null to distinguish this state from end.
486 assert(CurrentEndLabel != nullptr);
487 return *this;
488 }
489 // We've reported all state changes and hit the end state.
490 CurrentEndLabel = nullptr;
491 return *this;
492 }
493
494 /// Emit the language-specific data that __C_specific_handler expects. This
495 /// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
496 /// up after faults with __try, __except, and __finally. The typeinfo values
497 /// are not really RTTI data, but pointers to filter functions that return an
498 /// integer (1, 0, or -1) indicating how to handle the exception. For __finally
499 /// blocks and other cleanups, the landing pad label is zero, and the filter
500 /// function is actually a cleanup handler with the same prototype. A catch-all
501 /// entry is modeled with a null filter function field and a non-zero landing
502 /// pad label.
503 ///
504 /// Possible filter function return values:
505 /// EXCEPTION_EXECUTE_HANDLER (1):
506 /// Jump to the landing pad label after cleanups.
507 /// EXCEPTION_CONTINUE_SEARCH (0):
508 /// Continue searching this table or continue unwinding.
509 /// EXCEPTION_CONTINUE_EXECUTION (-1):
510 /// Resume execution at the trapping PC.
511 ///
512 /// Inferred table structure:
513 /// struct Table {
514 /// int NumEntries;
515 /// struct Entry {
516 /// imagerel32 LabelStart;
517 /// imagerel32 LabelEnd;
518 /// imagerel32 FilterOrFinally; // One means catch-all.
519 /// imagerel32 LabelLPad; // Zero means __finally.
520 /// } Entries[NumEntries];
521 /// };
emitCSpecificHandlerTable(const MachineFunction * MF)522 void WinException::emitCSpecificHandlerTable(const MachineFunction *MF) {
523 auto &OS = *Asm->OutStreamer;
524 MCContext &Ctx = Asm->OutContext;
525 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
526
527 bool VerboseAsm = OS.isVerboseAsm();
528 auto AddComment = [&](const Twine &Comment) {
529 if (VerboseAsm)
530 OS.AddComment(Comment);
531 };
532
533 // Emit a label assignment with the SEH frame offset so we can use it for
534 // llvm.x86.seh.recoverfp.
535 StringRef FLinkageName =
536 GlobalValue::dropLLVMManglingEscape(MF->getFunction().getName());
537 MCSymbol *ParentFrameOffset =
538 Ctx.getOrCreateParentFrameOffsetSymbol(FLinkageName);
539 const MCExpr *MCOffset =
540 MCConstantExpr::create(FuncInfo.SEHSetFrameOffset, Ctx);
541 Asm->OutStreamer->EmitAssignment(ParentFrameOffset, MCOffset);
542
543 // Use the assembler to compute the number of table entries through label
544 // difference and division.
545 MCSymbol *TableBegin =
546 Ctx.createTempSymbol("lsda_begin", /*AlwaysAddSuffix=*/true);
547 MCSymbol *TableEnd =
548 Ctx.createTempSymbol("lsda_end", /*AlwaysAddSuffix=*/true);
549 const MCExpr *LabelDiff = getOffset(TableEnd, TableBegin);
550 const MCExpr *EntrySize = MCConstantExpr::create(16, Ctx);
551 const MCExpr *EntryCount = MCBinaryExpr::createDiv(LabelDiff, EntrySize, Ctx);
552 AddComment("Number of call sites");
553 OS.EmitValue(EntryCount, 4);
554
555 OS.EmitLabel(TableBegin);
556
557 // Iterate over all the invoke try ranges. Unlike MSVC, LLVM currently only
558 // models exceptions from invokes. LLVM also allows arbitrary reordering of
559 // the code, so our tables end up looking a bit different. Rather than
560 // trying to match MSVC's tables exactly, we emit a denormalized table. For
561 // each range of invokes in the same state, we emit table entries for all
562 // the actions that would be taken in that state. This means our tables are
563 // slightly bigger, which is OK.
564 const MCSymbol *LastStartLabel = nullptr;
565 int LastEHState = -1;
566 // Break out before we enter into a finally funclet.
567 // FIXME: We need to emit separate EH tables for cleanups.
568 MachineFunction::const_iterator End = MF->end();
569 MachineFunction::const_iterator Stop = std::next(MF->begin());
570 while (Stop != End && !Stop->isEHFuncletEntry())
571 ++Stop;
572 for (const auto &StateChange :
573 InvokeStateChangeIterator::range(FuncInfo, MF->begin(), Stop)) {
574 // Emit all the actions for the state we just transitioned out of
575 // if it was not the null state
576 if (LastEHState != -1)
577 emitSEHActionsForRange(FuncInfo, LastStartLabel,
578 StateChange.PreviousEndLabel, LastEHState);
579 LastStartLabel = StateChange.NewStartLabel;
580 LastEHState = StateChange.NewState;
581 }
582
583 OS.EmitLabel(TableEnd);
584 }
585
emitSEHActionsForRange(const WinEHFuncInfo & FuncInfo,const MCSymbol * BeginLabel,const MCSymbol * EndLabel,int State)586 void WinException::emitSEHActionsForRange(const WinEHFuncInfo &FuncInfo,
587 const MCSymbol *BeginLabel,
588 const MCSymbol *EndLabel, int State) {
589 auto &OS = *Asm->OutStreamer;
590 MCContext &Ctx = Asm->OutContext;
591
592 bool VerboseAsm = OS.isVerboseAsm();
593 auto AddComment = [&](const Twine &Comment) {
594 if (VerboseAsm)
595 OS.AddComment(Comment);
596 };
597
598 assert(BeginLabel && EndLabel);
599 while (State != -1) {
600 const SEHUnwindMapEntry &UME = FuncInfo.SEHUnwindMap[State];
601 const MCExpr *FilterOrFinally;
602 const MCExpr *ExceptOrNull;
603 auto *Handler = UME.Handler.get<MachineBasicBlock *>();
604 if (UME.IsFinally) {
605 FilterOrFinally = create32bitRef(getMCSymbolForMBB(Asm, Handler));
606 ExceptOrNull = MCConstantExpr::create(0, Ctx);
607 } else {
608 // For an except, the filter can be 1 (catch-all) or a function
609 // label.
610 FilterOrFinally = UME.Filter ? create32bitRef(UME.Filter)
611 : MCConstantExpr::create(1, Ctx);
612 ExceptOrNull = create32bitRef(Handler->getSymbol());
613 }
614
615 AddComment("LabelStart");
616 OS.EmitValue(getLabelPlusOne(BeginLabel), 4);
617 AddComment("LabelEnd");
618 OS.EmitValue(getLabelPlusOne(EndLabel), 4);
619 AddComment(UME.IsFinally ? "FinallyFunclet" : UME.Filter ? "FilterFunction"
620 : "CatchAll");
621 OS.EmitValue(FilterOrFinally, 4);
622 AddComment(UME.IsFinally ? "Null" : "ExceptionHandler");
623 OS.EmitValue(ExceptOrNull, 4);
624
625 assert(UME.ToState < State && "states should decrease");
626 State = UME.ToState;
627 }
628 }
629
emitCXXFrameHandler3Table(const MachineFunction * MF)630 void WinException::emitCXXFrameHandler3Table(const MachineFunction *MF) {
631 const Function &F = MF->getFunction();
632 auto &OS = *Asm->OutStreamer;
633 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
634
635 StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
636
637 SmallVector<std::pair<const MCExpr *, int>, 4> IPToStateTable;
638 MCSymbol *FuncInfoXData = nullptr;
639 if (shouldEmitPersonality) {
640 // If we're 64-bit, emit a pointer to the C++ EH data, and build a map from
641 // IPs to state numbers.
642 FuncInfoXData =
643 Asm->OutContext.getOrCreateSymbol(Twine("$cppxdata$", FuncLinkageName));
644 computeIP2StateTable(MF, FuncInfo, IPToStateTable);
645 } else {
646 FuncInfoXData = Asm->OutContext.getOrCreateLSDASymbol(FuncLinkageName);
647 }
648
649 int UnwindHelpOffset = 0;
650 if (Asm->MAI->usesWindowsCFI())
651 UnwindHelpOffset =
652 getFrameIndexOffset(FuncInfo.UnwindHelpFrameIdx, FuncInfo);
653
654 MCSymbol *UnwindMapXData = nullptr;
655 MCSymbol *TryBlockMapXData = nullptr;
656 MCSymbol *IPToStateXData = nullptr;
657 if (!FuncInfo.CxxUnwindMap.empty())
658 UnwindMapXData = Asm->OutContext.getOrCreateSymbol(
659 Twine("$stateUnwindMap$", FuncLinkageName));
660 if (!FuncInfo.TryBlockMap.empty())
661 TryBlockMapXData =
662 Asm->OutContext.getOrCreateSymbol(Twine("$tryMap$", FuncLinkageName));
663 if (!IPToStateTable.empty())
664 IPToStateXData =
665 Asm->OutContext.getOrCreateSymbol(Twine("$ip2state$", FuncLinkageName));
666
667 bool VerboseAsm = OS.isVerboseAsm();
668 auto AddComment = [&](const Twine &Comment) {
669 if (VerboseAsm)
670 OS.AddComment(Comment);
671 };
672
673 // FuncInfo {
674 // uint32_t MagicNumber
675 // int32_t MaxState;
676 // UnwindMapEntry *UnwindMap;
677 // uint32_t NumTryBlocks;
678 // TryBlockMapEntry *TryBlockMap;
679 // uint32_t IPMapEntries; // always 0 for x86
680 // IPToStateMapEntry *IPToStateMap; // always 0 for x86
681 // uint32_t UnwindHelp; // non-x86 only
682 // ESTypeList *ESTypeList;
683 // int32_t EHFlags;
684 // }
685 // EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
686 // EHFlags & 2 -> ???
687 // EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
688 OS.EmitValueToAlignment(4);
689 OS.EmitLabel(FuncInfoXData);
690
691 AddComment("MagicNumber");
692 OS.EmitIntValue(0x19930522, 4);
693
694 AddComment("MaxState");
695 OS.EmitIntValue(FuncInfo.CxxUnwindMap.size(), 4);
696
697 AddComment("UnwindMap");
698 OS.EmitValue(create32bitRef(UnwindMapXData), 4);
699
700 AddComment("NumTryBlocks");
701 OS.EmitIntValue(FuncInfo.TryBlockMap.size(), 4);
702
703 AddComment("TryBlockMap");
704 OS.EmitValue(create32bitRef(TryBlockMapXData), 4);
705
706 AddComment("IPMapEntries");
707 OS.EmitIntValue(IPToStateTable.size(), 4);
708
709 AddComment("IPToStateXData");
710 OS.EmitValue(create32bitRef(IPToStateXData), 4);
711
712 if (Asm->MAI->usesWindowsCFI()) {
713 AddComment("UnwindHelp");
714 OS.EmitIntValue(UnwindHelpOffset, 4);
715 }
716
717 AddComment("ESTypeList");
718 OS.EmitIntValue(0, 4);
719
720 AddComment("EHFlags");
721 OS.EmitIntValue(1, 4);
722
723 // UnwindMapEntry {
724 // int32_t ToState;
725 // void (*Action)();
726 // };
727 if (UnwindMapXData) {
728 OS.EmitLabel(UnwindMapXData);
729 for (const CxxUnwindMapEntry &UME : FuncInfo.CxxUnwindMap) {
730 MCSymbol *CleanupSym =
731 getMCSymbolForMBB(Asm, UME.Cleanup.dyn_cast<MachineBasicBlock *>());
732 AddComment("ToState");
733 OS.EmitIntValue(UME.ToState, 4);
734
735 AddComment("Action");
736 OS.EmitValue(create32bitRef(CleanupSym), 4);
737 }
738 }
739
740 // TryBlockMap {
741 // int32_t TryLow;
742 // int32_t TryHigh;
743 // int32_t CatchHigh;
744 // int32_t NumCatches;
745 // HandlerType *HandlerArray;
746 // };
747 if (TryBlockMapXData) {
748 OS.EmitLabel(TryBlockMapXData);
749 SmallVector<MCSymbol *, 1> HandlerMaps;
750 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
751 const WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
752
753 MCSymbol *HandlerMapXData = nullptr;
754 if (!TBME.HandlerArray.empty())
755 HandlerMapXData =
756 Asm->OutContext.getOrCreateSymbol(Twine("$handlerMap$")
757 .concat(Twine(I))
758 .concat("$")
759 .concat(FuncLinkageName));
760 HandlerMaps.push_back(HandlerMapXData);
761
762 // TBMEs should form intervals.
763 assert(0 <= TBME.TryLow && "bad trymap interval");
764 assert(TBME.TryLow <= TBME.TryHigh && "bad trymap interval");
765 assert(TBME.TryHigh < TBME.CatchHigh && "bad trymap interval");
766 assert(TBME.CatchHigh < int(FuncInfo.CxxUnwindMap.size()) &&
767 "bad trymap interval");
768
769 AddComment("TryLow");
770 OS.EmitIntValue(TBME.TryLow, 4);
771
772 AddComment("TryHigh");
773 OS.EmitIntValue(TBME.TryHigh, 4);
774
775 AddComment("CatchHigh");
776 OS.EmitIntValue(TBME.CatchHigh, 4);
777
778 AddComment("NumCatches");
779 OS.EmitIntValue(TBME.HandlerArray.size(), 4);
780
781 AddComment("HandlerArray");
782 OS.EmitValue(create32bitRef(HandlerMapXData), 4);
783 }
784
785 // All funclets use the same parent frame offset currently.
786 unsigned ParentFrameOffset = 0;
787 if (shouldEmitPersonality) {
788 const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
789 ParentFrameOffset = TFI->getWinEHParentFrameOffset(*MF);
790 }
791
792 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
793 const WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
794 MCSymbol *HandlerMapXData = HandlerMaps[I];
795 if (!HandlerMapXData)
796 continue;
797 // HandlerType {
798 // int32_t Adjectives;
799 // TypeDescriptor *Type;
800 // int32_t CatchObjOffset;
801 // void (*Handler)();
802 // int32_t ParentFrameOffset; // x64 only
803 // };
804 OS.EmitLabel(HandlerMapXData);
805 for (const WinEHHandlerType &HT : TBME.HandlerArray) {
806 // Get the frame escape label with the offset of the catch object. If
807 // the index is INT_MAX, then there is no catch object, and we should
808 // emit an offset of zero, indicating that no copy will occur.
809 const MCExpr *FrameAllocOffsetRef = nullptr;
810 if (HT.CatchObj.FrameIndex != INT_MAX) {
811 int Offset = getFrameIndexOffset(HT.CatchObj.FrameIndex, FuncInfo);
812 assert(Offset != 0 && "Illegal offset for catch object!");
813 FrameAllocOffsetRef = MCConstantExpr::create(Offset, Asm->OutContext);
814 } else {
815 FrameAllocOffsetRef = MCConstantExpr::create(0, Asm->OutContext);
816 }
817
818 MCSymbol *HandlerSym =
819 getMCSymbolForMBB(Asm, HT.Handler.dyn_cast<MachineBasicBlock *>());
820
821 AddComment("Adjectives");
822 OS.EmitIntValue(HT.Adjectives, 4);
823
824 AddComment("Type");
825 OS.EmitValue(create32bitRef(HT.TypeDescriptor), 4);
826
827 AddComment("CatchObjOffset");
828 OS.EmitValue(FrameAllocOffsetRef, 4);
829
830 AddComment("Handler");
831 OS.EmitValue(create32bitRef(HandlerSym), 4);
832
833 if (shouldEmitPersonality) {
834 AddComment("ParentFrameOffset");
835 OS.EmitIntValue(ParentFrameOffset, 4);
836 }
837 }
838 }
839 }
840
841 // IPToStateMapEntry {
842 // void *IP;
843 // int32_t State;
844 // };
845 if (IPToStateXData) {
846 OS.EmitLabel(IPToStateXData);
847 for (auto &IPStatePair : IPToStateTable) {
848 AddComment("IP");
849 OS.EmitValue(IPStatePair.first, 4);
850 AddComment("ToState");
851 OS.EmitIntValue(IPStatePair.second, 4);
852 }
853 }
854 }
855
computeIP2StateTable(const MachineFunction * MF,const WinEHFuncInfo & FuncInfo,SmallVectorImpl<std::pair<const MCExpr *,int>> & IPToStateTable)856 void WinException::computeIP2StateTable(
857 const MachineFunction *MF, const WinEHFuncInfo &FuncInfo,
858 SmallVectorImpl<std::pair<const MCExpr *, int>> &IPToStateTable) {
859
860 for (MachineFunction::const_iterator FuncletStart = MF->begin(),
861 FuncletEnd = MF->begin(),
862 End = MF->end();
863 FuncletStart != End; FuncletStart = FuncletEnd) {
864 // Find the end of the funclet
865 while (++FuncletEnd != End) {
866 if (FuncletEnd->isEHFuncletEntry()) {
867 break;
868 }
869 }
870
871 // Don't emit ip2state entries for cleanup funclets. Any interesting
872 // exceptional actions in cleanups must be handled in a separate IR
873 // function.
874 if (FuncletStart->isCleanupFuncletEntry())
875 continue;
876
877 MCSymbol *StartLabel;
878 int BaseState;
879 if (FuncletStart == MF->begin()) {
880 BaseState = NullState;
881 StartLabel = Asm->getFunctionBegin();
882 } else {
883 auto *FuncletPad =
884 cast<FuncletPadInst>(FuncletStart->getBasicBlock()->getFirstNonPHI());
885 assert(FuncInfo.FuncletBaseStateMap.count(FuncletPad) != 0);
886 BaseState = FuncInfo.FuncletBaseStateMap.find(FuncletPad)->second;
887 StartLabel = getMCSymbolForMBB(Asm, &*FuncletStart);
888 }
889 assert(StartLabel && "need local function start label");
890 IPToStateTable.push_back(
891 std::make_pair(create32bitRef(StartLabel), BaseState));
892
893 for (const auto &StateChange : InvokeStateChangeIterator::range(
894 FuncInfo, FuncletStart, FuncletEnd, BaseState)) {
895 // Compute the label to report as the start of this entry; use the EH
896 // start label for the invoke if we have one, otherwise (this is a call
897 // which may unwind to our caller and does not have an EH start label, so)
898 // use the previous end label.
899 const MCSymbol *ChangeLabel = StateChange.NewStartLabel;
900 if (!ChangeLabel)
901 ChangeLabel = StateChange.PreviousEndLabel;
902 // Emit an entry indicating that PCs after 'Label' have this EH state.
903 IPToStateTable.push_back(
904 std::make_pair(getLabelPlusOne(ChangeLabel), StateChange.NewState));
905 // FIXME: assert that NewState is between CatchLow and CatchHigh.
906 }
907 }
908 }
909
emitEHRegistrationOffsetLabel(const WinEHFuncInfo & FuncInfo,StringRef FLinkageName)910 void WinException::emitEHRegistrationOffsetLabel(const WinEHFuncInfo &FuncInfo,
911 StringRef FLinkageName) {
912 // Outlined helpers called by the EH runtime need to know the offset of the EH
913 // registration in order to recover the parent frame pointer. Now that we know
914 // we've code generated the parent, we can emit the label assignment that
915 // those helpers use to get the offset of the registration node.
916
917 // Compute the parent frame offset. The EHRegNodeFrameIndex will be invalid if
918 // after optimization all the invokes were eliminated. We still need to emit
919 // the parent frame offset label, but it should be garbage and should never be
920 // used.
921 int64_t Offset = 0;
922 int FI = FuncInfo.EHRegNodeFrameIndex;
923 if (FI != INT_MAX) {
924 const TargetFrameLowering *TFI = Asm->MF->getSubtarget().getFrameLowering();
925 unsigned UnusedReg;
926 Offset = TFI->getFrameIndexReference(*Asm->MF, FI, UnusedReg);
927 }
928
929 MCContext &Ctx = Asm->OutContext;
930 MCSymbol *ParentFrameOffset =
931 Ctx.getOrCreateParentFrameOffsetSymbol(FLinkageName);
932 Asm->OutStreamer->EmitAssignment(ParentFrameOffset,
933 MCConstantExpr::create(Offset, Ctx));
934 }
935
936 /// Emit the language-specific data that _except_handler3 and 4 expect. This is
937 /// functionally equivalent to the __C_specific_handler table, except it is
938 /// indexed by state number instead of IP.
emitExceptHandlerTable(const MachineFunction * MF)939 void WinException::emitExceptHandlerTable(const MachineFunction *MF) {
940 MCStreamer &OS = *Asm->OutStreamer;
941 const Function &F = MF->getFunction();
942 StringRef FLinkageName = GlobalValue::dropLLVMManglingEscape(F.getName());
943
944 bool VerboseAsm = OS.isVerboseAsm();
945 auto AddComment = [&](const Twine &Comment) {
946 if (VerboseAsm)
947 OS.AddComment(Comment);
948 };
949
950 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
951 emitEHRegistrationOffsetLabel(FuncInfo, FLinkageName);
952
953 // Emit the __ehtable label that we use for llvm.x86.seh.lsda.
954 MCSymbol *LSDALabel = Asm->OutContext.getOrCreateLSDASymbol(FLinkageName);
955 OS.EmitValueToAlignment(4);
956 OS.EmitLabel(LSDALabel);
957
958 const Function *Per =
959 dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
960 StringRef PerName = Per->getName();
961 int BaseState = -1;
962 if (PerName == "_except_handler4") {
963 // The LSDA for _except_handler4 starts with this struct, followed by the
964 // scope table:
965 //
966 // struct EH4ScopeTable {
967 // int32_t GSCookieOffset;
968 // int32_t GSCookieXOROffset;
969 // int32_t EHCookieOffset;
970 // int32_t EHCookieXOROffset;
971 // ScopeTableEntry ScopeRecord[];
972 // };
973 //
974 // Offsets are %ebp relative.
975 //
976 // The GS cookie is present only if the function needs stack protection.
977 // GSCookieOffset = -2 means that GS cookie is not used.
978 //
979 // The EH cookie is always present.
980 //
981 // Check is done the following way:
982 // (ebp+CookieXOROffset) ^ [ebp+CookieOffset] == _security_cookie
983
984 // Retrieve the Guard Stack slot.
985 int GSCookieOffset = -2;
986 const MachineFrameInfo &MFI = MF->getFrameInfo();
987 if (MFI.hasStackProtectorIndex()) {
988 unsigned UnusedReg;
989 const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
990 int SSPIdx = MFI.getStackProtectorIndex();
991 GSCookieOffset = TFI->getFrameIndexReference(*MF, SSPIdx, UnusedReg);
992 }
993
994 // Retrieve the EH Guard slot.
995 // TODO(etienneb): Get rid of this value and change it for and assertion.
996 int EHCookieOffset = 9999;
997 if (FuncInfo.EHGuardFrameIndex != INT_MAX) {
998 unsigned UnusedReg;
999 const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
1000 int EHGuardIdx = FuncInfo.EHGuardFrameIndex;
1001 EHCookieOffset = TFI->getFrameIndexReference(*MF, EHGuardIdx, UnusedReg);
1002 }
1003
1004 AddComment("GSCookieOffset");
1005 OS.EmitIntValue(GSCookieOffset, 4);
1006 AddComment("GSCookieXOROffset");
1007 OS.EmitIntValue(0, 4);
1008 AddComment("EHCookieOffset");
1009 OS.EmitIntValue(EHCookieOffset, 4);
1010 AddComment("EHCookieXOROffset");
1011 OS.EmitIntValue(0, 4);
1012 BaseState = -2;
1013 }
1014
1015 assert(!FuncInfo.SEHUnwindMap.empty());
1016 for (const SEHUnwindMapEntry &UME : FuncInfo.SEHUnwindMap) {
1017 auto *Handler = UME.Handler.get<MachineBasicBlock *>();
1018 const MCSymbol *ExceptOrFinally =
1019 UME.IsFinally ? getMCSymbolForMBB(Asm, Handler) : Handler->getSymbol();
1020 // -1 is usually the base state for "unwind to caller", but for
1021 // _except_handler4 it's -2. Do that replacement here if necessary.
1022 int ToState = UME.ToState == -1 ? BaseState : UME.ToState;
1023 AddComment("ToState");
1024 OS.EmitIntValue(ToState, 4);
1025 AddComment(UME.IsFinally ? "Null" : "FilterFunction");
1026 OS.EmitValue(create32bitRef(UME.Filter), 4);
1027 AddComment(UME.IsFinally ? "FinallyFunclet" : "ExceptionHandler");
1028 OS.EmitValue(create32bitRef(ExceptOrFinally), 4);
1029 }
1030 }
1031
getTryRank(const WinEHFuncInfo & FuncInfo,int State)1032 static int getTryRank(const WinEHFuncInfo &FuncInfo, int State) {
1033 int Rank = 0;
1034 while (State != -1) {
1035 ++Rank;
1036 State = FuncInfo.ClrEHUnwindMap[State].TryParentState;
1037 }
1038 return Rank;
1039 }
1040
getTryAncestor(const WinEHFuncInfo & FuncInfo,int Left,int Right)1041 static int getTryAncestor(const WinEHFuncInfo &FuncInfo, int Left, int Right) {
1042 int LeftRank = getTryRank(FuncInfo, Left);
1043 int RightRank = getTryRank(FuncInfo, Right);
1044
1045 while (LeftRank < RightRank) {
1046 Right = FuncInfo.ClrEHUnwindMap[Right].TryParentState;
1047 --RightRank;
1048 }
1049
1050 while (RightRank < LeftRank) {
1051 Left = FuncInfo.ClrEHUnwindMap[Left].TryParentState;
1052 --LeftRank;
1053 }
1054
1055 while (Left != Right) {
1056 Left = FuncInfo.ClrEHUnwindMap[Left].TryParentState;
1057 Right = FuncInfo.ClrEHUnwindMap[Right].TryParentState;
1058 }
1059
1060 return Left;
1061 }
1062
emitCLRExceptionTable(const MachineFunction * MF)1063 void WinException::emitCLRExceptionTable(const MachineFunction *MF) {
1064 // CLR EH "states" are really just IDs that identify handlers/funclets;
1065 // states, handlers, and funclets all have 1:1 mappings between them, and a
1066 // handler/funclet's "state" is its index in the ClrEHUnwindMap.
1067 MCStreamer &OS = *Asm->OutStreamer;
1068 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
1069 MCSymbol *FuncBeginSym = Asm->getFunctionBegin();
1070 MCSymbol *FuncEndSym = Asm->getFunctionEnd();
1071
1072 // A ClrClause describes a protected region.
1073 struct ClrClause {
1074 const MCSymbol *StartLabel; // Start of protected region
1075 const MCSymbol *EndLabel; // End of protected region
1076 int State; // Index of handler protecting the protected region
1077 int EnclosingState; // Index of funclet enclosing the protected region
1078 };
1079 SmallVector<ClrClause, 8> Clauses;
1080
1081 // Build a map from handler MBBs to their corresponding states (i.e. their
1082 // indices in the ClrEHUnwindMap).
1083 int NumStates = FuncInfo.ClrEHUnwindMap.size();
1084 assert(NumStates > 0 && "Don't need exception table!");
1085 DenseMap<const MachineBasicBlock *, int> HandlerStates;
1086 for (int State = 0; State < NumStates; ++State) {
1087 MachineBasicBlock *HandlerBlock =
1088 FuncInfo.ClrEHUnwindMap[State].Handler.get<MachineBasicBlock *>();
1089 HandlerStates[HandlerBlock] = State;
1090 // Use this loop through all handlers to verify our assumption (used in
1091 // the MinEnclosingState computation) that enclosing funclets have lower
1092 // state numbers than their enclosed funclets.
1093 assert(FuncInfo.ClrEHUnwindMap[State].HandlerParentState < State &&
1094 "ill-formed state numbering");
1095 }
1096 // Map the main function to the NullState.
1097 HandlerStates[&MF->front()] = NullState;
1098
1099 // Write out a sentinel indicating the end of the standard (Windows) xdata
1100 // and the start of the additional (CLR) info.
1101 OS.EmitIntValue(0xffffffff, 4);
1102 // Write out the number of funclets
1103 OS.EmitIntValue(NumStates, 4);
1104
1105 // Walk the machine blocks/instrs, computing and emitting a few things:
1106 // 1. Emit a list of the offsets to each handler entry, in lexical order.
1107 // 2. Compute a map (EndSymbolMap) from each funclet to the symbol at its end.
1108 // 3. Compute the list of ClrClauses, in the required order (inner before
1109 // outer, earlier before later; the order by which a forward scan with
1110 // early termination will find the innermost enclosing clause covering
1111 // a given address).
1112 // 4. A map (MinClauseMap) from each handler index to the index of the
1113 // outermost funclet/function which contains a try clause targeting the
1114 // key handler. This will be used to determine IsDuplicate-ness when
1115 // emitting ClrClauses. The NullState value is used to indicate that the
1116 // top-level function contains a try clause targeting the key handler.
1117 // HandlerStack is a stack of (PendingStartLabel, PendingState) pairs for
1118 // try regions we entered before entering the PendingState try but which
1119 // we haven't yet exited.
1120 SmallVector<std::pair<const MCSymbol *, int>, 4> HandlerStack;
1121 // EndSymbolMap and MinClauseMap are maps described above.
1122 std::unique_ptr<MCSymbol *[]> EndSymbolMap(new MCSymbol *[NumStates]);
1123 SmallVector<int, 4> MinClauseMap((size_t)NumStates, NumStates);
1124
1125 // Visit the root function and each funclet.
1126 for (MachineFunction::const_iterator FuncletStart = MF->begin(),
1127 FuncletEnd = MF->begin(),
1128 End = MF->end();
1129 FuncletStart != End; FuncletStart = FuncletEnd) {
1130 int FuncletState = HandlerStates[&*FuncletStart];
1131 // Find the end of the funclet
1132 MCSymbol *EndSymbol = FuncEndSym;
1133 while (++FuncletEnd != End) {
1134 if (FuncletEnd->isEHFuncletEntry()) {
1135 EndSymbol = getMCSymbolForMBB(Asm, &*FuncletEnd);
1136 break;
1137 }
1138 }
1139 // Emit the function/funclet end and, if this is a funclet (and not the
1140 // root function), record it in the EndSymbolMap.
1141 OS.EmitValue(getOffset(EndSymbol, FuncBeginSym), 4);
1142 if (FuncletState != NullState) {
1143 // Record the end of the handler.
1144 EndSymbolMap[FuncletState] = EndSymbol;
1145 }
1146
1147 // Walk the state changes in this function/funclet and compute its clauses.
1148 // Funclets always start in the null state.
1149 const MCSymbol *CurrentStartLabel = nullptr;
1150 int CurrentState = NullState;
1151 assert(HandlerStack.empty());
1152 for (const auto &StateChange :
1153 InvokeStateChangeIterator::range(FuncInfo, FuncletStart, FuncletEnd)) {
1154 // Close any try regions we're not still under
1155 int StillPendingState =
1156 getTryAncestor(FuncInfo, CurrentState, StateChange.NewState);
1157 while (CurrentState != StillPendingState) {
1158 assert(CurrentState != NullState &&
1159 "Failed to find still-pending state!");
1160 // Close the pending clause
1161 Clauses.push_back({CurrentStartLabel, StateChange.PreviousEndLabel,
1162 CurrentState, FuncletState});
1163 // Now the next-outer try region is current
1164 CurrentState = FuncInfo.ClrEHUnwindMap[CurrentState].TryParentState;
1165 // Pop the new start label from the handler stack if we've exited all
1166 // inner try regions of the corresponding try region.
1167 if (HandlerStack.back().second == CurrentState)
1168 CurrentStartLabel = HandlerStack.pop_back_val().first;
1169 }
1170
1171 if (StateChange.NewState != CurrentState) {
1172 // For each clause we're starting, update the MinClauseMap so we can
1173 // know which is the topmost funclet containing a clause targeting
1174 // it.
1175 for (int EnteredState = StateChange.NewState;
1176 EnteredState != CurrentState;
1177 EnteredState =
1178 FuncInfo.ClrEHUnwindMap[EnteredState].TryParentState) {
1179 int &MinEnclosingState = MinClauseMap[EnteredState];
1180 if (FuncletState < MinEnclosingState)
1181 MinEnclosingState = FuncletState;
1182 }
1183 // Save the previous current start/label on the stack and update to
1184 // the newly-current start/state.
1185 HandlerStack.emplace_back(CurrentStartLabel, CurrentState);
1186 CurrentStartLabel = StateChange.NewStartLabel;
1187 CurrentState = StateChange.NewState;
1188 }
1189 }
1190 assert(HandlerStack.empty());
1191 }
1192
1193 // Now emit the clause info, starting with the number of clauses.
1194 OS.EmitIntValue(Clauses.size(), 4);
1195 for (ClrClause &Clause : Clauses) {
1196 // Emit a CORINFO_EH_CLAUSE :
1197 /*
1198 struct CORINFO_EH_CLAUSE
1199 {
1200 CORINFO_EH_CLAUSE_FLAGS Flags; // actually a CorExceptionFlag
1201 DWORD TryOffset;
1202 DWORD TryLength; // actually TryEndOffset
1203 DWORD HandlerOffset;
1204 DWORD HandlerLength; // actually HandlerEndOffset
1205 union
1206 {
1207 DWORD ClassToken; // use for catch clauses
1208 DWORD FilterOffset; // use for filter clauses
1209 };
1210 };
1211
1212 enum CORINFO_EH_CLAUSE_FLAGS
1213 {
1214 CORINFO_EH_CLAUSE_NONE = 0,
1215 CORINFO_EH_CLAUSE_FILTER = 0x0001, // This clause is for a filter
1216 CORINFO_EH_CLAUSE_FINALLY = 0x0002, // This clause is a finally clause
1217 CORINFO_EH_CLAUSE_FAULT = 0x0004, // This clause is a fault clause
1218 };
1219 typedef enum CorExceptionFlag
1220 {
1221 COR_ILEXCEPTION_CLAUSE_NONE,
1222 COR_ILEXCEPTION_CLAUSE_FILTER = 0x0001, // This is a filter clause
1223 COR_ILEXCEPTION_CLAUSE_FINALLY = 0x0002, // This is a finally clause
1224 COR_ILEXCEPTION_CLAUSE_FAULT = 0x0004, // This is a fault clause
1225 COR_ILEXCEPTION_CLAUSE_DUPLICATED = 0x0008, // duplicated clause. This
1226 // clause was duplicated
1227 // to a funclet which was
1228 // pulled out of line
1229 } CorExceptionFlag;
1230 */
1231 // Add 1 to the start/end of the EH clause; the IP associated with a
1232 // call when the runtime does its scan is the IP of the next instruction
1233 // (the one to which control will return after the call), so we need
1234 // to add 1 to the end of the clause to cover that offset. We also add
1235 // 1 to the start of the clause to make sure that the ranges reported
1236 // for all clauses are disjoint. Note that we'll need some additional
1237 // logic when machine traps are supported, since in that case the IP
1238 // that the runtime uses is the offset of the faulting instruction
1239 // itself; if such an instruction immediately follows a call but the
1240 // two belong to different clauses, we'll need to insert a nop between
1241 // them so the runtime can distinguish the point to which the call will
1242 // return from the point at which the fault occurs.
1243
1244 const MCExpr *ClauseBegin =
1245 getOffsetPlusOne(Clause.StartLabel, FuncBeginSym);
1246 const MCExpr *ClauseEnd = getOffsetPlusOne(Clause.EndLabel, FuncBeginSym);
1247
1248 const ClrEHUnwindMapEntry &Entry = FuncInfo.ClrEHUnwindMap[Clause.State];
1249 MachineBasicBlock *HandlerBlock = Entry.Handler.get<MachineBasicBlock *>();
1250 MCSymbol *BeginSym = getMCSymbolForMBB(Asm, HandlerBlock);
1251 const MCExpr *HandlerBegin = getOffset(BeginSym, FuncBeginSym);
1252 MCSymbol *EndSym = EndSymbolMap[Clause.State];
1253 const MCExpr *HandlerEnd = getOffset(EndSym, FuncBeginSym);
1254
1255 uint32_t Flags = 0;
1256 switch (Entry.HandlerType) {
1257 case ClrHandlerType::Catch:
1258 // Leaving bits 0-2 clear indicates catch.
1259 break;
1260 case ClrHandlerType::Filter:
1261 Flags |= 1;
1262 break;
1263 case ClrHandlerType::Finally:
1264 Flags |= 2;
1265 break;
1266 case ClrHandlerType::Fault:
1267 Flags |= 4;
1268 break;
1269 }
1270 if (Clause.EnclosingState != MinClauseMap[Clause.State]) {
1271 // This is a "duplicate" clause; the handler needs to be entered from a
1272 // frame above the one holding the invoke.
1273 assert(Clause.EnclosingState > MinClauseMap[Clause.State]);
1274 Flags |= 8;
1275 }
1276 OS.EmitIntValue(Flags, 4);
1277
1278 // Write the clause start/end
1279 OS.EmitValue(ClauseBegin, 4);
1280 OS.EmitValue(ClauseEnd, 4);
1281
1282 // Write out the handler start/end
1283 OS.EmitValue(HandlerBegin, 4);
1284 OS.EmitValue(HandlerEnd, 4);
1285
1286 // Write out the type token or filter offset
1287 assert(Entry.HandlerType != ClrHandlerType::Filter && "NYI: filters");
1288 OS.EmitIntValue(Entry.TypeToken, 4);
1289 }
1290 }
1291