1//===-- CodeGen/AsmPrinter/WinException.cpp - Dwarf Exception Impl ------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains support for writing Win64 exception info into asm files.
10//
11//===----------------------------------------------------------------------===//
12
13#include "WinException.h"
14#include "llvm/ADT/Twine.h"
15#include "llvm/BinaryFormat/COFF.h"
16#include "llvm/BinaryFormat/Dwarf.h"
17#include "llvm/CodeGen/AsmPrinter.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineModuleInfo.h"
21#include "llvm/CodeGen/TargetFrameLowering.h"
22#include "llvm/CodeGen/TargetLowering.h"
23#include "llvm/CodeGen/TargetSubtargetInfo.h"
24#include "llvm/CodeGen/WinEHFuncInfo.h"
25#include "llvm/IR/DataLayout.h"
26#include "llvm/IR/Module.h"
27#include "llvm/MC/MCAsmInfo.h"
28#include "llvm/MC/MCContext.h"
29#include "llvm/MC/MCExpr.h"
30#include "llvm/MC/MCStreamer.h"
31#include "llvm/Target/TargetLoweringObjectFile.h"
32#include "llvm/Target/TargetMachine.h"
33using namespace llvm;
34
35WinException::WinException(AsmPrinter *A) : EHStreamer(A) {
36 // MSVC's EH tables are always composed of 32-bit words. All known 64-bit
37 // platforms use an imagerel32 relocation to refer to symbols.
38 useImageRel32 = (A->getDataLayout().getPointerSizeInBits() == 64);
39 isAArch64 = Asm->TM.getTargetTriple().isAArch64();
40 isThumb = Asm->TM.getTargetTriple().isThumb();
41}
42
43WinException::~WinException() = default;
44
45/// endModule - Emit all exception information that should come after the
46/// content.
47void WinException::endModule() {
48 auto &OS = *Asm->OutStreamer;
49 const Module *M = MMI->getModule();
50 for (const Function &F : *M)
51 if (F.hasFnAttribute(Kind: "safeseh"))
52 OS.emitCOFFSafeSEH(Symbol: Asm->getSymbol(GV: &F));
53
54 if (M->getModuleFlag(Key: "ehcontguard") && !EHContTargets.empty()) {
55 // Emit the symbol index of each ehcont target.
56 OS.switchSection(Section: Asm->OutContext.getObjectFileInfo()->getGEHContSection());
57 for (const MCSymbol *S : EHContTargets) {
58 OS.emitCOFFSymbolIndex(Symbol: S);
59 }
60 }
61}
62
63void WinException::beginFunction(const MachineFunction *MF) {
64 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
65
66 // If any landing pads survive, we need an EH table.
67 bool hasLandingPads = !MF->getLandingPads().empty();
68 bool hasEHFunclets = MF->hasEHFunclets();
69
70 const Function &F = MF->getFunction();
71
72 shouldEmitMoves = Asm->needsSEHMoves() && MF->hasWinCFI();
73
74 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
75 unsigned PerEncoding = TLOF.getPersonalityEncoding();
76
77 EHPersonality Per = EHPersonality::Unknown;
78 const Function *PerFn = nullptr;
79 if (F.hasPersonalityFn()) {
80 PerFn = dyn_cast<Function>(Val: F.getPersonalityFn()->stripPointerCasts());
81 Per = classifyEHPersonality(Pers: PerFn);
82 }
83
84 bool forceEmitPersonality = F.hasPersonalityFn() &&
85 !isNoOpWithoutInvoke(Pers: Per) &&
86 F.needsUnwindTableEntry();
87
88 shouldEmitPersonality =
89 forceEmitPersonality || ((hasLandingPads || hasEHFunclets) &&
90 PerEncoding != dwarf::DW_EH_PE_omit && PerFn);
91
92 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
93 shouldEmitLSDA = shouldEmitPersonality &&
94 LSDAEncoding != dwarf::DW_EH_PE_omit;
95
96 // If we're not using CFI, we don't want the CFI or the personality, but we
97 // might want EH tables if we had EH pads.
98 if (!Asm->MAI->usesWindowsCFI()) {
99 if (Per == EHPersonality::MSVC_X86SEH && !hasEHFunclets) {
100 // If this is 32-bit SEH and we don't have any funclets (really invokes),
101 // make sure we emit the parent offset label. Some unreferenced filter
102 // functions may still refer to it.
103 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
104 StringRef FLinkageName =
105 GlobalValue::dropLLVMManglingEscape(Name: MF->getFunction().getName());
106 emitEHRegistrationOffsetLabel(FuncInfo, FLinkageName);
107 }
108 shouldEmitLSDA = hasEHFunclets;
109 shouldEmitPersonality = false;
110 return;
111 }
112
113 beginFunclet(MBB: MF->front(), Sym: Asm->CurrentFnSym);
114}
115
116void WinException::markFunctionEnd() {
117 if (isAArch64 && CurrentFuncletEntry &&
118 (shouldEmitMoves || shouldEmitPersonality))
119 Asm->OutStreamer->emitWinCFIFuncletOrFuncEnd();
120}
121
122/// endFunction - Gather and emit post-function exception information.
123///
124void WinException::endFunction(const MachineFunction *MF) {
125 if (!shouldEmitPersonality && !shouldEmitMoves && !shouldEmitLSDA)
126 return;
127
128 const Function &F = MF->getFunction();
129 EHPersonality Per = EHPersonality::Unknown;
130 if (F.hasPersonalityFn())
131 Per = classifyEHPersonality(Pers: F.getPersonalityFn()->stripPointerCasts());
132
133 endFuncletImpl();
134
135 // endFunclet will emit the necessary .xdata tables for table-based SEH.
136 if (Per == EHPersonality::MSVC_TableSEH && MF->hasEHFunclets())
137 return;
138
139 if (shouldEmitPersonality || shouldEmitLSDA) {
140 Asm->OutStreamer->pushSection();
141
142 // Just switch sections to the right xdata section.
143 MCSection *XData = Asm->OutStreamer->getAssociatedXDataSection(
144 TextSec: Asm->OutStreamer->getCurrentSectionOnly());
145 Asm->OutStreamer->switchSection(Section: XData);
146
147 // Emit the tables appropriate to the personality function in use. If we
148 // don't recognize the personality, assume it uses an Itanium-style LSDA.
149 if (Per == EHPersonality::MSVC_TableSEH)
150 emitCSpecificHandlerTable(MF);
151 else if (Per == EHPersonality::MSVC_X86SEH)
152 emitExceptHandlerTable(MF);
153 else if (Per == EHPersonality::MSVC_CXX)
154 emitCXXFrameHandler3Table(MF);
155 else if (Per == EHPersonality::CoreCLR)
156 emitCLRExceptionTable(MF);
157 else
158 emitExceptionTable();
159
160 Asm->OutStreamer->popSection();
161 }
162
163 if (!MF->getEHContTargets().empty()) {
164 // Copy the function's EH Continuation targets to a module-level list.
165 llvm::append_range(C&: EHContTargets, R: MF->getEHContTargets());
166 }
167}
168
169/// Retrieve the MCSymbol for a GlobalValue or MachineBasicBlock.
170static MCSymbol *getMCSymbolForMBB(AsmPrinter *Asm,
171 const MachineBasicBlock *MBB) {
172 if (!MBB)
173 return nullptr;
174
175 assert(MBB->isEHFuncletEntry());
176
177 // Give catches and cleanups a name based off of their parent function and
178 // their funclet entry block's number.
179 const MachineFunction *MF = MBB->getParent();
180 const Function &F = MF->getFunction();
181 StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(Name: F.getName());
182 MCContext &Ctx = MF->getContext();
183 StringRef HandlerPrefix = MBB->isCleanupFuncletEntry() ? "dtor" : "catch";
184 return Ctx.getOrCreateSymbol(Name: "?" + HandlerPrefix + "$" +
185 Twine(MBB->getNumber()) + "@?0?" +
186 FuncLinkageName + "@4HA");
187}
188
189void WinException::beginFunclet(const MachineBasicBlock &MBB,
190 MCSymbol *Sym) {
191 CurrentFuncletEntry = &MBB;
192
193 const Function &F = Asm->MF->getFunction();
194 // If a symbol was not provided for the funclet, invent one.
195 if (!Sym) {
196 Sym = getMCSymbolForMBB(Asm, MBB: &MBB);
197
198 // Describe our funclet symbol as a function with internal linkage.
199 Asm->OutStreamer->beginCOFFSymbolDef(Symbol: Sym);
200 Asm->OutStreamer->emitCOFFSymbolStorageClass(StorageClass: COFF::IMAGE_SYM_CLASS_STATIC);
201 Asm->OutStreamer->emitCOFFSymbolType(Type: COFF::IMAGE_SYM_DTYPE_FUNCTION
202 << COFF::SCT_COMPLEX_TYPE_SHIFT);
203 Asm->OutStreamer->endCOFFSymbolDef();
204
205 // We want our funclet's entry point to be aligned such that no nops will be
206 // present after the label.
207 Asm->emitAlignment(Alignment: std::max(a: Asm->MF->getAlignment(), b: MBB.getAlignment()),
208 GV: &F);
209
210 // Now that we've emitted the alignment directive, point at our funclet.
211 Asm->OutStreamer->emitLabel(Symbol: Sym);
212 }
213
214 // Mark 'Sym' as starting our funclet.
215 if (shouldEmitMoves || shouldEmitPersonality) {
216 CurrentFuncletTextSection = Asm->OutStreamer->getCurrentSectionOnly();
217 Asm->OutStreamer->emitWinCFIStartProc(Symbol: Sym);
218 }
219
220 if (shouldEmitPersonality) {
221 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
222 const Function *PerFn = nullptr;
223
224 // Determine which personality routine we are using for this funclet.
225 if (F.hasPersonalityFn())
226 PerFn = dyn_cast<Function>(Val: F.getPersonalityFn()->stripPointerCasts());
227 const MCSymbol *PersHandlerSym =
228 TLOF.getCFIPersonalitySymbol(GV: PerFn, TM: Asm->TM, MMI);
229
230 // Do not emit a .seh_handler directives for cleanup funclets.
231 // FIXME: This means cleanup funclets cannot handle exceptions. Given that
232 // Clang doesn't produce EH constructs inside cleanup funclets and LLVM's
233 // inliner doesn't allow inlining them, this isn't a major problem in
234 // practice.
235 if (!CurrentFuncletEntry->isCleanupFuncletEntry())
236 Asm->OutStreamer->emitWinEHHandler(Sym: PersHandlerSym, Unwind: true, Except: true);
237 }
238}
239
240void WinException::endFunclet() {
241 if (isAArch64 && CurrentFuncletEntry &&
242 (shouldEmitMoves || shouldEmitPersonality)) {
243 Asm->OutStreamer->switchSection(Section: CurrentFuncletTextSection);
244 Asm->OutStreamer->emitWinCFIFuncletOrFuncEnd();
245 }
246 endFuncletImpl();
247}
248
249void WinException::endFuncletImpl() {
250 // No funclet to process? Great, we have nothing to do.
251 if (!CurrentFuncletEntry)
252 return;
253
254 const MachineFunction *MF = Asm->MF;
255 if (shouldEmitMoves || shouldEmitPersonality) {
256 const Function &F = MF->getFunction();
257 EHPersonality Per = EHPersonality::Unknown;
258 if (F.hasPersonalityFn())
259 Per = classifyEHPersonality(Pers: F.getPersonalityFn()->stripPointerCasts());
260
261 if (Per == EHPersonality::MSVC_CXX && shouldEmitPersonality &&
262 !CurrentFuncletEntry->isCleanupFuncletEntry()) {
263 // Emit an UNWIND_INFO struct describing the prologue.
264 Asm->OutStreamer->emitWinEHHandlerData();
265
266 // If this is a C++ catch funclet (or the parent function),
267 // emit a reference to the LSDA for the parent function.
268 StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(Name: F.getName());
269 MCSymbol *FuncInfoXData = Asm->OutContext.getOrCreateSymbol(
270 Name: Twine("$cppxdata$", FuncLinkageName));
271 Asm->OutStreamer->emitValue(Value: create32bitRef(Value: FuncInfoXData), Size: 4);
272 } else if (Per == EHPersonality::MSVC_TableSEH && MF->hasEHFunclets() &&
273 !CurrentFuncletEntry->isEHFuncletEntry()) {
274 // Emit an UNWIND_INFO struct describing the prologue.
275 Asm->OutStreamer->emitWinEHHandlerData();
276
277 // If this is the parent function in Win64 SEH, emit the LSDA immediately
278 // following .seh_handlerdata.
279 emitCSpecificHandlerTable(MF);
280 } else if (shouldEmitPersonality || shouldEmitLSDA) {
281 // Emit an UNWIND_INFO struct describing the prologue.
282 Asm->OutStreamer->emitWinEHHandlerData();
283 // In these cases, no further info is written to the .xdata section
284 // right here, but is written by e.g. emitExceptionTable in endFunction()
285 // above.
286 } else {
287 // No need to emit the EH handler data right here if nothing needs
288 // writing to the .xdata section; it will be emitted for all
289 // functions that need it in the end anyway.
290 }
291
292 if (!MF->getEHContTargets().empty()) {
293 // Copy the function's EH Continuation targets to a module-level list.
294 llvm::append_range(C&: EHContTargets, R: MF->getEHContTargets());
295 }
296
297 // Switch back to the funclet start .text section now that we are done
298 // writing to .xdata, and emit an .seh_endproc directive to mark the end of
299 // the function.
300 Asm->OutStreamer->switchSection(Section: CurrentFuncletTextSection);
301 Asm->OutStreamer->emitWinCFIEndProc();
302 }
303
304 // Let's make sure we don't try to end the same funclet twice.
305 CurrentFuncletEntry = nullptr;
306}
307
308const MCExpr *WinException::create32bitRef(const MCSymbol *Value) {
309 if (!Value)
310 return MCConstantExpr::create(Value: 0, Ctx&: Asm->OutContext);
311 auto Spec = useImageRel32 ? uint16_t(MCSymbolRefExpr::VK_COFF_IMGREL32) : 0;
312 return MCSymbolRefExpr::create(Symbol: Value, specifier: Spec, Ctx&: Asm->OutContext);
313}
314
315const MCExpr *WinException::create32bitRef(const GlobalValue *GV) {
316 if (!GV)
317 return MCConstantExpr::create(Value: 0, Ctx&: Asm->OutContext);
318 return create32bitRef(Value: Asm->getSymbol(GV));
319}
320
321const MCExpr *WinException::getLabel(const MCSymbol *Label) {
322 return MCSymbolRefExpr::create(Symbol: Label, specifier: MCSymbolRefExpr::VK_COFF_IMGREL32,
323 Ctx&: Asm->OutContext);
324}
325
326const MCExpr *WinException::getOffset(const MCSymbol *OffsetOf,
327 const MCSymbol *OffsetFrom) {
328 return MCBinaryExpr::createSub(
329 LHS: MCSymbolRefExpr::create(Symbol: OffsetOf, Ctx&: Asm->OutContext),
330 RHS: MCSymbolRefExpr::create(Symbol: OffsetFrom, Ctx&: Asm->OutContext), Ctx&: Asm->OutContext);
331}
332
333const MCExpr *WinException::getOffsetPlusOne(const MCSymbol *OffsetOf,
334 const MCSymbol *OffsetFrom) {
335 return MCBinaryExpr::createAdd(LHS: getOffset(OffsetOf, OffsetFrom),
336 RHS: MCConstantExpr::create(Value: 1, Ctx&: Asm->OutContext),
337 Ctx&: Asm->OutContext);
338}
339
340int WinException::getFrameIndexOffset(int FrameIndex,
341 const WinEHFuncInfo &FuncInfo) {
342 const TargetFrameLowering &TFI = *Asm->MF->getSubtarget().getFrameLowering();
343 Register UnusedReg;
344 if (Asm->MAI->usesWindowsCFI()) {
345 StackOffset Offset =
346 TFI.getFrameIndexReferencePreferSP(MF: *Asm->MF, FI: FrameIndex, FrameReg&: UnusedReg,
347 /*IgnoreSPUpdates*/ true);
348 assert(UnusedReg ==
349 Asm->MF->getSubtarget()
350 .getTargetLowering()
351 ->getStackPointerRegisterToSaveRestore());
352 return Offset.getFixed();
353 }
354
355 // For 32-bit, offsets should be relative to the end of the EH registration
356 // node. For 64-bit, it's relative to SP at the end of the prologue.
357 assert(FuncInfo.EHRegNodeEndOffset != INT_MAX);
358 StackOffset Offset = TFI.getFrameIndexReference(MF: *Asm->MF, FI: FrameIndex, FrameReg&: UnusedReg);
359 Offset += StackOffset::getFixed(Fixed: FuncInfo.EHRegNodeEndOffset);
360 assert(!Offset.getScalable() &&
361 "Frame offsets with a scalable component are not supported");
362 return Offset.getFixed();
363}
364
365namespace {
366
367/// Top-level state used to represent unwind to caller
368const int NullState = -1;
369
370struct InvokeStateChange {
371 /// EH Label immediately after the last invoke in the previous state, or
372 /// nullptr if the previous state was the null state.
373 const MCSymbol *PreviousEndLabel;
374
375 /// EH label immediately before the first invoke in the new state, or nullptr
376 /// if the new state is the null state.
377 const MCSymbol *NewStartLabel;
378
379 /// State of the invoke following NewStartLabel, or NullState to indicate
380 /// the presence of calls which may unwind to caller.
381 int NewState;
382};
383
384/// Iterator that reports all the invoke state changes in a range of machine
385/// basic blocks. Changes to the null state are reported whenever a call that
386/// may unwind to caller is encountered. The MBB range is expected to be an
387/// entire function or funclet, and the start and end of the range are treated
388/// as being in the NullState even if there's not an unwind-to-caller call
389/// before the first invoke or after the last one (i.e., the first state change
390/// reported is the first change to something other than NullState, and a
391/// change back to NullState is always reported at the end of iteration).
392class InvokeStateChangeIterator {
393 InvokeStateChangeIterator(const WinEHFuncInfo &EHInfo,
394 MachineFunction::const_iterator MFI,
395 MachineFunction::const_iterator MFE,
396 MachineBasicBlock::const_iterator MBBI,
397 int BaseState)
398 : EHInfo(EHInfo), MFI(MFI), MFE(MFE), MBBI(MBBI), BaseState(BaseState) {
399 LastStateChange.PreviousEndLabel = nullptr;
400 LastStateChange.NewStartLabel = nullptr;
401 LastStateChange.NewState = BaseState;
402 scan();
403 }
404
405public:
406 static iterator_range<InvokeStateChangeIterator>
407 range(const WinEHFuncInfo &EHInfo, MachineFunction::const_iterator Begin,
408 MachineFunction::const_iterator End, int BaseState = NullState) {
409 // Reject empty ranges to simplify bookkeeping by ensuring that we can get
410 // the end of the last block.
411 assert(Begin != End);
412 auto BlockBegin = Begin->begin();
413 auto BlockEnd = std::prev(x: End)->end();
414 return make_range(
415 x: InvokeStateChangeIterator(EHInfo, Begin, End, BlockBegin, BaseState),
416 y: InvokeStateChangeIterator(EHInfo, End, End, BlockEnd, BaseState));
417 }
418
419 // Iterator methods.
420 bool operator==(const InvokeStateChangeIterator &O) const {
421 assert(BaseState == O.BaseState);
422 // Must be visiting same block.
423 if (MFI != O.MFI)
424 return false;
425 // Must be visiting same isntr.
426 if (MBBI != O.MBBI)
427 return false;
428 // At end of block/instr iteration, we can still have two distinct states:
429 // one to report the final EndLabel, and another indicating the end of the
430 // state change iteration. Check for CurrentEndLabel equality to
431 // distinguish these.
432 return CurrentEndLabel == O.CurrentEndLabel;
433 }
434
435 bool operator!=(const InvokeStateChangeIterator &O) const {
436 return !operator==(O);
437 }
438 InvokeStateChange &operator*() { return LastStateChange; }
439 InvokeStateChange *operator->() { return &LastStateChange; }
440 InvokeStateChangeIterator &operator++() { return scan(); }
441
442private:
443 InvokeStateChangeIterator &scan();
444
445 const WinEHFuncInfo &EHInfo;
446 const MCSymbol *CurrentEndLabel = nullptr;
447 MachineFunction::const_iterator MFI;
448 MachineFunction::const_iterator MFE;
449 MachineBasicBlock::const_iterator MBBI;
450 InvokeStateChange LastStateChange;
451 bool VisitingInvoke = false;
452 int BaseState;
453};
454
455} // end anonymous namespace
456
457InvokeStateChangeIterator &InvokeStateChangeIterator::scan() {
458 bool IsNewBlock = false;
459 for (; MFI != MFE; ++MFI, IsNewBlock = true) {
460 if (IsNewBlock)
461 MBBI = MFI->begin();
462 for (auto MBBE = MFI->end(); MBBI != MBBE; ++MBBI) {
463 const MachineInstr &MI = *MBBI;
464 if (!VisitingInvoke && LastStateChange.NewState != BaseState &&
465 MI.isCall() && !EHStreamer::callToNoUnwindFunction(MI: &MI)) {
466 // Indicate a change of state to the null state. We don't have
467 // start/end EH labels handy but the caller won't expect them for
468 // null state regions.
469 LastStateChange.PreviousEndLabel = CurrentEndLabel;
470 LastStateChange.NewStartLabel = nullptr;
471 LastStateChange.NewState = BaseState;
472 CurrentEndLabel = nullptr;
473 // Don't re-visit this instr on the next scan
474 ++MBBI;
475 return *this;
476 }
477
478 // All other state changes are at EH labels before/after invokes.
479 if (!MI.isEHLabel())
480 continue;
481 MCSymbol *Label = MI.getOperand(i: 0).getMCSymbol();
482 if (Label == CurrentEndLabel) {
483 VisitingInvoke = false;
484 continue;
485 }
486 auto InvokeMapIter = EHInfo.LabelToStateMap.find(Val: Label);
487 // Ignore EH labels that aren't the ones inserted before an invoke
488 if (InvokeMapIter == EHInfo.LabelToStateMap.end())
489 continue;
490 auto &StateAndEnd = InvokeMapIter->second;
491 int NewState = StateAndEnd.first;
492 // Keep track of the fact that we're between EH start/end labels so
493 // we know not to treat the inoke we'll see as unwinding to caller.
494 VisitingInvoke = true;
495 if (NewState == LastStateChange.NewState) {
496 // The state isn't actually changing here. Record the new end and
497 // keep going.
498 CurrentEndLabel = StateAndEnd.second;
499 continue;
500 }
501 // Found a state change to report
502 LastStateChange.PreviousEndLabel = CurrentEndLabel;
503 LastStateChange.NewStartLabel = Label;
504 LastStateChange.NewState = NewState;
505 // Start keeping track of the new current end
506 CurrentEndLabel = StateAndEnd.second;
507 // Don't re-visit this instr on the next scan
508 ++MBBI;
509 return *this;
510 }
511 }
512 // Iteration hit the end of the block range.
513 if (LastStateChange.NewState != BaseState) {
514 // Report the end of the last new state
515 LastStateChange.PreviousEndLabel = CurrentEndLabel;
516 LastStateChange.NewStartLabel = nullptr;
517 LastStateChange.NewState = BaseState;
518 // Leave CurrentEndLabel non-null to distinguish this state from end.
519 assert(CurrentEndLabel != nullptr);
520 return *this;
521 }
522 // We've reported all state changes and hit the end state.
523 CurrentEndLabel = nullptr;
524 return *this;
525}
526
527/// Emit the language-specific data that __C_specific_handler expects. This
528/// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
529/// up after faults with __try, __except, and __finally. The typeinfo values
530/// are not really RTTI data, but pointers to filter functions that return an
531/// integer (1, 0, or -1) indicating how to handle the exception. For __finally
532/// blocks and other cleanups, the landing pad label is zero, and the filter
533/// function is actually a cleanup handler with the same prototype. A catch-all
534/// entry is modeled with a null filter function field and a non-zero landing
535/// pad label.
536///
537/// Possible filter function return values:
538/// EXCEPTION_EXECUTE_HANDLER (1):
539/// Jump to the landing pad label after cleanups.
540/// EXCEPTION_CONTINUE_SEARCH (0):
541/// Continue searching this table or continue unwinding.
542/// EXCEPTION_CONTINUE_EXECUTION (-1):
543/// Resume execution at the trapping PC.
544///
545/// Inferred table structure:
546/// struct Table {
547/// int NumEntries;
548/// struct Entry {
549/// imagerel32 LabelStart; // Inclusive
550/// imagerel32 LabelEnd; // Exclusive
551/// imagerel32 FilterOrFinally; // One means catch-all.
552/// imagerel32 LabelLPad; // Zero means __finally.
553/// } Entries[NumEntries];
554/// };
555void WinException::emitCSpecificHandlerTable(const MachineFunction *MF) {
556 auto &OS = *Asm->OutStreamer;
557 MCContext &Ctx = Asm->OutContext;
558 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
559
560 bool VerboseAsm = OS.isVerboseAsm();
561 auto AddComment = [&](const Twine &Comment) {
562 if (VerboseAsm)
563 OS.AddComment(T: Comment);
564 };
565
566 if (!isAArch64) {
567 // Emit a label assignment with the SEH frame offset so we can use it for
568 // llvm.eh.recoverfp.
569 StringRef FLinkageName =
570 GlobalValue::dropLLVMManglingEscape(Name: MF->getFunction().getName());
571 MCSymbol *ParentFrameOffset =
572 Ctx.getOrCreateParentFrameOffsetSymbol(FuncName: FLinkageName);
573 const MCExpr *MCOffset =
574 MCConstantExpr::create(Value: FuncInfo.SEHSetFrameOffset, Ctx);
575 Asm->OutStreamer->emitAssignment(Symbol: ParentFrameOffset, Value: MCOffset);
576 }
577
578 // Use the assembler to compute the number of table entries through label
579 // difference and division.
580 MCSymbol *TableBegin =
581 Ctx.createTempSymbol(Name: "lsda_begin", /*AlwaysAddSuffix=*/true);
582 MCSymbol *TableEnd =
583 Ctx.createTempSymbol(Name: "lsda_end", /*AlwaysAddSuffix=*/true);
584 const MCExpr *LabelDiff = getOffset(OffsetOf: TableEnd, OffsetFrom: TableBegin);
585 const MCExpr *EntrySize = MCConstantExpr::create(Value: 16, Ctx);
586 const MCExpr *EntryCount = MCBinaryExpr::createDiv(LHS: LabelDiff, RHS: EntrySize, Ctx);
587 AddComment("Number of call sites");
588 OS.emitValue(Value: EntryCount, Size: 4);
589
590 OS.emitLabel(Symbol: TableBegin);
591
592 // Iterate over all the invoke try ranges. Unlike MSVC, LLVM currently only
593 // models exceptions from invokes. LLVM also allows arbitrary reordering of
594 // the code, so our tables end up looking a bit different. Rather than
595 // trying to match MSVC's tables exactly, we emit a denormalized table. For
596 // each range of invokes in the same state, we emit table entries for all
597 // the actions that would be taken in that state. This means our tables are
598 // slightly bigger, which is OK.
599 const MCSymbol *LastStartLabel = nullptr;
600 int LastEHState = -1;
601 // Break out before we enter into a finally funclet.
602 // FIXME: We need to emit separate EH tables for cleanups.
603 MachineFunction::const_iterator End = MF->end();
604 MachineFunction::const_iterator Stop = std::next(x: MF->begin());
605 while (Stop != End && !Stop->isEHFuncletEntry())
606 ++Stop;
607 for (const auto &StateChange :
608 InvokeStateChangeIterator::range(EHInfo: FuncInfo, Begin: MF->begin(), End: Stop)) {
609 // Emit all the actions for the state we just transitioned out of
610 // if it was not the null state
611 if (LastEHState != -1)
612 emitSEHActionsForRange(FuncInfo, BeginLabel: LastStartLabel,
613 EndLabel: StateChange.PreviousEndLabel, State: LastEHState);
614 LastStartLabel = StateChange.NewStartLabel;
615 LastEHState = StateChange.NewState;
616 }
617
618 OS.emitLabel(Symbol: TableEnd);
619}
620
621void WinException::emitSEHActionsForRange(const WinEHFuncInfo &FuncInfo,
622 const MCSymbol *BeginLabel,
623 const MCSymbol *EndLabel, int State) {
624 auto &OS = *Asm->OutStreamer;
625 MCContext &Ctx = Asm->OutContext;
626 bool VerboseAsm = OS.isVerboseAsm();
627 auto AddComment = [&](const Twine &Comment) {
628 if (VerboseAsm)
629 OS.AddComment(T: Comment);
630 };
631
632 assert(BeginLabel && EndLabel);
633 while (State != -1) {
634 const SEHUnwindMapEntry &UME = FuncInfo.SEHUnwindMap[State];
635 const MCExpr *FilterOrFinally;
636 const MCExpr *ExceptOrNull;
637 auto *Handler = cast<MachineBasicBlock *>(Val: UME.Handler);
638 if (UME.IsFinally) {
639 FilterOrFinally = create32bitRef(Value: getMCSymbolForMBB(Asm, MBB: Handler));
640 ExceptOrNull = MCConstantExpr::create(Value: 0, Ctx);
641 } else {
642 // For an except, the filter can be 1 (catch-all) or a function
643 // label.
644 FilterOrFinally = UME.Filter ? create32bitRef(GV: UME.Filter)
645 : MCConstantExpr::create(Value: 1, Ctx);
646 ExceptOrNull = create32bitRef(Value: Handler->getSymbol());
647 }
648
649 AddComment("LabelStart");
650 OS.emitValue(Value: getLabel(Label: BeginLabel), Size: 4);
651 AddComment("LabelEnd");
652 OS.emitValue(Value: getLabel(Label: EndLabel), Size: 4);
653 AddComment(UME.IsFinally ? "FinallyFunclet" : UME.Filter ? "FilterFunction"
654 : "CatchAll");
655 OS.emitValue(Value: FilterOrFinally, Size: 4);
656 AddComment(UME.IsFinally ? "Null" : "ExceptionHandler");
657 OS.emitValue(Value: ExceptOrNull, Size: 4);
658
659 assert(UME.ToState < State && "states should decrease");
660 State = UME.ToState;
661 }
662}
663
664void WinException::emitCXXFrameHandler3Table(const MachineFunction *MF) {
665 const Function &F = MF->getFunction();
666 auto &OS = *Asm->OutStreamer;
667 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
668
669 StringRef FuncLinkageName = GlobalValue::dropLLVMManglingEscape(Name: F.getName());
670
671 SmallVector<std::pair<const MCExpr *, int>, 4> IPToStateTable;
672 MCSymbol *FuncInfoXData = nullptr;
673 if (shouldEmitPersonality) {
674 // If we're 64-bit, emit a pointer to the C++ EH data, and build a map from
675 // IPs to state numbers.
676 FuncInfoXData =
677 Asm->OutContext.getOrCreateSymbol(Name: Twine("$cppxdata$", FuncLinkageName));
678 computeIP2StateTable(MF, FuncInfo, IPToStateTable);
679 } else {
680 FuncInfoXData = Asm->OutContext.getOrCreateLSDASymbol(FuncName: FuncLinkageName);
681 }
682
683 int UnwindHelpOffset = 0;
684 // TODO: The check for UnwindHelpFrameIdx against max() below (and the
685 // second check further below) can be removed if MS C++ unwinding is
686 // implemented for ARM, when test/CodeGen/ARM/Windows/wineh-basic.ll
687 // passes without the check.
688 if (Asm->MAI->usesWindowsCFI() &&
689 FuncInfo.UnwindHelpFrameIdx != std::numeric_limits<int>::max())
690 UnwindHelpOffset =
691 getFrameIndexOffset(FrameIndex: FuncInfo.UnwindHelpFrameIdx, FuncInfo);
692
693 MCSymbol *UnwindMapXData = nullptr;
694 MCSymbol *TryBlockMapXData = nullptr;
695 MCSymbol *IPToStateXData = nullptr;
696 if (!FuncInfo.CxxUnwindMap.empty())
697 UnwindMapXData = Asm->OutContext.getOrCreateSymbol(
698 Name: Twine("$stateUnwindMap$", FuncLinkageName));
699 if (!FuncInfo.TryBlockMap.empty())
700 TryBlockMapXData =
701 Asm->OutContext.getOrCreateSymbol(Name: Twine("$tryMap$", FuncLinkageName));
702 if (!IPToStateTable.empty())
703 IPToStateXData =
704 Asm->OutContext.getOrCreateSymbol(Name: Twine("$ip2state$", FuncLinkageName));
705
706 bool VerboseAsm = OS.isVerboseAsm();
707 auto AddComment = [&](const Twine &Comment) {
708 if (VerboseAsm)
709 OS.AddComment(T: Comment);
710 };
711
712 // FuncInfo {
713 // uint32_t MagicNumber
714 // int32_t MaxState;
715 // UnwindMapEntry *UnwindMap;
716 // uint32_t NumTryBlocks;
717 // TryBlockMapEntry *TryBlockMap;
718 // uint32_t IPMapEntries; // always 0 for x86
719 // IPToStateMapEntry *IPToStateMap; // always 0 for x86
720 // uint32_t UnwindHelp; // non-x86 only
721 // ESTypeList *ESTypeList;
722 // int32_t EHFlags;
723 // }
724 // EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
725 // EHFlags & 2 -> ???
726 // EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
727 OS.emitValueToAlignment(Alignment: Align(4));
728 OS.emitLabel(Symbol: FuncInfoXData);
729
730 AddComment("MagicNumber");
731 OS.emitInt32(Value: 0x19930522);
732
733 AddComment("MaxState");
734 OS.emitInt32(Value: FuncInfo.CxxUnwindMap.size());
735
736 AddComment("UnwindMap");
737 OS.emitValue(Value: create32bitRef(Value: UnwindMapXData), Size: 4);
738
739 AddComment("NumTryBlocks");
740 OS.emitInt32(Value: FuncInfo.TryBlockMap.size());
741
742 AddComment("TryBlockMap");
743 OS.emitValue(Value: create32bitRef(Value: TryBlockMapXData), Size: 4);
744
745 AddComment("IPMapEntries");
746 OS.emitInt32(Value: IPToStateTable.size());
747
748 AddComment("IPToStateXData");
749 OS.emitValue(Value: create32bitRef(Value: IPToStateXData), Size: 4);
750
751 if (Asm->MAI->usesWindowsCFI() &&
752 FuncInfo.UnwindHelpFrameIdx != std::numeric_limits<int>::max()) {
753 AddComment("UnwindHelp");
754 OS.emitInt32(Value: UnwindHelpOffset);
755 }
756
757 AddComment("ESTypeList");
758 OS.emitInt32(Value: 0);
759
760 AddComment("EHFlags");
761 if (MMI->getModule()->getModuleFlag(Key: "eh-asynch")) {
762 OS.emitInt32(Value: 0);
763 } else {
764 OS.emitInt32(Value: 1);
765 }
766
767 // UnwindMapEntry {
768 // int32_t ToState;
769 // void (*Action)();
770 // };
771 if (UnwindMapXData) {
772 OS.emitLabel(Symbol: UnwindMapXData);
773 for (const CxxUnwindMapEntry &UME : FuncInfo.CxxUnwindMap) {
774 MCSymbol *CleanupSym = getMCSymbolForMBB(
775 Asm, MBB: dyn_cast_if_present<MachineBasicBlock *>(Val: UME.Cleanup));
776 AddComment("ToState");
777 OS.emitInt32(Value: UME.ToState);
778
779 AddComment("Action");
780 OS.emitValue(Value: create32bitRef(Value: CleanupSym), Size: 4);
781 }
782 }
783
784 // TryBlockMap {
785 // int32_t TryLow;
786 // int32_t TryHigh;
787 // int32_t CatchHigh;
788 // int32_t NumCatches;
789 // HandlerType *HandlerArray;
790 // };
791 if (TryBlockMapXData) {
792 OS.emitLabel(Symbol: TryBlockMapXData);
793 SmallVector<MCSymbol *, 1> HandlerMaps;
794 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
795 const WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
796
797 MCSymbol *HandlerMapXData = nullptr;
798 if (!TBME.HandlerArray.empty())
799 HandlerMapXData =
800 Asm->OutContext.getOrCreateSymbol(Name: Twine("$handlerMap$")
801 .concat(Suffix: Twine(I))
802 .concat(Suffix: "$")
803 .concat(Suffix: FuncLinkageName));
804 HandlerMaps.push_back(Elt: HandlerMapXData);
805
806 // TBMEs should form intervals.
807 assert(0 <= TBME.TryLow && "bad trymap interval");
808 assert(TBME.TryLow <= TBME.TryHigh && "bad trymap interval");
809 assert(TBME.TryHigh < TBME.CatchHigh && "bad trymap interval");
810 assert(TBME.CatchHigh < int(FuncInfo.CxxUnwindMap.size()) &&
811 "bad trymap interval");
812
813 AddComment("TryLow");
814 OS.emitInt32(Value: TBME.TryLow);
815
816 AddComment("TryHigh");
817 OS.emitInt32(Value: TBME.TryHigh);
818
819 AddComment("CatchHigh");
820 OS.emitInt32(Value: TBME.CatchHigh);
821
822 AddComment("NumCatches");
823 OS.emitInt32(Value: TBME.HandlerArray.size());
824
825 AddComment("HandlerArray");
826 OS.emitValue(Value: create32bitRef(Value: HandlerMapXData), Size: 4);
827 }
828
829 // All funclets use the same parent frame offset currently.
830 unsigned ParentFrameOffset = 0;
831 if (shouldEmitPersonality) {
832 const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
833 ParentFrameOffset = TFI->getWinEHParentFrameOffset(MF: *MF);
834 }
835
836 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
837 const WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
838 MCSymbol *HandlerMapXData = HandlerMaps[I];
839 if (!HandlerMapXData)
840 continue;
841 // HandlerType {
842 // int32_t Adjectives;
843 // TypeDescriptor *Type;
844 // int32_t CatchObjOffset;
845 // void (*Handler)();
846 // int32_t ParentFrameOffset; // x64 and AArch64 only
847 // };
848 OS.emitLabel(Symbol: HandlerMapXData);
849 for (const WinEHHandlerType &HT : TBME.HandlerArray) {
850 // Get the frame escape label with the offset of the catch object. If
851 // the index is INT_MAX, then there is no catch object, and we should
852 // emit an offset of zero, indicating that no copy will occur.
853 const MCExpr *FrameAllocOffsetRef = nullptr;
854 if (HT.CatchObj.FrameIndex != INT_MAX) {
855 int Offset = getFrameIndexOffset(FrameIndex: HT.CatchObj.FrameIndex, FuncInfo);
856 assert(Offset != 0 && "Illegal offset for catch object!");
857 FrameAllocOffsetRef = MCConstantExpr::create(Value: Offset, Ctx&: Asm->OutContext);
858 } else {
859 FrameAllocOffsetRef = MCConstantExpr::create(Value: 0, Ctx&: Asm->OutContext);
860 }
861
862 MCSymbol *HandlerSym = getMCSymbolForMBB(
863 Asm, MBB: dyn_cast_if_present<MachineBasicBlock *>(Val: HT.Handler));
864
865 AddComment("Adjectives");
866 OS.emitInt32(Value: HT.Adjectives);
867
868 AddComment("Type");
869 OS.emitValue(Value: create32bitRef(GV: HT.TypeDescriptor), Size: 4);
870
871 AddComment("CatchObjOffset");
872 OS.emitValue(Value: FrameAllocOffsetRef, Size: 4);
873
874 AddComment("Handler");
875 OS.emitValue(Value: create32bitRef(Value: HandlerSym), Size: 4);
876
877 if (shouldEmitPersonality) {
878 AddComment("ParentFrameOffset");
879 OS.emitInt32(Value: ParentFrameOffset);
880 }
881 }
882 }
883 }
884
885 // IPToStateMapEntry {
886 // void *IP;
887 // int32_t State;
888 // };
889 if (IPToStateXData) {
890 OS.emitLabel(Symbol: IPToStateXData);
891 for (auto &IPStatePair : IPToStateTable) {
892 AddComment("IP");
893 OS.emitValue(Value: IPStatePair.first, Size: 4);
894 AddComment("ToState");
895 OS.emitInt32(Value: IPStatePair.second);
896 }
897 }
898}
899
900void WinException::computeIP2StateTable(
901 const MachineFunction *MF, const WinEHFuncInfo &FuncInfo,
902 SmallVectorImpl<std::pair<const MCExpr *, int>> &IPToStateTable) {
903
904 for (MachineFunction::const_iterator FuncletStart = MF->begin(),
905 FuncletEnd = MF->begin(),
906 End = MF->end();
907 FuncletStart != End; FuncletStart = FuncletEnd) {
908 // Find the end of the funclet
909 while (++FuncletEnd != End) {
910 if (FuncletEnd->isEHFuncletEntry()) {
911 break;
912 }
913 }
914
915 // Don't emit ip2state entries for cleanup funclets. Any interesting
916 // exceptional actions in cleanups must be handled in a separate IR
917 // function.
918 if (FuncletStart->isCleanupFuncletEntry())
919 continue;
920
921 MCSymbol *StartLabel;
922 int BaseState;
923 if (FuncletStart == MF->begin()) {
924 BaseState = NullState;
925 StartLabel = Asm->getFunctionBegin();
926 } else {
927 auto *FuncletPad = cast<FuncletPadInst>(
928 Val: FuncletStart->getBasicBlock()->getFirstNonPHIIt());
929 assert(FuncInfo.FuncletBaseStateMap.count(FuncletPad) != 0);
930 BaseState = FuncInfo.FuncletBaseStateMap.find(Val: FuncletPad)->second;
931 StartLabel = getMCSymbolForMBB(Asm, MBB: &*FuncletStart);
932 }
933 assert(StartLabel && "need local function start label");
934 IPToStateTable.push_back(
935 Elt: std::make_pair(x: create32bitRef(Value: StartLabel), y&: BaseState));
936
937 for (const auto &StateChange : InvokeStateChangeIterator::range(
938 EHInfo: FuncInfo, Begin: FuncletStart, End: FuncletEnd, BaseState)) {
939 // Compute the label to report as the start of this entry; use the EH
940 // start label for the invoke if we have one, otherwise (this is a call
941 // which may unwind to our caller and does not have an EH start label, so)
942 // use the previous end label.
943 const MCSymbol *ChangeLabel = StateChange.NewStartLabel;
944 if (!ChangeLabel)
945 ChangeLabel = StateChange.PreviousEndLabel;
946 // Emit an entry indicating that PCs after 'Label' have this EH state.
947 const MCExpr *LabelExpression = getLabel(Label: ChangeLabel);
948 IPToStateTable.push_back(
949 Elt: std::make_pair(x&: LabelExpression, y: StateChange.NewState));
950 // FIXME: assert that NewState is between CatchLow and CatchHigh.
951 }
952 }
953}
954
955void WinException::emitEHRegistrationOffsetLabel(const WinEHFuncInfo &FuncInfo,
956 StringRef FLinkageName) {
957 // Outlined helpers called by the EH runtime need to know the offset of the EH
958 // registration in order to recover the parent frame pointer. Now that we know
959 // we've code generated the parent, we can emit the label assignment that
960 // those helpers use to get the offset of the registration node.
961
962 // Compute the parent frame offset. The EHRegNodeFrameIndex will be invalid if
963 // after optimization all the invokes were eliminated. We still need to emit
964 // the parent frame offset label, but it should be garbage and should never be
965 // used.
966 int64_t Offset = 0;
967 int FI = FuncInfo.EHRegNodeFrameIndex;
968 if (FI != INT_MAX) {
969 const TargetFrameLowering *TFI = Asm->MF->getSubtarget().getFrameLowering();
970 Offset = TFI->getNonLocalFrameIndexReference(MF: *Asm->MF, FI).getFixed();
971 }
972
973 MCContext &Ctx = Asm->OutContext;
974 MCSymbol *ParentFrameOffset =
975 Ctx.getOrCreateParentFrameOffsetSymbol(FuncName: FLinkageName);
976 Asm->OutStreamer->emitAssignment(Symbol: ParentFrameOffset,
977 Value: MCConstantExpr::create(Value: Offset, Ctx));
978}
979
980/// Emit the language-specific data that _except_handler3 and 4 expect. This is
981/// functionally equivalent to the __C_specific_handler table, except it is
982/// indexed by state number instead of IP.
983void WinException::emitExceptHandlerTable(const MachineFunction *MF) {
984 MCStreamer &OS = *Asm->OutStreamer;
985 const Function &F = MF->getFunction();
986 StringRef FLinkageName = GlobalValue::dropLLVMManglingEscape(Name: F.getName());
987
988 bool VerboseAsm = OS.isVerboseAsm();
989 auto AddComment = [&](const Twine &Comment) {
990 if (VerboseAsm)
991 OS.AddComment(T: Comment);
992 };
993
994 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
995 emitEHRegistrationOffsetLabel(FuncInfo, FLinkageName);
996
997 // Emit the __ehtable label that we use for llvm.x86.seh.lsda.
998 MCSymbol *LSDALabel = Asm->OutContext.getOrCreateLSDASymbol(FuncName: FLinkageName);
999 OS.emitValueToAlignment(Alignment: Align(4));
1000 OS.emitLabel(Symbol: LSDALabel);
1001
1002 const auto *Per = cast<Function>(Val: F.getPersonalityFn()->stripPointerCasts());
1003 StringRef PerName = Per->getName();
1004 int BaseState = -1;
1005 if (PerName == "_except_handler4") {
1006 // The LSDA for _except_handler4 starts with this struct, followed by the
1007 // scope table:
1008 //
1009 // struct EH4ScopeTable {
1010 // int32_t GSCookieOffset;
1011 // int32_t GSCookieXOROffset;
1012 // int32_t EHCookieOffset;
1013 // int32_t EHCookieXOROffset;
1014 // ScopeTableEntry ScopeRecord[];
1015 // };
1016 //
1017 // Offsets are %ebp relative.
1018 //
1019 // The GS cookie is present only if the function needs stack protection.
1020 // GSCookieOffset = -2 means that GS cookie is not used.
1021 //
1022 // The EH cookie is always present.
1023 //
1024 // Check is done the following way:
1025 // (ebp+CookieXOROffset) ^ [ebp+CookieOffset] == _security_cookie
1026
1027 // Retrieve the Guard Stack slot.
1028 int GSCookieOffset = -2;
1029 const MachineFrameInfo &MFI = MF->getFrameInfo();
1030 if (MFI.hasStackProtectorIndex()) {
1031 Register UnusedReg;
1032 const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
1033 int SSPIdx = MFI.getStackProtectorIndex();
1034 GSCookieOffset =
1035 TFI->getFrameIndexReference(MF: *MF, FI: SSPIdx, FrameReg&: UnusedReg).getFixed();
1036 }
1037
1038 // Retrieve the EH Guard slot.
1039 // TODO(etienneb): Get rid of this value and change it for and assertion.
1040 int EHCookieOffset = 9999;
1041 if (FuncInfo.EHGuardFrameIndex != INT_MAX) {
1042 Register UnusedReg;
1043 const TargetFrameLowering *TFI = MF->getSubtarget().getFrameLowering();
1044 int EHGuardIdx = FuncInfo.EHGuardFrameIndex;
1045 EHCookieOffset =
1046 TFI->getFrameIndexReference(MF: *MF, FI: EHGuardIdx, FrameReg&: UnusedReg).getFixed();
1047 }
1048
1049 AddComment("GSCookieOffset");
1050 OS.emitInt32(Value: GSCookieOffset);
1051 AddComment("GSCookieXOROffset");
1052 OS.emitInt32(Value: 0);
1053 AddComment("EHCookieOffset");
1054 OS.emitInt32(Value: EHCookieOffset);
1055 AddComment("EHCookieXOROffset");
1056 OS.emitInt32(Value: 0);
1057 BaseState = -2;
1058 }
1059
1060 assert(!FuncInfo.SEHUnwindMap.empty());
1061 for (const SEHUnwindMapEntry &UME : FuncInfo.SEHUnwindMap) {
1062 auto *Handler = cast<MachineBasicBlock *>(Val: UME.Handler);
1063 const MCSymbol *ExceptOrFinally =
1064 UME.IsFinally ? getMCSymbolForMBB(Asm, MBB: Handler) : Handler->getSymbol();
1065 // -1 is usually the base state for "unwind to caller", but for
1066 // _except_handler4 it's -2. Do that replacement here if necessary.
1067 int ToState = UME.ToState == -1 ? BaseState : UME.ToState;
1068 AddComment("ToState");
1069 OS.emitInt32(Value: ToState);
1070 AddComment(UME.IsFinally ? "Null" : "FilterFunction");
1071 OS.emitValue(Value: create32bitRef(GV: UME.Filter), Size: 4);
1072 AddComment(UME.IsFinally ? "FinallyFunclet" : "ExceptionHandler");
1073 OS.emitValue(Value: create32bitRef(Value: ExceptOrFinally), Size: 4);
1074 }
1075}
1076
1077static int getTryRank(const WinEHFuncInfo &FuncInfo, int State) {
1078 int Rank = 0;
1079 while (State != -1) {
1080 ++Rank;
1081 State = FuncInfo.ClrEHUnwindMap[State].TryParentState;
1082 }
1083 return Rank;
1084}
1085
1086static int getTryAncestor(const WinEHFuncInfo &FuncInfo, int Left, int Right) {
1087 int LeftRank = getTryRank(FuncInfo, State: Left);
1088 int RightRank = getTryRank(FuncInfo, State: Right);
1089
1090 while (LeftRank < RightRank) {
1091 Right = FuncInfo.ClrEHUnwindMap[Right].TryParentState;
1092 --RightRank;
1093 }
1094
1095 while (RightRank < LeftRank) {
1096 Left = FuncInfo.ClrEHUnwindMap[Left].TryParentState;
1097 --LeftRank;
1098 }
1099
1100 while (Left != Right) {
1101 Left = FuncInfo.ClrEHUnwindMap[Left].TryParentState;
1102 Right = FuncInfo.ClrEHUnwindMap[Right].TryParentState;
1103 }
1104
1105 return Left;
1106}
1107
1108void WinException::emitCLRExceptionTable(const MachineFunction *MF) {
1109 // CLR EH "states" are really just IDs that identify handlers/funclets;
1110 // states, handlers, and funclets all have 1:1 mappings between them, and a
1111 // handler/funclet's "state" is its index in the ClrEHUnwindMap.
1112 MCStreamer &OS = *Asm->OutStreamer;
1113 const WinEHFuncInfo &FuncInfo = *MF->getWinEHFuncInfo();
1114 MCSymbol *FuncBeginSym = Asm->getFunctionBegin();
1115 MCSymbol *FuncEndSym = Asm->getFunctionEnd();
1116
1117 // A ClrClause describes a protected region.
1118 struct ClrClause {
1119 const MCSymbol *StartLabel; // Start of protected region
1120 const MCSymbol *EndLabel; // End of protected region
1121 int State; // Index of handler protecting the protected region
1122 int EnclosingState; // Index of funclet enclosing the protected region
1123 };
1124 SmallVector<ClrClause, 8> Clauses;
1125
1126 // Build a map from handler MBBs to their corresponding states (i.e. their
1127 // indices in the ClrEHUnwindMap).
1128 int NumStates = FuncInfo.ClrEHUnwindMap.size();
1129 assert(NumStates > 0 && "Don't need exception table!");
1130 DenseMap<const MachineBasicBlock *, int> HandlerStates;
1131 for (int State = 0; State < NumStates; ++State) {
1132 MachineBasicBlock *HandlerBlock =
1133 cast<MachineBasicBlock *>(Val: FuncInfo.ClrEHUnwindMap[State].Handler);
1134 HandlerStates[HandlerBlock] = State;
1135 // Use this loop through all handlers to verify our assumption (used in
1136 // the MinEnclosingState computation) that enclosing funclets have lower
1137 // state numbers than their enclosed funclets.
1138 assert(FuncInfo.ClrEHUnwindMap[State].HandlerParentState < State &&
1139 "ill-formed state numbering");
1140 }
1141 // Map the main function to the NullState.
1142 HandlerStates[&MF->front()] = NullState;
1143
1144 // Write out a sentinel indicating the end of the standard (Windows) xdata
1145 // and the start of the additional (CLR) info.
1146 OS.emitInt32(Value: 0xffffffff);
1147 // Write out the number of funclets
1148 OS.emitInt32(Value: NumStates);
1149
1150 // Walk the machine blocks/instrs, computing and emitting a few things:
1151 // 1. Emit a list of the offsets to each handler entry, in lexical order.
1152 // 2. Compute a map (EndSymbolMap) from each funclet to the symbol at its end.
1153 // 3. Compute the list of ClrClauses, in the required order (inner before
1154 // outer, earlier before later; the order by which a forward scan with
1155 // early termination will find the innermost enclosing clause covering
1156 // a given address).
1157 // 4. A map (MinClauseMap) from each handler index to the index of the
1158 // outermost funclet/function which contains a try clause targeting the
1159 // key handler. This will be used to determine IsDuplicate-ness when
1160 // emitting ClrClauses. The NullState value is used to indicate that the
1161 // top-level function contains a try clause targeting the key handler.
1162 // HandlerStack is a stack of (PendingStartLabel, PendingState) pairs for
1163 // try regions we entered before entering the PendingState try but which
1164 // we haven't yet exited.
1165 SmallVector<std::pair<const MCSymbol *, int>, 4> HandlerStack;
1166 // EndSymbolMap and MinClauseMap are maps described above.
1167 std::unique_ptr<MCSymbol *[]> EndSymbolMap(new MCSymbol *[NumStates]);
1168 SmallVector<int, 4> MinClauseMap((size_t)NumStates, NumStates);
1169
1170 // Visit the root function and each funclet.
1171 for (MachineFunction::const_iterator FuncletStart = MF->begin(),
1172 FuncletEnd = MF->begin(),
1173 End = MF->end();
1174 FuncletStart != End; FuncletStart = FuncletEnd) {
1175 int FuncletState = HandlerStates[&*FuncletStart];
1176 // Find the end of the funclet
1177 MCSymbol *EndSymbol = FuncEndSym;
1178 while (++FuncletEnd != End) {
1179 if (FuncletEnd->isEHFuncletEntry()) {
1180 EndSymbol = getMCSymbolForMBB(Asm, MBB: &*FuncletEnd);
1181 break;
1182 }
1183 }
1184 // Emit the function/funclet end and, if this is a funclet (and not the
1185 // root function), record it in the EndSymbolMap.
1186 OS.emitValue(Value: getOffset(OffsetOf: EndSymbol, OffsetFrom: FuncBeginSym), Size: 4);
1187 if (FuncletState != NullState) {
1188 // Record the end of the handler.
1189 EndSymbolMap[FuncletState] = EndSymbol;
1190 }
1191
1192 // Walk the state changes in this function/funclet and compute its clauses.
1193 // Funclets always start in the null state.
1194 const MCSymbol *CurrentStartLabel = nullptr;
1195 int CurrentState = NullState;
1196 assert(HandlerStack.empty());
1197 for (const auto &StateChange :
1198 InvokeStateChangeIterator::range(EHInfo: FuncInfo, Begin: FuncletStart, End: FuncletEnd)) {
1199 // Close any try regions we're not still under
1200 int StillPendingState =
1201 getTryAncestor(FuncInfo, Left: CurrentState, Right: StateChange.NewState);
1202 while (CurrentState != StillPendingState) {
1203 assert(CurrentState != NullState &&
1204 "Failed to find still-pending state!");
1205 // Close the pending clause
1206 Clauses.push_back(Elt: {.StartLabel: CurrentStartLabel, .EndLabel: StateChange.PreviousEndLabel,
1207 .State: CurrentState, .EnclosingState: FuncletState});
1208 // Now the next-outer try region is current
1209 CurrentState = FuncInfo.ClrEHUnwindMap[CurrentState].TryParentState;
1210 // Pop the new start label from the handler stack if we've exited all
1211 // inner try regions of the corresponding try region.
1212 if (HandlerStack.back().second == CurrentState)
1213 CurrentStartLabel = HandlerStack.pop_back_val().first;
1214 }
1215
1216 if (StateChange.NewState != CurrentState) {
1217 // For each clause we're starting, update the MinClauseMap so we can
1218 // know which is the topmost funclet containing a clause targeting
1219 // it.
1220 for (int EnteredState = StateChange.NewState;
1221 EnteredState != CurrentState;
1222 EnteredState =
1223 FuncInfo.ClrEHUnwindMap[EnteredState].TryParentState) {
1224 int &MinEnclosingState = MinClauseMap[EnteredState];
1225 if (FuncletState < MinEnclosingState)
1226 MinEnclosingState = FuncletState;
1227 }
1228 // Save the previous current start/label on the stack and update to
1229 // the newly-current start/state.
1230 HandlerStack.emplace_back(Args&: CurrentStartLabel, Args&: CurrentState);
1231 CurrentStartLabel = StateChange.NewStartLabel;
1232 CurrentState = StateChange.NewState;
1233 }
1234 }
1235 assert(HandlerStack.empty());
1236 }
1237
1238 // Now emit the clause info, starting with the number of clauses.
1239 OS.emitInt32(Value: Clauses.size());
1240 for (ClrClause &Clause : Clauses) {
1241 // Emit a CORINFO_EH_CLAUSE :
1242 /*
1243 struct CORINFO_EH_CLAUSE
1244 {
1245 CORINFO_EH_CLAUSE_FLAGS Flags; // actually a CorExceptionFlag
1246 DWORD TryOffset;
1247 DWORD TryLength; // actually TryEndOffset
1248 DWORD HandlerOffset;
1249 DWORD HandlerLength; // actually HandlerEndOffset
1250 union
1251 {
1252 DWORD ClassToken; // use for catch clauses
1253 DWORD FilterOffset; // use for filter clauses
1254 };
1255 };
1256
1257 enum CORINFO_EH_CLAUSE_FLAGS
1258 {
1259 CORINFO_EH_CLAUSE_NONE = 0,
1260 CORINFO_EH_CLAUSE_FILTER = 0x0001, // This clause is for a filter
1261 CORINFO_EH_CLAUSE_FINALLY = 0x0002, // This clause is a finally clause
1262 CORINFO_EH_CLAUSE_FAULT = 0x0004, // This clause is a fault clause
1263 };
1264 typedef enum CorExceptionFlag
1265 {
1266 COR_ILEXCEPTION_CLAUSE_NONE,
1267 COR_ILEXCEPTION_CLAUSE_FILTER = 0x0001, // This is a filter clause
1268 COR_ILEXCEPTION_CLAUSE_FINALLY = 0x0002, // This is a finally clause
1269 COR_ILEXCEPTION_CLAUSE_FAULT = 0x0004, // This is a fault clause
1270 COR_ILEXCEPTION_CLAUSE_DUPLICATED = 0x0008, // duplicated clause. This
1271 // clause was duplicated
1272 // to a funclet which was
1273 // pulled out of line
1274 } CorExceptionFlag;
1275 */
1276 // Add 1 to the start/end of the EH clause; the IP associated with a
1277 // call when the runtime does its scan is the IP of the next instruction
1278 // (the one to which control will return after the call), so we need
1279 // to add 1 to the end of the clause to cover that offset. We also add
1280 // 1 to the start of the clause to make sure that the ranges reported
1281 // for all clauses are disjoint. Note that we'll need some additional
1282 // logic when machine traps are supported, since in that case the IP
1283 // that the runtime uses is the offset of the faulting instruction
1284 // itself; if such an instruction immediately follows a call but the
1285 // two belong to different clauses, we'll need to insert a nop between
1286 // them so the runtime can distinguish the point to which the call will
1287 // return from the point at which the fault occurs.
1288
1289 const MCExpr *ClauseBegin =
1290 getOffsetPlusOne(OffsetOf: Clause.StartLabel, OffsetFrom: FuncBeginSym);
1291 const MCExpr *ClauseEnd = getOffsetPlusOne(OffsetOf: Clause.EndLabel, OffsetFrom: FuncBeginSym);
1292
1293 const ClrEHUnwindMapEntry &Entry = FuncInfo.ClrEHUnwindMap[Clause.State];
1294 MachineBasicBlock *HandlerBlock = cast<MachineBasicBlock *>(Val: Entry.Handler);
1295 MCSymbol *BeginSym = getMCSymbolForMBB(Asm, MBB: HandlerBlock);
1296 const MCExpr *HandlerBegin = getOffset(OffsetOf: BeginSym, OffsetFrom: FuncBeginSym);
1297 MCSymbol *EndSym = EndSymbolMap[Clause.State];
1298 const MCExpr *HandlerEnd = getOffset(OffsetOf: EndSym, OffsetFrom: FuncBeginSym);
1299
1300 uint32_t Flags = 0;
1301 switch (Entry.HandlerType) {
1302 case ClrHandlerType::Catch:
1303 // Leaving bits 0-2 clear indicates catch.
1304 break;
1305 case ClrHandlerType::Filter:
1306 Flags |= 1;
1307 break;
1308 case ClrHandlerType::Finally:
1309 Flags |= 2;
1310 break;
1311 case ClrHandlerType::Fault:
1312 Flags |= 4;
1313 break;
1314 }
1315 if (Clause.EnclosingState != MinClauseMap[Clause.State]) {
1316 // This is a "duplicate" clause; the handler needs to be entered from a
1317 // frame above the one holding the invoke.
1318 assert(Clause.EnclosingState > MinClauseMap[Clause.State]);
1319 Flags |= 8;
1320 }
1321 OS.emitInt32(Value: Flags);
1322
1323 // Write the clause start/end
1324 OS.emitValue(Value: ClauseBegin, Size: 4);
1325 OS.emitValue(Value: ClauseEnd, Size: 4);
1326
1327 // Write out the handler start/end
1328 OS.emitValue(Value: HandlerBegin, Size: 4);
1329 OS.emitValue(Value: HandlerEnd, Size: 4);
1330
1331 // Write out the type token or filter offset
1332 assert(Entry.HandlerType != ClrHandlerType::Filter && "NYI: filters");
1333 OS.emitInt32(Value: Entry.TypeToken);
1334 }
1335}
1336