1//===--- CGException.cpp - Emit LLVM Code for C++ exceptions ----*- C++ -*-===//
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 contains code dealing with C++ exception related code generation.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CGCXXABI.h"
16#include "CGCleanup.h"
17#include "CGObjCRuntime.h"
18#include "TargetInfo.h"
19#include "clang/AST/Mangle.h"
20#include "clang/AST/StmtCXX.h"
21#include "clang/AST/StmtObjC.h"
22#include "clang/AST/StmtVisitor.h"
23#include "clang/Basic/TargetBuiltins.h"
24#include "llvm/IR/CallSite.h"
25#include "llvm/IR/Intrinsics.h"
26#include "llvm/IR/IntrinsicInst.h"
27#include "llvm/Support/SaveAndRestore.h"
28
29using namespace clang;
30using namespace CodeGen;
31
32static llvm::Constant *getFreeExceptionFn(CodeGenModule &CGM) {
33  // void __cxa_free_exception(void *thrown_exception);
34
35  llvm::FunctionType *FTy =
36    llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
37
38  return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
39}
40
41static llvm::Constant *getUnexpectedFn(CodeGenModule &CGM) {
42  // void __cxa_call_unexpected(void *thrown_exception);
43
44  llvm::FunctionType *FTy =
45    llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
46
47  return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
48}
49
50llvm::Constant *CodeGenModule::getTerminateFn() {
51  // void __terminate();
52
53  llvm::FunctionType *FTy =
54    llvm::FunctionType::get(VoidTy, /*IsVarArgs=*/false);
55
56  StringRef name;
57
58  // In C++, use std::terminate().
59  if (getLangOpts().CPlusPlus &&
60      getTarget().getCXXABI().isItaniumFamily()) {
61    name = "_ZSt9terminatev";
62  } else if (getLangOpts().CPlusPlus &&
63             getTarget().getCXXABI().isMicrosoft()) {
64    if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
65      name = "__std_terminate";
66    else
67      name = "\01?terminate@@YAXXZ";
68  } else if (getLangOpts().ObjC1 &&
69             getLangOpts().ObjCRuntime.hasTerminate())
70    name = "objc_terminate";
71  else
72    name = "abort";
73  return CreateRuntimeFunction(FTy, name);
74}
75
76static llvm::Constant *getCatchallRethrowFn(CodeGenModule &CGM,
77                                            StringRef Name) {
78  llvm::FunctionType *FTy =
79    llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
80
81  return CGM.CreateRuntimeFunction(FTy, Name);
82}
83
84const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr };
85const EHPersonality
86EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr };
87const EHPersonality
88EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr };
89const EHPersonality
90EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr };
91const EHPersonality
92EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr };
93const EHPersonality
94EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr };
95const EHPersonality
96EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr };
97const EHPersonality
98EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"};
99const EHPersonality
100EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr };
101const EHPersonality
102EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr };
103const EHPersonality
104EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr };
105const EHPersonality
106EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr };
107const EHPersonality
108EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr };
109
110/// On Win64, use libgcc's SEH personality function. We fall back to dwarf on
111/// other platforms, unless the user asked for SjLj exceptions.
112static bool useLibGCCSEHPersonality(const llvm::Triple &T) {
113  return T.isOSWindows() && T.getArch() == llvm::Triple::x86_64;
114}
115
116static const EHPersonality &getCPersonality(const llvm::Triple &T,
117                                            const LangOptions &L) {
118  if (L.SjLjExceptions)
119    return EHPersonality::GNU_C_SJLJ;
120  else if (useLibGCCSEHPersonality(T))
121    return EHPersonality::GNU_C_SEH;
122  return EHPersonality::GNU_C;
123}
124
125static const EHPersonality &getObjCPersonality(const llvm::Triple &T,
126                                               const LangOptions &L) {
127  switch (L.ObjCRuntime.getKind()) {
128  case ObjCRuntime::FragileMacOSX:
129    return getCPersonality(T, L);
130  case ObjCRuntime::MacOSX:
131  case ObjCRuntime::iOS:
132  case ObjCRuntime::WatchOS:
133    return EHPersonality::NeXT_ObjC;
134  case ObjCRuntime::GNUstep:
135    if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
136      return EHPersonality::GNUstep_ObjC;
137    // fallthrough
138  case ObjCRuntime::GCC:
139  case ObjCRuntime::ObjFW:
140    return EHPersonality::GNU_ObjC;
141  }
142  llvm_unreachable("bad runtime kind");
143}
144
145static const EHPersonality &getCXXPersonality(const llvm::Triple &T,
146                                              const LangOptions &L) {
147  if (L.SjLjExceptions)
148    return EHPersonality::GNU_CPlusPlus_SJLJ;
149  else if (useLibGCCSEHPersonality(T))
150    return EHPersonality::GNU_CPlusPlus_SEH;
151  return EHPersonality::GNU_CPlusPlus;
152}
153
154/// Determines the personality function to use when both C++
155/// and Objective-C exceptions are being caught.
156static const EHPersonality &getObjCXXPersonality(const llvm::Triple &T,
157                                                 const LangOptions &L) {
158  switch (L.ObjCRuntime.getKind()) {
159  // The ObjC personality defers to the C++ personality for non-ObjC
160  // handlers.  Unlike the C++ case, we use the same personality
161  // function on targets using (backend-driven) SJLJ EH.
162  case ObjCRuntime::MacOSX:
163  case ObjCRuntime::iOS:
164  case ObjCRuntime::WatchOS:
165    return EHPersonality::NeXT_ObjC;
166
167  // In the fragile ABI, just use C++ exception handling and hope
168  // they're not doing crazy exception mixing.
169  case ObjCRuntime::FragileMacOSX:
170    return getCXXPersonality(T, L);
171
172  // The GCC runtime's personality function inherently doesn't support
173  // mixed EH.  Use the C++ personality just to avoid returning null.
174  case ObjCRuntime::GCC:
175  case ObjCRuntime::ObjFW: // XXX: this will change soon
176    return EHPersonality::GNU_ObjC;
177  case ObjCRuntime::GNUstep:
178    return EHPersonality::GNU_ObjCXX;
179  }
180  llvm_unreachable("bad runtime kind");
181}
182
183static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) {
184  if (T.getArch() == llvm::Triple::x86)
185    return EHPersonality::MSVC_except_handler;
186  return EHPersonality::MSVC_C_specific_handler;
187}
188
189const EHPersonality &EHPersonality::get(CodeGenModule &CGM,
190                                        const FunctionDecl *FD) {
191  const llvm::Triple &T = CGM.getTarget().getTriple();
192  const LangOptions &L = CGM.getLangOpts();
193
194  // Functions using SEH get an SEH personality.
195  if (FD && FD->usesSEHTry())
196    return getSEHPersonalityMSVC(T);
197
198  // Try to pick a personality function that is compatible with MSVC if we're
199  // not compiling Obj-C. Obj-C users better have an Obj-C runtime that supports
200  // the GCC-style personality function.
201  if (T.isWindowsMSVCEnvironment() && !L.ObjC1) {
202    if (L.SjLjExceptions)
203      return EHPersonality::GNU_CPlusPlus_SJLJ;
204    else
205      return EHPersonality::MSVC_CxxFrameHandler3;
206  }
207
208  if (L.CPlusPlus && L.ObjC1)
209    return getObjCXXPersonality(T, L);
210  else if (L.CPlusPlus)
211    return getCXXPersonality(T, L);
212  else if (L.ObjC1)
213    return getObjCPersonality(T, L);
214  else
215    return getCPersonality(T, L);
216}
217
218const EHPersonality &EHPersonality::get(CodeGenFunction &CGF) {
219  return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(CGF.CurCodeDecl));
220}
221
222static llvm::Constant *getPersonalityFn(CodeGenModule &CGM,
223                                        const EHPersonality &Personality) {
224  llvm::Constant *Fn =
225    CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true),
226                              Personality.PersonalityFn);
227  return Fn;
228}
229
230static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM,
231                                        const EHPersonality &Personality) {
232  llvm::Constant *Fn = getPersonalityFn(CGM, Personality);
233  return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy);
234}
235
236/// Check whether a landingpad instruction only uses C++ features.
237static bool LandingPadHasOnlyCXXUses(llvm::LandingPadInst *LPI) {
238  for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) {
239    // Look for something that would've been returned by the ObjC
240    // runtime's GetEHType() method.
241    llvm::Value *Val = LPI->getClause(I)->stripPointerCasts();
242    if (LPI->isCatch(I)) {
243      // Check if the catch value has the ObjC prefix.
244      if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val))
245        // ObjC EH selector entries are always global variables with
246        // names starting like this.
247        if (GV->getName().startswith("OBJC_EHTYPE"))
248          return false;
249    } else {
250      // Check if any of the filter values have the ObjC prefix.
251      llvm::Constant *CVal = cast<llvm::Constant>(Val);
252      for (llvm::User::op_iterator
253              II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) {
254        if (llvm::GlobalVariable *GV =
255            cast<llvm::GlobalVariable>((*II)->stripPointerCasts()))
256          // ObjC EH selector entries are always global variables with
257          // names starting like this.
258          if (GV->getName().startswith("OBJC_EHTYPE"))
259            return false;
260      }
261    }
262  }
263  return true;
264}
265
266/// Check whether a personality function could reasonably be swapped
267/// for a C++ personality function.
268static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) {
269  for (llvm::User *U : Fn->users()) {
270    // Conditionally white-list bitcasts.
271    if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(U)) {
272      if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
273      if (!PersonalityHasOnlyCXXUses(CE))
274        return false;
275      continue;
276    }
277
278    // Otherwise it must be a function.
279    llvm::Function *F = dyn_cast<llvm::Function>(U);
280    if (!F) return false;
281
282    for (auto BB = F->begin(), E = F->end(); BB != E; ++BB) {
283      if (BB->isLandingPad())
284        if (!LandingPadHasOnlyCXXUses(BB->getLandingPadInst()))
285          return false;
286    }
287  }
288
289  return true;
290}
291
292/// Try to use the C++ personality function in ObjC++.  Not doing this
293/// can cause some incompatibilities with gcc, which is more
294/// aggressive about only using the ObjC++ personality in a function
295/// when it really needs it.
296void CodeGenModule::SimplifyPersonality() {
297  // If we're not in ObjC++ -fexceptions, there's nothing to do.
298  if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions)
299    return;
300
301  // Both the problem this endeavors to fix and the way the logic
302  // above works is specific to the NeXT runtime.
303  if (!LangOpts.ObjCRuntime.isNeXTFamily())
304    return;
305
306  const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr);
307  const EHPersonality &CXX =
308      getCXXPersonality(getTarget().getTriple(), LangOpts);
309  if (&ObjCXX == &CXX)
310    return;
311
312  assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 &&
313         "Different EHPersonalities using the same personality function.");
314
315  llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn);
316
317  // Nothing to do if it's unused.
318  if (!Fn || Fn->use_empty()) return;
319
320  // Can't do the optimization if it has non-C++ uses.
321  if (!PersonalityHasOnlyCXXUses(Fn)) return;
322
323  // Create the C++ personality function and kill off the old
324  // function.
325  llvm::Constant *CXXFn = getPersonalityFn(*this, CXX);
326
327  // This can happen if the user is screwing with us.
328  if (Fn->getType() != CXXFn->getType()) return;
329
330  Fn->replaceAllUsesWith(CXXFn);
331  Fn->eraseFromParent();
332}
333
334/// Returns the value to inject into a selector to indicate the
335/// presence of a catch-all.
336static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) {
337  // Possibly we should use @llvm.eh.catch.all.value here.
338  return llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
339}
340
341namespace {
342  /// A cleanup to free the exception object if its initialization
343  /// throws.
344  struct FreeException final : EHScopeStack::Cleanup {
345    llvm::Value *exn;
346    FreeException(llvm::Value *exn) : exn(exn) {}
347    void Emit(CodeGenFunction &CGF, Flags flags) override {
348      CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn);
349    }
350  };
351} // end anonymous namespace
352
353// Emits an exception expression into the given location.  This
354// differs from EmitAnyExprToMem only in that, if a final copy-ctor
355// call is required, an exception within that copy ctor causes
356// std::terminate to be invoked.
357void CodeGenFunction::EmitAnyExprToExn(const Expr *e, Address addr) {
358  // Make sure the exception object is cleaned up if there's an
359  // exception during initialization.
360  pushFullExprCleanup<FreeException>(EHCleanup, addr.getPointer());
361  EHScopeStack::stable_iterator cleanup = EHStack.stable_begin();
362
363  // __cxa_allocate_exception returns a void*;  we need to cast this
364  // to the appropriate type for the object.
365  llvm::Type *ty = ConvertTypeForMem(e->getType())->getPointerTo();
366  Address typedAddr = Builder.CreateBitCast(addr, ty);
367
368  // FIXME: this isn't quite right!  If there's a final unelided call
369  // to a copy constructor, then according to [except.terminate]p1 we
370  // must call std::terminate() if that constructor throws, because
371  // technically that copy occurs after the exception expression is
372  // evaluated but before the exception is caught.  But the best way
373  // to handle that is to teach EmitAggExpr to do the final copy
374  // differently if it can't be elided.
375  EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
376                   /*IsInit*/ true);
377
378  // Deactivate the cleanup block.
379  DeactivateCleanupBlock(cleanup,
380                         cast<llvm::Instruction>(typedAddr.getPointer()));
381}
382
383Address CodeGenFunction::getExceptionSlot() {
384  if (!ExceptionSlot)
385    ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
386  return Address(ExceptionSlot, getPointerAlign());
387}
388
389Address CodeGenFunction::getEHSelectorSlot() {
390  if (!EHSelectorSlot)
391    EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
392  return Address(EHSelectorSlot, CharUnits::fromQuantity(4));
393}
394
395llvm::Value *CodeGenFunction::getExceptionFromSlot() {
396  return Builder.CreateLoad(getExceptionSlot(), "exn");
397}
398
399llvm::Value *CodeGenFunction::getSelectorFromSlot() {
400  return Builder.CreateLoad(getEHSelectorSlot(), "sel");
401}
402
403void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E,
404                                       bool KeepInsertionPoint) {
405  if (const Expr *SubExpr = E->getSubExpr()) {
406    QualType ThrowType = SubExpr->getType();
407    if (ThrowType->isObjCObjectPointerType()) {
408      const Stmt *ThrowStmt = E->getSubExpr();
409      const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(ThrowStmt));
410      CGM.getObjCRuntime().EmitThrowStmt(*this, S, false);
411    } else {
412      CGM.getCXXABI().emitThrow(*this, E);
413    }
414  } else {
415    CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true);
416  }
417
418  // throw is an expression, and the expression emitters expect us
419  // to leave ourselves at a valid insertion point.
420  if (KeepInsertionPoint)
421    EmitBlock(createBasicBlock("throw.cont"));
422}
423
424void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
425  if (!CGM.getLangOpts().CXXExceptions)
426    return;
427
428  const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
429  if (!FD) {
430    // Check if CapturedDecl is nothrow and create terminate scope for it.
431    if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
432      if (CD->isNothrow())
433        EHStack.pushTerminate();
434    }
435    return;
436  }
437  const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
438  if (!Proto)
439    return;
440
441  ExceptionSpecificationType EST = Proto->getExceptionSpecType();
442  if (isNoexceptExceptionSpec(EST)) {
443    if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
444      // noexcept functions are simple terminate scopes.
445      EHStack.pushTerminate();
446    }
447  } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
448    // TODO: Revisit exception specifications for the MS ABI.  There is a way to
449    // encode these in an object file but MSVC doesn't do anything with it.
450    if (getTarget().getCXXABI().isMicrosoft())
451      return;
452    unsigned NumExceptions = Proto->getNumExceptions();
453    EHFilterScope *Filter = EHStack.pushFilter(NumExceptions);
454
455    for (unsigned I = 0; I != NumExceptions; ++I) {
456      QualType Ty = Proto->getExceptionType(I);
457      QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType();
458      llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType,
459                                                        /*ForEH=*/true);
460      Filter->setFilter(I, EHType);
461    }
462  }
463}
464
465/// Emit the dispatch block for a filter scope if necessary.
466static void emitFilterDispatchBlock(CodeGenFunction &CGF,
467                                    EHFilterScope &filterScope) {
468  llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock();
469  if (!dispatchBlock) return;
470  if (dispatchBlock->use_empty()) {
471    delete dispatchBlock;
472    return;
473  }
474
475  CGF.EmitBlockAfterUses(dispatchBlock);
476
477  // If this isn't a catch-all filter, we need to check whether we got
478  // here because the filter triggered.
479  if (filterScope.getNumFilters()) {
480    // Load the selector value.
481    llvm::Value *selector = CGF.getSelectorFromSlot();
482    llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected");
483
484    llvm::Value *zero = CGF.Builder.getInt32(0);
485    llvm::Value *failsFilter =
486        CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails");
487    CGF.Builder.CreateCondBr(failsFilter, unexpectedBB,
488                             CGF.getEHResumeBlock(false));
489
490    CGF.EmitBlock(unexpectedBB);
491  }
492
493  // Call __cxa_call_unexpected.  This doesn't need to be an invoke
494  // because __cxa_call_unexpected magically filters exceptions
495  // according to the last landing pad the exception was thrown
496  // into.  Seriously.
497  llvm::Value *exn = CGF.getExceptionFromSlot();
498  CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn)
499    ->setDoesNotReturn();
500  CGF.Builder.CreateUnreachable();
501}
502
503void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
504  if (!CGM.getLangOpts().CXXExceptions)
505    return;
506
507  const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
508  if (!FD) {
509    // Check if CapturedDecl is nothrow and pop terminate scope for it.
510    if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
511      if (CD->isNothrow())
512        EHStack.popTerminate();
513    }
514    return;
515  }
516  const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
517  if (!Proto)
518    return;
519
520  ExceptionSpecificationType EST = Proto->getExceptionSpecType();
521  if (isNoexceptExceptionSpec(EST)) {
522    if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
523      EHStack.popTerminate();
524    }
525  } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
526    // TODO: Revisit exception specifications for the MS ABI.  There is a way to
527    // encode these in an object file but MSVC doesn't do anything with it.
528    if (getTarget().getCXXABI().isMicrosoft())
529      return;
530    EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
531    emitFilterDispatchBlock(*this, filterScope);
532    EHStack.popFilter();
533  }
534}
535
536void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
537  EnterCXXTryStmt(S);
538  EmitStmt(S.getTryBlock());
539  ExitCXXTryStmt(S);
540}
541
542void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
543  unsigned NumHandlers = S.getNumHandlers();
544  EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers);
545
546  for (unsigned I = 0; I != NumHandlers; ++I) {
547    const CXXCatchStmt *C = S.getHandler(I);
548
549    llvm::BasicBlock *Handler = createBasicBlock("catch");
550    if (C->getExceptionDecl()) {
551      // FIXME: Dropping the reference type on the type into makes it
552      // impossible to correctly implement catch-by-reference
553      // semantics for pointers.  Unfortunately, this is what all
554      // existing compilers do, and it's not clear that the standard
555      // personality routine is capable of doing this right.  See C++ DR 388:
556      //   http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
557      Qualifiers CaughtTypeQuals;
558      QualType CaughtType = CGM.getContext().getUnqualifiedArrayType(
559          C->getCaughtType().getNonReferenceType(), CaughtTypeQuals);
560
561      CatchTypeInfo TypeInfo{nullptr, 0};
562      if (CaughtType->isObjCObjectPointerType())
563        TypeInfo.RTTI = CGM.getObjCRuntime().GetEHType(CaughtType);
564      else
565        TypeInfo = CGM.getCXXABI().getAddrOfCXXCatchHandlerType(
566            CaughtType, C->getCaughtType());
567      CatchScope->setHandler(I, TypeInfo, Handler);
568    } else {
569      // No exception decl indicates '...', a catch-all.
570      CatchScope->setHandler(I, CGM.getCXXABI().getCatchAllTypeInfo(), Handler);
571    }
572  }
573}
574
575llvm::BasicBlock *
576CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) {
577  if (EHPersonality::get(*this).usesFuncletPads())
578    return getMSVCDispatchBlock(si);
579
580  // The dispatch block for the end of the scope chain is a block that
581  // just resumes unwinding.
582  if (si == EHStack.stable_end())
583    return getEHResumeBlock(true);
584
585  // Otherwise, we should look at the actual scope.
586  EHScope &scope = *EHStack.find(si);
587
588  llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock();
589  if (!dispatchBlock) {
590    switch (scope.getKind()) {
591    case EHScope::Catch: {
592      // Apply a special case to a single catch-all.
593      EHCatchScope &catchScope = cast<EHCatchScope>(scope);
594      if (catchScope.getNumHandlers() == 1 &&
595          catchScope.getHandler(0).isCatchAll()) {
596        dispatchBlock = catchScope.getHandler(0).Block;
597
598      // Otherwise, make a dispatch block.
599      } else {
600        dispatchBlock = createBasicBlock("catch.dispatch");
601      }
602      break;
603    }
604
605    case EHScope::Cleanup:
606      dispatchBlock = createBasicBlock("ehcleanup");
607      break;
608
609    case EHScope::Filter:
610      dispatchBlock = createBasicBlock("filter.dispatch");
611      break;
612
613    case EHScope::Terminate:
614      dispatchBlock = getTerminateHandler();
615      break;
616
617    case EHScope::PadEnd:
618      llvm_unreachable("PadEnd unnecessary for Itanium!");
619    }
620    scope.setCachedEHDispatchBlock(dispatchBlock);
621  }
622  return dispatchBlock;
623}
624
625llvm::BasicBlock *
626CodeGenFunction::getMSVCDispatchBlock(EHScopeStack::stable_iterator SI) {
627  // Returning nullptr indicates that the previous dispatch block should unwind
628  // to caller.
629  if (SI == EHStack.stable_end())
630    return nullptr;
631
632  // Otherwise, we should look at the actual scope.
633  EHScope &EHS = *EHStack.find(SI);
634
635  llvm::BasicBlock *DispatchBlock = EHS.getCachedEHDispatchBlock();
636  if (DispatchBlock)
637    return DispatchBlock;
638
639  if (EHS.getKind() == EHScope::Terminate)
640    DispatchBlock = getTerminateHandler();
641  else
642    DispatchBlock = createBasicBlock();
643  CGBuilderTy Builder(*this, DispatchBlock);
644
645  switch (EHS.getKind()) {
646  case EHScope::Catch:
647    DispatchBlock->setName("catch.dispatch");
648    break;
649
650  case EHScope::Cleanup:
651    DispatchBlock->setName("ehcleanup");
652    break;
653
654  case EHScope::Filter:
655    llvm_unreachable("exception specifications not handled yet!");
656
657  case EHScope::Terminate:
658    DispatchBlock->setName("terminate");
659    break;
660
661  case EHScope::PadEnd:
662    llvm_unreachable("PadEnd dispatch block missing!");
663  }
664  EHS.setCachedEHDispatchBlock(DispatchBlock);
665  return DispatchBlock;
666}
667
668/// Check whether this is a non-EH scope, i.e. a scope which doesn't
669/// affect exception handling.  Currently, the only non-EH scopes are
670/// normal-only cleanup scopes.
671static bool isNonEHScope(const EHScope &S) {
672  switch (S.getKind()) {
673  case EHScope::Cleanup:
674    return !cast<EHCleanupScope>(S).isEHCleanup();
675  case EHScope::Filter:
676  case EHScope::Catch:
677  case EHScope::Terminate:
678  case EHScope::PadEnd:
679    return false;
680  }
681
682  llvm_unreachable("Invalid EHScope Kind!");
683}
684
685llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
686  assert(EHStack.requiresLandingPad());
687  assert(!EHStack.empty());
688
689  // If exceptions are disabled, there are usually no landingpads. However, when
690  // SEH is enabled, functions using SEH still get landingpads.
691  const LangOptions &LO = CGM.getLangOpts();
692  if (!LO.Exceptions) {
693    if (!LO.Borland && !LO.MicrosoftExt)
694      return nullptr;
695    if (!currentFunctionUsesSEHTry())
696      return nullptr;
697  }
698
699  // Check the innermost scope for a cached landing pad.  If this is
700  // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
701  llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad();
702  if (LP) return LP;
703
704  const EHPersonality &Personality = EHPersonality::get(*this);
705
706  if (!CurFn->hasPersonalityFn())
707    CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
708
709  if (Personality.usesFuncletPads()) {
710    // We don't need separate landing pads in the funclet model.
711    LP = getEHDispatchBlock(EHStack.getInnermostEHScope());
712  } else {
713    // Build the landing pad for this scope.
714    LP = EmitLandingPad();
715  }
716
717  assert(LP);
718
719  // Cache the landing pad on the innermost scope.  If this is a
720  // non-EH scope, cache the landing pad on the enclosing scope, too.
721  for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) {
722    ir->setCachedLandingPad(LP);
723    if (!isNonEHScope(*ir)) break;
724  }
725
726  return LP;
727}
728
729llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
730  assert(EHStack.requiresLandingPad());
731
732  EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope());
733  switch (innermostEHScope.getKind()) {
734  case EHScope::Terminate:
735    return getTerminateLandingPad();
736
737  case EHScope::PadEnd:
738    llvm_unreachable("PadEnd unnecessary for Itanium!");
739
740  case EHScope::Catch:
741  case EHScope::Cleanup:
742  case EHScope::Filter:
743    if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad())
744      return lpad;
745  }
746
747  // Save the current IR generation state.
748  CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP();
749  auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation);
750
751  // Create and configure the landing pad.
752  llvm::BasicBlock *lpad = createBasicBlock("lpad");
753  EmitBlock(lpad);
754
755  llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(
756      llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0);
757
758  llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
759  Builder.CreateStore(LPadExn, getExceptionSlot());
760  llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
761  Builder.CreateStore(LPadSel, getEHSelectorSlot());
762
763  // Save the exception pointer.  It's safe to use a single exception
764  // pointer per function because EH cleanups can never have nested
765  // try/catches.
766  // Build the landingpad instruction.
767
768  // Accumulate all the handlers in scope.
769  bool hasCatchAll = false;
770  bool hasCleanup = false;
771  bool hasFilter = false;
772  SmallVector<llvm::Value*, 4> filterTypes;
773  llvm::SmallPtrSet<llvm::Value*, 4> catchTypes;
774  for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E;
775       ++I) {
776
777    switch (I->getKind()) {
778    case EHScope::Cleanup:
779      // If we have a cleanup, remember that.
780      hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup());
781      continue;
782
783    case EHScope::Filter: {
784      assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
785      assert(!hasCatchAll && "EH filter reached after catch-all");
786
787      // Filter scopes get added to the landingpad in weird ways.
788      EHFilterScope &filter = cast<EHFilterScope>(*I);
789      hasFilter = true;
790
791      // Add all the filter values.
792      for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i)
793        filterTypes.push_back(filter.getFilter(i));
794      goto done;
795    }
796
797    case EHScope::Terminate:
798      // Terminate scopes are basically catch-alls.
799      assert(!hasCatchAll);
800      hasCatchAll = true;
801      goto done;
802
803    case EHScope::Catch:
804      break;
805
806    case EHScope::PadEnd:
807      llvm_unreachable("PadEnd unnecessary for Itanium!");
808    }
809
810    EHCatchScope &catchScope = cast<EHCatchScope>(*I);
811    for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) {
812      EHCatchScope::Handler handler = catchScope.getHandler(hi);
813      assert(handler.Type.Flags == 0 &&
814             "landingpads do not support catch handler flags");
815
816      // If this is a catch-all, register that and abort.
817      if (!handler.Type.RTTI) {
818        assert(!hasCatchAll);
819        hasCatchAll = true;
820        goto done;
821      }
822
823      // Check whether we already have a handler for this type.
824      if (catchTypes.insert(handler.Type.RTTI).second)
825        // If not, add it directly to the landingpad.
826        LPadInst->addClause(handler.Type.RTTI);
827    }
828  }
829
830 done:
831  // If we have a catch-all, add null to the landingpad.
832  assert(!(hasCatchAll && hasFilter));
833  if (hasCatchAll) {
834    LPadInst->addClause(getCatchAllValue(*this));
835
836  // If we have an EH filter, we need to add those handlers in the
837  // right place in the landingpad, which is to say, at the end.
838  } else if (hasFilter) {
839    // Create a filter expression: a constant array indicating which filter
840    // types there are. The personality routine only lands here if the filter
841    // doesn't match.
842    SmallVector<llvm::Constant*, 8> Filters;
843    llvm::ArrayType *AType =
844      llvm::ArrayType::get(!filterTypes.empty() ?
845                             filterTypes[0]->getType() : Int8PtrTy,
846                           filterTypes.size());
847
848    for (unsigned i = 0, e = filterTypes.size(); i != e; ++i)
849      Filters.push_back(cast<llvm::Constant>(filterTypes[i]));
850    llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters);
851    LPadInst->addClause(FilterArray);
852
853    // Also check whether we need a cleanup.
854    if (hasCleanup)
855      LPadInst->setCleanup(true);
856
857  // Otherwise, signal that we at least have cleanups.
858  } else if (hasCleanup) {
859    LPadInst->setCleanup(true);
860  }
861
862  assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) &&
863         "landingpad instruction has no clauses!");
864
865  // Tell the backend how to generate the landing pad.
866  Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope()));
867
868  // Restore the old IR generation state.
869  Builder.restoreIP(savedIP);
870
871  return lpad;
872}
873
874static void emitCatchPadBlock(CodeGenFunction &CGF, EHCatchScope &CatchScope) {
875  llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock();
876  assert(DispatchBlock);
877
878  CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP();
879  CGF.EmitBlockAfterUses(DispatchBlock);
880
881  llvm::Value *ParentPad = CGF.CurrentFuncletPad;
882  if (!ParentPad)
883    ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext());
884  llvm::BasicBlock *UnwindBB =
885      CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope());
886
887  unsigned NumHandlers = CatchScope.getNumHandlers();
888  llvm::CatchSwitchInst *CatchSwitch =
889      CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers);
890
891  // Test against each of the exception types we claim to catch.
892  for (unsigned I = 0; I < NumHandlers; ++I) {
893    const EHCatchScope::Handler &Handler = CatchScope.getHandler(I);
894
895    CatchTypeInfo TypeInfo = Handler.Type;
896    if (!TypeInfo.RTTI)
897      TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy);
898
899    CGF.Builder.SetInsertPoint(Handler.Block);
900
901    if (EHPersonality::get(CGF).isMSVCXXPersonality()) {
902      CGF.Builder.CreateCatchPad(
903          CatchSwitch, {TypeInfo.RTTI, CGF.Builder.getInt32(TypeInfo.Flags),
904                        llvm::Constant::getNullValue(CGF.VoidPtrTy)});
905    } else {
906      CGF.Builder.CreateCatchPad(CatchSwitch, {TypeInfo.RTTI});
907    }
908
909    CatchSwitch->addHandler(Handler.Block);
910  }
911  CGF.Builder.restoreIP(SavedIP);
912}
913
914/// Emit the structure of the dispatch block for the given catch scope.
915/// It is an invariant that the dispatch block already exists.
916static void emitCatchDispatchBlock(CodeGenFunction &CGF,
917                                   EHCatchScope &catchScope) {
918  if (EHPersonality::get(CGF).usesFuncletPads())
919    return emitCatchPadBlock(CGF, catchScope);
920
921  llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock();
922  assert(dispatchBlock);
923
924  // If there's only a single catch-all, getEHDispatchBlock returned
925  // that catch-all as the dispatch block.
926  if (catchScope.getNumHandlers() == 1 &&
927      catchScope.getHandler(0).isCatchAll()) {
928    assert(dispatchBlock == catchScope.getHandler(0).Block);
929    return;
930  }
931
932  CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP();
933  CGF.EmitBlockAfterUses(dispatchBlock);
934
935  // Select the right handler.
936  llvm::Value *llvm_eh_typeid_for =
937    CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
938
939  // Load the selector value.
940  llvm::Value *selector = CGF.getSelectorFromSlot();
941
942  // Test against each of the exception types we claim to catch.
943  for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) {
944    assert(i < e && "ran off end of handlers!");
945    const EHCatchScope::Handler &handler = catchScope.getHandler(i);
946
947    llvm::Value *typeValue = handler.Type.RTTI;
948    assert(handler.Type.Flags == 0 &&
949           "landingpads do not support catch handler flags");
950    assert(typeValue && "fell into catch-all case!");
951    typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy);
952
953    // Figure out the next block.
954    bool nextIsEnd;
955    llvm::BasicBlock *nextBlock;
956
957    // If this is the last handler, we're at the end, and the next
958    // block is the block for the enclosing EH scope.
959    if (i + 1 == e) {
960      nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope());
961      nextIsEnd = true;
962
963    // If the next handler is a catch-all, we're at the end, and the
964    // next block is that handler.
965    } else if (catchScope.getHandler(i+1).isCatchAll()) {
966      nextBlock = catchScope.getHandler(i+1).Block;
967      nextIsEnd = true;
968
969    // Otherwise, we're not at the end and we need a new block.
970    } else {
971      nextBlock = CGF.createBasicBlock("catch.fallthrough");
972      nextIsEnd = false;
973    }
974
975    // Figure out the catch type's index in the LSDA's type table.
976    llvm::CallInst *typeIndex =
977      CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue);
978    typeIndex->setDoesNotThrow();
979
980    llvm::Value *matchesTypeIndex =
981      CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches");
982    CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock);
983
984    // If the next handler is a catch-all, we're completely done.
985    if (nextIsEnd) {
986      CGF.Builder.restoreIP(savedIP);
987      return;
988    }
989    // Otherwise we need to emit and continue at that block.
990    CGF.EmitBlock(nextBlock);
991  }
992}
993
994void CodeGenFunction::popCatchScope() {
995  EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin());
996  if (catchScope.hasEHBranches())
997    emitCatchDispatchBlock(*this, catchScope);
998  EHStack.popCatch();
999}
1000
1001void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
1002  unsigned NumHandlers = S.getNumHandlers();
1003  EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1004  assert(CatchScope.getNumHandlers() == NumHandlers);
1005
1006  // If the catch was not required, bail out now.
1007  if (!CatchScope.hasEHBranches()) {
1008    CatchScope.clearHandlerBlocks();
1009    EHStack.popCatch();
1010    return;
1011  }
1012
1013  // Emit the structure of the EH dispatch for this catch.
1014  emitCatchDispatchBlock(*this, CatchScope);
1015
1016  // Copy the handler blocks off before we pop the EH stack.  Emitting
1017  // the handlers might scribble on this memory.
1018  SmallVector<EHCatchScope::Handler, 8> Handlers(
1019      CatchScope.begin(), CatchScope.begin() + NumHandlers);
1020
1021  EHStack.popCatch();
1022
1023  // The fall-through block.
1024  llvm::BasicBlock *ContBB = createBasicBlock("try.cont");
1025
1026  // We just emitted the body of the try; jump to the continue block.
1027  if (HaveInsertPoint())
1028    Builder.CreateBr(ContBB);
1029
1030  // Determine if we need an implicit rethrow for all these catch handlers;
1031  // see the comment below.
1032  bool doImplicitRethrow = false;
1033  if (IsFnTryBlock)
1034    doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
1035                        isa<CXXConstructorDecl>(CurCodeDecl);
1036
1037  // Perversely, we emit the handlers backwards precisely because we
1038  // want them to appear in source order.  In all of these cases, the
1039  // catch block will have exactly one predecessor, which will be a
1040  // particular block in the catch dispatch.  However, in the case of
1041  // a catch-all, one of the dispatch blocks will branch to two
1042  // different handlers, and EmitBlockAfterUses will cause the second
1043  // handler to be moved before the first.
1044  for (unsigned I = NumHandlers; I != 0; --I) {
1045    llvm::BasicBlock *CatchBlock = Handlers[I-1].Block;
1046    EmitBlockAfterUses(CatchBlock);
1047
1048    // Catch the exception if this isn't a catch-all.
1049    const CXXCatchStmt *C = S.getHandler(I-1);
1050
1051    // Enter a cleanup scope, including the catch variable and the
1052    // end-catch.
1053    RunCleanupsScope CatchScope(*this);
1054
1055    // Initialize the catch variable and set up the cleanups.
1056    SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
1057        CurrentFuncletPad);
1058    CGM.getCXXABI().emitBeginCatch(*this, C);
1059
1060    // Emit the PGO counter increment.
1061    incrementProfileCounter(C);
1062
1063    // Perform the body of the catch.
1064    EmitStmt(C->getHandlerBlock());
1065
1066    // [except.handle]p11:
1067    //   The currently handled exception is rethrown if control
1068    //   reaches the end of a handler of the function-try-block of a
1069    //   constructor or destructor.
1070
1071    // It is important that we only do this on fallthrough and not on
1072    // return.  Note that it's illegal to put a return in a
1073    // constructor function-try-block's catch handler (p14), so this
1074    // really only applies to destructors.
1075    if (doImplicitRethrow && HaveInsertPoint()) {
1076      CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false);
1077      Builder.CreateUnreachable();
1078      Builder.ClearInsertionPoint();
1079    }
1080
1081    // Fall out through the catch cleanups.
1082    CatchScope.ForceCleanup();
1083
1084    // Branch out of the try.
1085    if (HaveInsertPoint())
1086      Builder.CreateBr(ContBB);
1087  }
1088
1089  EmitBlock(ContBB);
1090  incrementProfileCounter(&S);
1091}
1092
1093namespace {
1094  struct CallEndCatchForFinally final : EHScopeStack::Cleanup {
1095    llvm::Value *ForEHVar;
1096    llvm::Value *EndCatchFn;
1097    CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn)
1098      : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {}
1099
1100    void Emit(CodeGenFunction &CGF, Flags flags) override {
1101      llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch");
1102      llvm::BasicBlock *CleanupContBB =
1103        CGF.createBasicBlock("finally.cleanup.cont");
1104
1105      llvm::Value *ShouldEndCatch =
1106        CGF.Builder.CreateFlagLoad(ForEHVar, "finally.endcatch");
1107      CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB);
1108      CGF.EmitBlock(EndCatchBB);
1109      CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw
1110      CGF.EmitBlock(CleanupContBB);
1111    }
1112  };
1113
1114  struct PerformFinally final : EHScopeStack::Cleanup {
1115    const Stmt *Body;
1116    llvm::Value *ForEHVar;
1117    llvm::Value *EndCatchFn;
1118    llvm::Value *RethrowFn;
1119    llvm::Value *SavedExnVar;
1120
1121    PerformFinally(const Stmt *Body, llvm::Value *ForEHVar,
1122                   llvm::Value *EndCatchFn,
1123                   llvm::Value *RethrowFn, llvm::Value *SavedExnVar)
1124      : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn),
1125        RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {}
1126
1127    void Emit(CodeGenFunction &CGF, Flags flags) override {
1128      // Enter a cleanup to call the end-catch function if one was provided.
1129      if (EndCatchFn)
1130        CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup,
1131                                                        ForEHVar, EndCatchFn);
1132
1133      // Save the current cleanup destination in case there are
1134      // cleanups in the finally block.
1135      llvm::Value *SavedCleanupDest =
1136        CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(),
1137                               "cleanup.dest.saved");
1138
1139      // Emit the finally block.
1140      CGF.EmitStmt(Body);
1141
1142      // If the end of the finally is reachable, check whether this was
1143      // for EH.  If so, rethrow.
1144      if (CGF.HaveInsertPoint()) {
1145        llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow");
1146        llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont");
1147
1148        llvm::Value *ShouldRethrow =
1149          CGF.Builder.CreateFlagLoad(ForEHVar, "finally.shouldthrow");
1150        CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB);
1151
1152        CGF.EmitBlock(RethrowBB);
1153        if (SavedExnVar) {
1154          CGF.EmitRuntimeCallOrInvoke(RethrowFn,
1155            CGF.Builder.CreateAlignedLoad(SavedExnVar, CGF.getPointerAlign()));
1156        } else {
1157          CGF.EmitRuntimeCallOrInvoke(RethrowFn);
1158        }
1159        CGF.Builder.CreateUnreachable();
1160
1161        CGF.EmitBlock(ContBB);
1162
1163        // Restore the cleanup destination.
1164        CGF.Builder.CreateStore(SavedCleanupDest,
1165                                CGF.getNormalCleanupDestSlot());
1166      }
1167
1168      // Leave the end-catch cleanup.  As an optimization, pretend that
1169      // the fallthrough path was inaccessible; we've dynamically proven
1170      // that we're not in the EH case along that path.
1171      if (EndCatchFn) {
1172        CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
1173        CGF.PopCleanupBlock();
1174        CGF.Builder.restoreIP(SavedIP);
1175      }
1176
1177      // Now make sure we actually have an insertion point or the
1178      // cleanup gods will hate us.
1179      CGF.EnsureInsertPoint();
1180    }
1181  };
1182} // end anonymous namespace
1183
1184/// Enters a finally block for an implementation using zero-cost
1185/// exceptions.  This is mostly general, but hard-codes some
1186/// language/ABI-specific behavior in the catch-all sections.
1187void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF,
1188                                         const Stmt *body,
1189                                         llvm::Constant *beginCatchFn,
1190                                         llvm::Constant *endCatchFn,
1191                                         llvm::Constant *rethrowFn) {
1192  assert((beginCatchFn != nullptr) == (endCatchFn != nullptr) &&
1193         "begin/end catch functions not paired");
1194  assert(rethrowFn && "rethrow function is required");
1195
1196  BeginCatchFn = beginCatchFn;
1197
1198  // The rethrow function has one of the following two types:
1199  //   void (*)()
1200  //   void (*)(void*)
1201  // In the latter case we need to pass it the exception object.
1202  // But we can't use the exception slot because the @finally might
1203  // have a landing pad (which would overwrite the exception slot).
1204  llvm::FunctionType *rethrowFnTy =
1205    cast<llvm::FunctionType>(
1206      cast<llvm::PointerType>(rethrowFn->getType())->getElementType());
1207  SavedExnVar = nullptr;
1208  if (rethrowFnTy->getNumParams())
1209    SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn");
1210
1211  // A finally block is a statement which must be executed on any edge
1212  // out of a given scope.  Unlike a cleanup, the finally block may
1213  // contain arbitrary control flow leading out of itself.  In
1214  // addition, finally blocks should always be executed, even if there
1215  // are no catch handlers higher on the stack.  Therefore, we
1216  // surround the protected scope with a combination of a normal
1217  // cleanup (to catch attempts to break out of the block via normal
1218  // control flow) and an EH catch-all (semantically "outside" any try
1219  // statement to which the finally block might have been attached).
1220  // The finally block itself is generated in the context of a cleanup
1221  // which conditionally leaves the catch-all.
1222
1223  // Jump destination for performing the finally block on an exception
1224  // edge.  We'll never actually reach this block, so unreachable is
1225  // fine.
1226  RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock());
1227
1228  // Whether the finally block is being executed for EH purposes.
1229  ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh");
1230  CGF.Builder.CreateFlagStore(false, ForEHVar);
1231
1232  // Enter a normal cleanup which will perform the @finally block.
1233  CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body,
1234                                          ForEHVar, endCatchFn,
1235                                          rethrowFn, SavedExnVar);
1236
1237  // Enter a catch-all scope.
1238  llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall");
1239  EHCatchScope *catchScope = CGF.EHStack.pushCatch(1);
1240  catchScope->setCatchAllHandler(0, catchBB);
1241}
1242
1243void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) {
1244  // Leave the finally catch-all.
1245  EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin());
1246  llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block;
1247
1248  CGF.popCatchScope();
1249
1250  // If there are any references to the catch-all block, emit it.
1251  if (catchBB->use_empty()) {
1252    delete catchBB;
1253  } else {
1254    CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP();
1255    CGF.EmitBlock(catchBB);
1256
1257    llvm::Value *exn = nullptr;
1258
1259    // If there's a begin-catch function, call it.
1260    if (BeginCatchFn) {
1261      exn = CGF.getExceptionFromSlot();
1262      CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn);
1263    }
1264
1265    // If we need to remember the exception pointer to rethrow later, do so.
1266    if (SavedExnVar) {
1267      if (!exn) exn = CGF.getExceptionFromSlot();
1268      CGF.Builder.CreateAlignedStore(exn, SavedExnVar, CGF.getPointerAlign());
1269    }
1270
1271    // Tell the cleanups in the finally block that we're do this for EH.
1272    CGF.Builder.CreateFlagStore(true, ForEHVar);
1273
1274    // Thread a jump through the finally cleanup.
1275    CGF.EmitBranchThroughCleanup(RethrowDest);
1276
1277    CGF.Builder.restoreIP(savedIP);
1278  }
1279
1280  // Finally, leave the @finally cleanup.
1281  CGF.PopCleanupBlock();
1282}
1283
1284llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
1285  if (TerminateLandingPad)
1286    return TerminateLandingPad;
1287
1288  CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1289
1290  // This will get inserted at the end of the function.
1291  TerminateLandingPad = createBasicBlock("terminate.lpad");
1292  Builder.SetInsertPoint(TerminateLandingPad);
1293
1294  // Tell the backend that this is a landing pad.
1295  const EHPersonality &Personality = EHPersonality::get(*this);
1296
1297  if (!CurFn->hasPersonalityFn())
1298    CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
1299
1300  llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(
1301      llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0);
1302  LPadInst->addClause(getCatchAllValue(*this));
1303
1304  llvm::Value *Exn = nullptr;
1305  if (getLangOpts().CPlusPlus)
1306    Exn = Builder.CreateExtractValue(LPadInst, 0);
1307  llvm::CallInst *terminateCall =
1308      CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1309  terminateCall->setDoesNotReturn();
1310  Builder.CreateUnreachable();
1311
1312  // Restore the saved insertion state.
1313  Builder.restoreIP(SavedIP);
1314
1315  return TerminateLandingPad;
1316}
1317
1318llvm::BasicBlock *CodeGenFunction::getTerminateHandler() {
1319  if (TerminateHandler)
1320    return TerminateHandler;
1321
1322  CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1323
1324  // Set up the terminate handler.  This block is inserted at the very
1325  // end of the function by FinishFunction.
1326  TerminateHandler = createBasicBlock("terminate.handler");
1327  Builder.SetInsertPoint(TerminateHandler);
1328  llvm::Value *Exn = nullptr;
1329  if (EHPersonality::get(*this).usesFuncletPads()) {
1330    llvm::Value *ParentPad = CurrentFuncletPad;
1331    if (!ParentPad)
1332      ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());
1333    Builder.CreateCleanupPad(ParentPad);
1334  } else {
1335    if (getLangOpts().CPlusPlus)
1336      Exn = getExceptionFromSlot();
1337  }
1338  llvm::CallInst *terminateCall =
1339      CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1340  terminateCall->setDoesNotReturn();
1341  Builder.CreateUnreachable();
1342
1343  // Restore the saved insertion state.
1344  Builder.restoreIP(SavedIP);
1345
1346  return TerminateHandler;
1347}
1348
1349llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) {
1350  if (EHResumeBlock) return EHResumeBlock;
1351
1352  CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
1353
1354  // We emit a jump to a notional label at the outermost unwind state.
1355  EHResumeBlock = createBasicBlock("eh.resume");
1356  Builder.SetInsertPoint(EHResumeBlock);
1357
1358  const EHPersonality &Personality = EHPersonality::get(*this);
1359
1360  // This can always be a call because we necessarily didn't find
1361  // anything on the EH stack which needs our help.
1362  const char *RethrowName = Personality.CatchallRethrowFn;
1363  if (RethrowName != nullptr && !isCleanup) {
1364    EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName),
1365                    getExceptionFromSlot())->setDoesNotReturn();
1366    Builder.CreateUnreachable();
1367    Builder.restoreIP(SavedIP);
1368    return EHResumeBlock;
1369  }
1370
1371  // Recreate the landingpad's return value for the 'resume' instruction.
1372  llvm::Value *Exn = getExceptionFromSlot();
1373  llvm::Value *Sel = getSelectorFromSlot();
1374
1375  llvm::Type *LPadType = llvm::StructType::get(Exn->getType(),
1376                                               Sel->getType(), nullptr);
1377  llvm::Value *LPadVal = llvm::UndefValue::get(LPadType);
1378  LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val");
1379  LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val");
1380
1381  Builder.CreateResume(LPadVal);
1382  Builder.restoreIP(SavedIP);
1383  return EHResumeBlock;
1384}
1385
1386void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) {
1387  EnterSEHTryStmt(S);
1388  {
1389    JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave");
1390
1391    SEHTryEpilogueStack.push_back(&TryExit);
1392    EmitStmt(S.getTryBlock());
1393    SEHTryEpilogueStack.pop_back();
1394
1395    if (!TryExit.getBlock()->use_empty())
1396      EmitBlock(TryExit.getBlock(), /*IsFinished=*/true);
1397    else
1398      delete TryExit.getBlock();
1399  }
1400  ExitSEHTryStmt(S);
1401}
1402
1403namespace {
1404struct PerformSEHFinally final : EHScopeStack::Cleanup {
1405  llvm::Function *OutlinedFinally;
1406  PerformSEHFinally(llvm::Function *OutlinedFinally)
1407      : OutlinedFinally(OutlinedFinally) {}
1408
1409  void Emit(CodeGenFunction &CGF, Flags F) override {
1410    ASTContext &Context = CGF.getContext();
1411    CodeGenModule &CGM = CGF.CGM;
1412
1413    CallArgList Args;
1414
1415    // Compute the two argument values.
1416    QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy};
1417    llvm::Value *LocalAddrFn = CGM.getIntrinsic(llvm::Intrinsic::localaddress);
1418    llvm::Value *FP = CGF.Builder.CreateCall(LocalAddrFn);
1419    llvm::Value *IsForEH =
1420        llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup());
1421    Args.add(RValue::get(IsForEH), ArgTys[0]);
1422    Args.add(RValue::get(FP), ArgTys[1]);
1423
1424    // Arrange a two-arg function info and type.
1425    FunctionProtoType::ExtProtoInfo EPI;
1426    const auto *FPT = cast<FunctionProtoType>(
1427        Context.getFunctionType(Context.VoidTy, ArgTys, EPI));
1428    const CGFunctionInfo &FnInfo =
1429        CGM.getTypes().arrangeFreeFunctionCall(Args, FPT,
1430                                               /*chainCall=*/false);
1431
1432    CGF.EmitCall(FnInfo, OutlinedFinally, ReturnValueSlot(), Args);
1433  }
1434};
1435} // end anonymous namespace
1436
1437namespace {
1438/// Find all local variable captures in the statement.
1439struct CaptureFinder : ConstStmtVisitor<CaptureFinder> {
1440  CodeGenFunction &ParentCGF;
1441  const VarDecl *ParentThis;
1442  llvm::SmallSetVector<const VarDecl *, 4> Captures;
1443  Address SEHCodeSlot = Address::invalid();
1444  CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis)
1445      : ParentCGF(ParentCGF), ParentThis(ParentThis) {}
1446
1447  // Return true if we need to do any capturing work.
1448  bool foundCaptures() {
1449    return !Captures.empty() || SEHCodeSlot.isValid();
1450  }
1451
1452  void Visit(const Stmt *S) {
1453    // See if this is a capture, then recurse.
1454    ConstStmtVisitor<CaptureFinder>::Visit(S);
1455    for (const Stmt *Child : S->children())
1456      if (Child)
1457        Visit(Child);
1458  }
1459
1460  void VisitDeclRefExpr(const DeclRefExpr *E) {
1461    // If this is already a capture, just make sure we capture 'this'.
1462    if (E->refersToEnclosingVariableOrCapture()) {
1463      Captures.insert(ParentThis);
1464      return;
1465    }
1466
1467    const auto *D = dyn_cast<VarDecl>(E->getDecl());
1468    if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage())
1469      Captures.insert(D);
1470  }
1471
1472  void VisitCXXThisExpr(const CXXThisExpr *E) {
1473    Captures.insert(ParentThis);
1474  }
1475
1476  void VisitCallExpr(const CallExpr *E) {
1477    // We only need to add parent frame allocations for these builtins in x86.
1478    if (ParentCGF.getTarget().getTriple().getArch() != llvm::Triple::x86)
1479      return;
1480
1481    unsigned ID = E->getBuiltinCallee();
1482    switch (ID) {
1483    case Builtin::BI__exception_code:
1484    case Builtin::BI_exception_code:
1485      // This is the simple case where we are the outermost finally. All we
1486      // have to do here is make sure we escape this and recover it in the
1487      // outlined handler.
1488      if (!SEHCodeSlot.isValid())
1489        SEHCodeSlot = ParentCGF.SEHCodeSlotStack.back();
1490      break;
1491    }
1492  }
1493};
1494} // end anonymous namespace
1495
1496Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF,
1497                                                   Address ParentVar,
1498                                                   llvm::Value *ParentFP) {
1499  llvm::CallInst *RecoverCall = nullptr;
1500  CGBuilderTy Builder(*this, AllocaInsertPt);
1501  if (auto *ParentAlloca = dyn_cast<llvm::AllocaInst>(ParentVar.getPointer())) {
1502    // Mark the variable escaped if nobody else referenced it and compute the
1503    // localescape index.
1504    auto InsertPair = ParentCGF.EscapedLocals.insert(
1505        std::make_pair(ParentAlloca, ParentCGF.EscapedLocals.size()));
1506    int FrameEscapeIdx = InsertPair.first->second;
1507    // call i8* @llvm.localrecover(i8* bitcast(@parentFn), i8* %fp, i32 N)
1508    llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
1509        &CGM.getModule(), llvm::Intrinsic::localrecover);
1510    llvm::Constant *ParentI8Fn =
1511        llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1512    RecoverCall = Builder.CreateCall(
1513        FrameRecoverFn, {ParentI8Fn, ParentFP,
1514                         llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
1515
1516  } else {
1517    // If the parent didn't have an alloca, we're doing some nested outlining.
1518    // Just clone the existing localrecover call, but tweak the FP argument to
1519    // use our FP value. All other arguments are constants.
1520    auto *ParentRecover =
1521        cast<llvm::IntrinsicInst>(ParentVar.getPointer()->stripPointerCasts());
1522    assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover &&
1523           "expected alloca or localrecover in parent LocalDeclMap");
1524    RecoverCall = cast<llvm::CallInst>(ParentRecover->clone());
1525    RecoverCall->setArgOperand(1, ParentFP);
1526    RecoverCall->insertBefore(AllocaInsertPt);
1527  }
1528
1529  // Bitcast the variable, rename it, and insert it in the local decl map.
1530  llvm::Value *ChildVar =
1531      Builder.CreateBitCast(RecoverCall, ParentVar.getType());
1532  ChildVar->setName(ParentVar.getName());
1533  return Address(ChildVar, ParentVar.getAlignment());
1534}
1535
1536void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF,
1537                                         const Stmt *OutlinedStmt,
1538                                         bool IsFilter) {
1539  // Find all captures in the Stmt.
1540  CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl);
1541  Finder.Visit(OutlinedStmt);
1542
1543  // We can exit early on x86_64 when there are no captures. We just have to
1544  // save the exception code in filters so that __exception_code() works.
1545  if (!Finder.foundCaptures() &&
1546      CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1547    if (IsFilter)
1548      EmitSEHExceptionCodeSave(ParentCGF, nullptr, nullptr);
1549    return;
1550  }
1551
1552  llvm::Value *EntryFP = nullptr;
1553  CGBuilderTy Builder(CGM, AllocaInsertPt);
1554  if (IsFilter && CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) {
1555    // 32-bit SEH filters need to be careful about FP recovery.  The end of the
1556    // EH registration is passed in as the EBP physical register.  We can
1557    // recover that with llvm.frameaddress(1).
1558    EntryFP = Builder.CreateCall(
1559        CGM.getIntrinsic(llvm::Intrinsic::frameaddress), {Builder.getInt32(1)});
1560  } else {
1561    // Otherwise, for x64 and 32-bit finally functions, the parent FP is the
1562    // second parameter.
1563    auto AI = CurFn->arg_begin();
1564    ++AI;
1565    EntryFP = &*AI;
1566  }
1567
1568  llvm::Value *ParentFP = EntryFP;
1569  if (IsFilter) {
1570    // Given whatever FP the runtime provided us in EntryFP, recover the true
1571    // frame pointer of the parent function. We only need to do this in filters,
1572    // since finally funclets recover the parent FP for us.
1573    llvm::Function *RecoverFPIntrin =
1574        CGM.getIntrinsic(llvm::Intrinsic::x86_seh_recoverfp);
1575    llvm::Constant *ParentI8Fn =
1576        llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1577    ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryFP});
1578  }
1579
1580  // Create llvm.localrecover calls for all captures.
1581  for (const VarDecl *VD : Finder.Captures) {
1582    if (isa<ImplicitParamDecl>(VD)) {
1583      CGM.ErrorUnsupported(VD, "'this' captured by SEH");
1584      CXXThisValue = llvm::UndefValue::get(ConvertTypeForMem(VD->getType()));
1585      continue;
1586    }
1587    if (VD->getType()->isVariablyModifiedType()) {
1588      CGM.ErrorUnsupported(VD, "VLA captured by SEH");
1589      continue;
1590    }
1591    assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) &&
1592           "captured non-local variable");
1593
1594    // If this decl hasn't been declared yet, it will be declared in the
1595    // OutlinedStmt.
1596    auto I = ParentCGF.LocalDeclMap.find(VD);
1597    if (I == ParentCGF.LocalDeclMap.end())
1598      continue;
1599
1600    Address ParentVar = I->second;
1601    setAddrOfLocalVar(
1602        VD, recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP));
1603  }
1604
1605  if (Finder.SEHCodeSlot.isValid()) {
1606    SEHCodeSlotStack.push_back(
1607        recoverAddrOfEscapedLocal(ParentCGF, Finder.SEHCodeSlot, ParentFP));
1608  }
1609
1610  if (IsFilter)
1611    EmitSEHExceptionCodeSave(ParentCGF, ParentFP, EntryFP);
1612}
1613
1614/// Arrange a function prototype that can be called by Windows exception
1615/// handling personalities. On Win64, the prototype looks like:
1616/// RetTy func(void *EHPtrs, void *ParentFP);
1617void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
1618                                             bool IsFilter,
1619                                             const Stmt *OutlinedStmt) {
1620  SourceLocation StartLoc = OutlinedStmt->getLocStart();
1621
1622  // Get the mangled function name.
1623  SmallString<128> Name;
1624  {
1625    llvm::raw_svector_ostream OS(Name);
1626    const Decl *ParentCodeDecl = ParentCGF.CurCodeDecl;
1627    const NamedDecl *Parent = dyn_cast_or_null<NamedDecl>(ParentCodeDecl);
1628    assert(Parent && "FIXME: handle unnamed decls (lambdas, blocks) with SEH");
1629    MangleContext &Mangler = CGM.getCXXABI().getMangleContext();
1630    if (IsFilter)
1631      Mangler.mangleSEHFilterExpression(Parent, OS);
1632    else
1633      Mangler.mangleSEHFinallyBlock(Parent, OS);
1634  }
1635
1636  FunctionArgList Args;
1637  if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 || !IsFilter) {
1638    // All SEH finally functions take two parameters. Win64 filters take two
1639    // parameters. Win32 filters take no parameters.
1640    if (IsFilter) {
1641      Args.push_back(ImplicitParamDecl::Create(
1642          getContext(), nullptr, StartLoc,
1643          &getContext().Idents.get("exception_pointers"),
1644          getContext().VoidPtrTy));
1645    } else {
1646      Args.push_back(ImplicitParamDecl::Create(
1647          getContext(), nullptr, StartLoc,
1648          &getContext().Idents.get("abnormal_termination"),
1649          getContext().UnsignedCharTy));
1650    }
1651    Args.push_back(ImplicitParamDecl::Create(
1652        getContext(), nullptr, StartLoc,
1653        &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy));
1654  }
1655
1656  QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy;
1657
1658  llvm::Function *ParentFn = ParentCGF.CurFn;
1659  const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionDeclaration(
1660      RetTy, Args, FunctionType::ExtInfo(), /*isVariadic=*/false);
1661
1662  llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
1663  llvm::Function *Fn = llvm::Function::Create(
1664      FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
1665  // The filter is either in the same comdat as the function, or it's internal.
1666  if (llvm::Comdat *C = ParentFn->getComdat()) {
1667    Fn->setComdat(C);
1668  } else if (ParentFn->hasWeakLinkage() || ParentFn->hasLinkOnceLinkage()) {
1669    llvm::Comdat *C = CGM.getModule().getOrInsertComdat(ParentFn->getName());
1670    ParentFn->setComdat(C);
1671    Fn->setComdat(C);
1672  } else {
1673    Fn->setLinkage(llvm::GlobalValue::InternalLinkage);
1674  }
1675
1676  IsOutlinedSEHHelper = true;
1677
1678  StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
1679                OutlinedStmt->getLocStart(), OutlinedStmt->getLocStart());
1680
1681  CGM.SetLLVMFunctionAttributes(nullptr, FnInfo, CurFn);
1682  EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter);
1683}
1684
1685/// Create a stub filter function that will ultimately hold the code of the
1686/// filter expression. The EH preparation passes in LLVM will outline the code
1687/// from the main function body into this stub.
1688llvm::Function *
1689CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF,
1690                                           const SEHExceptStmt &Except) {
1691  const Expr *FilterExpr = Except.getFilterExpr();
1692  startOutlinedSEHHelper(ParentCGF, true, FilterExpr);
1693
1694  // Emit the original filter expression, convert to i32, and return.
1695  llvm::Value *R = EmitScalarExpr(FilterExpr);
1696  R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy),
1697                            FilterExpr->getType()->isSignedIntegerType());
1698  Builder.CreateStore(R, ReturnValue);
1699
1700  FinishFunction(FilterExpr->getLocEnd());
1701
1702  return CurFn;
1703}
1704
1705llvm::Function *
1706CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF,
1707                                            const SEHFinallyStmt &Finally) {
1708  const Stmt *FinallyBlock = Finally.getBlock();
1709  startOutlinedSEHHelper(ParentCGF, false, FinallyBlock);
1710
1711  // Mark finally block calls as nounwind and noinline to make LLVM's job a
1712  // little easier.
1713  // FIXME: Remove these restrictions in the future.
1714  CurFn->addFnAttr(llvm::Attribute::NoUnwind);
1715  CurFn->addFnAttr(llvm::Attribute::NoInline);
1716
1717  // Emit the original filter expression, convert to i32, and return.
1718  EmitStmt(FinallyBlock);
1719
1720  FinishFunction(FinallyBlock->getLocEnd());
1721
1722  return CurFn;
1723}
1724
1725void CodeGenFunction::EmitSEHExceptionCodeSave(CodeGenFunction &ParentCGF,
1726                                               llvm::Value *ParentFP,
1727                                               llvm::Value *EntryFP) {
1728  // Get the pointer to the EXCEPTION_POINTERS struct. This is returned by the
1729  // __exception_info intrinsic.
1730  if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1731    // On Win64, the info is passed as the first parameter to the filter.
1732    SEHInfo = &*CurFn->arg_begin();
1733    SEHCodeSlotStack.push_back(
1734        CreateMemTemp(getContext().IntTy, "__exception_code"));
1735  } else {
1736    // On Win32, the EBP on entry to the filter points to the end of an
1737    // exception registration object. It contains 6 32-bit fields, and the info
1738    // pointer is stored in the second field. So, GEP 20 bytes backwards and
1739    // load the pointer.
1740    SEHInfo = Builder.CreateConstInBoundsGEP1_32(Int8Ty, EntryFP, -20);
1741    SEHInfo = Builder.CreateBitCast(SEHInfo, Int8PtrTy->getPointerTo());
1742    SEHInfo = Builder.CreateAlignedLoad(Int8PtrTy, SEHInfo, getPointerAlign());
1743    SEHCodeSlotStack.push_back(recoverAddrOfEscapedLocal(
1744        ParentCGF, ParentCGF.SEHCodeSlotStack.back(), ParentFP));
1745  }
1746
1747  // Save the exception code in the exception slot to unify exception access in
1748  // the filter function and the landing pad.
1749  // struct EXCEPTION_POINTERS {
1750  //   EXCEPTION_RECORD *ExceptionRecord;
1751  //   CONTEXT *ContextRecord;
1752  // };
1753  // int exceptioncode = exception_pointers->ExceptionRecord->ExceptionCode;
1754  llvm::Type *RecordTy = CGM.Int32Ty->getPointerTo();
1755  llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy, nullptr);
1756  llvm::Value *Ptrs = Builder.CreateBitCast(SEHInfo, PtrsTy->getPointerTo());
1757  llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0);
1758  Rec = Builder.CreateAlignedLoad(Rec, getPointerAlign());
1759  llvm::Value *Code = Builder.CreateAlignedLoad(Rec, getIntAlign());
1760  assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
1761  Builder.CreateStore(Code, SEHCodeSlotStack.back());
1762}
1763
1764llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() {
1765  // Sema should diagnose calling this builtin outside of a filter context, but
1766  // don't crash if we screw up.
1767  if (!SEHInfo)
1768    return llvm::UndefValue::get(Int8PtrTy);
1769  assert(SEHInfo->getType() == Int8PtrTy);
1770  return SEHInfo;
1771}
1772
1773llvm::Value *CodeGenFunction::EmitSEHExceptionCode() {
1774  assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
1775  return Builder.CreateLoad(SEHCodeSlotStack.back());
1776}
1777
1778llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() {
1779  // Abnormal termination is just the first parameter to the outlined finally
1780  // helper.
1781  auto AI = CurFn->arg_begin();
1782  return Builder.CreateZExt(&*AI, Int32Ty);
1783}
1784
1785void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
1786  CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
1787  if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
1788    // Outline the finally block.
1789    llvm::Function *FinallyFunc =
1790        HelperCGF.GenerateSEHFinallyFunction(*this, *Finally);
1791
1792    // Push a cleanup for __finally blocks.
1793    EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, FinallyFunc);
1794    return;
1795  }
1796
1797  // Otherwise, we must have an __except block.
1798  const SEHExceptStmt *Except = S.getExceptHandler();
1799  assert(Except);
1800  EHCatchScope *CatchScope = EHStack.pushCatch(1);
1801  SEHCodeSlotStack.push_back(
1802      CreateMemTemp(getContext().IntTy, "__exception_code"));
1803
1804  // If the filter is known to evaluate to 1, then we can use the clause
1805  // "catch i8* null". We can't do this on x86 because the filter has to save
1806  // the exception code.
1807  llvm::Constant *C =
1808      CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this);
1809  if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 && C &&
1810      C->isOneValue()) {
1811    CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
1812    return;
1813  }
1814
1815  // In general, we have to emit an outlined filter function. Use the function
1816  // in place of the RTTI typeinfo global that C++ EH uses.
1817  llvm::Function *FilterFunc =
1818      HelperCGF.GenerateSEHFilterFunction(*this, *Except);
1819  llvm::Constant *OpaqueFunc =
1820      llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy);
1821  CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except.ret"));
1822}
1823
1824void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
1825  // Just pop the cleanup if it's a __finally block.
1826  if (S.getFinallyHandler()) {
1827    PopCleanupBlock();
1828    return;
1829  }
1830
1831  // Otherwise, we must have an __except block.
1832  const SEHExceptStmt *Except = S.getExceptHandler();
1833  assert(Except && "__try must have __finally xor __except");
1834  EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1835
1836  // Don't emit the __except block if the __try block lacked invokes.
1837  // TODO: Model unwind edges from instructions, either with iload / istore or
1838  // a try body function.
1839  if (!CatchScope.hasEHBranches()) {
1840    CatchScope.clearHandlerBlocks();
1841    EHStack.popCatch();
1842    SEHCodeSlotStack.pop_back();
1843    return;
1844  }
1845
1846  // The fall-through block.
1847  llvm::BasicBlock *ContBB = createBasicBlock("__try.cont");
1848
1849  // We just emitted the body of the __try; jump to the continue block.
1850  if (HaveInsertPoint())
1851    Builder.CreateBr(ContBB);
1852
1853  // Check if our filter function returned true.
1854  emitCatchDispatchBlock(*this, CatchScope);
1855
1856  // Grab the block before we pop the handler.
1857  llvm::BasicBlock *CatchPadBB = CatchScope.getHandler(0).Block;
1858  EHStack.popCatch();
1859
1860  EmitBlockAfterUses(CatchPadBB);
1861
1862  // __except blocks don't get outlined into funclets, so immediately do a
1863  // catchret.
1864  llvm::CatchPadInst *CPI =
1865      cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHI());
1866  llvm::BasicBlock *ExceptBB = createBasicBlock("__except");
1867  Builder.CreateCatchRet(CPI, ExceptBB);
1868  EmitBlock(ExceptBB);
1869
1870  // On Win64, the exception code is returned in EAX. Copy it into the slot.
1871  if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1872    llvm::Function *SEHCodeIntrin =
1873        CGM.getIntrinsic(llvm::Intrinsic::eh_exceptioncode);
1874    llvm::Value *Code = Builder.CreateCall(SEHCodeIntrin, {CPI});
1875    Builder.CreateStore(Code, SEHCodeSlotStack.back());
1876  }
1877
1878  // Emit the __except body.
1879  EmitStmt(Except->getBlock());
1880
1881  // End the lifetime of the exception code.
1882  SEHCodeSlotStack.pop_back();
1883
1884  if (HaveInsertPoint())
1885    Builder.CreateBr(ContBB);
1886
1887  EmitBlock(ContBB);
1888}
1889
1890void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) {
1891  // If this code is reachable then emit a stop point (if generating
1892  // debug info). We have to do this ourselves because we are on the
1893  // "simple" statement path.
1894  if (HaveInsertPoint())
1895    EmitStopPoint(&S);
1896
1897  // This must be a __leave from a __finally block, which we warn on and is UB.
1898  // Just emit unreachable.
1899  if (!isSEHTryScope()) {
1900    Builder.CreateUnreachable();
1901    Builder.ClearInsertionPoint();
1902    return;
1903  }
1904
1905  EmitBranchThroughCleanup(*SEHTryEpilogueStack.back());
1906}
1907