1 //===--- CGException.cpp - Emit LLVM Code for C++ exceptions --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This contains code dealing with C++ exception related code generation.
12 //===----------------------------------------------------------------------===//
14 #include "clang/AST/StmtCXX.h"
16 #include "llvm/Intrinsics.h"
17 #include "llvm/IntrinsicInst.h"
18 #include "llvm/Support/CallSite.h"
20 #include "CGObjCRuntime.h"
21 #include "CodeGenFunction.h"
22 #include "CGException.h"
23 #include "CGCleanup.h"
24 #include "TargetInfo.h"
26 using namespace clang;
27 using namespace CodeGen;
29 static llvm::Constant *getAllocateExceptionFn(CodeGenFunction &CGF) {
30 // void *__cxa_allocate_exception(size_t thrown_size);
32 llvm::Type *ArgTys[] = { CGF.SizeTy };
33 const llvm::FunctionType *FTy =
34 llvm::FunctionType::get(CGF.Int8PtrTy, ArgTys, /*IsVarArgs=*/false);
36 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception");
39 static llvm::Constant *getFreeExceptionFn(CodeGenFunction &CGF) {
40 // void __cxa_free_exception(void *thrown_exception);
42 llvm::Type *ArgTys[] = { CGF.Int8PtrTy };
43 const llvm::FunctionType *FTy =
44 llvm::FunctionType::get(CGF.VoidTy, ArgTys, /*IsVarArgs=*/false);
46 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
49 static llvm::Constant *getThrowFn(CodeGenFunction &CGF) {
50 // void __cxa_throw(void *thrown_exception, std::type_info *tinfo,
51 // void (*dest) (void *));
53 llvm::Type *Args[3] = { CGF.Int8PtrTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
54 const llvm::FunctionType *FTy =
55 llvm::FunctionType::get(CGF.VoidTy, Args, /*IsVarArgs=*/false);
57 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_throw");
60 static llvm::Constant *getReThrowFn(CodeGenFunction &CGF) {
61 // void __cxa_rethrow();
63 const llvm::FunctionType *FTy =
64 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false);
66 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow");
69 static llvm::Constant *getGetExceptionPtrFn(CodeGenFunction &CGF) {
70 // void *__cxa_get_exception_ptr(void*);
72 llvm::Type *ArgTys[] = { CGF.Int8PtrTy };
73 const llvm::FunctionType *FTy =
74 llvm::FunctionType::get(CGF.Int8PtrTy, ArgTys, /*IsVarArgs=*/false);
76 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr");
79 static llvm::Constant *getBeginCatchFn(CodeGenFunction &CGF) {
80 // void *__cxa_begin_catch(void*);
82 llvm::Type *ArgTys[] = { CGF.Int8PtrTy };
83 const llvm::FunctionType *FTy =
84 llvm::FunctionType::get(CGF.Int8PtrTy, ArgTys, /*IsVarArgs=*/false);
86 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch");
89 static llvm::Constant *getEndCatchFn(CodeGenFunction &CGF) {
90 // void __cxa_end_catch();
92 const llvm::FunctionType *FTy =
93 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false);
95 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch");
98 static llvm::Constant *getUnexpectedFn(CodeGenFunction &CGF) {
99 // void __cxa_call_unexepcted(void *thrown_exception);
101 llvm::Type *ArgTys[] = { CGF.Int8PtrTy };
102 const llvm::FunctionType *FTy =
103 llvm::FunctionType::get(CGF.VoidTy, ArgTys, /*IsVarArgs=*/false);
105 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
108 llvm::Constant *CodeGenFunction::getUnwindResumeFn() {
109 llvm::Type *ArgTys[] = { Int8PtrTy };
110 const llvm::FunctionType *FTy =
111 llvm::FunctionType::get(VoidTy, ArgTys, /*IsVarArgs=*/false);
113 if (CGM.getLangOptions().SjLjExceptions)
114 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume");
115 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume");
118 llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() {
119 llvm::Type *ArgTys[] = { Int8PtrTy };
120 const llvm::FunctionType *FTy =
121 llvm::FunctionType::get(VoidTy, ArgTys, /*IsVarArgs=*/false);
123 if (CGM.getLangOptions().SjLjExceptions)
124 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume_or_Rethrow");
125 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume_or_Rethrow");
128 static llvm::Constant *getTerminateFn(CodeGenFunction &CGF) {
129 // void __terminate();
131 const llvm::FunctionType *FTy =
132 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false);
134 llvm::StringRef name;
136 // In C++, use std::terminate().
137 if (CGF.getLangOptions().CPlusPlus)
138 name = "_ZSt9terminatev"; // FIXME: mangling!
139 else if (CGF.getLangOptions().ObjC1 &&
140 CGF.CGM.getCodeGenOpts().ObjCRuntimeHasTerminate)
141 name = "objc_terminate";
144 return CGF.CGM.CreateRuntimeFunction(FTy, name);
147 static llvm::Constant *getCatchallRethrowFn(CodeGenFunction &CGF,
148 llvm::StringRef Name) {
149 llvm::Type *ArgTys[] = { CGF.Int8PtrTy };
150 const llvm::FunctionType *FTy =
151 llvm::FunctionType::get(CGF.VoidTy, ArgTys, /*IsVarArgs=*/false);
153 return CGF.CGM.CreateRuntimeFunction(FTy, Name);
156 const EHPersonality EHPersonality::GNU_C("__gcc_personality_v0");
157 const EHPersonality EHPersonality::GNU_C_SJLJ("__gcc_personality_sj0");
158 const EHPersonality EHPersonality::NeXT_ObjC("__objc_personality_v0");
159 const EHPersonality EHPersonality::GNU_CPlusPlus("__gxx_personality_v0");
160 const EHPersonality EHPersonality::GNU_CPlusPlus_SJLJ("__gxx_personality_sj0");
161 const EHPersonality EHPersonality::GNU_ObjC("__gnu_objc_personality_v0",
162 "objc_exception_throw");
163 const EHPersonality EHPersonality::GNU_ObjCXX("__gnustep_objcxx_personality_v0");
165 static const EHPersonality &getCPersonality(const LangOptions &L) {
166 if (L.SjLjExceptions)
167 return EHPersonality::GNU_C_SJLJ;
168 return EHPersonality::GNU_C;
171 static const EHPersonality &getObjCPersonality(const LangOptions &L) {
173 if (L.ObjCNonFragileABI) return EHPersonality::NeXT_ObjC;
174 else return getCPersonality(L);
176 return EHPersonality::GNU_ObjC;
180 static const EHPersonality &getCXXPersonality(const LangOptions &L) {
181 if (L.SjLjExceptions)
182 return EHPersonality::GNU_CPlusPlus_SJLJ;
184 return EHPersonality::GNU_CPlusPlus;
187 /// Determines the personality function to use when both C++
188 /// and Objective-C exceptions are being caught.
189 static const EHPersonality &getObjCXXPersonality(const LangOptions &L) {
190 // The ObjC personality defers to the C++ personality for non-ObjC
191 // handlers. Unlike the C++ case, we use the same personality
192 // function on targets using (backend-driven) SJLJ EH.
194 if (L.ObjCNonFragileABI)
195 return EHPersonality::NeXT_ObjC;
197 // In the fragile ABI, just use C++ exception handling and hope
198 // they're not doing crazy exception mixing.
200 return getCXXPersonality(L);
203 // The GNU runtime's personality function inherently doesn't support
204 // mixed EH. Use the C++ personality just to avoid returning null.
205 return EHPersonality::GNU_ObjCXX;
208 const EHPersonality &EHPersonality::get(const LangOptions &L) {
209 if (L.CPlusPlus && L.ObjC1)
210 return getObjCXXPersonality(L);
211 else if (L.CPlusPlus)
212 return getCXXPersonality(L);
214 return getObjCPersonality(L);
216 return getCPersonality(L);
219 static llvm::Constant *getPersonalityFn(CodeGenModule &CGM,
220 const EHPersonality &Personality) {
222 CGM.CreateRuntimeFunction(llvm::FunctionType::get(
223 llvm::Type::getInt32Ty(CGM.getLLVMContext()),
225 Personality.getPersonalityFnName());
229 static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM,
230 const EHPersonality &Personality) {
231 llvm::Constant *Fn = getPersonalityFn(CGM, Personality);
232 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy);
235 /// Check whether a personality function could reasonably be swapped
236 /// for a C++ personality function.
237 static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) {
238 for (llvm::Constant::use_iterator
239 I = Fn->use_begin(), E = Fn->use_end(); I != E; ++I) {
240 llvm::User *User = *I;
242 // Conditionally white-list bitcasts.
243 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(User)) {
244 if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
245 if (!PersonalityHasOnlyCXXUses(CE))
250 // Otherwise, it has to be a selector call.
251 if (!isa<llvm::EHSelectorInst>(User)) return false;
253 llvm::EHSelectorInst *Selector = cast<llvm::EHSelectorInst>(User);
254 for (unsigned I = 2, E = Selector->getNumArgOperands(); I != E; ++I) {
255 // Look for something that would've been returned by the ObjC
256 // runtime's GetEHType() method.
257 llvm::GlobalVariable *GV
258 = dyn_cast<llvm::GlobalVariable>(Selector->getArgOperand(I));
261 // ObjC EH selector entries are always global variables with
262 // names starting like this.
263 if (GV->getName().startswith("OBJC_EHTYPE"))
271 /// Try to use the C++ personality function in ObjC++. Not doing this
272 /// can cause some incompatibilities with gcc, which is more
273 /// aggressive about only using the ObjC++ personality in a function
274 /// when it really needs it.
275 void CodeGenModule::SimplifyPersonality() {
276 // For now, this is really a Darwin-specific operation.
277 if (!Context.Target.getTriple().isOSDarwin())
280 // If we're not in ObjC++ -fexceptions, there's nothing to do.
281 if (!Features.CPlusPlus || !Features.ObjC1 || !Features.Exceptions)
284 const EHPersonality &ObjCXX = EHPersonality::get(Features);
285 const EHPersonality &CXX = getCXXPersonality(Features);
286 if (&ObjCXX == &CXX ||
287 ObjCXX.getPersonalityFnName() == CXX.getPersonalityFnName())
291 getModule().getFunction(ObjCXX.getPersonalityFnName());
293 // Nothing to do if it's unused.
294 if (!Fn || Fn->use_empty()) return;
296 // Can't do the optimization if it has non-C++ uses.
297 if (!PersonalityHasOnlyCXXUses(Fn)) return;
299 // Create the C++ personality function and kill off the old
301 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX);
303 // This can happen if the user is screwing with us.
304 if (Fn->getType() != CXXFn->getType()) return;
306 Fn->replaceAllUsesWith(CXXFn);
307 Fn->eraseFromParent();
310 /// Returns the value to inject into a selector to indicate the
311 /// presence of a catch-all.
312 static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) {
313 // Possibly we should use @llvm.eh.catch.all.value here.
314 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
317 /// Returns the value to inject into a selector to indicate the
318 /// presence of a cleanup.
319 static llvm::Constant *getCleanupValue(CodeGenFunction &CGF) {
320 return llvm::ConstantInt::get(CGF.Builder.getInt32Ty(), 0);
324 /// A cleanup to free the exception object if its initialization
326 struct FreeException : EHScopeStack::Cleanup {
328 FreeException(llvm::Value *exn) : exn(exn) {}
329 void Emit(CodeGenFunction &CGF, Flags flags) {
330 CGF.Builder.CreateCall(getFreeExceptionFn(CGF), exn)
336 // Emits an exception expression into the given location. This
337 // differs from EmitAnyExprToMem only in that, if a final copy-ctor
338 // call is required, an exception within that copy ctor causes
339 // std::terminate to be invoked.
340 static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *e,
342 // Make sure the exception object is cleaned up if there's an
343 // exception during initialization.
344 CGF.pushFullExprCleanup<FreeException>(EHCleanup, addr);
345 EHScopeStack::stable_iterator cleanup = CGF.EHStack.stable_begin();
347 // __cxa_allocate_exception returns a void*; we need to cast this
348 // to the appropriate type for the object.
349 const llvm::Type *ty = CGF.ConvertTypeForMem(e->getType())->getPointerTo();
350 llvm::Value *typedAddr = CGF.Builder.CreateBitCast(addr, ty);
352 // FIXME: this isn't quite right! If there's a final unelided call
353 // to a copy constructor, then according to [except.terminate]p1 we
354 // must call std::terminate() if that constructor throws, because
355 // technically that copy occurs after the exception expression is
356 // evaluated but before the exception is caught. But the best way
357 // to handle that is to teach EmitAggExpr to do the final copy
358 // differently if it can't be elided.
359 CGF.EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
362 // Deactivate the cleanup block.
363 CGF.DeactivateCleanupBlock(cleanup);
366 llvm::Value *CodeGenFunction::getExceptionSlot() {
368 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
369 return ExceptionSlot;
372 llvm::Value *CodeGenFunction::getEHSelectorSlot() {
374 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
375 return EHSelectorSlot;
378 void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) {
379 if (!E->getSubExpr()) {
380 if (getInvokeDest()) {
381 Builder.CreateInvoke(getReThrowFn(*this),
382 getUnreachableBlock(),
384 ->setDoesNotReturn();
386 Builder.CreateCall(getReThrowFn(*this))->setDoesNotReturn();
387 Builder.CreateUnreachable();
390 // throw is an expression, and the expression emitters expect us
391 // to leave ourselves at a valid insertion point.
392 EmitBlock(createBasicBlock("throw.cont"));
397 QualType ThrowType = E->getSubExpr()->getType();
399 // Now allocate the exception object.
400 const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
401 uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity();
403 llvm::Constant *AllocExceptionFn = getAllocateExceptionFn(*this);
404 llvm::CallInst *ExceptionPtr =
405 Builder.CreateCall(AllocExceptionFn,
406 llvm::ConstantInt::get(SizeTy, TypeSize),
408 ExceptionPtr->setDoesNotThrow();
410 EmitAnyExprToExn(*this, E->getSubExpr(), ExceptionPtr);
412 // Now throw the exception.
413 llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType,
416 // The address of the destructor. If the exception type has a
417 // trivial destructor (or isn't a record), we just pass null.
418 llvm::Constant *Dtor = 0;
419 if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) {
420 CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
421 if (!Record->hasTrivialDestructor()) {
422 CXXDestructorDecl *DtorD = Record->getDestructor();
423 Dtor = CGM.GetAddrOfCXXDestructor(DtorD, Dtor_Complete);
424 Dtor = llvm::ConstantExpr::getBitCast(Dtor, Int8PtrTy);
427 if (!Dtor) Dtor = llvm::Constant::getNullValue(Int8PtrTy);
429 if (getInvokeDest()) {
430 llvm::InvokeInst *ThrowCall =
431 Builder.CreateInvoke3(getThrowFn(*this),
432 getUnreachableBlock(), getInvokeDest(),
433 ExceptionPtr, TypeInfo, Dtor);
434 ThrowCall->setDoesNotReturn();
436 llvm::CallInst *ThrowCall =
437 Builder.CreateCall3(getThrowFn(*this), ExceptionPtr, TypeInfo, Dtor);
438 ThrowCall->setDoesNotReturn();
439 Builder.CreateUnreachable();
442 // throw is an expression, and the expression emitters expect us
443 // to leave ourselves at a valid insertion point.
444 EmitBlock(createBasicBlock("throw.cont"));
447 void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
448 if (!CGM.getLangOptions().CXXExceptions)
451 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
454 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
458 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
459 if (isNoexceptExceptionSpec(EST)) {
460 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
461 // noexcept functions are simple terminate scopes.
462 EHStack.pushTerminate();
464 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
465 unsigned NumExceptions = Proto->getNumExceptions();
466 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions);
468 for (unsigned I = 0; I != NumExceptions; ++I) {
469 QualType Ty = Proto->getExceptionType(I);
470 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType();
471 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType,
473 Filter->setFilter(I, EHType);
478 void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
479 if (!CGM.getLangOptions().CXXExceptions)
482 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
485 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
489 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
490 if (isNoexceptExceptionSpec(EST)) {
491 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
492 EHStack.popTerminate();
494 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
499 void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
501 EmitStmt(S.getTryBlock());
505 void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
506 unsigned NumHandlers = S.getNumHandlers();
507 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers);
509 for (unsigned I = 0; I != NumHandlers; ++I) {
510 const CXXCatchStmt *C = S.getHandler(I);
512 llvm::BasicBlock *Handler = createBasicBlock("catch");
513 if (C->getExceptionDecl()) {
514 // FIXME: Dropping the reference type on the type into makes it
515 // impossible to correctly implement catch-by-reference
516 // semantics for pointers. Unfortunately, this is what all
517 // existing compilers do, and it's not clear that the standard
518 // personality routine is capable of doing this right. See C++ DR 388:
519 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
520 QualType CaughtType = C->getCaughtType();
521 CaughtType = CaughtType.getNonReferenceType().getUnqualifiedType();
523 llvm::Value *TypeInfo = 0;
524 if (CaughtType->isObjCObjectPointerType())
525 TypeInfo = CGM.getObjCRuntime().GetEHType(CaughtType);
527 TypeInfo = CGM.GetAddrOfRTTIDescriptor(CaughtType, /*ForEH=*/true);
528 CatchScope->setHandler(I, TypeInfo, Handler);
530 // No exception decl indicates '...', a catch-all.
531 CatchScope->setCatchAllHandler(I, Handler);
536 /// Check whether this is a non-EH scope, i.e. a scope which doesn't
537 /// affect exception handling. Currently, the only non-EH scopes are
538 /// normal-only cleanup scopes.
539 static bool isNonEHScope(const EHScope &S) {
540 switch (S.getKind()) {
541 case EHScope::Cleanup:
542 return !cast<EHCleanupScope>(S).isEHCleanup();
543 case EHScope::Filter:
545 case EHScope::Terminate:
553 llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
554 assert(EHStack.requiresLandingPad());
555 assert(!EHStack.empty());
557 if (!CGM.getLangOptions().Exceptions)
560 // Check the innermost scope for a cached landing pad. If this is
561 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
562 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad();
565 // Build the landing pad for this scope.
566 LP = EmitLandingPad();
569 // Cache the landing pad on the innermost scope. If this is a
570 // non-EH scope, cache the landing pad on the enclosing scope, too.
571 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) {
572 ir->setCachedLandingPad(LP);
573 if (!isNonEHScope(*ir)) break;
579 // This code contains a hack to work around a design flaw in
580 // LLVM's EH IR which breaks semantics after inlining. This same
581 // hack is implemented in llvm-gcc.
583 // The LLVM EH abstraction is basically a thin veneer over the
584 // traditional GCC zero-cost design: for each range of instructions
585 // in the function, there is (at most) one "landing pad" with an
586 // associated chain of EH actions. A language-specific personality
587 // function interprets this chain of actions and (1) decides whether
588 // or not to resume execution at the landing pad and (2) if so,
589 // provides an integer indicating why it's stopping. In LLVM IR,
590 // the association of a landing pad with a range of instructions is
591 // achieved via an invoke instruction, the chain of actions becomes
592 // the arguments to the @llvm.eh.selector call, and the selector
593 // call returns the integer indicator. Other than the required
594 // presence of two intrinsic function calls in the landing pad,
595 // the IR exactly describes the layout of the output code.
597 // A principal advantage of this design is that it is completely
598 // language-agnostic; in theory, the LLVM optimizers can treat
599 // landing pads neutrally, and targets need only know how to lower
600 // the intrinsics to have a functioning exceptions system (assuming
601 // that platform exceptions follow something approximately like the
602 // GCC design). Unfortunately, landing pads cannot be combined in a
603 // language-agnostic way: given selectors A and B, there is no way
604 // to make a single landing pad which faithfully represents the
605 // semantics of propagating an exception first through A, then
606 // through B, without knowing how the personality will interpret the
607 // (lowered form of the) selectors. This means that inlining has no
608 // choice but to crudely chain invokes (i.e., to ignore invokes in
609 // the inlined function, but to turn all unwindable calls into
610 // invokes), which is only semantically valid if every unwind stops
611 // at every landing pad.
613 // Therefore, the invoke-inline hack is to guarantee that every
614 // landing pad has a catch-all.
615 enum CleanupHackLevel_t {
616 /// A level of hack that requires that all landing pads have
618 CHL_MandatoryCatchall,
620 /// A level of hack that requires that all landing pads handle
622 CHL_MandatoryCleanup,
624 /// No hacks at all; ideal IR generation.
627 const CleanupHackLevel_t CleanupHackLevel = CHL_MandatoryCleanup;
629 llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
630 assert(EHStack.requiresLandingPad());
632 for (EHScopeStack::iterator ir = EHStack.begin(); ; ) {
633 assert(ir != EHStack.end() &&
634 "stack requiring landing pad is nothing but non-EH scopes?");
636 // If this is a terminate scope, just use the singleton terminate
638 if (isa<EHTerminateScope>(*ir))
639 return getTerminateLandingPad();
641 // If this isn't an EH scope, iterate; otherwise break out.
642 if (!isNonEHScope(*ir)) break;
645 // We haven't checked this scope for a cached landing pad yet.
646 if (llvm::BasicBlock *LP = ir->getCachedLandingPad())
650 // Save the current IR generation state.
651 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
653 const EHPersonality &Personality = EHPersonality::get(getLangOptions());
655 // Create and configure the landing pad.
656 llvm::BasicBlock *LP = createBasicBlock("lpad");
659 // Save the exception pointer. It's safe to use a single exception
660 // pointer per function because EH cleanups can never have nested
662 llvm::CallInst *Exn =
663 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_exception), "exn");
664 Exn->setDoesNotThrow();
665 Builder.CreateStore(Exn, getExceptionSlot());
667 // Build the selector arguments.
668 llvm::SmallVector<llvm::Value*, 8> EHSelector;
669 EHSelector.push_back(Exn);
670 EHSelector.push_back(getOpaquePersonalityFn(CGM, Personality));
672 // Accumulate all the handlers in scope.
673 llvm::DenseMap<llvm::Value*, UnwindDest> EHHandlers;
675 bool HasEHCleanup = false;
676 bool HasEHFilter = false;
677 llvm::SmallVector<llvm::Value*, 8> EHFilters;
678 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end();
681 switch (I->getKind()) {
682 case EHScope::Cleanup:
684 HasEHCleanup = cast<EHCleanupScope>(*I).isEHCleanup();
685 // We otherwise don't care about cleanups.
688 case EHScope::Filter: {
689 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
690 assert(!CatchAll.isValid() && "EH filter reached after catch-all");
692 // Filter scopes get added to the selector in weird ways.
693 EHFilterScope &Filter = cast<EHFilterScope>(*I);
696 // Add all the filter values which we aren't already explicitly
698 for (unsigned I = 0, E = Filter.getNumFilters(); I != E; ++I) {
699 llvm::Value *FV = Filter.getFilter(I);
700 if (!EHHandlers.count(FV))
701 EHFilters.push_back(FV);
706 case EHScope::Terminate:
707 // Terminate scopes are basically catch-alls.
708 assert(!CatchAll.isValid());
709 CatchAll = UnwindDest(getTerminateHandler(),
710 EHStack.getEnclosingEHCleanup(I),
711 cast<EHTerminateScope>(*I).getDestIndex());
718 EHCatchScope &Catch = cast<EHCatchScope>(*I);
719 for (unsigned HI = 0, HE = Catch.getNumHandlers(); HI != HE; ++HI) {
720 EHCatchScope::Handler Handler = Catch.getHandler(HI);
722 // Catch-all. We should only have one of these per catch.
724 assert(!CatchAll.isValid());
725 CatchAll = UnwindDest(Handler.Block,
726 EHStack.getEnclosingEHCleanup(I),
731 // Check whether we already have a handler for this type.
732 UnwindDest &Dest = EHHandlers[Handler.Type];
733 if (Dest.isValid()) continue;
735 EHSelector.push_back(Handler.Type);
736 Dest = UnwindDest(Handler.Block,
737 EHStack.getEnclosingEHCleanup(I),
741 // Stop if we found a catch-all.
742 if (CatchAll.isValid()) break;
746 unsigned LastToEmitInLoop = EHSelector.size();
748 // If we have a catch-all, add null to the selector.
749 if (CatchAll.isValid()) {
750 EHSelector.push_back(getCatchAllValue(*this));
752 // If we have an EH filter, we need to add those handlers in the
753 // right place in the selector, which is to say, at the end.
754 } else if (HasEHFilter) {
755 // Create a filter expression: an integer constant saying how many
756 // filters there are (+1 to avoid ambiguity with 0 for cleanup),
757 // followed by the filter types. The personality routine only
758 // lands here if the filter doesn't match.
759 EHSelector.push_back(llvm::ConstantInt::get(Builder.getInt32Ty(),
760 EHFilters.size() + 1));
761 EHSelector.append(EHFilters.begin(), EHFilters.end());
763 // Also check whether we need a cleanup.
764 if (CleanupHackLevel == CHL_MandatoryCatchall || HasEHCleanup)
765 EHSelector.push_back(CleanupHackLevel == CHL_MandatoryCatchall
766 ? getCatchAllValue(*this)
767 : getCleanupValue(*this));
769 // Otherwise, signal that we at least have cleanups.
770 } else if (CleanupHackLevel == CHL_MandatoryCatchall || HasEHCleanup) {
771 EHSelector.push_back(CleanupHackLevel == CHL_MandatoryCatchall
772 ? getCatchAllValue(*this)
773 : getCleanupValue(*this));
775 // At the MandatoryCleanup hack level, we don't need to actually
776 // spuriously tell the unwinder that we have cleanups, but we do
777 // need to always be prepared to handle cleanups.
778 } else if (CleanupHackLevel == CHL_MandatoryCleanup) {
779 // Just don't decrement LastToEmitInLoop.
782 assert(LastToEmitInLoop > 2);
786 assert(EHSelector.size() >= 3 && "selector call has only two arguments!");
788 // Tell the backend how to generate the landing pad.
789 llvm::CallInst *Selection =
790 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector),
791 EHSelector, "eh.selector");
792 Selection->setDoesNotThrow();
794 // Save the selector value in mandatory-cleanup mode.
795 if (CleanupHackLevel == CHL_MandatoryCleanup)
796 Builder.CreateStore(Selection, getEHSelectorSlot());
798 // Select the right handler.
799 llvm::Value *llvm_eh_typeid_for =
800 CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
802 // The results of llvm_eh_typeid_for aren't reliable --- at least
803 // not locally --- so we basically have to do this as an 'if' chain.
804 // We walk through the first N-1 catch clauses, testing and chaining,
805 // and then fall into the final clause (which is either a cleanup, a
806 // filter (possibly with a cleanup), a catch-all, or another catch).
807 for (unsigned I = 2; I != LastToEmitInLoop; ++I) {
808 llvm::Value *Type = EHSelector[I];
809 UnwindDest Dest = EHHandlers[Type];
810 assert(Dest.isValid() && "no handler entry for value in selector?");
812 // Figure out where to branch on a match. As a debug code-size
813 // optimization, if the scope depth matches the innermost cleanup,
814 // we branch directly to the catch handler.
815 llvm::BasicBlock *Match = Dest.getBlock();
816 bool MatchNeedsCleanup =
817 Dest.getScopeDepth() != EHStack.getInnermostEHCleanup();
818 if (MatchNeedsCleanup)
819 Match = createBasicBlock("eh.match");
821 llvm::BasicBlock *Next = createBasicBlock("eh.next");
823 // Check whether the exception matches.
825 = Builder.CreateCall(llvm_eh_typeid_for,
826 Builder.CreateBitCast(Type, Int8PtrTy));
827 Id->setDoesNotThrow();
828 Builder.CreateCondBr(Builder.CreateICmpEQ(Selection, Id),
831 // Emit match code if necessary.
832 if (MatchNeedsCleanup) {
834 EmitBranchThroughEHCleanup(Dest);
837 // Continue to the next match.
841 // Emit the final case in the selector.
842 // This might be a catch-all....
843 if (CatchAll.isValid()) {
844 assert(isa<llvm::ConstantPointerNull>(EHSelector.back()));
845 EmitBranchThroughEHCleanup(CatchAll);
847 // ...or an EH filter...
848 } else if (HasEHFilter) {
849 llvm::Value *SavedSelection = Selection;
851 // First, unwind out to the outermost scope if necessary.
852 if (EHStack.hasEHCleanups()) {
853 // The end here might not dominate the beginning, so we might need to
854 // save the selector if we need it.
855 llvm::AllocaInst *SelectorVar = 0;
857 SelectorVar = CreateTempAlloca(Builder.getInt32Ty(), "selector.var");
858 Builder.CreateStore(Selection, SelectorVar);
861 llvm::BasicBlock *CleanupContBB = createBasicBlock("ehspec.cleanup.cont");
862 EmitBranchThroughEHCleanup(UnwindDest(CleanupContBB, EHStack.stable_end(),
863 EHStack.getNextEHDestIndex()));
864 EmitBlock(CleanupContBB);
867 SavedSelection = Builder.CreateLoad(SelectorVar, "ehspec.saved-selector");
870 // If there was a cleanup, we'll need to actually check whether we
871 // landed here because the filter triggered.
872 if (CleanupHackLevel != CHL_Ideal || HasEHCleanup) {
873 llvm::BasicBlock *UnexpectedBB = createBasicBlock("ehspec.unexpected");
875 llvm::Constant *Zero = llvm::ConstantInt::get(Int32Ty, 0);
876 llvm::Value *FailsFilter =
877 Builder.CreateICmpSLT(SavedSelection, Zero, "ehspec.fails");
878 Builder.CreateCondBr(FailsFilter, UnexpectedBB, getRethrowDest().getBlock());
880 EmitBlock(UnexpectedBB);
883 // Call __cxa_call_unexpected. This doesn't need to be an invoke
884 // because __cxa_call_unexpected magically filters exceptions
885 // according to the last landing pad the exception was thrown
887 Builder.CreateCall(getUnexpectedFn(*this),
888 Builder.CreateLoad(getExceptionSlot()))
889 ->setDoesNotReturn();
890 Builder.CreateUnreachable();
892 // ...or a normal catch handler...
893 } else if (CleanupHackLevel == CHL_Ideal && !HasEHCleanup) {
894 llvm::Value *Type = EHSelector.back();
895 EmitBranchThroughEHCleanup(EHHandlers[Type]);
899 EmitBranchThroughEHCleanup(getRethrowDest());
902 // Restore the old IR generation state.
903 Builder.restoreIP(SavedIP);
909 /// A cleanup to call __cxa_end_catch. In many cases, the caught
910 /// exception type lets us state definitively that the thrown exception
911 /// type does not have a destructor. In particular:
912 /// - Catch-alls tell us nothing, so we have to conservatively
913 /// assume that the thrown exception might have a destructor.
914 /// - Catches by reference behave according to their base types.
915 /// - Catches of non-record types will only trigger for exceptions
916 /// of non-record types, which never have destructors.
917 /// - Catches of record types can trigger for arbitrary subclasses
918 /// of the caught type, so we have to assume the actual thrown
919 /// exception type might have a throwing destructor, even if the
920 /// caught type's destructor is trivial or nothrow.
921 struct CallEndCatch : EHScopeStack::Cleanup {
922 CallEndCatch(bool MightThrow) : MightThrow(MightThrow) {}
925 void Emit(CodeGenFunction &CGF, Flags flags) {
927 CGF.Builder.CreateCall(getEndCatchFn(CGF))->setDoesNotThrow();
931 CGF.EmitCallOrInvoke(getEndCatchFn(CGF));
936 /// Emits a call to __cxa_begin_catch and enters a cleanup to call
939 /// \param EndMightThrow - true if __cxa_end_catch might throw
940 static llvm::Value *CallBeginCatch(CodeGenFunction &CGF,
942 bool EndMightThrow) {
943 llvm::CallInst *Call = CGF.Builder.CreateCall(getBeginCatchFn(CGF), Exn);
944 Call->setDoesNotThrow();
946 CGF.EHStack.pushCleanup<CallEndCatch>(NormalAndEHCleanup, EndMightThrow);
951 /// A "special initializer" callback for initializing a catch
952 /// parameter during catch initialization.
953 static void InitCatchParam(CodeGenFunction &CGF,
954 const VarDecl &CatchParam,
955 llvm::Value *ParamAddr) {
956 // Load the exception from where the landing pad saved it.
957 llvm::Value *Exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot(), "exn");
959 CanQualType CatchType =
960 CGF.CGM.getContext().getCanonicalType(CatchParam.getType());
961 const llvm::Type *LLVMCatchTy = CGF.ConvertTypeForMem(CatchType);
963 // If we're catching by reference, we can just cast the object
964 // pointer to the appropriate pointer.
965 if (isa<ReferenceType>(CatchType)) {
966 QualType CaughtType = cast<ReferenceType>(CatchType)->getPointeeType();
967 bool EndCatchMightThrow = CaughtType->isRecordType();
969 // __cxa_begin_catch returns the adjusted object pointer.
970 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, EndCatchMightThrow);
972 // We have no way to tell the personality function that we're
973 // catching by reference, so if we're catching a pointer,
974 // __cxa_begin_catch will actually return that pointer by value.
975 if (const PointerType *PT = dyn_cast<PointerType>(CaughtType)) {
976 QualType PointeeType = PT->getPointeeType();
978 // When catching by reference, generally we should just ignore
979 // this by-value pointer and use the exception object instead.
980 if (!PointeeType->isRecordType()) {
982 // Exn points to the struct _Unwind_Exception header, which
983 // we have to skip past in order to reach the exception data.
984 unsigned HeaderSize =
985 CGF.CGM.getTargetCodeGenInfo().getSizeOfUnwindException();
986 AdjustedExn = CGF.Builder.CreateConstGEP1_32(Exn, HeaderSize);
988 // However, if we're catching a pointer-to-record type that won't
989 // work, because the personality function might have adjusted
990 // the pointer. There's actually no way for us to fully satisfy
991 // the language/ABI contract here: we can't use Exn because it
992 // might have the wrong adjustment, but we can't use the by-value
993 // pointer because it's off by a level of abstraction.
995 // The current solution is to dump the adjusted pointer into an
996 // alloca, which breaks language semantics (because changing the
997 // pointer doesn't change the exception) but at least works.
998 // The better solution would be to filter out non-exact matches
999 // and rethrow them, but this is tricky because the rethrow
1000 // really needs to be catchable by other sites at this landing
1001 // pad. The best solution is to fix the personality function.
1003 // Pull the pointer for the reference type off.
1004 const llvm::Type *PtrTy =
1005 cast<llvm::PointerType>(LLVMCatchTy)->getElementType();
1007 // Create the temporary and write the adjusted pointer into it.
1008 llvm::Value *ExnPtrTmp = CGF.CreateTempAlloca(PtrTy, "exn.byref.tmp");
1009 llvm::Value *Casted = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
1010 CGF.Builder.CreateStore(Casted, ExnPtrTmp);
1012 // Bind the reference to the temporary.
1013 AdjustedExn = ExnPtrTmp;
1017 llvm::Value *ExnCast =
1018 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.byref");
1019 CGF.Builder.CreateStore(ExnCast, ParamAddr);
1023 // Non-aggregates (plus complexes).
1024 bool IsComplex = false;
1025 if (!CGF.hasAggregateLLVMType(CatchType) ||
1026 (IsComplex = CatchType->isAnyComplexType())) {
1027 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, false);
1029 // If the catch type is a pointer type, __cxa_begin_catch returns
1030 // the pointer by value.
1031 if (CatchType->hasPointerRepresentation()) {
1032 llvm::Value *CastExn =
1033 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted");
1034 CGF.Builder.CreateStore(CastExn, ParamAddr);
1038 // Otherwise, it returns a pointer into the exception object.
1040 const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
1041 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
1044 CGF.StoreComplexToAddr(CGF.LoadComplexFromAddr(Cast, /*volatile*/ false),
1045 ParamAddr, /*volatile*/ false);
1047 unsigned Alignment =
1048 CGF.getContext().getDeclAlign(&CatchParam).getQuantity();
1049 llvm::Value *ExnLoad = CGF.Builder.CreateLoad(Cast, "exn.scalar");
1050 CGF.EmitStoreOfScalar(ExnLoad, ParamAddr, /*volatile*/ false, Alignment,
1056 assert(isa<RecordType>(CatchType) && "unexpected catch type!");
1058 const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
1060 // Check for a copy expression. If we don't have a copy expression,
1061 // that means a trivial copy is okay.
1062 const Expr *copyExpr = CatchParam.getInit();
1064 llvm::Value *rawAdjustedExn = CallBeginCatch(CGF, Exn, true);
1065 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy);
1066 CGF.EmitAggregateCopy(ParamAddr, adjustedExn, CatchType);
1070 // We have to call __cxa_get_exception_ptr to get the adjusted
1071 // pointer before copying.
1072 llvm::CallInst *rawAdjustedExn =
1073 CGF.Builder.CreateCall(getGetExceptionPtrFn(CGF), Exn);
1074 rawAdjustedExn->setDoesNotThrow();
1076 // Cast that to the appropriate type.
1077 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy);
1079 // The copy expression is defined in terms of an OpaqueValueExpr.
1080 // Find it and map it to the adjusted expression.
1081 CodeGenFunction::OpaqueValueMapping
1082 opaque(CGF, OpaqueValueExpr::findInCopyConstruct(copyExpr),
1083 CGF.MakeAddrLValue(adjustedExn, CatchParam.getType()));
1085 // Call the copy ctor in a terminate scope.
1086 CGF.EHStack.pushTerminate();
1088 // Perform the copy construction.
1089 CGF.EmitAggExpr(copyExpr, AggValueSlot::forAddr(ParamAddr, Qualifiers(),
1092 // Leave the terminate scope.
1093 CGF.EHStack.popTerminate();
1095 // Undo the opaque value mapping.
1098 // Finally we can call __cxa_begin_catch.
1099 CallBeginCatch(CGF, Exn, true);
1102 /// Begins a catch statement by initializing the catch variable and
1103 /// calling __cxa_begin_catch.
1104 static void BeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *S) {
1105 // We have to be very careful with the ordering of cleanups here:
1106 // C++ [except.throw]p4:
1107 // The destruction [of the exception temporary] occurs
1108 // immediately after the destruction of the object declared in
1109 // the exception-declaration in the handler.
1111 // So the precise ordering is:
1112 // 1. Construct catch variable.
1113 // 2. __cxa_begin_catch
1114 // 3. Enter __cxa_end_catch cleanup
1115 // 4. Enter dtor cleanup
1117 // We do this by using a slightly abnormal initialization process.
1118 // Delegation sequence:
1119 // - ExitCXXTryStmt opens a RunCleanupsScope
1120 // - EmitAutoVarAlloca creates the variable and debug info
1121 // - InitCatchParam initializes the variable from the exception
1122 // - CallBeginCatch calls __cxa_begin_catch
1123 // - CallBeginCatch enters the __cxa_end_catch cleanup
1124 // - EmitAutoVarCleanups enters the variable destructor cleanup
1125 // - EmitCXXTryStmt emits the code for the catch body
1126 // - EmitCXXTryStmt close the RunCleanupsScope
1128 VarDecl *CatchParam = S->getExceptionDecl();
1130 llvm::Value *Exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot(), "exn");
1131 CallBeginCatch(CGF, Exn, true);
1136 CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam);
1137 InitCatchParam(CGF, *CatchParam, var.getObjectAddress(CGF));
1138 CGF.EmitAutoVarCleanups(var);
1142 struct CallRethrow : EHScopeStack::Cleanup {
1143 void Emit(CodeGenFunction &CGF, Flags flags) {
1144 CGF.EmitCallOrInvoke(getReThrowFn(CGF));
1149 void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
1150 unsigned NumHandlers = S.getNumHandlers();
1151 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1152 assert(CatchScope.getNumHandlers() == NumHandlers);
1154 // Copy the handler blocks off before we pop the EH stack. Emitting
1155 // the handlers might scribble on this memory.
1156 llvm::SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers);
1157 memcpy(Handlers.data(), CatchScope.begin(),
1158 NumHandlers * sizeof(EHCatchScope::Handler));
1161 // The fall-through block.
1162 llvm::BasicBlock *ContBB = createBasicBlock("try.cont");
1164 // We just emitted the body of the try; jump to the continue block.
1165 if (HaveInsertPoint())
1166 Builder.CreateBr(ContBB);
1168 // Determine if we need an implicit rethrow for all these catch handlers.
1169 bool ImplicitRethrow = false;
1171 ImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
1172 isa<CXXConstructorDecl>(CurCodeDecl);
1174 for (unsigned I = 0; I != NumHandlers; ++I) {
1175 llvm::BasicBlock *CatchBlock = Handlers[I].Block;
1176 EmitBlock(CatchBlock);
1178 // Catch the exception if this isn't a catch-all.
1179 const CXXCatchStmt *C = S.getHandler(I);
1181 // Enter a cleanup scope, including the catch variable and the
1183 RunCleanupsScope CatchScope(*this);
1185 // Initialize the catch variable and set up the cleanups.
1186 BeginCatch(*this, C);
1188 // If there's an implicit rethrow, push a normal "cleanup" to call
1189 // _cxa_rethrow. This needs to happen before __cxa_end_catch is
1190 // called, and so it is pushed after BeginCatch.
1191 if (ImplicitRethrow)
1192 EHStack.pushCleanup<CallRethrow>(NormalCleanup);
1194 // Perform the body of the catch.
1195 EmitStmt(C->getHandlerBlock());
1197 // Fall out through the catch cleanups.
1198 CatchScope.ForceCleanup();
1200 // Branch out of the try.
1201 if (HaveInsertPoint())
1202 Builder.CreateBr(ContBB);
1209 struct CallEndCatchForFinally : EHScopeStack::Cleanup {
1210 llvm::Value *ForEHVar;
1211 llvm::Value *EndCatchFn;
1212 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn)
1213 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {}
1215 void Emit(CodeGenFunction &CGF, Flags flags) {
1216 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch");
1217 llvm::BasicBlock *CleanupContBB =
1218 CGF.createBasicBlock("finally.cleanup.cont");
1220 llvm::Value *ShouldEndCatch =
1221 CGF.Builder.CreateLoad(ForEHVar, "finally.endcatch");
1222 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB);
1223 CGF.EmitBlock(EndCatchBB);
1224 CGF.EmitCallOrInvoke(EndCatchFn); // catch-all, so might throw
1225 CGF.EmitBlock(CleanupContBB);
1229 struct PerformFinally : EHScopeStack::Cleanup {
1231 llvm::Value *ForEHVar;
1232 llvm::Value *EndCatchFn;
1233 llvm::Value *RethrowFn;
1234 llvm::Value *SavedExnVar;
1236 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar,
1237 llvm::Value *EndCatchFn,
1238 llvm::Value *RethrowFn, llvm::Value *SavedExnVar)
1239 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn),
1240 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {}
1242 void Emit(CodeGenFunction &CGF, Flags flags) {
1243 // Enter a cleanup to call the end-catch function if one was provided.
1245 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup,
1246 ForEHVar, EndCatchFn);
1248 // Save the current cleanup destination in case there are
1249 // cleanups in the finally block.
1250 llvm::Value *SavedCleanupDest =
1251 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(),
1252 "cleanup.dest.saved");
1254 // Emit the finally block.
1257 // If the end of the finally is reachable, check whether this was
1258 // for EH. If so, rethrow.
1259 if (CGF.HaveInsertPoint()) {
1260 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow");
1261 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont");
1263 llvm::Value *ShouldRethrow =
1264 CGF.Builder.CreateLoad(ForEHVar, "finally.shouldthrow");
1265 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB);
1267 CGF.EmitBlock(RethrowBB);
1269 CGF.EmitCallOrInvoke(RethrowFn, CGF.Builder.CreateLoad(SavedExnVar));
1271 CGF.EmitCallOrInvoke(RethrowFn);
1273 CGF.Builder.CreateUnreachable();
1275 CGF.EmitBlock(ContBB);
1277 // Restore the cleanup destination.
1278 CGF.Builder.CreateStore(SavedCleanupDest,
1279 CGF.getNormalCleanupDestSlot());
1282 // Leave the end-catch cleanup. As an optimization, pretend that
1283 // the fallthrough path was inaccessible; we've dynamically proven
1284 // that we're not in the EH case along that path.
1286 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
1287 CGF.PopCleanupBlock();
1288 CGF.Builder.restoreIP(SavedIP);
1291 // Now make sure we actually have an insertion point or the
1292 // cleanup gods will hate us.
1293 CGF.EnsureInsertPoint();
1298 /// Enters a finally block for an implementation using zero-cost
1299 /// exceptions. This is mostly general, but hard-codes some
1300 /// language/ABI-specific behavior in the catch-all sections.
1301 void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF,
1303 llvm::Constant *beginCatchFn,
1304 llvm::Constant *endCatchFn,
1305 llvm::Constant *rethrowFn) {
1306 assert((beginCatchFn != 0) == (endCatchFn != 0) &&
1307 "begin/end catch functions not paired");
1308 assert(rethrowFn && "rethrow function is required");
1310 BeginCatchFn = beginCatchFn;
1312 // The rethrow function has one of the following two types:
1315 // In the latter case we need to pass it the exception object.
1316 // But we can't use the exception slot because the @finally might
1317 // have a landing pad (which would overwrite the exception slot).
1318 const llvm::FunctionType *rethrowFnTy =
1319 cast<llvm::FunctionType>(
1320 cast<llvm::PointerType>(rethrowFn->getType())->getElementType());
1322 if (rethrowFnTy->getNumParams())
1323 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn");
1325 // A finally block is a statement which must be executed on any edge
1326 // out of a given scope. Unlike a cleanup, the finally block may
1327 // contain arbitrary control flow leading out of itself. In
1328 // addition, finally blocks should always be executed, even if there
1329 // are no catch handlers higher on the stack. Therefore, we
1330 // surround the protected scope with a combination of a normal
1331 // cleanup (to catch attempts to break out of the block via normal
1332 // control flow) and an EH catch-all (semantically "outside" any try
1333 // statement to which the finally block might have been attached).
1334 // The finally block itself is generated in the context of a cleanup
1335 // which conditionally leaves the catch-all.
1337 // Jump destination for performing the finally block on an exception
1338 // edge. We'll never actually reach this block, so unreachable is
1340 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock());
1342 // Whether the finally block is being executed for EH purposes.
1343 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh");
1344 CGF.Builder.CreateStore(CGF.Builder.getFalse(), ForEHVar);
1346 // Enter a normal cleanup which will perform the @finally block.
1347 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body,
1348 ForEHVar, endCatchFn,
1349 rethrowFn, SavedExnVar);
1351 // Enter a catch-all scope.
1352 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall");
1353 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1);
1354 catchScope->setCatchAllHandler(0, catchBB);
1357 void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) {
1358 // Leave the finally catch-all.
1359 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin());
1360 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block;
1361 CGF.EHStack.popCatch();
1363 // If there are any references to the catch-all block, emit it.
1364 if (catchBB->use_empty()) {
1367 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP();
1368 CGF.EmitBlock(catchBB);
1370 llvm::Value *exn = 0;
1372 // If there's a begin-catch function, call it.
1374 exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot());
1375 CGF.Builder.CreateCall(BeginCatchFn, exn)->setDoesNotThrow();
1378 // If we need to remember the exception pointer to rethrow later, do so.
1380 if (!exn) exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot());
1381 CGF.Builder.CreateStore(exn, SavedExnVar);
1384 // Tell the cleanups in the finally block that we're do this for EH.
1385 CGF.Builder.CreateStore(CGF.Builder.getTrue(), ForEHVar);
1387 // Thread a jump through the finally cleanup.
1388 CGF.EmitBranchThroughCleanup(RethrowDest);
1390 CGF.Builder.restoreIP(savedIP);
1393 // Finally, leave the @finally cleanup.
1394 CGF.PopCleanupBlock();
1397 llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
1398 if (TerminateLandingPad)
1399 return TerminateLandingPad;
1401 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1403 // This will get inserted at the end of the function.
1404 TerminateLandingPad = createBasicBlock("terminate.lpad");
1405 Builder.SetInsertPoint(TerminateLandingPad);
1407 // Tell the backend that this is a landing pad.
1408 llvm::CallInst *Exn =
1409 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_exception), "exn");
1410 Exn->setDoesNotThrow();
1412 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOptions());
1414 // Tell the backend what the exception table should be:
1415 // nothing but a catch-all.
1416 llvm::Value *Args[3] = { Exn, getOpaquePersonalityFn(CGM, Personality),
1417 getCatchAllValue(*this) };
1418 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector),
1419 Args, "eh.selector")
1420 ->setDoesNotThrow();
1422 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this));
1423 TerminateCall->setDoesNotReturn();
1424 TerminateCall->setDoesNotThrow();
1425 Builder.CreateUnreachable();
1427 // Restore the saved insertion state.
1428 Builder.restoreIP(SavedIP);
1430 return TerminateLandingPad;
1433 llvm::BasicBlock *CodeGenFunction::getTerminateHandler() {
1434 if (TerminateHandler)
1435 return TerminateHandler;
1437 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1439 // Set up the terminate handler. This block is inserted at the very
1440 // end of the function by FinishFunction.
1441 TerminateHandler = createBasicBlock("terminate.handler");
1442 Builder.SetInsertPoint(TerminateHandler);
1443 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this));
1444 TerminateCall->setDoesNotReturn();
1445 TerminateCall->setDoesNotThrow();
1446 Builder.CreateUnreachable();
1448 // Restore the saved insertion state.
1449 Builder.restoreIP(SavedIP);
1451 return TerminateHandler;
1454 CodeGenFunction::UnwindDest CodeGenFunction::getRethrowDest() {
1455 if (RethrowBlock.isValid()) return RethrowBlock;
1457 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
1459 // We emit a jump to a notional label at the outermost unwind state.
1460 llvm::BasicBlock *Unwind = createBasicBlock("eh.resume");
1461 Builder.SetInsertPoint(Unwind);
1463 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOptions());
1465 // This can always be a call because we necessarily didn't find
1466 // anything on the EH stack which needs our help.
1467 llvm::StringRef RethrowName = Personality.getCatchallRethrowFnName();
1468 if (!RethrowName.empty()) {
1469 Builder.CreateCall(getCatchallRethrowFn(*this, RethrowName),
1470 Builder.CreateLoad(getExceptionSlot()))
1471 ->setDoesNotReturn();
1473 llvm::Value *Exn = Builder.CreateLoad(getExceptionSlot());
1475 switch (CleanupHackLevel) {
1476 case CHL_MandatoryCatchall:
1477 // In mandatory-catchall mode, we need to use
1478 // _Unwind_Resume_or_Rethrow, or whatever the personality's
1480 Builder.CreateCall(getUnwindResumeOrRethrowFn(), Exn)
1481 ->setDoesNotReturn();
1483 case CHL_MandatoryCleanup: {
1484 // In mandatory-cleanup mode, we should use llvm.eh.resume.
1485 llvm::Value *Selector = Builder.CreateLoad(getEHSelectorSlot());
1486 Builder.CreateCall2(CGM.getIntrinsic(llvm::Intrinsic::eh_resume),
1488 ->setDoesNotReturn();
1492 // In an idealized mode where we don't have to worry about the
1493 // optimizer combining landing pads, we should just use
1494 // _Unwind_Resume (or the personality's equivalent).
1495 Builder.CreateCall(getUnwindResumeFn(), Exn)
1496 ->setDoesNotReturn();
1501 Builder.CreateUnreachable();
1503 Builder.restoreIP(SavedIP);
1505 RethrowBlock = UnwindDest(Unwind, EHStack.stable_end(), 0);
1506 return RethrowBlock;