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 "CodeGenFunction.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"
29 using namespace clang;
30 using namespace CodeGen;
32 static llvm::Constant *getFreeExceptionFn(CodeGenModule &CGM) {
33 // void __cxa_free_exception(void *thrown_exception);
35 llvm::FunctionType *FTy =
36 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
38 return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
41 static llvm::Constant *getUnexpectedFn(CodeGenModule &CGM) {
42 // void __cxa_call_unexpected(void *thrown_exception);
44 llvm::FunctionType *FTy =
45 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
47 return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
50 llvm::Constant *CodeGenModule::getTerminateFn() {
51 // void __terminate();
53 llvm::FunctionType *FTy =
54 llvm::FunctionType::get(VoidTy, /*IsVarArgs=*/false);
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";
67 name = "\01?terminate@@YAXXZ";
68 } else if (getLangOpts().ObjC1 &&
69 getLangOpts().ObjCRuntime.hasTerminate())
70 name = "objc_terminate";
73 return CreateRuntimeFunction(FTy, name);
76 static llvm::Constant *getCatchallRethrowFn(CodeGenModule &CGM,
78 llvm::FunctionType *FTy =
79 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
81 return CGM.CreateRuntimeFunction(FTy, Name);
85 /// The exceptions personality for a function.
86 struct EHPersonality {
87 const char *PersonalityFn;
89 // If this is non-null, this personality requires a non-standard
90 // function for rethrowing an exception after a catchall cleanup.
91 // This function must have prototype void(void*).
92 const char *CatchallRethrowFn;
94 static const EHPersonality &get(CodeGenModule &CGM,
95 const FunctionDecl *FD);
96 static const EHPersonality &get(CodeGenFunction &CGF) {
97 return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(CGF.CurCodeDecl));
100 static const EHPersonality GNU_C;
101 static const EHPersonality GNU_C_SJLJ;
102 static const EHPersonality GNU_C_SEH;
103 static const EHPersonality GNU_ObjC;
104 static const EHPersonality GNUstep_ObjC;
105 static const EHPersonality GNU_ObjCXX;
106 static const EHPersonality NeXT_ObjC;
107 static const EHPersonality GNU_CPlusPlus;
108 static const EHPersonality GNU_CPlusPlus_SJLJ;
109 static const EHPersonality GNU_CPlusPlus_SEH;
110 static const EHPersonality MSVC_except_handler;
111 static const EHPersonality MSVC_C_specific_handler;
112 static const EHPersonality MSVC_CxxFrameHandler3;
116 const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr };
118 EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr };
120 EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr };
122 EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr };
124 EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr };
126 EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr };
128 EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr };
130 EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"};
132 EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr };
134 EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr };
136 EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr };
138 EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr };
140 EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr };
142 /// On Win64, use libgcc's SEH personality function. We fall back to dwarf on
143 /// other platforms, unless the user asked for SjLj exceptions.
144 static bool useLibGCCSEHPersonality(const llvm::Triple &T) {
145 return T.isOSWindows() && T.getArch() == llvm::Triple::x86_64;
148 static const EHPersonality &getCPersonality(const llvm::Triple &T,
149 const LangOptions &L) {
150 if (L.SjLjExceptions)
151 return EHPersonality::GNU_C_SJLJ;
152 else if (useLibGCCSEHPersonality(T))
153 return EHPersonality::GNU_C_SEH;
154 return EHPersonality::GNU_C;
157 static const EHPersonality &getObjCPersonality(const llvm::Triple &T,
158 const LangOptions &L) {
159 switch (L.ObjCRuntime.getKind()) {
160 case ObjCRuntime::FragileMacOSX:
161 return getCPersonality(T, L);
162 case ObjCRuntime::MacOSX:
163 case ObjCRuntime::iOS:
164 return EHPersonality::NeXT_ObjC;
165 case ObjCRuntime::GNUstep:
166 if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
167 return EHPersonality::GNUstep_ObjC;
169 case ObjCRuntime::GCC:
170 case ObjCRuntime::ObjFW:
171 return EHPersonality::GNU_ObjC;
173 llvm_unreachable("bad runtime kind");
176 static const EHPersonality &getCXXPersonality(const llvm::Triple &T,
177 const LangOptions &L) {
178 if (L.SjLjExceptions)
179 return EHPersonality::GNU_CPlusPlus_SJLJ;
180 else if (useLibGCCSEHPersonality(T))
181 return EHPersonality::GNU_CPlusPlus_SEH;
182 return EHPersonality::GNU_CPlusPlus;
185 /// Determines the personality function to use when both C++
186 /// and Objective-C exceptions are being caught.
187 static const EHPersonality &getObjCXXPersonality(const llvm::Triple &T,
188 const LangOptions &L) {
189 switch (L.ObjCRuntime.getKind()) {
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.
193 case ObjCRuntime::MacOSX:
194 case ObjCRuntime::iOS:
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.
199 case ObjCRuntime::FragileMacOSX:
200 return getCXXPersonality(T, L);
202 // The GCC runtime's personality function inherently doesn't support
203 // mixed EH. Use the C++ personality just to avoid returning null.
204 case ObjCRuntime::GCC:
205 case ObjCRuntime::ObjFW: // XXX: this will change soon
206 return EHPersonality::GNU_ObjC;
207 case ObjCRuntime::GNUstep:
208 return EHPersonality::GNU_ObjCXX;
210 llvm_unreachable("bad runtime kind");
213 static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) {
214 if (T.getArch() == llvm::Triple::x86)
215 return EHPersonality::MSVC_except_handler;
216 return EHPersonality::MSVC_C_specific_handler;
219 const EHPersonality &EHPersonality::get(CodeGenModule &CGM,
220 const FunctionDecl *FD) {
221 const llvm::Triple &T = CGM.getTarget().getTriple();
222 const LangOptions &L = CGM.getLangOpts();
224 // Try to pick a personality function that is compatible with MSVC if we're
225 // not compiling Obj-C. Obj-C users better have an Obj-C runtime that supports
226 // the GCC-style personality function.
227 if (T.isWindowsMSVCEnvironment() && !L.ObjC1) {
228 if (L.SjLjExceptions)
229 return EHPersonality::GNU_CPlusPlus_SJLJ;
230 else if (FD && FD->usesSEHTry())
231 return getSEHPersonalityMSVC(T);
233 return EHPersonality::MSVC_CxxFrameHandler3;
236 if (L.CPlusPlus && L.ObjC1)
237 return getObjCXXPersonality(T, L);
238 else if (L.CPlusPlus)
239 return getCXXPersonality(T, L);
241 return getObjCPersonality(T, L);
243 return getCPersonality(T, L);
246 static llvm::Constant *getPersonalityFn(CodeGenModule &CGM,
247 const EHPersonality &Personality) {
249 CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true),
250 Personality.PersonalityFn);
254 static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM,
255 const EHPersonality &Personality) {
256 llvm::Constant *Fn = getPersonalityFn(CGM, Personality);
257 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy);
260 /// Check whether a personality function could reasonably be swapped
261 /// for a C++ personality function.
262 static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) {
263 for (llvm::User *U : Fn->users()) {
264 // Conditionally white-list bitcasts.
265 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(U)) {
266 if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
267 if (!PersonalityHasOnlyCXXUses(CE))
272 // Otherwise, it has to be a landingpad instruction.
273 llvm::LandingPadInst *LPI = dyn_cast<llvm::LandingPadInst>(U);
274 if (!LPI) return false;
276 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) {
277 // Look for something that would've been returned by the ObjC
278 // runtime's GetEHType() method.
279 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts();
280 if (LPI->isCatch(I)) {
281 // Check if the catch value has the ObjC prefix.
282 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val))
283 // ObjC EH selector entries are always global variables with
284 // names starting like this.
285 if (GV->getName().startswith("OBJC_EHTYPE"))
288 // Check if any of the filter values have the ObjC prefix.
289 llvm::Constant *CVal = cast<llvm::Constant>(Val);
290 for (llvm::User::op_iterator
291 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) {
292 if (llvm::GlobalVariable *GV =
293 cast<llvm::GlobalVariable>((*II)->stripPointerCasts()))
294 // ObjC EH selector entries are always global variables with
295 // names starting like this.
296 if (GV->getName().startswith("OBJC_EHTYPE"))
306 /// Try to use the C++ personality function in ObjC++. Not doing this
307 /// can cause some incompatibilities with gcc, which is more
308 /// aggressive about only using the ObjC++ personality in a function
309 /// when it really needs it.
310 void CodeGenModule::SimplifyPersonality() {
311 // If we're not in ObjC++ -fexceptions, there's nothing to do.
312 if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions)
315 // Both the problem this endeavors to fix and the way the logic
316 // above works is specific to the NeXT runtime.
317 if (!LangOpts.ObjCRuntime.isNeXTFamily())
320 const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr);
321 const EHPersonality &CXX =
322 getCXXPersonality(getTarget().getTriple(), LangOpts);
326 assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 &&
327 "Different EHPersonalities using the same personality function.");
329 llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn);
331 // Nothing to do if it's unused.
332 if (!Fn || Fn->use_empty()) return;
334 // Can't do the optimization if it has non-C++ uses.
335 if (!PersonalityHasOnlyCXXUses(Fn)) return;
337 // Create the C++ personality function and kill off the old
339 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX);
341 // This can happen if the user is screwing with us.
342 if (Fn->getType() != CXXFn->getType()) return;
344 Fn->replaceAllUsesWith(CXXFn);
345 Fn->eraseFromParent();
348 /// Returns the value to inject into a selector to indicate the
349 /// presence of a catch-all.
350 static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) {
351 // Possibly we should use @llvm.eh.catch.all.value here.
352 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
356 /// A cleanup to free the exception object if its initialization
358 struct FreeException : EHScopeStack::Cleanup {
360 FreeException(llvm::Value *exn) : exn(exn) {}
361 void Emit(CodeGenFunction &CGF, Flags flags) override {
362 CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn);
367 // Emits an exception expression into the given location. This
368 // differs from EmitAnyExprToMem only in that, if a final copy-ctor
369 // call is required, an exception within that copy ctor causes
370 // std::terminate to be invoked.
371 void CodeGenFunction::EmitAnyExprToExn(const Expr *e, llvm::Value *addr) {
372 // Make sure the exception object is cleaned up if there's an
373 // exception during initialization.
374 pushFullExprCleanup<FreeException>(EHCleanup, addr);
375 EHScopeStack::stable_iterator cleanup = EHStack.stable_begin();
377 // __cxa_allocate_exception returns a void*; we need to cast this
378 // to the appropriate type for the object.
379 llvm::Type *ty = ConvertTypeForMem(e->getType())->getPointerTo();
380 llvm::Value *typedAddr = Builder.CreateBitCast(addr, ty);
382 // FIXME: this isn't quite right! If there's a final unelided call
383 // to a copy constructor, then according to [except.terminate]p1 we
384 // must call std::terminate() if that constructor throws, because
385 // technically that copy occurs after the exception expression is
386 // evaluated but before the exception is caught. But the best way
387 // to handle that is to teach EmitAggExpr to do the final copy
388 // differently if it can't be elided.
389 EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
392 // Deactivate the cleanup block.
393 DeactivateCleanupBlock(cleanup, cast<llvm::Instruction>(typedAddr));
396 llvm::Value *CodeGenFunction::getExceptionSlot() {
398 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
399 return ExceptionSlot;
402 llvm::Value *CodeGenFunction::getEHSelectorSlot() {
404 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
405 return EHSelectorSlot;
408 llvm::Value *CodeGenFunction::getExceptionFromSlot() {
409 return Builder.CreateLoad(getExceptionSlot(), "exn");
412 llvm::Value *CodeGenFunction::getSelectorFromSlot() {
413 return Builder.CreateLoad(getEHSelectorSlot(), "sel");
416 void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E,
417 bool KeepInsertionPoint) {
418 if (const Expr *SubExpr = E->getSubExpr()) {
419 QualType ThrowType = SubExpr->getType();
420 if (ThrowType->isObjCObjectPointerType()) {
421 const Stmt *ThrowStmt = E->getSubExpr();
422 const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(ThrowStmt));
423 CGM.getObjCRuntime().EmitThrowStmt(*this, S, false);
425 CGM.getCXXABI().emitThrow(*this, E);
428 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true);
431 // throw is an expression, and the expression emitters expect us
432 // to leave ourselves at a valid insertion point.
433 if (KeepInsertionPoint)
434 EmitBlock(createBasicBlock("throw.cont"));
437 void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
438 if (!CGM.getLangOpts().CXXExceptions)
441 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
443 // Check if CapturedDecl is nothrow and create terminate scope for it.
444 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
446 EHStack.pushTerminate();
450 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
454 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
455 if (isNoexceptExceptionSpec(EST)) {
456 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
457 // noexcept functions are simple terminate scopes.
458 EHStack.pushTerminate();
460 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
461 // TODO: Revisit exception specifications for the MS ABI. There is a way to
462 // encode these in an object file but MSVC doesn't do anything with it.
463 if (getTarget().getCXXABI().isMicrosoft())
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 /// Emit the dispatch block for a filter scope if necessary.
479 static void emitFilterDispatchBlock(CodeGenFunction &CGF,
480 EHFilterScope &filterScope) {
481 llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock();
482 if (!dispatchBlock) return;
483 if (dispatchBlock->use_empty()) {
484 delete dispatchBlock;
488 CGF.EmitBlockAfterUses(dispatchBlock);
490 // If this isn't a catch-all filter, we need to check whether we got
491 // here because the filter triggered.
492 if (filterScope.getNumFilters()) {
493 // Load the selector value.
494 llvm::Value *selector = CGF.getSelectorFromSlot();
495 llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected");
497 llvm::Value *zero = CGF.Builder.getInt32(0);
498 llvm::Value *failsFilter =
499 CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails");
500 CGF.Builder.CreateCondBr(failsFilter, unexpectedBB,
501 CGF.getEHResumeBlock(false));
503 CGF.EmitBlock(unexpectedBB);
506 // Call __cxa_call_unexpected. This doesn't need to be an invoke
507 // because __cxa_call_unexpected magically filters exceptions
508 // according to the last landing pad the exception was thrown
510 llvm::Value *exn = CGF.getExceptionFromSlot();
511 CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn)
512 ->setDoesNotReturn();
513 CGF.Builder.CreateUnreachable();
516 void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
517 if (!CGM.getLangOpts().CXXExceptions)
520 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
522 // Check if CapturedDecl is nothrow and pop terminate scope for it.
523 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
525 EHStack.popTerminate();
529 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
533 ExceptionSpecificationType EST = Proto->getExceptionSpecType();
534 if (isNoexceptExceptionSpec(EST)) {
535 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
536 EHStack.popTerminate();
538 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
539 // TODO: Revisit exception specifications for the MS ABI. There is a way to
540 // encode these in an object file but MSVC doesn't do anything with it.
541 if (getTarget().getCXXABI().isMicrosoft())
543 EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
544 emitFilterDispatchBlock(*this, filterScope);
549 void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
551 EmitStmt(S.getTryBlock());
555 void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
556 unsigned NumHandlers = S.getNumHandlers();
557 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers);
559 for (unsigned I = 0; I != NumHandlers; ++I) {
560 const CXXCatchStmt *C = S.getHandler(I);
562 llvm::BasicBlock *Handler = createBasicBlock("catch");
563 if (C->getExceptionDecl()) {
564 // FIXME: Dropping the reference type on the type into makes it
565 // impossible to correctly implement catch-by-reference
566 // semantics for pointers. Unfortunately, this is what all
567 // existing compilers do, and it's not clear that the standard
568 // personality routine is capable of doing this right. See C++ DR 388:
569 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
570 Qualifiers CaughtTypeQuals;
571 QualType CaughtType = CGM.getContext().getUnqualifiedArrayType(
572 C->getCaughtType().getNonReferenceType(), CaughtTypeQuals);
574 llvm::Constant *TypeInfo = nullptr;
575 if (CaughtType->isObjCObjectPointerType())
576 TypeInfo = CGM.getObjCRuntime().GetEHType(CaughtType);
579 CGM.getAddrOfCXXCatchHandlerType(CaughtType, C->getCaughtType());
580 CatchScope->setHandler(I, TypeInfo, Handler);
582 // No exception decl indicates '...', a catch-all.
583 CatchScope->setCatchAllHandler(I, Handler);
589 CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) {
590 // The dispatch block for the end of the scope chain is a block that
591 // just resumes unwinding.
592 if (si == EHStack.stable_end())
593 return getEHResumeBlock(true);
595 // Otherwise, we should look at the actual scope.
596 EHScope &scope = *EHStack.find(si);
598 llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock();
599 if (!dispatchBlock) {
600 switch (scope.getKind()) {
601 case EHScope::Catch: {
602 // Apply a special case to a single catch-all.
603 EHCatchScope &catchScope = cast<EHCatchScope>(scope);
604 if (catchScope.getNumHandlers() == 1 &&
605 catchScope.getHandler(0).isCatchAll()) {
606 dispatchBlock = catchScope.getHandler(0).Block;
608 // Otherwise, make a dispatch block.
610 dispatchBlock = createBasicBlock("catch.dispatch");
615 case EHScope::Cleanup:
616 dispatchBlock = createBasicBlock("ehcleanup");
619 case EHScope::Filter:
620 dispatchBlock = createBasicBlock("filter.dispatch");
623 case EHScope::Terminate:
624 dispatchBlock = getTerminateHandler();
627 scope.setCachedEHDispatchBlock(dispatchBlock);
629 return dispatchBlock;
632 /// Check whether this is a non-EH scope, i.e. a scope which doesn't
633 /// affect exception handling. Currently, the only non-EH scopes are
634 /// normal-only cleanup scopes.
635 static bool isNonEHScope(const EHScope &S) {
636 switch (S.getKind()) {
637 case EHScope::Cleanup:
638 return !cast<EHCleanupScope>(S).isEHCleanup();
639 case EHScope::Filter:
641 case EHScope::Terminate:
645 llvm_unreachable("Invalid EHScope Kind!");
648 llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
649 assert(EHStack.requiresLandingPad());
650 assert(!EHStack.empty());
652 // If exceptions are disabled, there are usually no landingpads. However, when
653 // SEH is enabled, functions using SEH still get landingpads.
654 const LangOptions &LO = CGM.getLangOpts();
655 if (!LO.Exceptions) {
656 if (!LO.Borland && !LO.MicrosoftExt)
658 if (!currentFunctionUsesSEHTry())
662 // Check the innermost scope for a cached landing pad. If this is
663 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
664 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad();
667 // Build the landing pad for this scope.
668 LP = EmitLandingPad();
671 // Cache the landing pad on the innermost scope. If this is a
672 // non-EH scope, cache the landing pad on the enclosing scope, too.
673 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) {
674 ir->setCachedLandingPad(LP);
675 if (!isNonEHScope(*ir)) break;
681 llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
682 assert(EHStack.requiresLandingPad());
684 EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope());
685 switch (innermostEHScope.getKind()) {
686 case EHScope::Terminate:
687 return getTerminateLandingPad();
690 case EHScope::Cleanup:
691 case EHScope::Filter:
692 if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad())
696 // Save the current IR generation state.
697 CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP();
698 auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation);
700 const EHPersonality &personality = EHPersonality::get(*this);
702 if (!CurFn->hasPersonalityFn())
703 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, personality));
705 // Create and configure the landing pad.
706 llvm::BasicBlock *lpad = createBasicBlock("lpad");
709 llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(
710 llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0);
712 llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
713 Builder.CreateStore(LPadExn, getExceptionSlot());
714 llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
715 Builder.CreateStore(LPadSel, getEHSelectorSlot());
717 // Save the exception pointer. It's safe to use a single exception
718 // pointer per function because EH cleanups can never have nested
720 // Build the landingpad instruction.
722 // Accumulate all the handlers in scope.
723 bool hasCatchAll = false;
724 bool hasCleanup = false;
725 bool hasFilter = false;
726 SmallVector<llvm::Value*, 4> filterTypes;
727 llvm::SmallPtrSet<llvm::Value*, 4> catchTypes;
728 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E;
731 switch (I->getKind()) {
732 case EHScope::Cleanup:
733 // If we have a cleanup, remember that.
734 hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup());
737 case EHScope::Filter: {
738 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
739 assert(!hasCatchAll && "EH filter reached after catch-all");
741 // Filter scopes get added to the landingpad in weird ways.
742 EHFilterScope &filter = cast<EHFilterScope>(*I);
745 // Add all the filter values.
746 for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i)
747 filterTypes.push_back(filter.getFilter(i));
751 case EHScope::Terminate:
752 // Terminate scopes are basically catch-alls.
753 assert(!hasCatchAll);
761 EHCatchScope &catchScope = cast<EHCatchScope>(*I);
762 for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) {
763 EHCatchScope::Handler handler = catchScope.getHandler(hi);
765 // If this is a catch-all, register that and abort.
767 assert(!hasCatchAll);
772 // Check whether we already have a handler for this type.
773 if (catchTypes.insert(handler.Type).second)
774 // If not, add it directly to the landingpad.
775 LPadInst->addClause(handler.Type);
780 // If we have a catch-all, add null to the landingpad.
781 assert(!(hasCatchAll && hasFilter));
783 LPadInst->addClause(getCatchAllValue(*this));
785 // If we have an EH filter, we need to add those handlers in the
786 // right place in the landingpad, which is to say, at the end.
787 } else if (hasFilter) {
788 // Create a filter expression: a constant array indicating which filter
789 // types there are. The personality routine only lands here if the filter
791 SmallVector<llvm::Constant*, 8> Filters;
792 llvm::ArrayType *AType =
793 llvm::ArrayType::get(!filterTypes.empty() ?
794 filterTypes[0]->getType() : Int8PtrTy,
797 for (unsigned i = 0, e = filterTypes.size(); i != e; ++i)
798 Filters.push_back(cast<llvm::Constant>(filterTypes[i]));
799 llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters);
800 LPadInst->addClause(FilterArray);
802 // Also check whether we need a cleanup.
804 LPadInst->setCleanup(true);
806 // Otherwise, signal that we at least have cleanups.
807 } else if (hasCleanup) {
808 LPadInst->setCleanup(true);
811 assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) &&
812 "landingpad instruction has no clauses!");
814 // Tell the backend how to generate the landing pad.
815 Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope()));
817 // Restore the old IR generation state.
818 Builder.restoreIP(savedIP);
823 /// Emit the structure of the dispatch block for the given catch scope.
824 /// It is an invariant that the dispatch block already exists.
825 static void emitCatchDispatchBlock(CodeGenFunction &CGF,
826 EHCatchScope &catchScope) {
827 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock();
828 assert(dispatchBlock);
830 // If there's only a single catch-all, getEHDispatchBlock returned
831 // that catch-all as the dispatch block.
832 if (catchScope.getNumHandlers() == 1 &&
833 catchScope.getHandler(0).isCatchAll()) {
834 assert(dispatchBlock == catchScope.getHandler(0).Block);
838 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP();
839 CGF.EmitBlockAfterUses(dispatchBlock);
841 // Select the right handler.
842 llvm::Value *llvm_eh_typeid_for =
843 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
845 // Load the selector value.
846 llvm::Value *selector = CGF.getSelectorFromSlot();
848 // Test against each of the exception types we claim to catch.
849 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) {
850 assert(i < e && "ran off end of handlers!");
851 const EHCatchScope::Handler &handler = catchScope.getHandler(i);
853 llvm::Value *typeValue = handler.Type;
854 assert(typeValue && "fell into catch-all case!");
855 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy);
857 // Figure out the next block.
859 llvm::BasicBlock *nextBlock;
861 // If this is the last handler, we're at the end, and the next
862 // block is the block for the enclosing EH scope.
864 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope());
867 // If the next handler is a catch-all, we're at the end, and the
868 // next block is that handler.
869 } else if (catchScope.getHandler(i+1).isCatchAll()) {
870 nextBlock = catchScope.getHandler(i+1).Block;
873 // Otherwise, we're not at the end and we need a new block.
875 nextBlock = CGF.createBasicBlock("catch.fallthrough");
879 // Figure out the catch type's index in the LSDA's type table.
880 llvm::CallInst *typeIndex =
881 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue);
882 typeIndex->setDoesNotThrow();
884 llvm::Value *matchesTypeIndex =
885 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches");
886 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock);
888 // If the next handler is a catch-all, we're completely done.
890 CGF.Builder.restoreIP(savedIP);
893 // Otherwise we need to emit and continue at that block.
894 CGF.EmitBlock(nextBlock);
898 void CodeGenFunction::popCatchScope() {
899 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin());
900 if (catchScope.hasEHBranches())
901 emitCatchDispatchBlock(*this, catchScope);
905 void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
906 unsigned NumHandlers = S.getNumHandlers();
907 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
908 assert(CatchScope.getNumHandlers() == NumHandlers);
910 // If the catch was not required, bail out now.
911 if (!CatchScope.hasEHBranches()) {
912 CatchScope.clearHandlerBlocks();
917 // Emit the structure of the EH dispatch for this catch.
918 emitCatchDispatchBlock(*this, CatchScope);
920 // Copy the handler blocks off before we pop the EH stack. Emitting
921 // the handlers might scribble on this memory.
922 SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers);
923 memcpy(Handlers.data(), CatchScope.begin(),
924 NumHandlers * sizeof(EHCatchScope::Handler));
928 // The fall-through block.
929 llvm::BasicBlock *ContBB = createBasicBlock("try.cont");
931 // We just emitted the body of the try; jump to the continue block.
932 if (HaveInsertPoint())
933 Builder.CreateBr(ContBB);
935 // Determine if we need an implicit rethrow for all these catch handlers;
936 // see the comment below.
937 bool doImplicitRethrow = false;
939 doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
940 isa<CXXConstructorDecl>(CurCodeDecl);
942 // Perversely, we emit the handlers backwards precisely because we
943 // want them to appear in source order. In all of these cases, the
944 // catch block will have exactly one predecessor, which will be a
945 // particular block in the catch dispatch. However, in the case of
946 // a catch-all, one of the dispatch blocks will branch to two
947 // different handlers, and EmitBlockAfterUses will cause the second
948 // handler to be moved before the first.
949 for (unsigned I = NumHandlers; I != 0; --I) {
950 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block;
951 EmitBlockAfterUses(CatchBlock);
953 // Catch the exception if this isn't a catch-all.
954 const CXXCatchStmt *C = S.getHandler(I-1);
956 // Enter a cleanup scope, including the catch variable and the
958 RunCleanupsScope CatchScope(*this);
960 // Initialize the catch variable and set up the cleanups.
961 CGM.getCXXABI().emitBeginCatch(*this, C);
963 // Emit the PGO counter increment.
964 incrementProfileCounter(C);
966 // Perform the body of the catch.
967 EmitStmt(C->getHandlerBlock());
969 // [except.handle]p11:
970 // The currently handled exception is rethrown if control
971 // reaches the end of a handler of the function-try-block of a
972 // constructor or destructor.
974 // It is important that we only do this on fallthrough and not on
975 // return. Note that it's illegal to put a return in a
976 // constructor function-try-block's catch handler (p14), so this
977 // really only applies to destructors.
978 if (doImplicitRethrow && HaveInsertPoint()) {
979 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false);
980 Builder.CreateUnreachable();
981 Builder.ClearInsertionPoint();
984 // Fall out through the catch cleanups.
985 CatchScope.ForceCleanup();
987 // Branch out of the try.
988 if (HaveInsertPoint())
989 Builder.CreateBr(ContBB);
993 incrementProfileCounter(&S);
997 struct CallEndCatchForFinally : EHScopeStack::Cleanup {
998 llvm::Value *ForEHVar;
999 llvm::Value *EndCatchFn;
1000 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn)
1001 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {}
1003 void Emit(CodeGenFunction &CGF, Flags flags) override {
1004 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch");
1005 llvm::BasicBlock *CleanupContBB =
1006 CGF.createBasicBlock("finally.cleanup.cont");
1008 llvm::Value *ShouldEndCatch =
1009 CGF.Builder.CreateLoad(ForEHVar, "finally.endcatch");
1010 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB);
1011 CGF.EmitBlock(EndCatchBB);
1012 CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw
1013 CGF.EmitBlock(CleanupContBB);
1017 struct PerformFinally : EHScopeStack::Cleanup {
1019 llvm::Value *ForEHVar;
1020 llvm::Value *EndCatchFn;
1021 llvm::Value *RethrowFn;
1022 llvm::Value *SavedExnVar;
1024 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar,
1025 llvm::Value *EndCatchFn,
1026 llvm::Value *RethrowFn, llvm::Value *SavedExnVar)
1027 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn),
1028 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {}
1030 void Emit(CodeGenFunction &CGF, Flags flags) override {
1031 // Enter a cleanup to call the end-catch function if one was provided.
1033 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup,
1034 ForEHVar, EndCatchFn);
1036 // Save the current cleanup destination in case there are
1037 // cleanups in the finally block.
1038 llvm::Value *SavedCleanupDest =
1039 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(),
1040 "cleanup.dest.saved");
1042 // Emit the finally block.
1045 // If the end of the finally is reachable, check whether this was
1046 // for EH. If so, rethrow.
1047 if (CGF.HaveInsertPoint()) {
1048 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow");
1049 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont");
1051 llvm::Value *ShouldRethrow =
1052 CGF.Builder.CreateLoad(ForEHVar, "finally.shouldthrow");
1053 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB);
1055 CGF.EmitBlock(RethrowBB);
1057 CGF.EmitRuntimeCallOrInvoke(RethrowFn,
1058 CGF.Builder.CreateLoad(SavedExnVar));
1060 CGF.EmitRuntimeCallOrInvoke(RethrowFn);
1062 CGF.Builder.CreateUnreachable();
1064 CGF.EmitBlock(ContBB);
1066 // Restore the cleanup destination.
1067 CGF.Builder.CreateStore(SavedCleanupDest,
1068 CGF.getNormalCleanupDestSlot());
1071 // Leave the end-catch cleanup. As an optimization, pretend that
1072 // the fallthrough path was inaccessible; we've dynamically proven
1073 // that we're not in the EH case along that path.
1075 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
1076 CGF.PopCleanupBlock();
1077 CGF.Builder.restoreIP(SavedIP);
1080 // Now make sure we actually have an insertion point or the
1081 // cleanup gods will hate us.
1082 CGF.EnsureInsertPoint();
1087 /// Enters a finally block for an implementation using zero-cost
1088 /// exceptions. This is mostly general, but hard-codes some
1089 /// language/ABI-specific behavior in the catch-all sections.
1090 void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF,
1092 llvm::Constant *beginCatchFn,
1093 llvm::Constant *endCatchFn,
1094 llvm::Constant *rethrowFn) {
1095 assert((beginCatchFn != nullptr) == (endCatchFn != nullptr) &&
1096 "begin/end catch functions not paired");
1097 assert(rethrowFn && "rethrow function is required");
1099 BeginCatchFn = beginCatchFn;
1101 // The rethrow function has one of the following two types:
1104 // In the latter case we need to pass it the exception object.
1105 // But we can't use the exception slot because the @finally might
1106 // have a landing pad (which would overwrite the exception slot).
1107 llvm::FunctionType *rethrowFnTy =
1108 cast<llvm::FunctionType>(
1109 cast<llvm::PointerType>(rethrowFn->getType())->getElementType());
1110 SavedExnVar = nullptr;
1111 if (rethrowFnTy->getNumParams())
1112 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn");
1114 // A finally block is a statement which must be executed on any edge
1115 // out of a given scope. Unlike a cleanup, the finally block may
1116 // contain arbitrary control flow leading out of itself. In
1117 // addition, finally blocks should always be executed, even if there
1118 // are no catch handlers higher on the stack. Therefore, we
1119 // surround the protected scope with a combination of a normal
1120 // cleanup (to catch attempts to break out of the block via normal
1121 // control flow) and an EH catch-all (semantically "outside" any try
1122 // statement to which the finally block might have been attached).
1123 // The finally block itself is generated in the context of a cleanup
1124 // which conditionally leaves the catch-all.
1126 // Jump destination for performing the finally block on an exception
1127 // edge. We'll never actually reach this block, so unreachable is
1129 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock());
1131 // Whether the finally block is being executed for EH purposes.
1132 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh");
1133 CGF.Builder.CreateStore(CGF.Builder.getFalse(), ForEHVar);
1135 // Enter a normal cleanup which will perform the @finally block.
1136 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body,
1137 ForEHVar, endCatchFn,
1138 rethrowFn, SavedExnVar);
1140 // Enter a catch-all scope.
1141 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall");
1142 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1);
1143 catchScope->setCatchAllHandler(0, catchBB);
1146 void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) {
1147 // Leave the finally catch-all.
1148 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin());
1149 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block;
1151 CGF.popCatchScope();
1153 // If there are any references to the catch-all block, emit it.
1154 if (catchBB->use_empty()) {
1157 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP();
1158 CGF.EmitBlock(catchBB);
1160 llvm::Value *exn = nullptr;
1162 // If there's a begin-catch function, call it.
1164 exn = CGF.getExceptionFromSlot();
1165 CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn);
1168 // If we need to remember the exception pointer to rethrow later, do so.
1170 if (!exn) exn = CGF.getExceptionFromSlot();
1171 CGF.Builder.CreateStore(exn, SavedExnVar);
1174 // Tell the cleanups in the finally block that we're do this for EH.
1175 CGF.Builder.CreateStore(CGF.Builder.getTrue(), ForEHVar);
1177 // Thread a jump through the finally cleanup.
1178 CGF.EmitBranchThroughCleanup(RethrowDest);
1180 CGF.Builder.restoreIP(savedIP);
1183 // Finally, leave the @finally cleanup.
1184 CGF.PopCleanupBlock();
1187 llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
1188 if (TerminateLandingPad)
1189 return TerminateLandingPad;
1191 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1193 // This will get inserted at the end of the function.
1194 TerminateLandingPad = createBasicBlock("terminate.lpad");
1195 Builder.SetInsertPoint(TerminateLandingPad);
1197 // Tell the backend that this is a landing pad.
1198 const EHPersonality &Personality = EHPersonality::get(*this);
1200 if (!CurFn->hasPersonalityFn())
1201 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality));
1203 llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(
1204 llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0);
1205 LPadInst->addClause(getCatchAllValue(*this));
1207 llvm::Value *Exn = 0;
1208 if (getLangOpts().CPlusPlus)
1209 Exn = Builder.CreateExtractValue(LPadInst, 0);
1210 llvm::CallInst *terminateCall =
1211 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1212 terminateCall->setDoesNotReturn();
1213 Builder.CreateUnreachable();
1215 // Restore the saved insertion state.
1216 Builder.restoreIP(SavedIP);
1218 return TerminateLandingPad;
1221 llvm::BasicBlock *CodeGenFunction::getTerminateHandler() {
1222 if (TerminateHandler)
1223 return TerminateHandler;
1225 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1227 // Set up the terminate handler. This block is inserted at the very
1228 // end of the function by FinishFunction.
1229 TerminateHandler = createBasicBlock("terminate.handler");
1230 Builder.SetInsertPoint(TerminateHandler);
1231 llvm::Value *Exn = 0;
1232 if (getLangOpts().CPlusPlus)
1233 Exn = getExceptionFromSlot();
1234 llvm::CallInst *terminateCall =
1235 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
1236 terminateCall->setDoesNotReturn();
1237 Builder.CreateUnreachable();
1239 // Restore the saved insertion state.
1240 Builder.restoreIP(SavedIP);
1242 return TerminateHandler;
1245 llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) {
1246 if (EHResumeBlock) return EHResumeBlock;
1248 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
1250 // We emit a jump to a notional label at the outermost unwind state.
1251 EHResumeBlock = createBasicBlock("eh.resume");
1252 Builder.SetInsertPoint(EHResumeBlock);
1254 const EHPersonality &Personality = EHPersonality::get(*this);
1256 // This can always be a call because we necessarily didn't find
1257 // anything on the EH stack which needs our help.
1258 const char *RethrowName = Personality.CatchallRethrowFn;
1259 if (RethrowName != nullptr && !isCleanup) {
1260 EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName),
1261 getExceptionFromSlot())->setDoesNotReturn();
1262 Builder.CreateUnreachable();
1263 Builder.restoreIP(SavedIP);
1264 return EHResumeBlock;
1267 // Recreate the landingpad's return value for the 'resume' instruction.
1268 llvm::Value *Exn = getExceptionFromSlot();
1269 llvm::Value *Sel = getSelectorFromSlot();
1271 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(),
1272 Sel->getType(), nullptr);
1273 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType);
1274 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val");
1275 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val");
1277 Builder.CreateResume(LPadVal);
1278 Builder.restoreIP(SavedIP);
1279 return EHResumeBlock;
1282 void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) {
1285 JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave");
1287 SEHTryEpilogueStack.push_back(&TryExit);
1288 EmitStmt(S.getTryBlock());
1289 SEHTryEpilogueStack.pop_back();
1291 if (!TryExit.getBlock()->use_empty())
1292 EmitBlock(TryExit.getBlock(), /*IsFinished=*/true);
1294 delete TryExit.getBlock();
1300 struct PerformSEHFinally : EHScopeStack::Cleanup {
1301 llvm::Function *OutlinedFinally;
1302 PerformSEHFinally(llvm::Function *OutlinedFinally)
1303 : OutlinedFinally(OutlinedFinally) {}
1305 void Emit(CodeGenFunction &CGF, Flags F) override {
1306 ASTContext &Context = CGF.getContext();
1307 CodeGenModule &CGM = CGF.CGM;
1311 // Compute the two argument values.
1312 QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy};
1313 llvm::Value *LocalAddrFn = CGM.getIntrinsic(llvm::Intrinsic::localaddress);
1314 llvm::Value *FP = CGF.Builder.CreateCall(LocalAddrFn);
1315 llvm::Value *IsForEH =
1316 llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup());
1317 Args.add(RValue::get(IsForEH), ArgTys[0]);
1318 Args.add(RValue::get(FP), ArgTys[1]);
1320 // Arrange a two-arg function info and type.
1321 FunctionProtoType::ExtProtoInfo EPI;
1322 const auto *FPT = cast<FunctionProtoType>(
1323 Context.getFunctionType(Context.VoidTy, ArgTys, EPI));
1324 const CGFunctionInfo &FnInfo =
1325 CGM.getTypes().arrangeFreeFunctionCall(Args, FPT,
1326 /*chainCall=*/false);
1328 CGF.EmitCall(FnInfo, OutlinedFinally, ReturnValueSlot(), Args);
1334 /// Find all local variable captures in the statement.
1335 struct CaptureFinder : ConstStmtVisitor<CaptureFinder> {
1336 CodeGenFunction &ParentCGF;
1337 const VarDecl *ParentThis;
1338 SmallVector<const VarDecl *, 4> Captures;
1339 llvm::Value *SEHCodeSlot = nullptr;
1340 CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis)
1341 : ParentCGF(ParentCGF), ParentThis(ParentThis) {}
1343 // Return true if we need to do any capturing work.
1344 bool foundCaptures() {
1345 return !Captures.empty() || SEHCodeSlot;
1348 void Visit(const Stmt *S) {
1349 // See if this is a capture, then recurse.
1350 ConstStmtVisitor<CaptureFinder>::Visit(S);
1351 for (const Stmt *Child : S->children())
1356 void VisitDeclRefExpr(const DeclRefExpr *E) {
1357 // If this is already a capture, just make sure we capture 'this'.
1358 if (E->refersToEnclosingVariableOrCapture()) {
1359 Captures.push_back(ParentThis);
1363 const auto *D = dyn_cast<VarDecl>(E->getDecl());
1364 if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage())
1365 Captures.push_back(D);
1368 void VisitCXXThisExpr(const CXXThisExpr *E) {
1369 Captures.push_back(ParentThis);
1372 void VisitCallExpr(const CallExpr *E) {
1373 // We only need to add parent frame allocations for these builtins in x86.
1374 if (ParentCGF.getTarget().getTriple().getArch() != llvm::Triple::x86)
1377 unsigned ID = E->getBuiltinCallee();
1379 case Builtin::BI__exception_code:
1380 case Builtin::BI_exception_code:
1381 // This is the simple case where we are the outermost finally. All we
1382 // have to do here is make sure we escape this and recover it in the
1383 // outlined handler.
1385 SEHCodeSlot = ParentCGF.SEHCodeSlotStack.back();
1392 llvm::Value *CodeGenFunction::recoverAddrOfEscapedLocal(
1393 CodeGenFunction &ParentCGF, llvm::Value *ParentVar, llvm::Value *ParentFP) {
1394 llvm::CallInst *RecoverCall = nullptr;
1395 CGBuilderTy Builder(AllocaInsertPt);
1396 if (auto *ParentAlloca = dyn_cast<llvm::AllocaInst>(ParentVar)) {
1397 // Mark the variable escaped if nobody else referenced it and compute the
1398 // localescape index.
1399 auto InsertPair = ParentCGF.EscapedLocals.insert(
1400 std::make_pair(ParentAlloca, ParentCGF.EscapedLocals.size()));
1401 int FrameEscapeIdx = InsertPair.first->second;
1402 // call i8* @llvm.localrecover(i8* bitcast(@parentFn), i8* %fp, i32 N)
1403 llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
1404 &CGM.getModule(), llvm::Intrinsic::localrecover);
1405 llvm::Constant *ParentI8Fn =
1406 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1407 RecoverCall = Builder.CreateCall(
1408 FrameRecoverFn, {ParentI8Fn, ParentFP,
1409 llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
1412 // If the parent didn't have an alloca, we're doing some nested outlining.
1413 // Just clone the existing localrecover call, but tweak the FP argument to
1414 // use our FP value. All other arguments are constants.
1415 auto *ParentRecover =
1416 cast<llvm::IntrinsicInst>(ParentVar->stripPointerCasts());
1417 assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover &&
1418 "expected alloca or localrecover in parent LocalDeclMap");
1419 RecoverCall = cast<llvm::CallInst>(ParentRecover->clone());
1420 RecoverCall->setArgOperand(1, ParentFP);
1421 RecoverCall->insertBefore(AllocaInsertPt);
1424 // Bitcast the variable, rename it, and insert it in the local decl map.
1425 llvm::Value *ChildVar =
1426 Builder.CreateBitCast(RecoverCall, ParentVar->getType());
1427 ChildVar->setName(ParentVar->getName());
1431 void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF,
1432 const Stmt *OutlinedStmt,
1434 // Find all captures in the Stmt.
1435 CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl);
1436 Finder.Visit(OutlinedStmt);
1438 // We can exit early on x86_64 when there are no captures. We just have to
1439 // save the exception code in filters so that __exception_code() works.
1440 if (!Finder.foundCaptures() &&
1441 CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1443 EmitSEHExceptionCodeSave(ParentCGF, nullptr, nullptr);
1447 llvm::Value *EntryEBP = nullptr;
1448 llvm::Value *ParentFP;
1449 if (IsFilter && CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) {
1450 // 32-bit SEH filters need to be careful about FP recovery. The end of the
1451 // EH registration is passed in as the EBP physical register. We can
1452 // recover that with llvm.frameaddress(1), and adjust that to recover the
1453 // parent's true frame pointer.
1454 CGBuilderTy Builder(AllocaInsertPt);
1455 EntryEBP = Builder.CreateCall(
1456 CGM.getIntrinsic(llvm::Intrinsic::frameaddress), {Builder.getInt32(1)});
1457 llvm::Function *RecoverFPIntrin =
1458 CGM.getIntrinsic(llvm::Intrinsic::x86_seh_recoverfp);
1459 llvm::Constant *ParentI8Fn =
1460 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
1461 ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryEBP});
1463 // Otherwise, for x64 and 32-bit finally functions, the parent FP is the
1464 // second parameter.
1465 auto AI = CurFn->arg_begin();
1470 // Create llvm.localrecover calls for all captures.
1471 for (const VarDecl *VD : Finder.Captures) {
1472 if (isa<ImplicitParamDecl>(VD)) {
1473 CGM.ErrorUnsupported(VD, "'this' captured by SEH");
1474 CXXThisValue = llvm::UndefValue::get(ConvertTypeForMem(VD->getType()));
1477 if (VD->getType()->isVariablyModifiedType()) {
1478 CGM.ErrorUnsupported(VD, "VLA captured by SEH");
1481 assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) &&
1482 "captured non-local variable");
1484 // If this decl hasn't been declared yet, it will be declared in the
1486 auto I = ParentCGF.LocalDeclMap.find(VD);
1487 if (I == ParentCGF.LocalDeclMap.end())
1489 llvm::Value *ParentVar = I->second;
1492 recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP);
1495 if (Finder.SEHCodeSlot) {
1496 SEHCodeSlotStack.push_back(
1497 recoverAddrOfEscapedLocal(ParentCGF, Finder.SEHCodeSlot, ParentFP));
1501 EmitSEHExceptionCodeSave(ParentCGF, ParentFP, EntryEBP);
1504 /// Arrange a function prototype that can be called by Windows exception
1505 /// handling personalities. On Win64, the prototype looks like:
1506 /// RetTy func(void *EHPtrs, void *ParentFP);
1507 void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
1509 const Stmt *OutlinedStmt) {
1510 SourceLocation StartLoc = OutlinedStmt->getLocStart();
1512 // Get the mangled function name.
1513 SmallString<128> Name;
1515 llvm::raw_svector_ostream OS(Name);
1516 const Decl *ParentCodeDecl = ParentCGF.CurCodeDecl;
1517 const NamedDecl *Parent = dyn_cast_or_null<NamedDecl>(ParentCodeDecl);
1518 assert(Parent && "FIXME: handle unnamed decls (lambdas, blocks) with SEH");
1519 MangleContext &Mangler = CGM.getCXXABI().getMangleContext();
1521 Mangler.mangleSEHFilterExpression(Parent, OS);
1523 Mangler.mangleSEHFinallyBlock(Parent, OS);
1526 FunctionArgList Args;
1527 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 || !IsFilter) {
1528 // All SEH finally functions take two parameters. Win64 filters take two
1529 // parameters. Win32 filters take no parameters.
1531 Args.push_back(ImplicitParamDecl::Create(
1532 getContext(), nullptr, StartLoc,
1533 &getContext().Idents.get("exception_pointers"),
1534 getContext().VoidPtrTy));
1536 Args.push_back(ImplicitParamDecl::Create(
1537 getContext(), nullptr, StartLoc,
1538 &getContext().Idents.get("abnormal_termination"),
1539 getContext().UnsignedCharTy));
1541 Args.push_back(ImplicitParamDecl::Create(
1542 getContext(), nullptr, StartLoc,
1543 &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy));
1546 QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy;
1548 llvm::Function *ParentFn = ParentCGF.CurFn;
1549 const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionDeclaration(
1550 RetTy, Args, FunctionType::ExtInfo(), /*isVariadic=*/false);
1552 llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
1553 llvm::Function *Fn = llvm::Function::Create(
1554 FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
1555 // The filter is either in the same comdat as the function, or it's internal.
1556 if (llvm::Comdat *C = ParentFn->getComdat()) {
1558 } else if (ParentFn->hasWeakLinkage() || ParentFn->hasLinkOnceLinkage()) {
1559 llvm::Comdat *C = CGM.getModule().getOrInsertComdat(ParentFn->getName());
1560 ParentFn->setComdat(C);
1563 Fn->setLinkage(llvm::GlobalValue::InternalLinkage);
1566 IsOutlinedSEHHelper = true;
1568 StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
1569 OutlinedStmt->getLocStart(), OutlinedStmt->getLocStart());
1571 CGM.SetLLVMFunctionAttributes(nullptr, FnInfo, CurFn);
1572 EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter);
1575 /// Create a stub filter function that will ultimately hold the code of the
1576 /// filter expression. The EH preparation passes in LLVM will outline the code
1577 /// from the main function body into this stub.
1579 CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF,
1580 const SEHExceptStmt &Except) {
1581 const Expr *FilterExpr = Except.getFilterExpr();
1582 startOutlinedSEHHelper(ParentCGF, true, FilterExpr);
1584 // Emit the original filter expression, convert to i32, and return.
1585 llvm::Value *R = EmitScalarExpr(FilterExpr);
1586 R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy),
1587 FilterExpr->getType()->isSignedIntegerType());
1588 Builder.CreateStore(R, ReturnValue);
1590 FinishFunction(FilterExpr->getLocEnd());
1596 CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF,
1597 const SEHFinallyStmt &Finally) {
1598 const Stmt *FinallyBlock = Finally.getBlock();
1599 startOutlinedSEHHelper(ParentCGF, false, FinallyBlock);
1601 // Mark finally block calls as nounwind and noinline to make LLVM's job a
1603 // FIXME: Remove these restrictions in the future.
1604 CurFn->addFnAttr(llvm::Attribute::NoUnwind);
1605 CurFn->addFnAttr(llvm::Attribute::NoInline);
1607 // Emit the original filter expression, convert to i32, and return.
1608 EmitStmt(FinallyBlock);
1610 FinishFunction(FinallyBlock->getLocEnd());
1615 void CodeGenFunction::EmitSEHExceptionCodeSave(CodeGenFunction &ParentCGF,
1616 llvm::Value *ParentFP,
1617 llvm::Value *EntryEBP) {
1618 // Get the pointer to the EXCEPTION_POINTERS struct. This is returned by the
1619 // __exception_info intrinsic.
1620 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1621 // On Win64, the info is passed as the first parameter to the filter.
1622 auto AI = CurFn->arg_begin();
1624 SEHCodeSlotStack.push_back(
1625 CreateMemTemp(getContext().IntTy, "__exception_code"));
1627 // On Win32, the EBP on entry to the filter points to the end of an
1628 // exception registration object. It contains 6 32-bit fields, and the info
1629 // pointer is stored in the second field. So, GEP 20 bytes backwards and
1630 // load the pointer.
1631 SEHInfo = Builder.CreateConstInBoundsGEP1_32(Int8Ty, EntryEBP, -20);
1632 SEHInfo = Builder.CreateBitCast(SEHInfo, Int8PtrTy->getPointerTo());
1633 SEHInfo = Builder.CreateLoad(Int8PtrTy, SEHInfo);
1634 SEHCodeSlotStack.push_back(recoverAddrOfEscapedLocal(
1635 ParentCGF, ParentCGF.SEHCodeSlotStack.back(), ParentFP));
1638 // Save the exception code in the exception slot to unify exception access in
1639 // the filter function and the landing pad.
1640 // struct EXCEPTION_POINTERS {
1641 // EXCEPTION_RECORD *ExceptionRecord;
1642 // CONTEXT *ContextRecord;
1644 // int exceptioncode = exception_pointers->ExceptionRecord->ExceptionCode;
1645 llvm::Type *RecordTy = CGM.Int32Ty->getPointerTo();
1646 llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy, nullptr);
1647 llvm::Value *Ptrs = Builder.CreateBitCast(SEHInfo, PtrsTy->getPointerTo());
1648 llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0);
1649 Rec = Builder.CreateLoad(Rec);
1650 llvm::Value *Code = Builder.CreateLoad(Rec);
1651 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
1652 Builder.CreateStore(Code, SEHCodeSlotStack.back());
1655 llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() {
1656 // Sema should diagnose calling this builtin outside of a filter context, but
1657 // don't crash if we screw up.
1659 return llvm::UndefValue::get(Int8PtrTy);
1660 assert(SEHInfo->getType() == Int8PtrTy);
1664 llvm::Value *CodeGenFunction::EmitSEHExceptionCode() {
1665 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except");
1666 return Builder.CreateLoad(Int32Ty, SEHCodeSlotStack.back());
1669 llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() {
1670 // Abnormal termination is just the first parameter to the outlined finally
1672 auto AI = CurFn->arg_begin();
1673 return Builder.CreateZExt(&*AI, Int32Ty);
1676 void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
1677 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
1678 if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
1679 // Outline the finally block.
1680 llvm::Function *FinallyFunc =
1681 HelperCGF.GenerateSEHFinallyFunction(*this, *Finally);
1683 // Push a cleanup for __finally blocks.
1684 EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, FinallyFunc);
1688 // Otherwise, we must have an __except block.
1689 const SEHExceptStmt *Except = S.getExceptHandler();
1691 EHCatchScope *CatchScope = EHStack.pushCatch(1);
1692 SEHCodeSlotStack.push_back(
1693 CreateMemTemp(getContext().IntTy, "__exception_code"));
1695 // If the filter is known to evaluate to 1, then we can use the clause
1696 // "catch i8* null". We can't do this on x86 because the filter has to save
1697 // the exception code.
1699 CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this);
1700 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 && C &&
1702 CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
1706 // In general, we have to emit an outlined filter function. Use the function
1707 // in place of the RTTI typeinfo global that C++ EH uses.
1708 llvm::Function *FilterFunc =
1709 HelperCGF.GenerateSEHFilterFunction(*this, *Except);
1710 llvm::Constant *OpaqueFunc =
1711 llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy);
1712 CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except"));
1715 void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
1716 // Just pop the cleanup if it's a __finally block.
1717 if (S.getFinallyHandler()) {
1722 // Otherwise, we must have an __except block.
1723 const SEHExceptStmt *Except = S.getExceptHandler();
1724 assert(Except && "__try must have __finally xor __except");
1725 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
1727 // Don't emit the __except block if the __try block lacked invokes.
1728 // TODO: Model unwind edges from instructions, either with iload / istore or
1729 // a try body function.
1730 if (!CatchScope.hasEHBranches()) {
1731 CatchScope.clearHandlerBlocks();
1733 SEHCodeSlotStack.pop_back();
1737 // The fall-through block.
1738 llvm::BasicBlock *ContBB = createBasicBlock("__try.cont");
1740 // We just emitted the body of the __try; jump to the continue block.
1741 if (HaveInsertPoint())
1742 Builder.CreateBr(ContBB);
1744 // Check if our filter function returned true.
1745 emitCatchDispatchBlock(*this, CatchScope);
1747 // Grab the block before we pop the handler.
1748 llvm::BasicBlock *ExceptBB = CatchScope.getHandler(0).Block;
1751 EmitBlockAfterUses(ExceptBB);
1753 // On Win64, the exception pointer is the exception code. Copy it to the slot.
1754 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) {
1756 Builder.CreatePtrToInt(getExceptionFromSlot(), IntPtrTy);
1757 Code = Builder.CreateTrunc(Code, Int32Ty);
1758 Builder.CreateStore(Code, SEHCodeSlotStack.back());
1761 // Emit the __except body.
1762 EmitStmt(Except->getBlock());
1764 // End the lifetime of the exception code.
1765 SEHCodeSlotStack.pop_back();
1767 if (HaveInsertPoint())
1768 Builder.CreateBr(ContBB);
1773 void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) {
1774 // If this code is reachable then emit a stop point (if generating
1775 // debug info). We have to do this ourselves because we are on the
1776 // "simple" statement path.
1777 if (HaveInsertPoint())
1780 // This must be a __leave from a __finally block, which we warn on and is UB.
1781 // Just emit unreachable.
1782 if (!isSEHTryScope()) {
1783 Builder.CreateUnreachable();
1784 Builder.ClearInsertionPoint();
1788 EmitBranchThroughCleanup(*SEHTryEpilogueStack.back());