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clang-1/lib/CodeGen/CGException.cpp

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//===--- CGException.cpp - Emit LLVM Code for C++ exceptions --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with C++ exception related code generation.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/StmtCXX.h"
#include "llvm/Intrinsics.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Support/CallSite.h"
#include "CGObjCRuntime.h"
#include "CodeGenFunction.h"
#include "CGException.h"
#include "TargetInfo.h"
using namespace clang;
using namespace CodeGen;
/// Push an entry of the given size onto this protected-scope stack.
char *EHScopeStack::allocate(size_t Size) {
if (!StartOfBuffer) {
unsigned Capacity = 1024;
while (Capacity < Size) Capacity *= 2;
StartOfBuffer = new char[Capacity];
StartOfData = EndOfBuffer = StartOfBuffer + Capacity;
} else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) {
unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer;
unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer);
unsigned NewCapacity = CurrentCapacity;
do {
NewCapacity *= 2;
} while (NewCapacity < UsedCapacity + Size);
char *NewStartOfBuffer = new char[NewCapacity];
char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity;
char *NewStartOfData = NewEndOfBuffer - UsedCapacity;
memcpy(NewStartOfData, StartOfData, UsedCapacity);
delete [] StartOfBuffer;
StartOfBuffer = NewStartOfBuffer;
EndOfBuffer = NewEndOfBuffer;
StartOfData = NewStartOfData;
}
assert(StartOfBuffer + Size <= StartOfData);
StartOfData -= Size;
return StartOfData;
}
EHScopeStack::stable_iterator
EHScopeStack::getEnclosingEHCleanup(iterator it) const {
assert(it != end());
do {
if (isa<EHCleanupScope>(*it)) {
if (cast<EHCleanupScope>(*it).isEHCleanup())
return stabilize(it);
return cast<EHCleanupScope>(*it).getEnclosingEHCleanup();
}
++it;
} while (it != end());
return stable_end();
}
void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
assert(((Size % sizeof(void*)) == 0) && "cleanup type is misaligned");
char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size));
bool IsNormalCleanup = Kind & NormalCleanup;
bool IsEHCleanup = Kind & EHCleanup;
bool IsActive = !(Kind & InactiveCleanup);
EHCleanupScope *Scope =
new (Buffer) EHCleanupScope(IsNormalCleanup,
IsEHCleanup,
IsActive,
Size,
BranchFixups.size(),
InnermostNormalCleanup,
InnermostEHCleanup);
if (IsNormalCleanup)
InnermostNormalCleanup = stable_begin();
if (IsEHCleanup)
InnermostEHCleanup = stable_begin();
return Scope->getCleanupBuffer();
}
void EHScopeStack::popCleanup() {
assert(!empty() && "popping exception stack when not empty");
assert(isa<EHCleanupScope>(*begin()));
EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin());
InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup();
InnermostEHCleanup = Cleanup.getEnclosingEHCleanup();
StartOfData += Cleanup.getAllocatedSize();
if (empty()) NextEHDestIndex = FirstEHDestIndex;
// Destroy the cleanup.
Cleanup.~EHCleanupScope();
// Check whether we can shrink the branch-fixups stack.
if (!BranchFixups.empty()) {
// If we no longer have any normal cleanups, all the fixups are
// complete.
if (!hasNormalCleanups())
BranchFixups.clear();
// Otherwise we can still trim out unnecessary nulls.
else
popNullFixups();
}
}
EHFilterScope *EHScopeStack::pushFilter(unsigned NumFilters) {
char *Buffer = allocate(EHFilterScope::getSizeForNumFilters(NumFilters));
CatchDepth++;
return new (Buffer) EHFilterScope(NumFilters);
}
void EHScopeStack::popFilter() {
assert(!empty() && "popping exception stack when not empty");
EHFilterScope &Filter = cast<EHFilterScope>(*begin());
StartOfData += EHFilterScope::getSizeForNumFilters(Filter.getNumFilters());
if (empty()) NextEHDestIndex = FirstEHDestIndex;
assert(CatchDepth > 0 && "mismatched filter push/pop");
CatchDepth--;
}
EHCatchScope *EHScopeStack::pushCatch(unsigned NumHandlers) {
char *Buffer = allocate(EHCatchScope::getSizeForNumHandlers(NumHandlers));
CatchDepth++;
EHCatchScope *Scope = new (Buffer) EHCatchScope(NumHandlers);
for (unsigned I = 0; I != NumHandlers; ++I)
Scope->getHandlers()[I].Index = getNextEHDestIndex();
return Scope;
}
void EHScopeStack::pushTerminate() {
char *Buffer = allocate(EHTerminateScope::getSize());
CatchDepth++;
new (Buffer) EHTerminateScope(getNextEHDestIndex());
}
/// Remove any 'null' fixups on the stack. However, we can't pop more
/// fixups than the fixup depth on the innermost normal cleanup, or
/// else fixups that we try to add to that cleanup will end up in the
/// wrong place. We *could* try to shrink fixup depths, but that's
/// actually a lot of work for little benefit.
void EHScopeStack::popNullFixups() {
// We expect this to only be called when there's still an innermost
// normal cleanup; otherwise there really shouldn't be any fixups.
assert(hasNormalCleanups());
EHScopeStack::iterator it = find(InnermostNormalCleanup);
unsigned MinSize = cast<EHCleanupScope>(*it).getFixupDepth();
assert(BranchFixups.size() >= MinSize && "fixup stack out of order");
while (BranchFixups.size() > MinSize &&
BranchFixups.back().Destination == 0)
BranchFixups.pop_back();
}
static llvm::Constant *getAllocateExceptionFn(CodeGenFunction &CGF) {
// void *__cxa_allocate_exception(size_t thrown_size);
const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
std::vector<const llvm::Type*> Args(1, SizeTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getInt8PtrTy(CGF.getLLVMContext()),
Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception");
}
static llvm::Constant *getFreeExceptionFn(CodeGenFunction &CGF) {
// void __cxa_free_exception(void *thrown_exception);
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
std::vector<const llvm::Type*> Args(1, Int8PtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
}
static llvm::Constant *getThrowFn(CodeGenFunction &CGF) {
// void __cxa_throw(void *thrown_exception, std::type_info *tinfo,
// void (*dest) (void *));
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
std::vector<const llvm::Type*> Args(3, Int8PtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_throw");
}
static llvm::Constant *getReThrowFn(CodeGenFunction &CGF) {
// void __cxa_rethrow();
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow");
}
static llvm::Constant *getGetExceptionPtrFn(CodeGenFunction &CGF) {
// void *__cxa_get_exception_ptr(void*);
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
std::vector<const llvm::Type*> Args(1, Int8PtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(Int8PtrTy, Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr");
}
static llvm::Constant *getBeginCatchFn(CodeGenFunction &CGF) {
// void *__cxa_begin_catch(void*);
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
std::vector<const llvm::Type*> Args(1, Int8PtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(Int8PtrTy, Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch");
}
static llvm::Constant *getEndCatchFn(CodeGenFunction &CGF) {
// void __cxa_end_catch();
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch");
}
static llvm::Constant *getUnexpectedFn(CodeGenFunction &CGF) {
// void __cxa_call_unexepcted(void *thrown_exception);
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
std::vector<const llvm::Type*> Args(1, Int8PtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
}
llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() {
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(getLLVMContext());
std::vector<const llvm::Type*> Args(1, Int8PtrTy);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(getLLVMContext()), Args,
false);
if (CGM.getLangOptions().SjLjExceptions)
return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume_or_Rethrow");
return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume_or_Rethrow");
}
static llvm::Constant *getTerminateFn(CodeGenFunction &CGF) {
// void __terminate();
const llvm::FunctionType *FTy =
llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false);
return CGF.CGM.CreateRuntimeFunction(FTy,
CGF.CGM.getLangOptions().CPlusPlus ? "_ZSt9terminatev" : "abort");
}
static llvm::Constant *getCatchallRethrowFn(CodeGenFunction &CGF,
llvm::StringRef Name) {
const llvm::Type *Int8PtrTy =
llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
std::vector<const llvm::Type*> Args(1, Int8PtrTy);
const llvm::Type *VoidTy = llvm::Type::getVoidTy(CGF.getLLVMContext());
const llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, Args, false);
return CGF.CGM.CreateRuntimeFunction(FTy, Name);
}
const EHPersonality EHPersonality::GNU_C("__gcc_personality_v0");
const EHPersonality EHPersonality::GNU_C_SJLJ("__gcc_personality_sj0");
const EHPersonality EHPersonality::NeXT_ObjC("__objc_personality_v0");
const EHPersonality EHPersonality::GNU_CPlusPlus("__gxx_personality_v0");
const EHPersonality EHPersonality::GNU_CPlusPlus_SJLJ("__gxx_personality_sj0");
const EHPersonality EHPersonality::GNU_ObjC("__gnu_objc_personality_v0",
"objc_exception_throw");
static const EHPersonality &getCPersonality(const LangOptions &L) {
if (L.SjLjExceptions)
return EHPersonality::GNU_C_SJLJ;
return EHPersonality::GNU_C;
}
static const EHPersonality &getObjCPersonality(const LangOptions &L) {
if (L.NeXTRuntime) {
if (L.ObjCNonFragileABI) return EHPersonality::NeXT_ObjC;
else return getCPersonality(L);
} else {
return EHPersonality::GNU_ObjC;
}
}
static const EHPersonality &getCXXPersonality(const LangOptions &L) {
if (L.SjLjExceptions)
return EHPersonality::GNU_CPlusPlus_SJLJ;
else
return EHPersonality::GNU_CPlusPlus;
}
/// Determines the personality function to use when both C++
/// and Objective-C exceptions are being caught.
static const EHPersonality &getObjCXXPersonality(const LangOptions &L) {
// The ObjC personality defers to the C++ personality for non-ObjC
// handlers. Unlike the C++ case, we use the same personality
// function on targets using (backend-driven) SJLJ EH.
if (L.NeXTRuntime) {
if (L.ObjCNonFragileABI)
return EHPersonality::NeXT_ObjC;
// In the fragile ABI, just use C++ exception handling and hope
// they're not doing crazy exception mixing.
else
return getCXXPersonality(L);
}
// The GNU runtime's personality function inherently doesn't support
// mixed EH. Use the C++ personality just to avoid returning null.
return getCXXPersonality(L);
}
const EHPersonality &EHPersonality::get(const LangOptions &L) {
if (L.CPlusPlus && L.ObjC1)
return getObjCXXPersonality(L);
else if (L.CPlusPlus)
return getCXXPersonality(L);
else if (L.ObjC1)
return getObjCPersonality(L);
else
return getCPersonality(L);
}
static llvm::Constant *getPersonalityFn(CodeGenModule &CGM,
const EHPersonality &Personality) {
llvm::Constant *Fn =
CGM.CreateRuntimeFunction(llvm::FunctionType::get(
llvm::Type::getInt32Ty(CGM.getLLVMContext()),
true),
Personality.getPersonalityFnName());
return Fn;
}
static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM,
const EHPersonality &Personality) {
llvm::Constant *Fn = getPersonalityFn(CGM, Personality);
return llvm::ConstantExpr::getBitCast(Fn, CGM.PtrToInt8Ty);
}
/// Check whether a personality function could reasonably be swapped
/// for a C++ personality function.
static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) {
for (llvm::Constant::use_iterator
I = Fn->use_begin(), E = Fn->use_end(); I != E; ++I) {
llvm::User *User = *I;
// Conditionally white-list bitcasts.
if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(User)) {
if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
if (!PersonalityHasOnlyCXXUses(CE))
return false;
continue;
}
// Otherwise, it has to be a selector call.
if (!isa<llvm::EHSelectorInst>(User)) return false;
llvm::EHSelectorInst *Selector = cast<llvm::EHSelectorInst>(User);
for (unsigned I = 2, E = Selector->getNumArgOperands(); I != E; ++I) {
// Look for something that would've been returned by the ObjC
// runtime's GetEHType() method.
llvm::GlobalVariable *GV
= dyn_cast<llvm::GlobalVariable>(Selector->getArgOperand(I));
if (!GV) continue;
// ObjC EH selector entries are always global variables with
// names starting like this.
if (GV->getName().startswith("OBJC_EHTYPE"))
return false;
}
}
return true;
}
/// Try to use the C++ personality function in ObjC++. Not doing this
/// can cause some incompatibilities with gcc, which is more
/// aggressive about only using the ObjC++ personality in a function
/// when it really needs it.
void CodeGenModule::SimplifyPersonality() {
// For now, this is really a Darwin-specific operation.
if (Context.Target.getTriple().getOS() != llvm::Triple::Darwin)
return;
// If we're not in ObjC++ -fexceptions, there's nothing to do.
if (!Features.CPlusPlus || !Features.ObjC1 || !Features.Exceptions)
return;
const EHPersonality &ObjCXX = EHPersonality::get(Features);
const EHPersonality &CXX = getCXXPersonality(Features);
if (&ObjCXX == &CXX ||
ObjCXX.getPersonalityFnName() == CXX.getPersonalityFnName())
return;
llvm::Function *Fn =
getModule().getFunction(ObjCXX.getPersonalityFnName());
// Nothing to do if it's unused.
if (!Fn || Fn->use_empty()) return;
// Can't do the optimization if it has non-C++ uses.
if (!PersonalityHasOnlyCXXUses(Fn)) return;
// Create the C++ personality function and kill off the old
// function.
llvm::Constant *CXXFn = getPersonalityFn(*this, CXX);
// This can happen if the user is screwing with us.
if (Fn->getType() != CXXFn->getType()) return;
Fn->replaceAllUsesWith(CXXFn);
Fn->eraseFromParent();
}
/// Returns the value to inject into a selector to indicate the
/// presence of a catch-all.
static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) {
// Possibly we should use @llvm.eh.catch.all.value here.
return llvm::ConstantPointerNull::get(CGF.CGM.PtrToInt8Ty);
}
/// Returns the value to inject into a selector to indicate the
/// presence of a cleanup.
static llvm::Constant *getCleanupValue(CodeGenFunction &CGF) {
return llvm::ConstantInt::get(CGF.Builder.getInt32Ty(), 0);
}
namespace {
/// A cleanup to free the exception object if its initialization
/// throws.
struct FreeExceptionCleanup : EHScopeStack::Cleanup {
FreeExceptionCleanup(llvm::Value *ShouldFreeVar,
llvm::Value *ExnLocVar)
: ShouldFreeVar(ShouldFreeVar), ExnLocVar(ExnLocVar) {}
llvm::Value *ShouldFreeVar;
llvm::Value *ExnLocVar;
void Emit(CodeGenFunction &CGF, bool IsForEH) {
llvm::BasicBlock *FreeBB = CGF.createBasicBlock("free-exnobj");
llvm::BasicBlock *DoneBB = CGF.createBasicBlock("free-exnobj.done");
llvm::Value *ShouldFree = CGF.Builder.CreateLoad(ShouldFreeVar,
"should-free-exnobj");
CGF.Builder.CreateCondBr(ShouldFree, FreeBB, DoneBB);
CGF.EmitBlock(FreeBB);
llvm::Value *ExnLocLocal = CGF.Builder.CreateLoad(ExnLocVar, "exnobj");
CGF.Builder.CreateCall(getFreeExceptionFn(CGF), ExnLocLocal)
->setDoesNotThrow();
CGF.EmitBlock(DoneBB);
}
};
}
// Emits an exception expression into the given location. This
// differs from EmitAnyExprToMem only in that, if a final copy-ctor
// call is required, an exception within that copy ctor causes
// std::terminate to be invoked.
static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *E,
llvm::Value *ExnLoc) {
// We want to release the allocated exception object if this
// expression throws. We do this by pushing an EH-only cleanup
// block which, furthermore, deactivates itself after the expression
// is complete.
llvm::AllocaInst *ShouldFreeVar =
CGF.CreateTempAlloca(llvm::Type::getInt1Ty(CGF.getLLVMContext()),
"should-free-exnobj.var");
CGF.InitTempAlloca(ShouldFreeVar,
llvm::ConstantInt::getFalse(CGF.getLLVMContext()));
// A variable holding the exception pointer. This is necessary
// because the throw expression does not necessarily dominate the
// cleanup, for example if it appears in a conditional expression.
llvm::AllocaInst *ExnLocVar =
CGF.CreateTempAlloca(ExnLoc->getType(), "exnobj.var");
// Make sure the exception object is cleaned up if there's an
// exception during initialization.
// FIXME: stmt expressions might require this to be a normal
// cleanup, too.
CGF.EHStack.pushCleanup<FreeExceptionCleanup>(EHCleanup,
ShouldFreeVar,
ExnLocVar);
EHScopeStack::stable_iterator Cleanup = CGF.EHStack.stable_begin();
CGF.Builder.CreateStore(ExnLoc, ExnLocVar);
CGF.Builder.CreateStore(llvm::ConstantInt::getTrue(CGF.getLLVMContext()),
ShouldFreeVar);
// __cxa_allocate_exception returns a void*; we need to cast this
// to the appropriate type for the object.
const llvm::Type *Ty = CGF.ConvertTypeForMem(E->getType())->getPointerTo();
llvm::Value *TypedExnLoc = CGF.Builder.CreateBitCast(ExnLoc, Ty);
// FIXME: this isn't quite right! If there's a final unelided call
// to a copy constructor, then according to [except.terminate]p1 we
// must call std::terminate() if that constructor throws, because
// technically that copy occurs after the exception expression is
// evaluated but before the exception is caught. But the best way
// to handle that is to teach EmitAggExpr to do the final copy
// differently if it can't be elided.
CGF.EmitAnyExprToMem(E, TypedExnLoc, /*Volatile*/ false, /*IsInit*/ true);
CGF.Builder.CreateStore(llvm::ConstantInt::getFalse(CGF.getLLVMContext()),
ShouldFreeVar);
// Technically, the exception object is like a temporary; it has to
// be cleaned up when its full-expression is complete.
// Unfortunately, the AST represents full-expressions by creating a
// CXXExprWithTemporaries, which it only does when there are actually
// temporaries.
//
// If any cleanups have been added since we pushed ours, they must
// be from temporaries; this will get popped at the same time.
// Otherwise we need to pop ours off. FIXME: this is very brittle.
if (Cleanup == CGF.EHStack.stable_begin())
CGF.PopCleanupBlock();
}
llvm::Value *CodeGenFunction::getExceptionSlot() {
if (!ExceptionSlot) {
const llvm::Type *i8p = llvm::Type::getInt8PtrTy(getLLVMContext());
ExceptionSlot = CreateTempAlloca(i8p, "exn.slot");
}
return ExceptionSlot;
}
void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) {
if (!E->getSubExpr()) {
if (getInvokeDest()) {
Builder.CreateInvoke(getReThrowFn(*this),
getUnreachableBlock(),
getInvokeDest())
->setDoesNotReturn();
} else {
Builder.CreateCall(getReThrowFn(*this))->setDoesNotReturn();
Builder.CreateUnreachable();
}
// Clear the insertion point to indicate we are in unreachable code.
Builder.ClearInsertionPoint();
return;
}
QualType ThrowType = E->getSubExpr()->getType();
// Now allocate the exception object.
const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity();
llvm::Constant *AllocExceptionFn = getAllocateExceptionFn(*this);
llvm::CallInst *ExceptionPtr =
Builder.CreateCall(AllocExceptionFn,
llvm::ConstantInt::get(SizeTy, TypeSize),
"exception");
ExceptionPtr->setDoesNotThrow();
EmitAnyExprToExn(*this, E->getSubExpr(), ExceptionPtr);
// Now throw the exception.
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(getLLVMContext());
llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType, true);
// The address of the destructor. If the exception type has a
// trivial destructor (or isn't a record), we just pass null.
llvm::Constant *Dtor = 0;
if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) {
CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
if (!Record->hasTrivialDestructor()) {
CXXDestructorDecl *DtorD = Record->getDestructor();
Dtor = CGM.GetAddrOfCXXDestructor(DtorD, Dtor_Complete);
Dtor = llvm::ConstantExpr::getBitCast(Dtor, Int8PtrTy);
}
}
if (!Dtor) Dtor = llvm::Constant::getNullValue(Int8PtrTy);
if (getInvokeDest()) {
llvm::InvokeInst *ThrowCall =
Builder.CreateInvoke3(getThrowFn(*this),
getUnreachableBlock(), getInvokeDest(),
ExceptionPtr, TypeInfo, Dtor);
ThrowCall->setDoesNotReturn();
} else {
llvm::CallInst *ThrowCall =
Builder.CreateCall3(getThrowFn(*this), ExceptionPtr, TypeInfo, Dtor);
ThrowCall->setDoesNotReturn();
Builder.CreateUnreachable();
}
// Clear the insertion point to indicate we are in unreachable code.
Builder.ClearInsertionPoint();
// FIXME: For now, emit a dummy basic block because expr emitters in generally
// are not ready to handle emitting expressions at unreachable points.
EnsureInsertPoint();
}
void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
if (!Exceptions)
return;
const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
if (FD == 0)
return;
const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
if (Proto == 0)
return;
assert(!Proto->hasAnyExceptionSpec() && "function with parameter pack");
if (!Proto->hasExceptionSpec())
return;
unsigned NumExceptions = Proto->getNumExceptions();
EHFilterScope *Filter = EHStack.pushFilter(NumExceptions);
for (unsigned I = 0; I != NumExceptions; ++I) {
QualType Ty = Proto->getExceptionType(I);
QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType();
llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType, true);
Filter->setFilter(I, EHType);
}
}
void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
if (!Exceptions)
return;
const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
if (FD == 0)
return;
const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
if (Proto == 0)
return;
if (!Proto->hasExceptionSpec())
return;
EHStack.popFilter();
}
void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
EnterCXXTryStmt(S);
EmitStmt(S.getTryBlock());
ExitCXXTryStmt(S);
}
void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
unsigned NumHandlers = S.getNumHandlers();
EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers);
for (unsigned I = 0; I != NumHandlers; ++I) {
const CXXCatchStmt *C = S.getHandler(I);
llvm::BasicBlock *Handler = createBasicBlock("catch");
if (C->getExceptionDecl()) {
// FIXME: Dropping the reference type on the type into makes it
// impossible to correctly implement catch-by-reference
// semantics for pointers. Unfortunately, this is what all
// existing compilers do, and it's not clear that the standard
// personality routine is capable of doing this right. See C++ DR 388:
// http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388
QualType CaughtType = C->getCaughtType();
CaughtType = CaughtType.getNonReferenceType().getUnqualifiedType();
llvm::Value *TypeInfo = 0;
if (CaughtType->isObjCObjectPointerType())
TypeInfo = CGM.getObjCRuntime().GetEHType(CaughtType);
else
TypeInfo = CGM.GetAddrOfRTTIDescriptor(CaughtType, true);
CatchScope->setHandler(I, TypeInfo, Handler);
} else {
// No exception decl indicates '...', a catch-all.
CatchScope->setCatchAllHandler(I, Handler);
}
}
}
/// Check whether this is a non-EH scope, i.e. a scope which doesn't
/// affect exception handling. Currently, the only non-EH scopes are
/// normal-only cleanup scopes.
static bool isNonEHScope(const EHScope &S) {
switch (S.getKind()) {
case EHScope::Cleanup:
return !cast<EHCleanupScope>(S).isEHCleanup();
case EHScope::Filter:
case EHScope::Catch:
case EHScope::Terminate:
return false;
}
// Suppress warning.
return false;
}
llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
assert(EHStack.requiresLandingPad());
assert(!EHStack.empty());
if (!Exceptions)
return 0;
// Check the innermost scope for a cached landing pad. If this is
// a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad();
if (LP) return LP;
// Build the landing pad for this scope.
LP = EmitLandingPad();
assert(LP);
// Cache the landing pad on the innermost scope. If this is a
// non-EH scope, cache the landing pad on the enclosing scope, too.
for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) {
ir->setCachedLandingPad(LP);
if (!isNonEHScope(*ir)) break;
}
return LP;
}
llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
assert(EHStack.requiresLandingPad());
// This function contains a hack to work around a design flaw in
// LLVM's EH IR which breaks semantics after inlining. This same
// hack is implemented in llvm-gcc.
//
// The LLVM EH abstraction is basically a thin veneer over the
// traditional GCC zero-cost design: for each range of instructions
// in the function, there is (at most) one "landing pad" with an
// associated chain of EH actions. A language-specific personality
// function interprets this chain of actions and (1) decides whether
// or not to resume execution at the landing pad and (2) if so,
// provides an integer indicating why it's stopping. In LLVM IR,
// the association of a landing pad with a range of instructions is
// achieved via an invoke instruction, the chain of actions becomes
// the arguments to the @llvm.eh.selector call, and the selector
// call returns the integer indicator. Other than the required
// presence of two intrinsic function calls in the landing pad,
// the IR exactly describes the layout of the output code.
//
// A principal advantage of this design is that it is completely
// language-agnostic; in theory, the LLVM optimizers can treat
// landing pads neutrally, and targets need only know how to lower
// the intrinsics to have a functioning exceptions system (assuming
// that platform exceptions follow something approximately like the
// GCC design). Unfortunately, landing pads cannot be combined in a
// language-agnostic way: given selectors A and B, there is no way
// to make a single landing pad which faithfully represents the
// semantics of propagating an exception first through A, then
// through B, without knowing how the personality will interpret the
// (lowered form of the) selectors. This means that inlining has no
// choice but to crudely chain invokes (i.e., to ignore invokes in
// the inlined function, but to turn all unwindable calls into
// invokes), which is only semantically valid if every unwind stops
// at every landing pad.
//
// Therefore, the invoke-inline hack is to guarantee that every
// landing pad has a catch-all.
const bool UseInvokeInlineHack = true;
for (EHScopeStack::iterator ir = EHStack.begin(); ; ) {
assert(ir != EHStack.end() &&
"stack requiring landing pad is nothing but non-EH scopes?");
// If this is a terminate scope, just use the singleton terminate
// landing pad.
if (isa<EHTerminateScope>(*ir))
return getTerminateLandingPad();
// If this isn't an EH scope, iterate; otherwise break out.
if (!isNonEHScope(*ir)) break;
++ir;
// We haven't checked this scope for a cached landing pad yet.
if (llvm::BasicBlock *LP = ir->getCachedLandingPad())
return LP;
}
// Save the current IR generation state.
CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
const EHPersonality &Personality =
EHPersonality::get(CGF.CGM.getLangOptions());
// Create and configure the landing pad.
llvm::BasicBlock *LP = createBasicBlock("lpad");
EmitBlock(LP);
// Save the exception pointer. It's safe to use a single exception
// pointer per function because EH cleanups can never have nested
// try/catches.
llvm::CallInst *Exn =
Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_exception), "exn");
Exn->setDoesNotThrow();
Builder.CreateStore(Exn, getExceptionSlot());
// Build the selector arguments.
llvm::SmallVector<llvm::Value*, 8> EHSelector;
EHSelector.push_back(Exn);
EHSelector.push_back(getOpaquePersonalityFn(CGM, Personality));
// Accumulate all the handlers in scope.
llvm::DenseMap<llvm::Value*, UnwindDest> EHHandlers;
UnwindDest CatchAll;
bool HasEHCleanup = false;
bool HasEHFilter = false;
llvm::SmallVector<llvm::Value*, 8> EHFilters;
for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end();
I != E; ++I) {
switch (I->getKind()) {
case EHScope::Cleanup:
if (!HasEHCleanup)
HasEHCleanup = cast<EHCleanupScope>(*I).isEHCleanup();
// We otherwise don't care about cleanups.
continue;
case EHScope::Filter: {
assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
assert(!CatchAll.isValid() && "EH filter reached after catch-all");
// Filter scopes get added to the selector in wierd ways.
EHFilterScope &Filter = cast<EHFilterScope>(*I);
HasEHFilter = true;
// Add all the filter values which we aren't already explicitly
// catching.
for (unsigned I = 0, E = Filter.getNumFilters(); I != E; ++I) {
llvm::Value *FV = Filter.getFilter(I);
if (!EHHandlers.count(FV))
EHFilters.push_back(FV);
}
goto done;
}
case EHScope::Terminate:
// Terminate scopes are basically catch-alls.
assert(!CatchAll.isValid());
CatchAll = UnwindDest(getTerminateHandler(),
EHStack.getEnclosingEHCleanup(I),
cast<EHTerminateScope>(*I).getDestIndex());
goto done;
case EHScope::Catch:
break;
}
EHCatchScope &Catch = cast<EHCatchScope>(*I);
for (unsigned HI = 0, HE = Catch.getNumHandlers(); HI != HE; ++HI) {
EHCatchScope::Handler Handler = Catch.getHandler(HI);
// Catch-all. We should only have one of these per catch.
if (!Handler.Type) {
assert(!CatchAll.isValid());
CatchAll = UnwindDest(Handler.Block,
EHStack.getEnclosingEHCleanup(I),
Handler.Index);
continue;
}
// Check whether we already have a handler for this type.
UnwindDest &Dest = EHHandlers[Handler.Type];
if (Dest.isValid()) continue;
EHSelector.push_back(Handler.Type);
Dest = UnwindDest(Handler.Block,
EHStack.getEnclosingEHCleanup(I),
Handler.Index);
}
// Stop if we found a catch-all.
if (CatchAll.isValid()) break;
}
done:
unsigned LastToEmitInLoop = EHSelector.size();
// If we have a catch-all, add null to the selector.
if (CatchAll.isValid()) {
EHSelector.push_back(getCatchAllValue(CGF));
// If we have an EH filter, we need to add those handlers in the
// right place in the selector, which is to say, at the end.
} else if (HasEHFilter) {
// Create a filter expression: an integer constant saying how many
// filters there are (+1 to avoid ambiguity with 0 for cleanup),
// followed by the filter types. The personality routine only
// lands here if the filter doesn't match.
EHSelector.push_back(llvm::ConstantInt::get(Builder.getInt32Ty(),
EHFilters.size() + 1));
EHSelector.append(EHFilters.begin(), EHFilters.end());
// Also check whether we need a cleanup.
if (UseInvokeInlineHack || HasEHCleanup)
EHSelector.push_back(UseInvokeInlineHack
? getCatchAllValue(CGF)
: getCleanupValue(CGF));
// Otherwise, signal that we at least have cleanups.
} else if (UseInvokeInlineHack || HasEHCleanup) {
EHSelector.push_back(UseInvokeInlineHack
? getCatchAllValue(CGF)
: getCleanupValue(CGF));
} else {
assert(LastToEmitInLoop > 2);
LastToEmitInLoop--;
}
assert(EHSelector.size() >= 3 && "selector call has only two arguments!");
// Tell the backend how to generate the landing pad.
llvm::CallInst *Selection =
Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector),
EHSelector.begin(), EHSelector.end(), "eh.selector");
Selection->setDoesNotThrow();
// Select the right handler.
llvm::Value *llvm_eh_typeid_for =
CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
// The results of llvm_eh_typeid_for aren't reliable --- at least
// not locally --- so we basically have to do this as an 'if' chain.
// We walk through the first N-1 catch clauses, testing and chaining,
// and then fall into the final clause (which is either a cleanup, a
// filter (possibly with a cleanup), a catch-all, or another catch).
for (unsigned I = 2; I != LastToEmitInLoop; ++I) {
llvm::Value *Type = EHSelector[I];
UnwindDest Dest = EHHandlers[Type];
assert(Dest.isValid() && "no handler entry for value in selector?");
// Figure out where to branch on a match. As a debug code-size
// optimization, if the scope depth matches the innermost cleanup,
// we branch directly to the catch handler.
llvm::BasicBlock *Match = Dest.getBlock();
bool MatchNeedsCleanup =
Dest.getScopeDepth() != EHStack.getInnermostEHCleanup();
if (MatchNeedsCleanup)
Match = createBasicBlock("eh.match");
llvm::BasicBlock *Next = createBasicBlock("eh.next");
// Check whether the exception matches.
llvm::CallInst *Id
= Builder.CreateCall(llvm_eh_typeid_for,
Builder.CreateBitCast(Type, CGM.PtrToInt8Ty));
Id->setDoesNotThrow();
Builder.CreateCondBr(Builder.CreateICmpEQ(Selection, Id),
Match, Next);
// Emit match code if necessary.
if (MatchNeedsCleanup) {
EmitBlock(Match);
EmitBranchThroughEHCleanup(Dest);
}
// Continue to the next match.
EmitBlock(Next);
}
// Emit the final case in the selector.
// This might be a catch-all....
if (CatchAll.isValid()) {
assert(isa<llvm::ConstantPointerNull>(EHSelector.back()));
EmitBranchThroughEHCleanup(CatchAll);
// ...or an EH filter...
} else if (HasEHFilter) {
llvm::Value *SavedSelection = Selection;
// First, unwind out to the outermost scope if necessary.
if (EHStack.hasEHCleanups()) {
// The end here might not dominate the beginning, so we might need to
// save the selector if we need it.
llvm::AllocaInst *SelectorVar = 0;
if (HasEHCleanup) {
SelectorVar = CreateTempAlloca(Builder.getInt32Ty(), "selector.var");
Builder.CreateStore(Selection, SelectorVar);
}
llvm::BasicBlock *CleanupContBB = createBasicBlock("ehspec.cleanup.cont");
EmitBranchThroughEHCleanup(UnwindDest(CleanupContBB, EHStack.stable_end(),
EHStack.getNextEHDestIndex()));
EmitBlock(CleanupContBB);
if (HasEHCleanup)
SavedSelection = Builder.CreateLoad(SelectorVar, "ehspec.saved-selector");
}
// If there was a cleanup, we'll need to actually check whether we
// landed here because the filter triggered.
if (UseInvokeInlineHack || HasEHCleanup) {
llvm::BasicBlock *RethrowBB = createBasicBlock("cleanup");
llvm::BasicBlock *UnexpectedBB = createBasicBlock("ehspec.unexpected");
llvm::Constant *Zero = llvm::ConstantInt::get(Builder.getInt32Ty(), 0);
llvm::Value *FailsFilter =
Builder.CreateICmpSLT(SavedSelection, Zero, "ehspec.fails");
Builder.CreateCondBr(FailsFilter, UnexpectedBB, RethrowBB);
// The rethrow block is where we land if this was a cleanup.
// TODO: can this be _Unwind_Resume if the InvokeInlineHack is off?
EmitBlock(RethrowBB);
Builder.CreateCall(getUnwindResumeOrRethrowFn(),
Builder.CreateLoad(getExceptionSlot()))
->setDoesNotReturn();
Builder.CreateUnreachable();
EmitBlock(UnexpectedBB);
}
// Call __cxa_call_unexpected. This doesn't need to be an invoke
// because __cxa_call_unexpected magically filters exceptions
// according to the last landing pad the exception was thrown
// into. Seriously.
Builder.CreateCall(getUnexpectedFn(*this),
Builder.CreateLoad(getExceptionSlot()))
->setDoesNotReturn();
Builder.CreateUnreachable();
// ...or a normal catch handler...
} else if (!UseInvokeInlineHack && !HasEHCleanup) {
llvm::Value *Type = EHSelector.back();
EmitBranchThroughEHCleanup(EHHandlers[Type]);
// ...or a cleanup.
} else {
EmitBranchThroughEHCleanup(getRethrowDest());
}
// Restore the old IR generation state.
Builder.restoreIP(SavedIP);
return LP;
}
namespace {
/// A cleanup to call __cxa_end_catch. In many cases, the caught
/// exception type lets us state definitively that the thrown exception
/// type does not have a destructor. In particular:
/// - Catch-alls tell us nothing, so we have to conservatively
/// assume that the thrown exception might have a destructor.
/// - Catches by reference behave according to their base types.
/// - Catches of non-record types will only trigger for exceptions
/// of non-record types, which never have destructors.
/// - Catches of record types can trigger for arbitrary subclasses
/// of the caught type, so we have to assume the actual thrown
/// exception type might have a throwing destructor, even if the
/// caught type's destructor is trivial or nothrow.
struct CallEndCatch : EHScopeStack::Cleanup {
CallEndCatch(bool MightThrow) : MightThrow(MightThrow) {}
bool MightThrow;
void Emit(CodeGenFunction &CGF, bool IsForEH) {
if (!MightThrow) {
CGF.Builder.CreateCall(getEndCatchFn(CGF))->setDoesNotThrow();
return;
}
CGF.EmitCallOrInvoke(getEndCatchFn(CGF), 0, 0);
}
};
}
/// Emits a call to __cxa_begin_catch and enters a cleanup to call
/// __cxa_end_catch.
///
/// \param EndMightThrow - true if __cxa_end_catch might throw
static llvm::Value *CallBeginCatch(CodeGenFunction &CGF,
llvm::Value *Exn,
bool EndMightThrow) {
llvm::CallInst *Call = CGF.Builder.CreateCall(getBeginCatchFn(CGF), Exn);
Call->setDoesNotThrow();
CGF.EHStack.pushCleanup<CallEndCatch>(NormalAndEHCleanup, EndMightThrow);
return Call;
}
/// A "special initializer" callback for initializing a catch
/// parameter during catch initialization.
static void InitCatchParam(CodeGenFunction &CGF,
const VarDecl &CatchParam,
llvm::Value *ParamAddr) {
// Load the exception from where the landing pad saved it.
llvm::Value *Exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot(), "exn");
CanQualType CatchType =
CGF.CGM.getContext().getCanonicalType(CatchParam.getType());
const llvm::Type *LLVMCatchTy = CGF.ConvertTypeForMem(CatchType);
// If we're catching by reference, we can just cast the object
// pointer to the appropriate pointer.
if (isa<ReferenceType>(CatchType)) {
QualType CaughtType = cast<ReferenceType>(CatchType)->getPointeeType();
bool EndCatchMightThrow = CaughtType->isRecordType();
// __cxa_begin_catch returns the adjusted object pointer.
llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, EndCatchMightThrow);
// We have no way to tell the personality function that we're
// catching by reference, so if we're catching a pointer,
// __cxa_begin_catch will actually return that pointer by value.
if (const PointerType *PT = dyn_cast<PointerType>(CaughtType)) {
QualType PointeeType = PT->getPointeeType();
// When catching by reference, generally we should just ignore
// this by-value pointer and use the exception object instead.
if (!PointeeType->isRecordType()) {
// Exn points to the struct _Unwind_Exception header, which
// we have to skip past in order to reach the exception data.
unsigned HeaderSize =
CGF.CGM.getTargetCodeGenInfo().getSizeOfUnwindException();
AdjustedExn = CGF.Builder.CreateConstGEP1_32(Exn, HeaderSize);
// However, if we're catching a pointer-to-record type that won't
// work, because the personality function might have adjusted
// the pointer. There's actually no way for us to fully satisfy
// the language/ABI contract here: we can't use Exn because it
// might have the wrong adjustment, but we can't use the by-value
// pointer because it's off by a level of abstraction.
//
// The current solution is to dump the adjusted pointer into an
// alloca, which breaks language semantics (because changing the
// pointer doesn't change the exception) but at least works.
// The better solution would be to filter out non-exact matches
// and rethrow them, but this is tricky because the rethrow
// really needs to be catchable by other sites at this landing
// pad. The best solution is to fix the personality function.
} else {
// Pull the pointer for the reference type off.
const llvm::Type *PtrTy =
cast<llvm::PointerType>(LLVMCatchTy)->getElementType();
// Create the temporary and write the adjusted pointer into it.
llvm::Value *ExnPtrTmp = CGF.CreateTempAlloca(PtrTy, "exn.byref.tmp");
llvm::Value *Casted = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
CGF.Builder.CreateStore(Casted, ExnPtrTmp);
// Bind the reference to the temporary.
AdjustedExn = ExnPtrTmp;
}
}
llvm::Value *ExnCast =
CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.byref");
CGF.Builder.CreateStore(ExnCast, ParamAddr);
return;
}
// Non-aggregates (plus complexes).
bool IsComplex = false;
if (!CGF.hasAggregateLLVMType(CatchType) ||
(IsComplex = CatchType->isAnyComplexType())) {
llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, false);
// If the catch type is a pointer type, __cxa_begin_catch returns
// the pointer by value.
if (CatchType->hasPointerRepresentation()) {
llvm::Value *CastExn =
CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted");
CGF.Builder.CreateStore(CastExn, ParamAddr);
return;
}
// Otherwise, it returns a pointer into the exception object.
const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
if (IsComplex) {
CGF.StoreComplexToAddr(CGF.LoadComplexFromAddr(Cast, /*volatile*/ false),
ParamAddr, /*volatile*/ false);
} else {
unsigned Alignment =
CGF.getContext().getDeclAlign(&CatchParam).getQuantity();
llvm::Value *ExnLoad = CGF.Builder.CreateLoad(Cast, "exn.scalar");
CGF.EmitStoreOfScalar(ExnLoad, ParamAddr, /*volatile*/ false, Alignment,
CatchType);
}
return;
}
// FIXME: this *really* needs to be done via a proper, Sema-emitted
// initializer expression.
CXXRecordDecl *RD = CatchType.getTypePtr()->getAsCXXRecordDecl();
assert(RD && "aggregate catch type was not a record!");
const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
if (RD->hasTrivialCopyConstructor()) {
llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, true);
llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
CGF.EmitAggregateCopy(ParamAddr, Cast, CatchType);
return;
}
// We have to call __cxa_get_exception_ptr to get the adjusted
// pointer before copying.
llvm::CallInst *AdjustedExn =
CGF.Builder.CreateCall(getGetExceptionPtrFn(CGF), Exn);
AdjustedExn->setDoesNotThrow();
llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
CXXConstructorDecl *CD = RD->getCopyConstructor(CGF.getContext(), 0);
assert(CD && "record has no copy constructor!");
llvm::Value *CopyCtor = CGF.CGM.GetAddrOfCXXConstructor(CD, Ctor_Complete);
CallArgList CallArgs;
CallArgs.push_back(std::make_pair(RValue::get(ParamAddr),
CD->getThisType(CGF.getContext())));
CallArgs.push_back(std::make_pair(RValue::get(Cast),
CD->getParamDecl(0)->getType()));
const FunctionProtoType *FPT
= CD->getType()->getAs<FunctionProtoType>();
// Call the copy ctor in a terminate scope.
CGF.EHStack.pushTerminate();
CGF.EmitCall(CGF.CGM.getTypes().getFunctionInfo(CallArgs, FPT),
CopyCtor, ReturnValueSlot(), CallArgs, CD);
CGF.EHStack.popTerminate();
// Finally we can call __cxa_begin_catch.
CallBeginCatch(CGF, Exn, true);
}
/// Begins a catch statement by initializing the catch variable and
/// calling __cxa_begin_catch.
static void BeginCatch(CodeGenFunction &CGF,
const CXXCatchStmt *S) {
// We have to be very careful with the ordering of cleanups here:
// C++ [except.throw]p4:
// The destruction [of the exception temporary] occurs
// immediately after the destruction of the object declared in
// the exception-declaration in the handler.
//
// So the precise ordering is:
// 1. Construct catch variable.
// 2. __cxa_begin_catch
// 3. Enter __cxa_end_catch cleanup
// 4. Enter dtor cleanup
//
// We do this by initializing the exception variable with a
// "special initializer", InitCatchParam. Delegation sequence:
// - ExitCXXTryStmt opens a RunCleanupsScope
// - EmitLocalBlockVarDecl creates the variable and debug info
// - InitCatchParam initializes the variable from the exception
// - CallBeginCatch calls __cxa_begin_catch
// - CallBeginCatch enters the __cxa_end_catch cleanup
// - EmitLocalBlockVarDecl enters the variable destructor cleanup
// - EmitCXXTryStmt emits the code for the catch body
// - EmitCXXTryStmt close the RunCleanupsScope
VarDecl *CatchParam = S->getExceptionDecl();
if (!CatchParam) {
llvm::Value *Exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot(), "exn");
CallBeginCatch(CGF, Exn, true);
return;
}
// Emit the local.
CGF.EmitAutoVarDecl(*CatchParam, &InitCatchParam);
}
namespace {
struct CallRethrow : EHScopeStack::Cleanup {
void Emit(CodeGenFunction &CGF, bool IsForEH) {
CGF.EmitCallOrInvoke(getReThrowFn(CGF), 0, 0);
}
};
}
void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
unsigned NumHandlers = S.getNumHandlers();
EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
assert(CatchScope.getNumHandlers() == NumHandlers);
// Copy the handler blocks off before we pop the EH stack. Emitting
// the handlers might scribble on this memory.
llvm::SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers);
memcpy(Handlers.data(), CatchScope.begin(),
NumHandlers * sizeof(EHCatchScope::Handler));
EHStack.popCatch();
// The fall-through block.
llvm::BasicBlock *ContBB = createBasicBlock("try.cont");
// We just emitted the body of the try; jump to the continue block.
if (HaveInsertPoint())
Builder.CreateBr(ContBB);
// Determine if we need an implicit rethrow for all these catch handlers.
bool ImplicitRethrow = false;
if (IsFnTryBlock)
ImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
isa<CXXConstructorDecl>(CurCodeDecl);
for (unsigned I = 0; I != NumHandlers; ++I) {
llvm::BasicBlock *CatchBlock = Handlers[I].Block;
EmitBlock(CatchBlock);
// Catch the exception if this isn't a catch-all.
const CXXCatchStmt *C = S.getHandler(I);
// Enter a cleanup scope, including the catch variable and the
// end-catch.
RunCleanupsScope CatchScope(*this);
// Initialize the catch variable and set up the cleanups.
BeginCatch(*this, C);
// If there's an implicit rethrow, push a normal "cleanup" to call
// _cxa_rethrow. This needs to happen before __cxa_end_catch is
// called, and so it is pushed after BeginCatch.
if (ImplicitRethrow)
EHStack.pushCleanup<CallRethrow>(NormalCleanup);
// Perform the body of the catch.
EmitStmt(C->getHandlerBlock());
// Fall out through the catch cleanups.
CatchScope.ForceCleanup();
// Branch out of the try.
if (HaveInsertPoint())
Builder.CreateBr(ContBB);
}
EmitBlock(ContBB);
}
namespace {
struct CallEndCatchForFinally : EHScopeStack::Cleanup {
llvm::Value *ForEHVar;
llvm::Value *EndCatchFn;
CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn)
: ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {}
void Emit(CodeGenFunction &CGF, bool IsForEH) {
llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch");
llvm::BasicBlock *CleanupContBB =
CGF.createBasicBlock("finally.cleanup.cont");
llvm::Value *ShouldEndCatch =
CGF.Builder.CreateLoad(ForEHVar, "finally.endcatch");
CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB);
CGF.EmitBlock(EndCatchBB);
CGF.EmitCallOrInvoke(EndCatchFn, 0, 0); // catch-all, so might throw
CGF.EmitBlock(CleanupContBB);
}
};
struct PerformFinally : EHScopeStack::Cleanup {
const Stmt *Body;
llvm::Value *ForEHVar;
llvm::Value *EndCatchFn;
llvm::Value *RethrowFn;
llvm::Value *SavedExnVar;
PerformFinally(const Stmt *Body, llvm::Value *ForEHVar,
llvm::Value *EndCatchFn,
llvm::Value *RethrowFn, llvm::Value *SavedExnVar)
: Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn),
RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {}
void Emit(CodeGenFunction &CGF, bool IsForEH) {
// Enter a cleanup to call the end-catch function if one was provided.
if (EndCatchFn)
CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup,
ForEHVar, EndCatchFn);
// Save the current cleanup destination in case there are
// cleanups in the finally block.
llvm::Value *SavedCleanupDest =
CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(),
"cleanup.dest.saved");
// Emit the finally block.
CGF.EmitStmt(Body);
// If the end of the finally is reachable, check whether this was
// for EH. If so, rethrow.
if (CGF.HaveInsertPoint()) {
llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow");
llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont");
llvm::Value *ShouldRethrow =
CGF.Builder.CreateLoad(ForEHVar, "finally.shouldthrow");
CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB);
CGF.EmitBlock(RethrowBB);
if (SavedExnVar) {
llvm::Value *Args[] = { CGF.Builder.CreateLoad(SavedExnVar) };
CGF.EmitCallOrInvoke(RethrowFn, Args, Args+1);
} else {
CGF.EmitCallOrInvoke(RethrowFn, 0, 0);
}
CGF.Builder.CreateUnreachable();
CGF.EmitBlock(ContBB);
// Restore the cleanup destination.
CGF.Builder.CreateStore(SavedCleanupDest,
CGF.getNormalCleanupDestSlot());
}
// Leave the end-catch cleanup. As an optimization, pretend that
// the fallthrough path was inaccessible; we've dynamically proven
// that we're not in the EH case along that path.
if (EndCatchFn) {
CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
CGF.PopCleanupBlock();
CGF.Builder.restoreIP(SavedIP);
}
// Now make sure we actually have an insertion point or the
// cleanup gods will hate us.
CGF.EnsureInsertPoint();
}
};
}
/// Enters a finally block for an implementation using zero-cost
/// exceptions. This is mostly general, but hard-codes some
/// language/ABI-specific behavior in the catch-all sections.
CodeGenFunction::FinallyInfo
CodeGenFunction::EnterFinallyBlock(const Stmt *Body,
llvm::Constant *BeginCatchFn,
llvm::Constant *EndCatchFn,
llvm::Constant *RethrowFn) {
assert((BeginCatchFn != 0) == (EndCatchFn != 0) &&
"begin/end catch functions not paired");
assert(RethrowFn && "rethrow function is required");
// The rethrow function has one of the following two types:
// void (*)()
// void (*)(void*)
// In the latter case we need to pass it the exception object.
// But we can't use the exception slot because the @finally might
// have a landing pad (which would overwrite the exception slot).
const llvm::FunctionType *RethrowFnTy =
cast<llvm::FunctionType>(
cast<llvm::PointerType>(RethrowFn->getType())
->getElementType());
llvm::Value *SavedExnVar = 0;
if (RethrowFnTy->getNumParams())
SavedExnVar = CreateTempAlloca(Builder.getInt8PtrTy(), "finally.exn");
// A finally block is a statement which must be executed on any edge
// out of a given scope. Unlike a cleanup, the finally block may
// contain arbitrary control flow leading out of itself. In
// addition, finally blocks should always be executed, even if there
// are no catch handlers higher on the stack. Therefore, we
// surround the protected scope with a combination of a normal
// cleanup (to catch attempts to break out of the block via normal
// control flow) and an EH catch-all (semantically "outside" any try
// statement to which the finally block might have been attached).
// The finally block itself is generated in the context of a cleanup
// which conditionally leaves the catch-all.
FinallyInfo Info;
// Jump destination for performing the finally block on an exception
// edge. We'll never actually reach this block, so unreachable is
// fine.
JumpDest RethrowDest = getJumpDestInCurrentScope(getUnreachableBlock());
// Whether the finally block is being executed for EH purposes.
llvm::AllocaInst *ForEHVar = CreateTempAlloca(CGF.Builder.getInt1Ty(),
"finally.for-eh");
InitTempAlloca(ForEHVar, llvm::ConstantInt::getFalse(getLLVMContext()));
// Enter a normal cleanup which will perform the @finally block.
EHStack.pushCleanup<PerformFinally>(NormalCleanup, Body,
ForEHVar, EndCatchFn,
RethrowFn, SavedExnVar);
// Enter a catch-all scope.
llvm::BasicBlock *CatchAllBB = createBasicBlock("finally.catchall");
CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
Builder.SetInsertPoint(CatchAllBB);
// If there's a begin-catch function, call it.
if (BeginCatchFn) {
Builder.CreateCall(BeginCatchFn, Builder.CreateLoad(getExceptionSlot()))
->setDoesNotThrow();
}
// If we need to remember the exception pointer to rethrow later, do so.
if (SavedExnVar) {
llvm::Value *SavedExn = Builder.CreateLoad(getExceptionSlot());
Builder.CreateStore(SavedExn, SavedExnVar);
}
// Tell the finally block that we're in EH.
Builder.CreateStore(llvm::ConstantInt::getTrue(getLLVMContext()), ForEHVar);
// Thread a jump through the finally cleanup.
EmitBranchThroughCleanup(RethrowDest);
Builder.restoreIP(SavedIP);
EHCatchScope *CatchScope = EHStack.pushCatch(1);
CatchScope->setCatchAllHandler(0, CatchAllBB);
return Info;
}
void CodeGenFunction::ExitFinallyBlock(FinallyInfo &Info) {
// Leave the finally catch-all.
EHCatchScope &Catch = cast<EHCatchScope>(*EHStack.begin());
llvm::BasicBlock *CatchAllBB = Catch.getHandler(0).Block;
EHStack.popCatch();
// And leave the normal cleanup.
PopCleanupBlock();
CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
EmitBlock(CatchAllBB, true);
Builder.restoreIP(SavedIP);
}
llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
if (TerminateLandingPad)
return TerminateLandingPad;
CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
// This will get inserted at the end of the function.
TerminateLandingPad = createBasicBlock("terminate.lpad");
Builder.SetInsertPoint(TerminateLandingPad);
// Tell the backend that this is a landing pad.
llvm::CallInst *Exn =
Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_exception), "exn");
Exn->setDoesNotThrow();
const EHPersonality &Personality = EHPersonality::get(CGM.getLangOptions());
// Tell the backend what the exception table should be:
// nothing but a catch-all.
llvm::Value *Args[3] = { Exn, getOpaquePersonalityFn(CGM, Personality),
getCatchAllValue(*this) };
Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector),
Args, Args+3, "eh.selector")
->setDoesNotThrow();
llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this));
TerminateCall->setDoesNotReturn();
TerminateCall->setDoesNotThrow();
CGF.Builder.CreateUnreachable();
// Restore the saved insertion state.
Builder.restoreIP(SavedIP);
return TerminateLandingPad;
}
llvm::BasicBlock *CodeGenFunction::getTerminateHandler() {
if (TerminateHandler)
return TerminateHandler;
CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
// Set up the terminate handler. This block is inserted at the very
// end of the function by FinishFunction.
TerminateHandler = createBasicBlock("terminate.handler");
Builder.SetInsertPoint(TerminateHandler);
llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this));
TerminateCall->setDoesNotReturn();
TerminateCall->setDoesNotThrow();
Builder.CreateUnreachable();
// Restore the saved insertion state.
Builder.restoreIP(SavedIP);
return TerminateHandler;
}
CodeGenFunction::UnwindDest CodeGenFunction::getRethrowDest() {
if (RethrowBlock.isValid()) return RethrowBlock;
CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
// We emit a jump to a notional label at the outermost unwind state.
llvm::BasicBlock *Unwind = createBasicBlock("eh.resume");
Builder.SetInsertPoint(Unwind);
const EHPersonality &Personality = EHPersonality::get(CGM.getLangOptions());
// This can always be a call because we necessarily didn't find
// anything on the EH stack which needs our help.
llvm::StringRef RethrowName = Personality.getCatchallRethrowFnName();
llvm::Constant *RethrowFn;
if (!RethrowName.empty())
RethrowFn = getCatchallRethrowFn(*this, RethrowName);
else
RethrowFn = getUnwindResumeOrRethrowFn();
Builder.CreateCall(RethrowFn, Builder.CreateLoad(getExceptionSlot()))
->setDoesNotReturn();
Builder.CreateUnreachable();
Builder.restoreIP(SavedIP);
RethrowBlock = UnwindDest(Unwind, EHStack.stable_end(), 0);
return RethrowBlock;
}
EHScopeStack::Cleanup::~Cleanup() {
llvm_unreachable("Cleanup is indestructable");
}
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