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llvm-project/clang/lib/CodeGen/CGException.cpp
John McCall c07a0c7e48 Change the representation of GNU ?: expressions to use a different expression 
class and to bind the shared value using OpaqueValueExpr.  This fixes an
unnoticed problem with deserialization of these expressions where the
deserialized form would lose the vital pointer-equality trait;  or rather,
it fixes it because this patch also does the right thing for deserializing
OVEs.

Change OVEs to not be a "temporary object" in the sense that copy elision is
permitted.

This new representation is not totally unawkward to work with, but I think
that's really part and parcel with the semantics we're modelling here.  In
particular, it's much easier to fix things like the copy elision bug and to
make the CFG look right.

I've tried to update the analyzer to deal with this in at least some          
obvious cases, and I think we get a much better CFG out, but the printing
of OpaqueValueExprs probably needs some work.

llvm-svn: 125744
2011-02-17 10:25:35 +00:00

1457 lines
53 KiB
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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 "CGCleanup.h"
#include "TargetInfo.h"
using namespace clang;
using namespace CodeGen;
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.Int8PtrTy);
}
/// 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.Int8PtrTy);
}
/// 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 FreeException {
static void Emit(CodeGenFunction &CGF, bool forEH,
llvm::Value *exn) {
CGF.Builder.CreateCall(getFreeExceptionFn(CGF), exn)
->setDoesNotThrow();
}
};
}
// 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 *addr) {
// Make sure the exception object is cleaned up if there's an
// exception during initialization.
CGF.pushFullExprCleanup<FreeException>(EHCleanup, addr);
EHScopeStack::stable_iterator cleanup = CGF.EHStack.stable_begin();
// __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 *typedAddr = CGF.Builder.CreateBitCast(addr, 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, typedAddr, /*Volatile*/ false, /*IsInit*/ true);
// Deactivate the cleanup block.
CGF.DeactivateCleanupBlock(cleanup);
}
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();
}
// throw is an expression, and the expression emitters expect us
// to leave ourselves at a valid insertion point.
EmitBlock(createBasicBlock("throw.cont"));
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,
/*ForEH=*/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();
}
// throw is an expression, and the expression emitters expect us
// to leave ourselves at a valid insertion point.
EmitBlock(createBasicBlock("throw.cont"));
}
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,
/*ForEH=*/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, /*ForEH=*/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(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(*this));
// 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(*this)
: getCleanupValue(*this));
// Otherwise, signal that we at least have cleanups.
} else if (UseInvokeInlineHack || HasEHCleanup) {
EHSelector.push_back(UseInvokeInlineHack
? getCatchAllValue(*this)
: getCleanupValue(*this));
} 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, Int8PtrTy));
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;
}
assert(isa<RecordType>(CatchType) && "unexpected catch type!");
const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
// Check for a copy expression. If we don't have a copy expression,
// that means a trivial copy is okay.
const Expr *copyExpr = CatchParam.getInit();
if (!copyExpr) {
llvm::Value *rawAdjustedExn = CallBeginCatch(CGF, Exn, true);
llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy);
CGF.EmitAggregateCopy(ParamAddr, adjustedExn, CatchType);
return;
}
// We have to call __cxa_get_exception_ptr to get the adjusted
// pointer before copying.
llvm::CallInst *rawAdjustedExn =
CGF.Builder.CreateCall(getGetExceptionPtrFn(CGF), Exn);
rawAdjustedExn->setDoesNotThrow();
// Cast that to the appropriate type.
llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy);
// The copy expression is defined in terms of an OpaqueValueExpr.
// Find it and map it to the adjusted expression.
CodeGenFunction::OpaqueValueMapping
opaque(CGF, OpaqueValueExpr::findInCopyConstruct(copyExpr),
CGF.MakeAddrLValue(adjustedExn, CatchParam.getType()));
// Call the copy ctor in a terminate scope.
CGF.EHStack.pushTerminate();
// Perform the copy construction.
CGF.EmitAggExpr(copyExpr, AggValueSlot::forAddr(ParamAddr, false, false));
// Leave the terminate scope.
CGF.EHStack.popTerminate();
// Undo the opaque value mapping.
opaque.pop();
// 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(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();
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;
}
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