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llvm-project/clang/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 "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGCleanup.h"
#include "CGObjCRuntime.h"
#include "TargetInfo.h"
#include "clang/AST/Mangle.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtObjC.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/SaveAndRestore.h"
using namespace clang;
using namespace CodeGen;
static llvm::Constant *getFreeExceptionFn(CodeGenModule &CGM) {
// void __cxa_free_exception(void *thrown_exception);
llvm::FunctionType *FTy =
llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
}
static llvm::Constant *getUnexpectedFn(CodeGenModule &CGM) {
// void __cxa_call_unexpected(void *thrown_exception);
llvm::FunctionType *FTy =
llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
}
llvm::Constant *CodeGenModule::getTerminateFn() {
// void __terminate();
llvm::FunctionType *FTy =
llvm::FunctionType::get(VoidTy, /*IsVarArgs=*/false);
StringRef name;
// In C++, use std::terminate().
if (getLangOpts().CPlusPlus &&
getTarget().getCXXABI().isItaniumFamily()) {
name = "_ZSt9terminatev";
} else if (getLangOpts().CPlusPlus &&
getTarget().getCXXABI().isMicrosoft()) {
if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
name = "__std_terminate";
else
name = "\01?terminate@@YAXXZ";
} else if (getLangOpts().ObjC1 &&
getLangOpts().ObjCRuntime.hasTerminate())
name = "objc_terminate";
else
name = "abort";
return CreateRuntimeFunction(FTy, name);
}
static llvm::Constant *getCatchallRethrowFn(CodeGenModule &CGM,
StringRef Name) {
llvm::FunctionType *FTy =
llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
return CGM.CreateRuntimeFunction(FTy, Name);
}
namespace {
/// The exceptions personality for a function.
struct EHPersonality {
const char *PersonalityFn;
// If this is non-null, this personality requires a non-standard
// function for rethrowing an exception after a catchall cleanup.
// This function must have prototype void(void*).
const char *CatchallRethrowFn;
static const EHPersonality &get(CodeGenModule &CGM,
const FunctionDecl *FD);
static const EHPersonality &get(CodeGenFunction &CGF) {
return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(CGF.CurCodeDecl));
}
static const EHPersonality GNU_C;
static const EHPersonality GNU_C_SJLJ;
static const EHPersonality GNU_C_SEH;
static const EHPersonality GNU_ObjC;
static const EHPersonality GNUstep_ObjC;
static const EHPersonality GNU_ObjCXX;
static const EHPersonality NeXT_ObjC;
static const EHPersonality GNU_CPlusPlus;
static const EHPersonality GNU_CPlusPlus_SJLJ;
static const EHPersonality GNU_CPlusPlus_SEH;
static const EHPersonality MSVC_except_handler;
static const EHPersonality MSVC_C_specific_handler;
static const EHPersonality MSVC_CxxFrameHandler3;
};
}
const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr };
const EHPersonality
EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr };
const EHPersonality
EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr };
const EHPersonality
EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr };
const EHPersonality
EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr };
const EHPersonality
EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr };
const EHPersonality
EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr };
const EHPersonality
EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"};
const EHPersonality
EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr };
const EHPersonality
EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr };
const EHPersonality
EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr };
const EHPersonality
EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr };
const EHPersonality
EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr };
/// On Win64, use libgcc's SEH personality function. We fall back to dwarf on
/// other platforms, unless the user asked for SjLj exceptions.
static bool useLibGCCSEHPersonality(const llvm::Triple &T) {
return T.isOSWindows() && T.getArch() == llvm::Triple::x86_64;
}
static const EHPersonality &getCPersonality(const llvm::Triple &T,
const LangOptions &L) {
if (L.SjLjExceptions)
return EHPersonality::GNU_C_SJLJ;
else if (useLibGCCSEHPersonality(T))
return EHPersonality::GNU_C_SEH;
return EHPersonality::GNU_C;
}
static const EHPersonality &getObjCPersonality(const llvm::Triple &T,
const LangOptions &L) {
switch (L.ObjCRuntime.getKind()) {
case ObjCRuntime::FragileMacOSX:
return getCPersonality(T, L);
case ObjCRuntime::MacOSX:
case ObjCRuntime::iOS:
return EHPersonality::NeXT_ObjC;
case ObjCRuntime::GNUstep:
if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
return EHPersonality::GNUstep_ObjC;
// fallthrough
case ObjCRuntime::GCC:
case ObjCRuntime::ObjFW:
return EHPersonality::GNU_ObjC;
}
llvm_unreachable("bad runtime kind");
}
static const EHPersonality &getCXXPersonality(const llvm::Triple &T,
const LangOptions &L) {
if (L.SjLjExceptions)
return EHPersonality::GNU_CPlusPlus_SJLJ;
else if (useLibGCCSEHPersonality(T))
return EHPersonality::GNU_CPlusPlus_SEH;
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 llvm::Triple &T,
const LangOptions &L) {
switch (L.ObjCRuntime.getKind()) {
// 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.
case ObjCRuntime::MacOSX:
case ObjCRuntime::iOS:
return EHPersonality::NeXT_ObjC;
// In the fragile ABI, just use C++ exception handling and hope
// they're not doing crazy exception mixing.
case ObjCRuntime::FragileMacOSX:
return getCXXPersonality(T, L);
// The GCC runtime's personality function inherently doesn't support
// mixed EH. Use the C++ personality just to avoid returning null.
case ObjCRuntime::GCC:
case ObjCRuntime::ObjFW: // XXX: this will change soon
return EHPersonality::GNU_ObjC;
case ObjCRuntime::GNUstep:
return EHPersonality::GNU_ObjCXX;
}
llvm_unreachable("bad runtime kind");
}
static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) {
if (T.getArch() == llvm::Triple::x86)
return EHPersonality::MSVC_except_handler;
return EHPersonality::MSVC_C_specific_handler;
}
const EHPersonality &EHPersonality::get(CodeGenModule &CGM,
const FunctionDecl *FD) {
const llvm::Triple &T = CGM.getTarget().getTriple();
const LangOptions &L = CGM.getLangOpts();
// Try to pick a personality function that is compatible with MSVC if we're
// not compiling Obj-C. Obj-C users better have an Obj-C runtime that supports
// the GCC-style personality function.
if (T.isWindowsMSVCEnvironment() && !L.ObjC1) {
if (L.SjLjExceptions)
return EHPersonality::GNU_CPlusPlus_SJLJ;
else if (FD && FD->usesSEHTry())
return getSEHPersonalityMSVC(T);
else
return EHPersonality::MSVC_CxxFrameHandler3;
}
if (L.CPlusPlus && L.ObjC1)
return getObjCXXPersonality(T, L);
else if (L.CPlusPlus)
return getCXXPersonality(T, L);
else if (L.ObjC1)
return getObjCPersonality(T, L);
else
return getCPersonality(T, L);
}
static llvm::Constant *getPersonalityFn(CodeGenModule &CGM,
const EHPersonality &Personality) {
llvm::Constant *Fn =
CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true),
Personality.PersonalityFn);
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::User *U : Fn->users()) {
// Conditionally white-list bitcasts.
if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(U)) {
if (CE->getOpcode() != llvm::Instruction::BitCast) return false;
if (!PersonalityHasOnlyCXXUses(CE))
return false;
continue;
}
// Otherwise, it has to be a landingpad instruction.
llvm::LandingPadInst *LPI = dyn_cast<llvm::LandingPadInst>(U);
if (!LPI) return false;
for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) {
// Look for something that would've been returned by the ObjC
// runtime's GetEHType() method.
llvm::Value *Val = LPI->getClause(I)->stripPointerCasts();
if (LPI->isCatch(I)) {
// Check if the catch value has the ObjC prefix.
if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val))
// ObjC EH selector entries are always global variables with
// names starting like this.
if (GV->getName().startswith("OBJC_EHTYPE"))
return false;
} else {
// Check if any of the filter values have the ObjC prefix.
llvm::Constant *CVal = cast<llvm::Constant>(Val);
for (llvm::User::op_iterator
II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) {
if (llvm::GlobalVariable *GV =
cast<llvm::GlobalVariable>((*II)->stripPointerCasts()))
// 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() {
// If we're not in ObjC++ -fexceptions, there's nothing to do.
if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions)
return;
// Both the problem this endeavors to fix and the way the logic
// above works is specific to the NeXT runtime.
if (!LangOpts.ObjCRuntime.isNeXTFamily())
return;
const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr);
const EHPersonality &CXX =
getCXXPersonality(getTarget().getTriple(), LangOpts);
if (&ObjCXX == &CXX)
return;
assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 &&
"Different EHPersonalities using the same personality function.");
llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn);
// 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);
}
namespace {
/// A cleanup to free the exception object if its initialization
/// throws.
struct FreeException : EHScopeStack::Cleanup {
llvm::Value *exn;
FreeException(llvm::Value *exn) : exn(exn) {}
void Emit(CodeGenFunction &CGF, Flags flags) override {
CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn);
}
};
}
// 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.
void CodeGenFunction::EmitAnyExprToExn(const Expr *e, llvm::Value *addr) {
// Make sure the exception object is cleaned up if there's an
// exception during initialization.
pushFullExprCleanup<FreeException>(EHCleanup, addr);
EHScopeStack::stable_iterator cleanup = EHStack.stable_begin();
// __cxa_allocate_exception returns a void*; we need to cast this
// to the appropriate type for the object.
llvm::Type *ty = ConvertTypeForMem(e->getType())->getPointerTo();
llvm::Value *typedAddr = 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.
EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(),
/*IsInit*/ true);
// Deactivate the cleanup block.
DeactivateCleanupBlock(cleanup, cast<llvm::Instruction>(typedAddr));
}
llvm::Value *CodeGenFunction::getExceptionSlot() {
if (!ExceptionSlot)
ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
return ExceptionSlot;
}
llvm::Value *CodeGenFunction::getEHSelectorSlot() {
if (!EHSelectorSlot)
EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
return EHSelectorSlot;
}
llvm::Value *CodeGenFunction::getExceptionFromSlot() {
return Builder.CreateLoad(getExceptionSlot(), "exn");
}
llvm::Value *CodeGenFunction::getSelectorFromSlot() {
return Builder.CreateLoad(getEHSelectorSlot(), "sel");
}
void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E,
bool KeepInsertionPoint) {
if (const Expr *SubExpr = E->getSubExpr()) {
QualType ThrowType = SubExpr->getType();
if (ThrowType->isObjCObjectPointerType()) {
const Stmt *ThrowStmt = E->getSubExpr();
const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(ThrowStmt));
CGM.getObjCRuntime().EmitThrowStmt(*this, S, false);
} else {
CGM.getCXXABI().emitThrow(*this, E);
}
} else {
CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true);
}
// throw is an expression, and the expression emitters expect us
// to leave ourselves at a valid insertion point.
if (KeepInsertionPoint)
EmitBlock(createBasicBlock("throw.cont"));
}
void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
if (!CGM.getLangOpts().CXXExceptions)
return;
const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
if (!FD) {
// Check if CapturedDecl is nothrow and create terminate scope for it.
if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
if (CD->isNothrow())
EHStack.pushTerminate();
}
return;
}
const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
if (!Proto)
return;
ExceptionSpecificationType EST = Proto->getExceptionSpecType();
if (isNoexceptExceptionSpec(EST)) {
if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
// noexcept functions are simple terminate scopes.
EHStack.pushTerminate();
}
} else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
// TODO: Revisit exception specifications for the MS ABI. There is a way to
// encode these in an object file but MSVC doesn't do anything with it.
if (getTarget().getCXXABI().isMicrosoft())
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);
}
}
}
/// Emit the dispatch block for a filter scope if necessary.
static void emitFilterDispatchBlock(CodeGenFunction &CGF,
EHFilterScope &filterScope) {
llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock();
if (!dispatchBlock) return;
if (dispatchBlock->use_empty()) {
delete dispatchBlock;
return;
}
CGF.EmitBlockAfterUses(dispatchBlock);
// If this isn't a catch-all filter, we need to check whether we got
// here because the filter triggered.
if (filterScope.getNumFilters()) {
// Load the selector value.
llvm::Value *selector = CGF.getSelectorFromSlot();
llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected");
llvm::Value *zero = CGF.Builder.getInt32(0);
llvm::Value *failsFilter =
CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails");
CGF.Builder.CreateCondBr(failsFilter, unexpectedBB,
CGF.getEHResumeBlock(false));
CGF.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.
llvm::Value *exn = CGF.getExceptionFromSlot();
CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn)
->setDoesNotReturn();
CGF.Builder.CreateUnreachable();
}
void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
if (!CGM.getLangOpts().CXXExceptions)
return;
const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D);
if (!FD) {
// Check if CapturedDecl is nothrow and pop terminate scope for it.
if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
if (CD->isNothrow())
EHStack.popTerminate();
}
return;
}
const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
if (!Proto)
return;
ExceptionSpecificationType EST = Proto->getExceptionSpecType();
if (isNoexceptExceptionSpec(EST)) {
if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) {
EHStack.popTerminate();
}
} else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
// TODO: Revisit exception specifications for the MS ABI. There is a way to
// encode these in an object file but MSVC doesn't do anything with it.
if (getTarget().getCXXABI().isMicrosoft())
return;
EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
emitFilterDispatchBlock(*this, filterScope);
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
Qualifiers CaughtTypeQuals;
QualType CaughtType = CGM.getContext().getUnqualifiedArrayType(
C->getCaughtType().getNonReferenceType(), CaughtTypeQuals);
llvm::Constant *TypeInfo = nullptr;
if (CaughtType->isObjCObjectPointerType())
TypeInfo = CGM.getObjCRuntime().GetEHType(CaughtType);
else
TypeInfo =
CGM.getAddrOfCXXCatchHandlerType(CaughtType, C->getCaughtType());
CatchScope->setHandler(I, TypeInfo, Handler);
} else {
// No exception decl indicates '...', a catch-all.
CatchScope->setCatchAllHandler(I, Handler);
}
}
}
llvm::BasicBlock *
CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) {
// The dispatch block for the end of the scope chain is a block that
// just resumes unwinding.
if (si == EHStack.stable_end())
return getEHResumeBlock(true);
// Otherwise, we should look at the actual scope.
EHScope &scope = *EHStack.find(si);
llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock();
if (!dispatchBlock) {
switch (scope.getKind()) {
case EHScope::Catch: {
// Apply a special case to a single catch-all.
EHCatchScope &catchScope = cast<EHCatchScope>(scope);
if (catchScope.getNumHandlers() == 1 &&
catchScope.getHandler(0).isCatchAll()) {
dispatchBlock = catchScope.getHandler(0).Block;
// Otherwise, make a dispatch block.
} else {
dispatchBlock = createBasicBlock("catch.dispatch");
}
break;
}
case EHScope::Cleanup:
dispatchBlock = createBasicBlock("ehcleanup");
break;
case EHScope::Filter:
dispatchBlock = createBasicBlock("filter.dispatch");
break;
case EHScope::Terminate:
dispatchBlock = getTerminateHandler();
break;
}
scope.setCachedEHDispatchBlock(dispatchBlock);
}
return dispatchBlock;
}
/// 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;
}
llvm_unreachable("Invalid EHScope Kind!");
}
llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
assert(EHStack.requiresLandingPad());
assert(!EHStack.empty());
// If exceptions are disabled, there are usually no landingpads. However, when
// SEH is enabled, functions using SEH still get landingpads.
const LangOptions &LO = CGM.getLangOpts();
if (!LO.Exceptions) {
if (!LO.Borland && !LO.MicrosoftExt)
return nullptr;
if (!currentFunctionUsesSEHTry())
return nullptr;
}
// 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());
EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope());
switch (innermostEHScope.getKind()) {
case EHScope::Terminate:
return getTerminateLandingPad();
case EHScope::Catch:
case EHScope::Cleanup:
case EHScope::Filter:
if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad())
return lpad;
}
// Save the current IR generation state.
CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP();
auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation);
const EHPersonality &personality = EHPersonality::get(*this);
// Create and configure the landing pad.
llvm::BasicBlock *lpad = createBasicBlock("lpad");
EmitBlock(lpad);
llvm::LandingPadInst *LPadInst =
Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr),
getOpaquePersonalityFn(CGM, personality), 0);
llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0);
Builder.CreateStore(LPadExn, getExceptionSlot());
llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1);
Builder.CreateStore(LPadSel, getEHSelectorSlot());
// Save the exception pointer. It's safe to use a single exception
// pointer per function because EH cleanups can never have nested
// try/catches.
// Build the landingpad instruction.
// Accumulate all the handlers in scope.
bool hasCatchAll = false;
bool hasCleanup = false;
bool hasFilter = false;
SmallVector<llvm::Value*, 4> filterTypes;
llvm::SmallPtrSet<llvm::Value*, 4> catchTypes;
for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E;
++I) {
switch (I->getKind()) {
case EHScope::Cleanup:
// If we have a cleanup, remember that.
hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup());
continue;
case EHScope::Filter: {
assert(I.next() == EHStack.end() && "EH filter is not end of EH stack");
assert(!hasCatchAll && "EH filter reached after catch-all");
// Filter scopes get added to the landingpad in weird ways.
EHFilterScope &filter = cast<EHFilterScope>(*I);
hasFilter = true;
// Add all the filter values.
for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i)
filterTypes.push_back(filter.getFilter(i));
goto done;
}
case EHScope::Terminate:
// Terminate scopes are basically catch-alls.
assert(!hasCatchAll);
hasCatchAll = true;
goto done;
case EHScope::Catch:
break;
}
EHCatchScope &catchScope = cast<EHCatchScope>(*I);
for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) {
EHCatchScope::Handler handler = catchScope.getHandler(hi);
// If this is a catch-all, register that and abort.
if (!handler.Type) {
assert(!hasCatchAll);
hasCatchAll = true;
goto done;
}
// Check whether we already have a handler for this type.
if (catchTypes.insert(handler.Type).second)
// If not, add it directly to the landingpad.
LPadInst->addClause(handler.Type);
}
}
done:
// If we have a catch-all, add null to the landingpad.
assert(!(hasCatchAll && hasFilter));
if (hasCatchAll) {
LPadInst->addClause(getCatchAllValue(*this));
// If we have an EH filter, we need to add those handlers in the
// right place in the landingpad, which is to say, at the end.
} else if (hasFilter) {
// Create a filter expression: a constant array indicating which filter
// types there are. The personality routine only lands here if the filter
// doesn't match.
SmallVector<llvm::Constant*, 8> Filters;
llvm::ArrayType *AType =
llvm::ArrayType::get(!filterTypes.empty() ?
filterTypes[0]->getType() : Int8PtrTy,
filterTypes.size());
for (unsigned i = 0, e = filterTypes.size(); i != e; ++i)
Filters.push_back(cast<llvm::Constant>(filterTypes[i]));
llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters);
LPadInst->addClause(FilterArray);
// Also check whether we need a cleanup.
if (hasCleanup)
LPadInst->setCleanup(true);
// Otherwise, signal that we at least have cleanups.
} else if (hasCleanup) {
LPadInst->setCleanup(true);
}
assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) &&
"landingpad instruction has no clauses!");
// Tell the backend how to generate the landing pad.
Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope()));
// Restore the old IR generation state.
Builder.restoreIP(savedIP);
return lpad;
}
/// Emit the structure of the dispatch block for the given catch scope.
/// It is an invariant that the dispatch block already exists.
static void emitCatchDispatchBlock(CodeGenFunction &CGF,
EHCatchScope &catchScope) {
llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock();
assert(dispatchBlock);
// If there's only a single catch-all, getEHDispatchBlock returned
// that catch-all as the dispatch block.
if (catchScope.getNumHandlers() == 1 &&
catchScope.getHandler(0).isCatchAll()) {
assert(dispatchBlock == catchScope.getHandler(0).Block);
return;
}
CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP();
CGF.EmitBlockAfterUses(dispatchBlock);
// Select the right handler.
llvm::Value *llvm_eh_typeid_for =
CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for);
// Load the selector value.
llvm::Value *selector = CGF.getSelectorFromSlot();
// Test against each of the exception types we claim to catch.
for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) {
assert(i < e && "ran off end of handlers!");
const EHCatchScope::Handler &handler = catchScope.getHandler(i);
llvm::Value *typeValue = handler.Type;
assert(typeValue && "fell into catch-all case!");
typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy);
// Figure out the next block.
bool nextIsEnd;
llvm::BasicBlock *nextBlock;
// If this is the last handler, we're at the end, and the next
// block is the block for the enclosing EH scope.
if (i + 1 == e) {
nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope());
nextIsEnd = true;
// If the next handler is a catch-all, we're at the end, and the
// next block is that handler.
} else if (catchScope.getHandler(i+1).isCatchAll()) {
nextBlock = catchScope.getHandler(i+1).Block;
nextIsEnd = true;
// Otherwise, we're not at the end and we need a new block.
} else {
nextBlock = CGF.createBasicBlock("catch.fallthrough");
nextIsEnd = false;
}
// Figure out the catch type's index in the LSDA's type table.
llvm::CallInst *typeIndex =
CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue);
typeIndex->setDoesNotThrow();
llvm::Value *matchesTypeIndex =
CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches");
CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock);
// If the next handler is a catch-all, we're completely done.
if (nextIsEnd) {
CGF.Builder.restoreIP(savedIP);
return;
}
// Otherwise we need to emit and continue at that block.
CGF.EmitBlock(nextBlock);
}
}
void CodeGenFunction::popCatchScope() {
EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin());
if (catchScope.hasEHBranches())
emitCatchDispatchBlock(*this, catchScope);
EHStack.popCatch();
}
void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) {
unsigned NumHandlers = S.getNumHandlers();
EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
assert(CatchScope.getNumHandlers() == NumHandlers);
// If the catch was not required, bail out now.
if (!CatchScope.hasEHBranches()) {
CatchScope.clearHandlerBlocks();
EHStack.popCatch();
return;
}
// Emit the structure of the EH dispatch for this catch.
emitCatchDispatchBlock(*this, CatchScope);
// Copy the handler blocks off before we pop the EH stack. Emitting
// the handlers might scribble on this memory.
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;
// see the comment below.
bool doImplicitRethrow = false;
if (IsFnTryBlock)
doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) ||
isa<CXXConstructorDecl>(CurCodeDecl);
// Perversely, we emit the handlers backwards precisely because we
// want them to appear in source order. In all of these cases, the
// catch block will have exactly one predecessor, which will be a
// particular block in the catch dispatch. However, in the case of
// a catch-all, one of the dispatch blocks will branch to two
// different handlers, and EmitBlockAfterUses will cause the second
// handler to be moved before the first.
for (unsigned I = NumHandlers; I != 0; --I) {
llvm::BasicBlock *CatchBlock = Handlers[I-1].Block;
EmitBlockAfterUses(CatchBlock);
// Catch the exception if this isn't a catch-all.
const CXXCatchStmt *C = S.getHandler(I-1);
// Enter a cleanup scope, including the catch variable and the
// end-catch.
RunCleanupsScope CatchScope(*this);
// Initialize the catch variable and set up the cleanups.
CGM.getCXXABI().emitBeginCatch(*this, C);
// Emit the PGO counter increment.
incrementProfileCounter(C);
// Perform the body of the catch.
EmitStmt(C->getHandlerBlock());
// [except.handle]p11:
// The currently handled exception is rethrown if control
// reaches the end of a handler of the function-try-block of a
// constructor or destructor.
// It is important that we only do this on fallthrough and not on
// return. Note that it's illegal to put a return in a
// constructor function-try-block's catch handler (p14), so this
// really only applies to destructors.
if (doImplicitRethrow && HaveInsertPoint()) {
CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false);
Builder.CreateUnreachable();
Builder.ClearInsertionPoint();
}
// Fall out through the catch cleanups.
CatchScope.ForceCleanup();
// Branch out of the try.
if (HaveInsertPoint())
Builder.CreateBr(ContBB);
}
EmitBlock(ContBB);
incrementProfileCounter(&S);
}
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, Flags flags) override {
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.EmitRuntimeCallOrInvoke(EndCatchFn); // 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, Flags flags) override {
// 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) {
CGF.EmitRuntimeCallOrInvoke(RethrowFn,
CGF.Builder.CreateLoad(SavedExnVar));
} else {
CGF.EmitRuntimeCallOrInvoke(RethrowFn);
}
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.
void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF,
const Stmt *body,
llvm::Constant *beginCatchFn,
llvm::Constant *endCatchFn,
llvm::Constant *rethrowFn) {
assert((beginCatchFn != nullptr) == (endCatchFn != nullptr) &&
"begin/end catch functions not paired");
assert(rethrowFn && "rethrow function is required");
BeginCatchFn = beginCatchFn;
// 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).
llvm::FunctionType *rethrowFnTy =
cast<llvm::FunctionType>(
cast<llvm::PointerType>(rethrowFn->getType())->getElementType());
SavedExnVar = nullptr;
if (rethrowFnTy->getNumParams())
SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "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.
// Jump destination for performing the finally block on an exception
// edge. We'll never actually reach this block, so unreachable is
// fine.
RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock());
// Whether the finally block is being executed for EH purposes.
ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh");
CGF.Builder.CreateStore(CGF.Builder.getFalse(), ForEHVar);
// Enter a normal cleanup which will perform the @finally block.
CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body,
ForEHVar, endCatchFn,
rethrowFn, SavedExnVar);
// Enter a catch-all scope.
llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall");
EHCatchScope *catchScope = CGF.EHStack.pushCatch(1);
catchScope->setCatchAllHandler(0, catchBB);
}
void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) {
// Leave the finally catch-all.
EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin());
llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block;
CGF.popCatchScope();
// If there are any references to the catch-all block, emit it.
if (catchBB->use_empty()) {
delete catchBB;
} else {
CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP();
CGF.EmitBlock(catchBB);
llvm::Value *exn = nullptr;
// If there's a begin-catch function, call it.
if (BeginCatchFn) {
exn = CGF.getExceptionFromSlot();
CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn);
}
// If we need to remember the exception pointer to rethrow later, do so.
if (SavedExnVar) {
if (!exn) exn = CGF.getExceptionFromSlot();
CGF.Builder.CreateStore(exn, SavedExnVar);
}
// Tell the cleanups in the finally block that we're do this for EH.
CGF.Builder.CreateStore(CGF.Builder.getTrue(), ForEHVar);
// Thread a jump through the finally cleanup.
CGF.EmitBranchThroughCleanup(RethrowDest);
CGF.Builder.restoreIP(savedIP);
}
// Finally, leave the @finally cleanup.
CGF.PopCleanupBlock();
}
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.
const EHPersonality &Personality = EHPersonality::get(*this);
llvm::LandingPadInst *LPadInst =
Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr),
getOpaquePersonalityFn(CGM, Personality), 0);
LPadInst->addClause(getCatchAllValue(*this));
llvm::Value *Exn = 0;
if (getLangOpts().CPlusPlus)
Exn = Builder.CreateExtractValue(LPadInst, 0);
llvm::CallInst *terminateCall =
CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
terminateCall->setDoesNotReturn();
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::Value *Exn = 0;
if (getLangOpts().CPlusPlus)
Exn = getExceptionFromSlot();
llvm::CallInst *terminateCall =
CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
terminateCall->setDoesNotReturn();
Builder.CreateUnreachable();
// Restore the saved insertion state.
Builder.restoreIP(SavedIP);
return TerminateHandler;
}
llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) {
if (EHResumeBlock) return EHResumeBlock;
CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
// We emit a jump to a notional label at the outermost unwind state.
EHResumeBlock = createBasicBlock("eh.resume");
Builder.SetInsertPoint(EHResumeBlock);
const EHPersonality &Personality = EHPersonality::get(*this);
// This can always be a call because we necessarily didn't find
// anything on the EH stack which needs our help.
const char *RethrowName = Personality.CatchallRethrowFn;
if (RethrowName != nullptr && !isCleanup) {
EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName),
getExceptionFromSlot())->setDoesNotReturn();
Builder.CreateUnreachable();
Builder.restoreIP(SavedIP);
return EHResumeBlock;
}
// Recreate the landingpad's return value for the 'resume' instruction.
llvm::Value *Exn = getExceptionFromSlot();
llvm::Value *Sel = getSelectorFromSlot();
llvm::Type *LPadType = llvm::StructType::get(Exn->getType(),
Sel->getType(), nullptr);
llvm::Value *LPadVal = llvm::UndefValue::get(LPadType);
LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val");
LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val");
Builder.CreateResume(LPadVal);
Builder.restoreIP(SavedIP);
return EHResumeBlock;
}
void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) {
// FIXME: Implement SEH on other architectures.
const llvm::Triple &T = CGM.getTarget().getTriple();
if (T.getArch() != llvm::Triple::x86_64 ||
!T.isKnownWindowsMSVCEnvironment()) {
ErrorUnsupported(&S, "__try statement");
return;
}
EnterSEHTryStmt(S);
{
JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave");
SEHTryEpilogueStack.push_back(&TryExit);
EmitStmt(S.getTryBlock());
SEHTryEpilogueStack.pop_back();
if (!TryExit.getBlock()->use_empty())
EmitBlock(TryExit.getBlock(), /*IsFinished=*/true);
else
delete TryExit.getBlock();
}
ExitSEHTryStmt(S);
}
namespace {
struct PerformSEHFinally : EHScopeStack::Cleanup {
llvm::Function *OutlinedFinally;
PerformSEHFinally(llvm::Function *OutlinedFinally)
: OutlinedFinally(OutlinedFinally) {}
void Emit(CodeGenFunction &CGF, Flags F) override {
ASTContext &Context = CGF.getContext();
QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy};
FunctionProtoType::ExtProtoInfo EPI;
const auto *FTP = cast<FunctionType>(
Context.getFunctionType(Context.VoidTy, ArgTys, EPI));
CallArgList Args;
llvm::Value *IsForEH =
llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup());
Args.add(RValue::get(IsForEH), ArgTys[0]);
CodeGenModule &CGM = CGF.CGM;
llvm::Value *Zero = llvm::ConstantInt::get(CGM.Int32Ty, 0);
llvm::Value *FrameAddr = CGM.getIntrinsic(llvm::Intrinsic::frameaddress);
llvm::Value *FP = CGF.Builder.CreateCall(FrameAddr, Zero);
Args.add(RValue::get(FP), ArgTys[1]);
const CGFunctionInfo &FnInfo =
CGM.getTypes().arrangeFreeFunctionCall(Args, FTP, /*chainCall=*/false);
CGF.EmitCall(FnInfo, OutlinedFinally, ReturnValueSlot(), Args);
}
};
}
namespace {
/// Find all local variable captures in the statement.
struct CaptureFinder : ConstStmtVisitor<CaptureFinder> {
CodeGenFunction &ParentCGF;
const VarDecl *ParentThis;
SmallVector<const VarDecl *, 4> Captures;
CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis)
: ParentCGF(ParentCGF), ParentThis(ParentThis) {}
void Visit(const Stmt *S) {
// See if this is a capture, then recurse.
ConstStmtVisitor<CaptureFinder>::Visit(S);
for (const Stmt *Child : S->children())
if (Child)
Visit(Child);
}
void VisitDeclRefExpr(const DeclRefExpr *E) {
// If this is already a capture, just make sure we capture 'this'.
if (E->refersToEnclosingVariableOrCapture()) {
Captures.push_back(ParentThis);
return;
}
const auto *D = dyn_cast<VarDecl>(E->getDecl());
if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage())
Captures.push_back(D);
}
void VisitCXXThisExpr(const CXXThisExpr *E) {
Captures.push_back(ParentThis);
}
};
}
void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF,
const Stmt *OutlinedStmt,
llvm::Value *ParentFP) {
// Find all captures in the Stmt.
CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl);
Finder.Visit(OutlinedStmt);
// Typically there are no captures and we can exit early.
if (Finder.Captures.empty())
return;
// Prepare the first two arguments to llvm.framerecover.
llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
&CGM.getModule(), llvm::Intrinsic::framerecover);
llvm::Constant *ParentI8Fn =
llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
// Create llvm.framerecover calls for all captures.
for (const VarDecl *VD : Finder.Captures) {
if (isa<ImplicitParamDecl>(VD)) {
CGM.ErrorUnsupported(VD, "'this' captured by SEH");
CXXThisValue = llvm::UndefValue::get(ConvertTypeForMem(VD->getType()));
continue;
}
if (VD->getType()->isVariablyModifiedType()) {
CGM.ErrorUnsupported(VD, "VLA captured by SEH");
continue;
}
assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) &&
"captured non-local variable");
// If this decl hasn't been declared yet, it will be declared in the
// OutlinedStmt.
auto I = ParentCGF.LocalDeclMap.find(VD);
if (I == ParentCGF.LocalDeclMap.end())
continue;
llvm::Value *ParentVar = I->second;
llvm::CallInst *RecoverCall = nullptr;
CGBuilderTy Builder(AllocaInsertPt);
if (auto *ParentAlloca = dyn_cast<llvm::AllocaInst>(ParentVar)) {
// Mark the variable escaped if nobody else referenced it and compute the
// frameescape index.
auto InsertPair =
ParentCGF.EscapedLocals.insert(std::make_pair(ParentAlloca, -1));
if (InsertPair.second)
InsertPair.first->second = ParentCGF.EscapedLocals.size() - 1;
int FrameEscapeIdx = InsertPair.first->second;
// call i8* @llvm.framerecover(i8* bitcast(@parentFn), i8* %fp, i32 N)
RecoverCall = Builder.CreateCall(
FrameRecoverFn, {ParentI8Fn, ParentFP,
llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)});
} else {
// If the parent didn't have an alloca, we're doing some nested outlining.
// Just clone the existing framerecover call, but tweak the FP argument to
// use our FP value. All other arguments are constants.
auto *ParentRecover =
cast<llvm::IntrinsicInst>(ParentVar->stripPointerCasts());
assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::framerecover &&
"expected alloca or framerecover in parent LocalDeclMap");
RecoverCall = cast<llvm::CallInst>(ParentRecover->clone());
RecoverCall->setArgOperand(1, ParentFP);
RecoverCall->insertBefore(AllocaInsertPt);
}
// Bitcast the variable, rename it, and insert it in the local decl map.
llvm::Value *ChildVar =
Builder.CreateBitCast(RecoverCall, ParentVar->getType());
ChildVar->setName(ParentVar->getName());
LocalDeclMap[VD] = ChildVar;
}
}
/// Arrange a function prototype that can be called by Windows exception
/// handling personalities. On Win64, the prototype looks like:
/// RetTy func(void *EHPtrs, void *ParentFP);
void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF,
StringRef Name, QualType RetTy,
FunctionArgList &Args,
const Stmt *OutlinedStmt) {
llvm::Function *ParentFn = ParentCGF.CurFn;
const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionDeclaration(
RetTy, Args, FunctionType::ExtInfo(), /*isVariadic=*/false);
llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
llvm::Function *Fn = llvm::Function::Create(
FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
// The filter is either in the same comdat as the function, or it's internal.
if (llvm::Comdat *C = ParentFn->getComdat()) {
Fn->setComdat(C);
} else if (ParentFn->hasWeakLinkage() || ParentFn->hasLinkOnceLinkage()) {
llvm::Comdat *C = CGM.getModule().getOrInsertComdat(ParentFn->getName());
ParentFn->setComdat(C);
Fn->setComdat(C);
} else {
Fn->setLinkage(llvm::GlobalValue::InternalLinkage);
}
IsOutlinedSEHHelper = true;
StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
OutlinedStmt->getLocStart(), OutlinedStmt->getLocStart());
CGM.SetLLVMFunctionAttributes(nullptr, FnInfo, CurFn);
auto AI = Fn->arg_begin();
++AI;
EmitCapturedLocals(ParentCGF, OutlinedStmt, &*AI);
}
/// Create a stub filter function that will ultimately hold the code of the
/// filter expression. The EH preparation passes in LLVM will outline the code
/// from the main function body into this stub.
llvm::Function *
CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF,
const SEHExceptStmt &Except) {
const Expr *FilterExpr = Except.getFilterExpr();
SourceLocation StartLoc = FilterExpr->getLocStart();
SEHPointersDecl = ImplicitParamDecl::Create(
getContext(), nullptr, StartLoc,
&getContext().Idents.get("exception_pointers"), getContext().VoidPtrTy);
FunctionArgList Args;
Args.push_back(SEHPointersDecl);
Args.push_back(ImplicitParamDecl::Create(
getContext(), nullptr, StartLoc,
&getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy));
// Get the mangled function name.
SmallString<128> Name;
{
llvm::raw_svector_ostream OS(Name);
const Decl *ParentCodeDecl = ParentCGF.CurCodeDecl;
const NamedDecl *Parent = dyn_cast_or_null<NamedDecl>(ParentCodeDecl);
assert(Parent && "FIXME: handle unnamed decls (lambdas, blocks) with SEH");
CGM.getCXXABI().getMangleContext().mangleSEHFilterExpression(Parent, OS);
}
startOutlinedSEHHelper(ParentCGF, Name, getContext().LongTy, Args,
FilterExpr);
// Mark finally block calls as nounwind and noinline to make LLVM's job a
// little easier.
// FIXME: Remove these restrictions in the future.
CurFn->addFnAttr(llvm::Attribute::NoUnwind);
CurFn->addFnAttr(llvm::Attribute::NoInline);
EmitSEHExceptionCodeSave();
// Emit the original filter expression, convert to i32, and return.
llvm::Value *R = EmitScalarExpr(FilterExpr);
R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy),
FilterExpr->getType()->isSignedIntegerType());
Builder.CreateStore(R, ReturnValue);
FinishFunction(FilterExpr->getLocEnd());
return CurFn;
}
llvm::Function *
CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF,
const SEHFinallyStmt &Finally) {
const Stmt *FinallyBlock = Finally.getBlock();
SourceLocation StartLoc = FinallyBlock->getLocStart();
FunctionArgList Args;
Args.push_back(ImplicitParamDecl::Create(
getContext(), nullptr, StartLoc,
&getContext().Idents.get("abnormal_termination"),
getContext().UnsignedCharTy));
Args.push_back(ImplicitParamDecl::Create(
getContext(), nullptr, StartLoc,
&getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy));
// Get the mangled function name.
SmallString<128> Name;
{
llvm::raw_svector_ostream OS(Name);
const Decl *ParentCodeDecl = ParentCGF.CurCodeDecl;
const NamedDecl *Parent = dyn_cast_or_null<NamedDecl>(ParentCodeDecl);
assert(Parent && "FIXME: handle unnamed decls (lambdas, blocks) with SEH");
CGM.getCXXABI().getMangleContext().mangleSEHFinallyBlock(Parent, OS);
}
startOutlinedSEHHelper(ParentCGF, Name, getContext().VoidTy, Args,
FinallyBlock);
// Emit the original filter expression, convert to i32, and return.
EmitStmt(FinallyBlock);
FinishFunction(FinallyBlock->getLocEnd());
return CurFn;
}
void CodeGenFunction::EmitSEHExceptionCodeSave() {
// Save the exception code in the exception slot to unify exception access in
// the filter function and the landing pad.
// struct EXCEPTION_POINTERS {
// EXCEPTION_RECORD *ExceptionRecord;
// CONTEXT *ContextRecord;
// };
// void *exn.slot =
// (void *)(uintptr_t)exception_pointers->ExceptionRecord->ExceptionCode;
llvm::Value *Ptrs = Builder.CreateLoad(GetAddrOfLocalVar(SEHPointersDecl));
llvm::Type *RecordTy = CGM.Int32Ty->getPointerTo();
llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy, nullptr);
Ptrs = Builder.CreateBitCast(Ptrs, PtrsTy->getPointerTo());
llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0);
Rec = Builder.CreateLoad(Rec);
llvm::Value *Code = Builder.CreateLoad(Rec);
Code = Builder.CreateZExt(Code, CGM.IntPtrTy);
// FIXME: Change landing pads to produce {i32, i32} and make the exception
// slot an i32.
Code = Builder.CreateIntToPtr(Code, CGM.VoidPtrTy);
Builder.CreateStore(Code, getExceptionSlot());
}
llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() {
// Sema should diagnose calling this builtin outside of a filter context, but
// don't crash if we screw up.
if (!SEHPointersDecl)
return llvm::UndefValue::get(Int8PtrTy);
return Builder.CreateLoad(GetAddrOfLocalVar(SEHPointersDecl));
}
llvm::Value *CodeGenFunction::EmitSEHExceptionCode() {
// If we're in a landing pad or filter function, the exception slot contains
// the code.
assert(ExceptionSlot);
llvm::Value *Code =
Builder.CreatePtrToInt(getExceptionFromSlot(), CGM.IntPtrTy);
return Builder.CreateTrunc(Code, CGM.Int32Ty);
}
llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() {
// Abnormal termination is just the first parameter to the outlined finally
// helper.
auto AI = CurFn->arg_begin();
return Builder.CreateZExt(&*AI, Int32Ty);
}
void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) {
// Push a cleanup for __finally blocks.
llvm::Function *FinallyFunc =
HelperCGF.GenerateSEHFinallyFunction(*this, *Finally);
EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, FinallyFunc);
return;
}
// Otherwise, we must have an __except block.
const SEHExceptStmt *Except = S.getExceptHandler();
assert(Except);
EHCatchScope *CatchScope = EHStack.pushCatch(1);
// If the filter is known to evaluate to 1, then we can use the clause "catch
// i8* null".
llvm::Constant *C =
CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this);
if (C && C->isOneValue()) {
CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
return;
}
// In general, we have to emit an outlined filter function. Use the function
// in place of the RTTI typeinfo global that C++ EH uses.
llvm::Function *FilterFunc =
HelperCGF.GenerateSEHFilterFunction(*this, *Except);
llvm::Constant *OpaqueFunc =
llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy);
CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except"));
}
void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
// Just pop the cleanup if it's a __finally block.
if (S.getFinallyHandler()) {
PopCleanupBlock();
return;
}
// Otherwise, we must have an __except block.
const SEHExceptStmt *Except = S.getExceptHandler();
assert(Except && "__try must have __finally xor __except");
EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin());
// Don't emit the __except block if the __try block lacked invokes.
// TODO: Model unwind edges from instructions, either with iload / istore or
// a try body function.
if (!CatchScope.hasEHBranches()) {
CatchScope.clearHandlerBlocks();
EHStack.popCatch();
return;
}
// 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);
// Check if our filter function returned true.
emitCatchDispatchBlock(*this, CatchScope);
// Grab the block before we pop the handler.
llvm::BasicBlock *ExceptBB = CatchScope.getHandler(0).Block;
EHStack.popCatch();
EmitBlockAfterUses(ExceptBB);
// Emit the __except body.
EmitStmt(Except->getBlock());
if (HaveInsertPoint())
Builder.CreateBr(ContBB);
EmitBlock(ContBB);
}
void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) {
// If this code is reachable then emit a stop point (if generating
// debug info). We have to do this ourselves because we are on the
// "simple" statement path.
if (HaveInsertPoint())
EmitStopPoint(&S);
// This must be a __leave from a __finally block, which we warn on and is UB.
// Just emit unreachable.
if (!isSEHTryScope()) {
Builder.CreateUnreachable();
Builder.ClearInsertionPoint();
return;
}
EmitBranchThroughCleanup(*SEHTryEpilogueStack.back());
}
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