diff options
Diffstat (limited to 'contrib/llvm/tools/clang/lib/CodeGen/CGException.cpp')
| -rw-r--r-- | contrib/llvm/tools/clang/lib/CodeGen/CGException.cpp | 188 |
1 files changed, 119 insertions, 69 deletions
diff --git a/contrib/llvm/tools/clang/lib/CodeGen/CGException.cpp b/contrib/llvm/tools/clang/lib/CodeGen/CGException.cpp index 6cb9599..e8ad6da 100644 --- a/contrib/llvm/tools/clang/lib/CodeGen/CGException.cpp +++ b/contrib/llvm/tools/clang/lib/CodeGen/CGException.cpp @@ -112,11 +112,18 @@ static llvm::Constant *getUnexpectedFn(CodeGenFunction &CGF) { return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); } +llvm::Constant *CodeGenFunction::getUnwindResumeFn() { + const llvm::FunctionType *FTy = + llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); + + if (CGM.getLangOptions().SjLjExceptions) + return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume"); + return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume"); +} + llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() { - const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(getLLVMContext()); const llvm::FunctionType *FTy = - llvm::FunctionType::get(llvm::Type::getVoidTy(getLLVMContext()), Int8PtrTy, - /*IsVarArgs=*/false); + llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); if (CGM.getLangOptions().SjLjExceptions) return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume_or_Rethrow"); @@ -354,13 +361,17 @@ static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *e, } llvm::Value *CodeGenFunction::getExceptionSlot() { - if (!ExceptionSlot) { - const llvm::Type *i8p = llvm::Type::getInt8PtrTy(getLLVMContext()); - ExceptionSlot = CreateTempAlloca(i8p, "exn.slot"); - } + if (!ExceptionSlot) + ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot"); return ExceptionSlot; } +llvm::Value *CodeGenFunction::getEHSelectorSlot() { + if (!EHSelectorSlot) + EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot"); + return EHSelectorSlot; +} + void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) { if (!E->getSubExpr()) { if (getInvokeDest()) { @@ -563,47 +574,59 @@ llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() { return LP; } +// This code 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. +enum CleanupHackLevel_t { + /// A level of hack that requires that all landing pads have + /// catch-alls. + CHL_MandatoryCatchall, + + /// A level of hack that requires that all landing pads handle + /// cleanups. + CHL_MandatoryCleanup, + + /// No hacks at all; ideal IR generation. + CHL_Ideal +}; +const CleanupHackLevel_t CleanupHackLevel = CHL_MandatoryCleanup; + 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?"); @@ -736,16 +759,23 @@ llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { EHSelector.append(EHFilters.begin(), EHFilters.end()); // Also check whether we need a cleanup. - if (UseInvokeInlineHack || HasEHCleanup) - EHSelector.push_back(UseInvokeInlineHack + if (CleanupHackLevel == CHL_MandatoryCatchall || HasEHCleanup) + EHSelector.push_back(CleanupHackLevel == CHL_MandatoryCatchall ? getCatchAllValue(*this) : getCleanupValue(*this)); // Otherwise, signal that we at least have cleanups. - } else if (UseInvokeInlineHack || HasEHCleanup) { - EHSelector.push_back(UseInvokeInlineHack + } else if (CleanupHackLevel == CHL_MandatoryCatchall || HasEHCleanup) { + EHSelector.push_back(CleanupHackLevel == CHL_MandatoryCatchall ? getCatchAllValue(*this) : getCleanupValue(*this)); + + // At the MandatoryCleanup hack level, we don't need to actually + // spuriously tell the unwinder that we have cleanups, but we do + // need to always be prepared to handle cleanups. + } else if (CleanupHackLevel == CHL_MandatoryCleanup) { + // Just don't decrement LastToEmitInLoop. + } else { assert(LastToEmitInLoop > 2); LastToEmitInLoop--; @@ -758,6 +788,10 @@ llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector), EHSelector.begin(), EHSelector.end(), "eh.selector"); Selection->setDoesNotThrow(); + + // Save the selector value in mandatory-cleanup mode. + if (CleanupHackLevel == CHL_MandatoryCleanup) + Builder.CreateStore(Selection, getEHSelectorSlot()); // Select the right handler. llvm::Value *llvm_eh_typeid_for = @@ -833,22 +867,13 @@ llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { // 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"); + if (CleanupHackLevel != CHL_Ideal || HasEHCleanup) { llvm::BasicBlock *UnexpectedBB = createBasicBlock("ehspec.unexpected"); - llvm::Constant *Zero = llvm::ConstantInt::get(Builder.getInt32Ty(), 0); + llvm::Constant *Zero = llvm::ConstantInt::get(Int32Ty, 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(); + Builder.CreateCondBr(FailsFilter, UnexpectedBB, getRethrowDest().getBlock()); EmitBlock(UnexpectedBB); } @@ -863,7 +888,7 @@ llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { Builder.CreateUnreachable(); // ...or a normal catch handler... - } else if (!UseInvokeInlineHack && !HasEHCleanup) { + } else if (CleanupHackLevel == CHL_Ideal && !HasEHCleanup) { llvm::Value *Type = EHSelector.back(); EmitBranchThroughEHCleanup(EHHandlers[Type]); @@ -1440,14 +1465,39 @@ CodeGenFunction::UnwindDest CodeGenFunction::getRethrowDest() { // 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(); + if (!RethrowName.empty()) { + Builder.CreateCall(getCatchallRethrowFn(*this, RethrowName), + Builder.CreateLoad(getExceptionSlot())) + ->setDoesNotReturn(); + } else { + llvm::Value *Exn = Builder.CreateLoad(getExceptionSlot()); + + switch (CleanupHackLevel) { + case CHL_MandatoryCatchall: + // In mandatory-catchall mode, we need to use + // _Unwind_Resume_or_Rethrow, or whatever the personality's + // equivalent is. + Builder.CreateCall(getUnwindResumeOrRethrowFn(), Exn) + ->setDoesNotReturn(); + break; + case CHL_MandatoryCleanup: { + // In mandatory-cleanup mode, we should use llvm.eh.resume. + llvm::Value *Selector = Builder.CreateLoad(getEHSelectorSlot()); + Builder.CreateCall2(CGM.getIntrinsic(llvm::Intrinsic::eh_resume), + Exn, Selector) + ->setDoesNotReturn(); + break; + } + case CHL_Ideal: + // In an idealized mode where we don't have to worry about the + // optimizer combining landing pads, we should just use + // _Unwind_Resume (or the personality's equivalent). + Builder.CreateCall(getUnwindResumeFn(), Exn) + ->setDoesNotReturn(); + break; + } + } - Builder.CreateCall(RethrowFn, Builder.CreateLoad(getExceptionSlot())) - ->setDoesNotReturn(); Builder.CreateUnreachable(); Builder.restoreIP(SavedIP); |
