| //===-- EHScopeStack.h - Stack for cleanup IR generation --------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // These classes should be the minimum interface required for other parts of |
| // CodeGen to emit cleanups. The implementation is in CGCleanup.cpp and other |
| // implemenentation details that are not widely needed are in CGCleanup.h. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CLANG_LIB_CODEGEN_EHSCOPESTACK_H |
| #define LLVM_CLANG_LIB_CODEGEN_EHSCOPESTACK_H |
| |
| #include "clang/Basic/LLVM.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Value.h" |
| |
| namespace clang { |
| namespace CodeGen { |
| |
| class CodeGenFunction; |
| |
| /// A branch fixup. These are required when emitting a goto to a |
| /// label which hasn't been emitted yet. The goto is optimistically |
| /// emitted as a branch to the basic block for the label, and (if it |
| /// occurs in a scope with non-trivial cleanups) a fixup is added to |
| /// the innermost cleanup. When a (normal) cleanup is popped, any |
| /// unresolved fixups in that scope are threaded through the cleanup. |
| struct BranchFixup { |
| /// The block containing the terminator which needs to be modified |
| /// into a switch if this fixup is resolved into the current scope. |
| /// If null, LatestBranch points directly to the destination. |
| llvm::BasicBlock *OptimisticBranchBlock; |
| |
| /// The ultimate destination of the branch. |
| /// |
| /// This can be set to null to indicate that this fixup was |
| /// successfully resolved. |
| llvm::BasicBlock *Destination; |
| |
| /// The destination index value. |
| unsigned DestinationIndex; |
| |
| /// The initial branch of the fixup. |
| llvm::BranchInst *InitialBranch; |
| }; |
| |
| template <class T> struct InvariantValue { |
| typedef T type; |
| typedef T saved_type; |
| static bool needsSaving(type value) { return false; } |
| static saved_type save(CodeGenFunction &CGF, type value) { return value; } |
| static type restore(CodeGenFunction &CGF, saved_type value) { return value; } |
| }; |
| |
| /// A metaprogramming class for ensuring that a value will dominate an |
| /// arbitrary position in a function. |
| template <class T> struct DominatingValue : InvariantValue<T> {}; |
| |
| template <class T, bool mightBeInstruction = |
| std::is_base_of<llvm::Value, T>::value && |
| !std::is_base_of<llvm::Constant, T>::value && |
| !std::is_base_of<llvm::BasicBlock, T>::value> |
| struct DominatingPointer; |
| template <class T> struct DominatingPointer<T,false> : InvariantValue<T*> {}; |
| // template <class T> struct DominatingPointer<T,true> at end of file |
| |
| template <class T> struct DominatingValue<T*> : DominatingPointer<T> {}; |
| |
| enum CleanupKind : unsigned { |
| /// Denotes a cleanup that should run when a scope is exited using exceptional |
| /// control flow (a throw statement leading to stack unwinding, ). |
| EHCleanup = 0x1, |
| |
| /// Denotes a cleanup that should run when a scope is exited using normal |
| /// control flow (falling off the end of the scope, return, goto, ...). |
| NormalCleanup = 0x2, |
| |
| NormalAndEHCleanup = EHCleanup | NormalCleanup, |
| |
| LifetimeMarker = 0x8, |
| NormalEHLifetimeMarker = LifetimeMarker | NormalAndEHCleanup, |
| }; |
| |
| /// A stack of scopes which respond to exceptions, including cleanups |
| /// and catch blocks. |
| class EHScopeStack { |
| public: |
| /* Should switch to alignof(uint64_t) instead of 8, when EHCleanupScope can */ |
| enum { ScopeStackAlignment = 8 }; |
| |
| /// A saved depth on the scope stack. This is necessary because |
| /// pushing scopes onto the stack invalidates iterators. |
| class stable_iterator { |
| friend class EHScopeStack; |
| |
| /// Offset from StartOfData to EndOfBuffer. |
| ptrdiff_t Size; |
| |
| stable_iterator(ptrdiff_t Size) : Size(Size) {} |
| |
| public: |
| static stable_iterator invalid() { return stable_iterator(-1); } |
| stable_iterator() : Size(-1) {} |
| |
| bool isValid() const { return Size >= 0; } |
| |
| /// Returns true if this scope encloses I. |
| /// Returns false if I is invalid. |
| /// This scope must be valid. |
| bool encloses(stable_iterator I) const { return Size <= I.Size; } |
| |
| /// Returns true if this scope strictly encloses I: that is, |
| /// if it encloses I and is not I. |
| /// Returns false is I is invalid. |
| /// This scope must be valid. |
| bool strictlyEncloses(stable_iterator I) const { return Size < I.Size; } |
| |
| friend bool operator==(stable_iterator A, stable_iterator B) { |
| return A.Size == B.Size; |
| } |
| friend bool operator!=(stable_iterator A, stable_iterator B) { |
| return A.Size != B.Size; |
| } |
| }; |
| |
| /// Information for lazily generating a cleanup. Subclasses must be |
| /// POD-like: cleanups will not be destructed, and they will be |
| /// allocated on the cleanup stack and freely copied and moved |
| /// around. |
| /// |
| /// Cleanup implementations should generally be declared in an |
| /// anonymous namespace. |
| class Cleanup { |
| // Anchor the construction vtable. |
| virtual void anchor(); |
| |
| protected: |
| ~Cleanup() = default; |
| |
| public: |
| Cleanup(const Cleanup &) = default; |
| Cleanup(Cleanup &&) {} |
| Cleanup() = default; |
| |
| /// Generation flags. |
| class Flags { |
| enum { |
| F_IsForEH = 0x1, |
| F_IsNormalCleanupKind = 0x2, |
| F_IsEHCleanupKind = 0x4, |
| F_HasExitSwitch = 0x8, |
| }; |
| unsigned flags; |
| |
| public: |
| Flags() : flags(0) {} |
| |
| /// isForEH - true if the current emission is for an EH cleanup. |
| bool isForEHCleanup() const { return flags & F_IsForEH; } |
| bool isForNormalCleanup() const { return !isForEHCleanup(); } |
| void setIsForEHCleanup() { flags |= F_IsForEH; } |
| |
| bool isNormalCleanupKind() const { return flags & F_IsNormalCleanupKind; } |
| void setIsNormalCleanupKind() { flags |= F_IsNormalCleanupKind; } |
| |
| /// isEHCleanupKind - true if the cleanup was pushed as an EH |
| /// cleanup. |
| bool isEHCleanupKind() const { return flags & F_IsEHCleanupKind; } |
| void setIsEHCleanupKind() { flags |= F_IsEHCleanupKind; } |
| |
| bool hasExitSwitch() const { return flags & F_HasExitSwitch; } |
| void setHasExitSwitch() { flags |= F_HasExitSwitch; } |
| }; |
| |
| /// Emit the cleanup. For normal cleanups, this is run in the |
| /// same EH context as when the cleanup was pushed, i.e. the |
| /// immediately-enclosing context of the cleanup scope. For |
| /// EH cleanups, this is run in a terminate context. |
| /// |
| // \param flags cleanup kind. |
| virtual void Emit(CodeGenFunction &CGF, Flags flags) = 0; |
| }; |
| |
| /// ConditionalCleanup stores the saved form of its parameters, |
| /// then restores them and performs the cleanup. |
| template <class T, class... As> |
| class ConditionalCleanup final : public Cleanup { |
| typedef std::tuple<typename DominatingValue<As>::saved_type...> SavedTuple; |
| SavedTuple Saved; |
| |
| template <std::size_t... Is> |
| T restore(CodeGenFunction &CGF, std::index_sequence<Is...>) { |
| // It's important that the restores are emitted in order. The braced init |
| // list guarantees that. |
| return T{DominatingValue<As>::restore(CGF, std::get<Is>(Saved))...}; |
| } |
| |
| void Emit(CodeGenFunction &CGF, Flags flags) override { |
| restore(CGF, std::index_sequence_for<As...>()).Emit(CGF, flags); |
| } |
| |
| public: |
| ConditionalCleanup(typename DominatingValue<As>::saved_type... A) |
| : Saved(A...) {} |
| |
| ConditionalCleanup(SavedTuple Tuple) : Saved(std::move(Tuple)) {} |
| }; |
| |
| private: |
| // The implementation for this class is in CGException.h and |
| // CGException.cpp; the definition is here because it's used as a |
| // member of CodeGenFunction. |
| |
| /// The start of the scope-stack buffer, i.e. the allocated pointer |
| /// for the buffer. All of these pointers are either simultaneously |
| /// null or simultaneously valid. |
| char *StartOfBuffer; |
| |
| /// The end of the buffer. |
| char *EndOfBuffer; |
| |
| /// The first valid entry in the buffer. |
| char *StartOfData; |
| |
| /// The innermost normal cleanup on the stack. |
| stable_iterator InnermostNormalCleanup; |
| |
| /// The innermost EH scope on the stack. |
| stable_iterator InnermostEHScope; |
| |
| /// The current set of branch fixups. A branch fixup is a jump to |
| /// an as-yet unemitted label, i.e. a label for which we don't yet |
| /// know the EH stack depth. Whenever we pop a cleanup, we have |
| /// to thread all the current branch fixups through it. |
| /// |
| /// Fixups are recorded as the Use of the respective branch or |
| /// switch statement. The use points to the final destination. |
| /// When popping out of a cleanup, these uses are threaded through |
| /// the cleanup and adjusted to point to the new cleanup. |
| /// |
| /// Note that branches are allowed to jump into protected scopes |
| /// in certain situations; e.g. the following code is legal: |
| /// struct A { ~A(); }; // trivial ctor, non-trivial dtor |
| /// goto foo; |
| /// A a; |
| /// foo: |
| /// bar(); |
| SmallVector<BranchFixup, 8> BranchFixups; |
| |
| char *allocate(size_t Size); |
| void deallocate(size_t Size); |
| |
| void *pushCleanup(CleanupKind K, size_t DataSize); |
| |
| public: |
| EHScopeStack() : StartOfBuffer(nullptr), EndOfBuffer(nullptr), |
| StartOfData(nullptr), InnermostNormalCleanup(stable_end()), |
| InnermostEHScope(stable_end()) {} |
| ~EHScopeStack() { delete[] StartOfBuffer; } |
| |
| /// Push a lazily-created cleanup on the stack. |
| template <class T, class... As> void pushCleanup(CleanupKind Kind, As... A) { |
| static_assert(alignof(T) <= ScopeStackAlignment, |
| "Cleanup's alignment is too large."); |
| void *Buffer = pushCleanup(Kind, sizeof(T)); |
| Cleanup *Obj = new (Buffer) T(A...); |
| (void) Obj; |
| } |
| |
| /// Push a lazily-created cleanup on the stack. Tuple version. |
| template <class T, class... As> |
| void pushCleanupTuple(CleanupKind Kind, std::tuple<As...> A) { |
| static_assert(alignof(T) <= ScopeStackAlignment, |
| "Cleanup's alignment is too large."); |
| void *Buffer = pushCleanup(Kind, sizeof(T)); |
| Cleanup *Obj = new (Buffer) T(std::move(A)); |
| (void) Obj; |
| } |
| |
| // Feel free to add more variants of the following: |
| |
| /// Push a cleanup with non-constant storage requirements on the |
| /// stack. The cleanup type must provide an additional static method: |
| /// static size_t getExtraSize(size_t); |
| /// The argument to this method will be the value N, which will also |
| /// be passed as the first argument to the constructor. |
| /// |
| /// The data stored in the extra storage must obey the same |
| /// restrictions as normal cleanup member data. |
| /// |
| /// The pointer returned from this method is valid until the cleanup |
| /// stack is modified. |
| template <class T, class... As> |
| T *pushCleanupWithExtra(CleanupKind Kind, size_t N, As... A) { |
| static_assert(alignof(T) <= ScopeStackAlignment, |
| "Cleanup's alignment is too large."); |
| void *Buffer = pushCleanup(Kind, sizeof(T) + T::getExtraSize(N)); |
| return new (Buffer) T(N, A...); |
| } |
| |
| void pushCopyOfCleanup(CleanupKind Kind, const void *Cleanup, size_t Size) { |
| void *Buffer = pushCleanup(Kind, Size); |
| std::memcpy(Buffer, Cleanup, Size); |
| } |
| |
| /// Pops a cleanup scope off the stack. This is private to CGCleanup.cpp. |
| void popCleanup(); |
| |
| /// Push a set of catch handlers on the stack. The catch is |
| /// uninitialized and will need to have the given number of handlers |
| /// set on it. |
| class EHCatchScope *pushCatch(unsigned NumHandlers); |
| |
| /// Pops a catch scope off the stack. This is private to CGException.cpp. |
| void popCatch(); |
| |
| /// Push an exceptions filter on the stack. |
| class EHFilterScope *pushFilter(unsigned NumFilters); |
| |
| /// Pops an exceptions filter off the stack. |
| void popFilter(); |
| |
| /// Push a terminate handler on the stack. |
| void pushTerminate(); |
| |
| /// Pops a terminate handler off the stack. |
| void popTerminate(); |
| |
| // Returns true iff the current scope is either empty or contains only |
| // lifetime markers, i.e. no real cleanup code |
| bool containsOnlyLifetimeMarkers(stable_iterator Old) const; |
| |
| /// Determines whether the exception-scopes stack is empty. |
| bool empty() const { return StartOfData == EndOfBuffer; } |
| |
| bool requiresLandingPad() const; |
| |
| /// Determines whether there are any normal cleanups on the stack. |
| bool hasNormalCleanups() const { |
| return InnermostNormalCleanup != stable_end(); |
| } |
| |
| /// Returns the innermost normal cleanup on the stack, or |
| /// stable_end() if there are no normal cleanups. |
| stable_iterator getInnermostNormalCleanup() const { |
| return InnermostNormalCleanup; |
| } |
| stable_iterator getInnermostActiveNormalCleanup() const; |
| |
| stable_iterator getInnermostEHScope() const { |
| return InnermostEHScope; |
| } |
| |
| |
| /// An unstable reference to a scope-stack depth. Invalidated by |
| /// pushes but not pops. |
| class iterator; |
| |
| /// Returns an iterator pointing to the innermost EH scope. |
| iterator begin() const; |
| |
| /// Returns an iterator pointing to the outermost EH scope. |
| iterator end() const; |
| |
| /// Create a stable reference to the top of the EH stack. The |
| /// returned reference is valid until that scope is popped off the |
| /// stack. |
| stable_iterator stable_begin() const { |
| return stable_iterator(EndOfBuffer - StartOfData); |
| } |
| |
| /// Create a stable reference to the bottom of the EH stack. |
| static stable_iterator stable_end() { |
| return stable_iterator(0); |
| } |
| |
| /// Translates an iterator into a stable_iterator. |
| stable_iterator stabilize(iterator it) const; |
| |
| /// Turn a stable reference to a scope depth into a unstable pointer |
| /// to the EH stack. |
| iterator find(stable_iterator save) const; |
| |
| /// Add a branch fixup to the current cleanup scope. |
| BranchFixup &addBranchFixup() { |
| assert(hasNormalCleanups() && "adding fixup in scope without cleanups"); |
| BranchFixups.push_back(BranchFixup()); |
| return BranchFixups.back(); |
| } |
| |
| unsigned getNumBranchFixups() const { return BranchFixups.size(); } |
| BranchFixup &getBranchFixup(unsigned I) { |
| assert(I < getNumBranchFixups()); |
| return BranchFixups[I]; |
| } |
| |
| /// Pops lazily-removed fixups from the end of the list. This |
| /// should only be called by procedures which have just popped a |
| /// cleanup or resolved one or more fixups. |
| void popNullFixups(); |
| |
| /// Clears the branch-fixups list. This should only be called by |
| /// ResolveAllBranchFixups. |
| void clearFixups() { BranchFixups.clear(); } |
| }; |
| |
| } // namespace CodeGen |
| } // namespace clang |
| |
| #endif |