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-//===-- EHScopeStack.h - Stack for cleanup IR generation --------*- C++ -*-===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// 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,
-
- InactiveCleanup = 0x4,
- InactiveEHCleanup = EHCleanup | InactiveCleanup,
- InactiveNormalCleanup = NormalCleanup | InactiveCleanup,
- InactiveNormalAndEHCleanup = NormalAndEHCleanup | InactiveCleanup,
-
- 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
- };
- 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; }
- };
-
-
- /// 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, llvm::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, llvm::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
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