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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 CLANG_CODEGEN_EHSCOPESTACK_H
+#define CLANG_CODEGEN_EHSCOPESTACK_H
+
+#include "clang/Basic/LLVM.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Value.h"
+#include "llvm/IR/Instructions.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 =
+ llvm::is_base_of<llvm::Value, T>::value &&
+ !llvm::is_base_of<llvm::Constant, T>::value &&
+ !llvm::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 {
+ EHCleanup = 0x1,
+ NormalCleanup = 0x2,
+ NormalAndEHCleanup = EHCleanup | NormalCleanup,
+
+ InactiveCleanup = 0x4,
+ InactiveEHCleanup = EHCleanup | InactiveCleanup,
+ InactiveNormalCleanup = NormalCleanup | InactiveCleanup,
+ InactiveNormalAndEHCleanup = NormalAndEHCleanup | InactiveCleanup
+};
+
+/// A stack of scopes which respond to exceptions, including cleanups
+/// and catch blocks.
+class EHScopeStack {
+public:
+ /// 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();
+ public:
+ /// 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; }
+ };
+
+ // Provide a virtual destructor to suppress a very common warning
+ // that unfortunately cannot be suppressed without this. Cleanups
+ // should not rely on this destructor ever being called.
+ virtual ~Cleanup() {}
+
+ /// 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;
+ };
+
+ /// ConditionalCleanupN stores the saved form of its N parameters,
+ /// then restores them and performs the cleanup.
+ template <class T, class A0>
+ class ConditionalCleanup1 : public Cleanup {
+ typedef typename DominatingValue<A0>::saved_type A0_saved;
+ A0_saved a0_saved;
+
+ void Emit(CodeGenFunction &CGF, Flags flags) {
+ A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
+ T(a0).Emit(CGF, flags);
+ }
+
+ public:
+ ConditionalCleanup1(A0_saved a0)
+ : a0_saved(a0) {}
+ };
+
+ template <class T, class A0, class A1>
+ class ConditionalCleanup2 : public Cleanup {
+ typedef typename DominatingValue<A0>::saved_type A0_saved;
+ typedef typename DominatingValue<A1>::saved_type A1_saved;
+ A0_saved a0_saved;
+ A1_saved a1_saved;
+
+ void Emit(CodeGenFunction &CGF, Flags flags) {
+ A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
+ A1 a1 = DominatingValue<A1>::restore(CGF, a1_saved);
+ T(a0, a1).Emit(CGF, flags);
+ }
+
+ public:
+ ConditionalCleanup2(A0_saved a0, A1_saved a1)
+ : a0_saved(a0), a1_saved(a1) {}
+ };
+
+ template <class T, class A0, class A1, class A2>
+ class ConditionalCleanup3 : public Cleanup {
+ typedef typename DominatingValue<A0>::saved_type A0_saved;
+ typedef typename DominatingValue<A1>::saved_type A1_saved;
+ typedef typename DominatingValue<A2>::saved_type A2_saved;
+ A0_saved a0_saved;
+ A1_saved a1_saved;
+ A2_saved a2_saved;
+
+ void Emit(CodeGenFunction &CGF, Flags flags) {
+ A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
+ A1 a1 = DominatingValue<A1>::restore(CGF, a1_saved);
+ A2 a2 = DominatingValue<A2>::restore(CGF, a2_saved);
+ T(a0, a1, a2).Emit(CGF, flags);
+ }
+
+ public:
+ ConditionalCleanup3(A0_saved a0, A1_saved a1, A2_saved a2)
+ : a0_saved(a0), a1_saved(a1), a2_saved(a2) {}
+ };
+
+ template <class T, class A0, class A1, class A2, class A3>
+ class ConditionalCleanup4 : public Cleanup {
+ typedef typename DominatingValue<A0>::saved_type A0_saved;
+ typedef typename DominatingValue<A1>::saved_type A1_saved;
+ typedef typename DominatingValue<A2>::saved_type A2_saved;
+ typedef typename DominatingValue<A3>::saved_type A3_saved;
+ A0_saved a0_saved;
+ A1_saved a1_saved;
+ A2_saved a2_saved;
+ A3_saved a3_saved;
+
+ void Emit(CodeGenFunction &CGF, Flags flags) {
+ A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
+ A1 a1 = DominatingValue<A1>::restore(CGF, a1_saved);
+ A2 a2 = DominatingValue<A2>::restore(CGF, a2_saved);
+ A3 a3 = DominatingValue<A3>::restore(CGF, a3_saved);
+ T(a0, a1, a2, a3).Emit(CGF, flags);
+ }
+
+ public:
+ ConditionalCleanup4(A0_saved a0, A1_saved a1, A2_saved a2, A3_saved a3)
+ : a0_saved(a0), a1_saved(a1), a2_saved(a2), a3_saved(a3) {}
+ };
+
+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 *pushCleanup(CleanupKind K, size_t DataSize);
+
+public:
+ EHScopeStack() : StartOfBuffer(0), EndOfBuffer(0), StartOfData(0),
+ InnermostNormalCleanup(stable_end()),
+ InnermostEHScope(stable_end()) {}
+ ~EHScopeStack() { delete[] StartOfBuffer; }
+
+ // Variadic templates would make this not terrible.
+
+ /// Push a lazily-created cleanup on the stack.
+ template <class T>
+ void pushCleanup(CleanupKind Kind) {
+ void *Buffer = pushCleanup(Kind, sizeof(T));
+ Cleanup *Obj = new(Buffer) T();
+ (void) Obj;
+ }
+
+ /// Push a lazily-created cleanup on the stack.
+ template <class T, class A0>
+ void pushCleanup(CleanupKind Kind, A0 a0) {
+ void *Buffer = pushCleanup(Kind, sizeof(T));
+ Cleanup *Obj = new(Buffer) T(a0);
+ (void) Obj;
+ }
+
+ /// Push a lazily-created cleanup on the stack.
+ template <class T, class A0, class A1>
+ void pushCleanup(CleanupKind Kind, A0 a0, A1 a1) {
+ void *Buffer = pushCleanup(Kind, sizeof(T));
+ Cleanup *Obj = new(Buffer) T(a0, a1);
+ (void) Obj;
+ }
+
+ /// Push a lazily-created cleanup on the stack.
+ template <class T, class A0, class A1, class A2>
+ void pushCleanup(CleanupKind Kind, A0 a0, A1 a1, A2 a2) {
+ void *Buffer = pushCleanup(Kind, sizeof(T));
+ Cleanup *Obj = new(Buffer) T(a0, a1, a2);
+ (void) Obj;
+ }
+
+ /// Push a lazily-created cleanup on the stack.
+ template <class T, class A0, class A1, class A2, class A3>
+ void pushCleanup(CleanupKind Kind, A0 a0, A1 a1, A2 a2, A3 a3) {
+ void *Buffer = pushCleanup(Kind, sizeof(T));
+ Cleanup *Obj = new(Buffer) T(a0, a1, a2, a3);
+ (void) Obj;
+ }
+
+ /// Push a lazily-created cleanup on the stack.
+ template <class T, class A0, class A1, class A2, class A3, class A4>
+ void pushCleanup(CleanupKind Kind, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+ void *Buffer = pushCleanup(Kind, sizeof(T));
+ Cleanup *Obj = new(Buffer) T(a0, a1, a2, a3, a4);
+ (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 A0, class A1, class A2>
+ T *pushCleanupWithExtra(CleanupKind Kind, size_t N, A0 a0, A1 a1, A2 a2) {
+ void *Buffer = pushCleanup(Kind, sizeof(T) + T::getExtraSize(N));
+ return new (Buffer) T(N, a0, a1, a2);
+ }
+
+ 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();
+
+ /// Determines whether the exception-scopes stack is empty.
+ bool empty() const { return StartOfData == EndOfBuffer; }
+
+ bool requiresLandingPad() const {
+ return InnermostEHScope != stable_end();
+ }
+
+ /// 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;
+ }
+
+ stable_iterator getInnermostActiveEHScope() const;
+
+ /// 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;
+
+ /// Removes the cleanup pointed to by the given stable_iterator.
+ void removeCleanup(stable_iterator save);
+
+ /// 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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