489 lines
17 KiB
C++
489 lines
17 KiB
C++
//===-- EHScopeStack.h - Stack for cleanup IR generation --------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// These classes should be the minimum interface required for other parts of
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// CodeGen to emit cleanups. The implementation is in CGCleanup.cpp and other
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// implemenentation details that are not widely needed are in CGCleanup.h.
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//
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//===----------------------------------------------------------------------===//
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#ifndef CLANG_CODEGEN_EHSCOPESTACK_H
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#define CLANG_CODEGEN_EHSCOPESTACK_H
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#include "clang/Basic/LLVM.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Value.h"
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#include "llvm/IR/Instructions.h"
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namespace clang {
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namespace CodeGen {
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class CodeGenFunction;
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/// A branch fixup. These are required when emitting a goto to a
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/// label which hasn't been emitted yet. The goto is optimistically
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/// emitted as a branch to the basic block for the label, and (if it
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/// occurs in a scope with non-trivial cleanups) a fixup is added to
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/// the innermost cleanup. When a (normal) cleanup is popped, any
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/// unresolved fixups in that scope are threaded through the cleanup.
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struct BranchFixup {
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/// The block containing the terminator which needs to be modified
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/// into a switch if this fixup is resolved into the current scope.
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/// If null, LatestBranch points directly to the destination.
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llvm::BasicBlock *OptimisticBranchBlock;
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/// The ultimate destination of the branch.
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///
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/// This can be set to null to indicate that this fixup was
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/// successfully resolved.
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llvm::BasicBlock *Destination;
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/// The destination index value.
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unsigned DestinationIndex;
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/// The initial branch of the fixup.
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llvm::BranchInst *InitialBranch;
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};
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template <class T> struct InvariantValue {
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typedef T type;
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typedef T saved_type;
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static bool needsSaving(type value) { return false; }
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static saved_type save(CodeGenFunction &CGF, type value) { return value; }
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static type restore(CodeGenFunction &CGF, saved_type value) { return value; }
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};
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/// A metaprogramming class for ensuring that a value will dominate an
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/// arbitrary position in a function.
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template <class T> struct DominatingValue : InvariantValue<T> {};
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template <class T, bool mightBeInstruction =
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llvm::is_base_of<llvm::Value, T>::value &&
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!llvm::is_base_of<llvm::Constant, T>::value &&
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!llvm::is_base_of<llvm::BasicBlock, T>::value>
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struct DominatingPointer;
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template <class T> struct DominatingPointer<T,false> : InvariantValue<T*> {};
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// template <class T> struct DominatingPointer<T,true> at end of file
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template <class T> struct DominatingValue<T*> : DominatingPointer<T> {};
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enum CleanupKind {
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EHCleanup = 0x1,
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NormalCleanup = 0x2,
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NormalAndEHCleanup = EHCleanup | NormalCleanup,
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InactiveCleanup = 0x4,
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InactiveEHCleanup = EHCleanup | InactiveCleanup,
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InactiveNormalCleanup = NormalCleanup | InactiveCleanup,
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InactiveNormalAndEHCleanup = NormalAndEHCleanup | InactiveCleanup
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};
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/// A stack of scopes which respond to exceptions, including cleanups
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/// and catch blocks.
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class EHScopeStack {
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public:
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/// A saved depth on the scope stack. This is necessary because
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/// pushing scopes onto the stack invalidates iterators.
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class stable_iterator {
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friend class EHScopeStack;
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/// Offset from StartOfData to EndOfBuffer.
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ptrdiff_t Size;
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stable_iterator(ptrdiff_t Size) : Size(Size) {}
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public:
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static stable_iterator invalid() { return stable_iterator(-1); }
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stable_iterator() : Size(-1) {}
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bool isValid() const { return Size >= 0; }
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/// Returns true if this scope encloses I.
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/// Returns false if I is invalid.
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/// This scope must be valid.
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bool encloses(stable_iterator I) const { return Size <= I.Size; }
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/// Returns true if this scope strictly encloses I: that is,
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/// if it encloses I and is not I.
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/// Returns false is I is invalid.
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/// This scope must be valid.
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bool strictlyEncloses(stable_iterator I) const { return Size < I.Size; }
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friend bool operator==(stable_iterator A, stable_iterator B) {
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return A.Size == B.Size;
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}
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friend bool operator!=(stable_iterator A, stable_iterator B) {
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return A.Size != B.Size;
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}
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};
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/// Information for lazily generating a cleanup. Subclasses must be
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/// POD-like: cleanups will not be destructed, and they will be
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/// allocated on the cleanup stack and freely copied and moved
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/// around.
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///
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/// Cleanup implementations should generally be declared in an
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/// anonymous namespace.
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class Cleanup {
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// Anchor the construction vtable.
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virtual void anchor();
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public:
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/// Generation flags.
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class Flags {
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enum {
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F_IsForEH = 0x1,
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F_IsNormalCleanupKind = 0x2,
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F_IsEHCleanupKind = 0x4
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};
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unsigned flags;
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public:
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Flags() : flags(0) {}
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/// isForEH - true if the current emission is for an EH cleanup.
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bool isForEHCleanup() const { return flags & F_IsForEH; }
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bool isForNormalCleanup() const { return !isForEHCleanup(); }
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void setIsForEHCleanup() { flags |= F_IsForEH; }
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bool isNormalCleanupKind() const { return flags & F_IsNormalCleanupKind; }
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void setIsNormalCleanupKind() { flags |= F_IsNormalCleanupKind; }
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/// isEHCleanupKind - true if the cleanup was pushed as an EH
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/// cleanup.
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bool isEHCleanupKind() const { return flags & F_IsEHCleanupKind; }
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void setIsEHCleanupKind() { flags |= F_IsEHCleanupKind; }
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};
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// Provide a virtual destructor to suppress a very common warning
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// that unfortunately cannot be suppressed without this. Cleanups
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// should not rely on this destructor ever being called.
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virtual ~Cleanup() {}
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/// Emit the cleanup. For normal cleanups, this is run in the
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/// same EH context as when the cleanup was pushed, i.e. the
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/// immediately-enclosing context of the cleanup scope. For
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/// EH cleanups, this is run in a terminate context.
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///
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// \param flags cleanup kind.
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virtual void Emit(CodeGenFunction &CGF, Flags flags) = 0;
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};
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/// ConditionalCleanupN stores the saved form of its N parameters,
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/// then restores them and performs the cleanup.
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template <class T, class A0>
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class ConditionalCleanup1 : public Cleanup {
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typedef typename DominatingValue<A0>::saved_type A0_saved;
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A0_saved a0_saved;
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void Emit(CodeGenFunction &CGF, Flags flags) {
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A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
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T(a0).Emit(CGF, flags);
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}
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public:
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ConditionalCleanup1(A0_saved a0)
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: a0_saved(a0) {}
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};
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template <class T, class A0, class A1>
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class ConditionalCleanup2 : public Cleanup {
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typedef typename DominatingValue<A0>::saved_type A0_saved;
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typedef typename DominatingValue<A1>::saved_type A1_saved;
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A0_saved a0_saved;
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A1_saved a1_saved;
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void Emit(CodeGenFunction &CGF, Flags flags) {
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A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
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A1 a1 = DominatingValue<A1>::restore(CGF, a1_saved);
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T(a0, a1).Emit(CGF, flags);
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}
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public:
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ConditionalCleanup2(A0_saved a0, A1_saved a1)
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: a0_saved(a0), a1_saved(a1) {}
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};
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template <class T, class A0, class A1, class A2>
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class ConditionalCleanup3 : public Cleanup {
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typedef typename DominatingValue<A0>::saved_type A0_saved;
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typedef typename DominatingValue<A1>::saved_type A1_saved;
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typedef typename DominatingValue<A2>::saved_type A2_saved;
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A0_saved a0_saved;
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A1_saved a1_saved;
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A2_saved a2_saved;
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void Emit(CodeGenFunction &CGF, Flags flags) {
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A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
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A1 a1 = DominatingValue<A1>::restore(CGF, a1_saved);
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A2 a2 = DominatingValue<A2>::restore(CGF, a2_saved);
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T(a0, a1, a2).Emit(CGF, flags);
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}
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public:
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ConditionalCleanup3(A0_saved a0, A1_saved a1, A2_saved a2)
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: a0_saved(a0), a1_saved(a1), a2_saved(a2) {}
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};
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template <class T, class A0, class A1, class A2, class A3>
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class ConditionalCleanup4 : public Cleanup {
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typedef typename DominatingValue<A0>::saved_type A0_saved;
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typedef typename DominatingValue<A1>::saved_type A1_saved;
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typedef typename DominatingValue<A2>::saved_type A2_saved;
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typedef typename DominatingValue<A3>::saved_type A3_saved;
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A0_saved a0_saved;
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A1_saved a1_saved;
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A2_saved a2_saved;
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A3_saved a3_saved;
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void Emit(CodeGenFunction &CGF, Flags flags) {
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A0 a0 = DominatingValue<A0>::restore(CGF, a0_saved);
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A1 a1 = DominatingValue<A1>::restore(CGF, a1_saved);
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A2 a2 = DominatingValue<A2>::restore(CGF, a2_saved);
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A3 a3 = DominatingValue<A3>::restore(CGF, a3_saved);
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T(a0, a1, a2, a3).Emit(CGF, flags);
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}
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public:
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ConditionalCleanup4(A0_saved a0, A1_saved a1, A2_saved a2, A3_saved a3)
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: a0_saved(a0), a1_saved(a1), a2_saved(a2), a3_saved(a3) {}
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};
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private:
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// The implementation for this class is in CGException.h and
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// CGException.cpp; the definition is here because it's used as a
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// member of CodeGenFunction.
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/// The start of the scope-stack buffer, i.e. the allocated pointer
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/// for the buffer. All of these pointers are either simultaneously
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/// null or simultaneously valid.
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char *StartOfBuffer;
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/// The end of the buffer.
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char *EndOfBuffer;
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/// The first valid entry in the buffer.
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char *StartOfData;
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/// The innermost normal cleanup on the stack.
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stable_iterator InnermostNormalCleanup;
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/// The innermost EH scope on the stack.
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stable_iterator InnermostEHScope;
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/// The current set of branch fixups. A branch fixup is a jump to
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/// an as-yet unemitted label, i.e. a label for which we don't yet
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/// know the EH stack depth. Whenever we pop a cleanup, we have
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/// to thread all the current branch fixups through it.
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///
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/// Fixups are recorded as the Use of the respective branch or
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/// switch statement. The use points to the final destination.
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/// When popping out of a cleanup, these uses are threaded through
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/// the cleanup and adjusted to point to the new cleanup.
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///
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/// Note that branches are allowed to jump into protected scopes
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/// in certain situations; e.g. the following code is legal:
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/// struct A { ~A(); }; // trivial ctor, non-trivial dtor
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/// goto foo;
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/// A a;
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/// foo:
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/// bar();
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SmallVector<BranchFixup, 8> BranchFixups;
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char *allocate(size_t Size);
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void *pushCleanup(CleanupKind K, size_t DataSize);
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public:
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EHScopeStack() : StartOfBuffer(0), EndOfBuffer(0), StartOfData(0),
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InnermostNormalCleanup(stable_end()),
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InnermostEHScope(stable_end()) {}
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~EHScopeStack() { delete[] StartOfBuffer; }
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// Variadic templates would make this not terrible.
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/// Push a lazily-created cleanup on the stack.
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template <class T>
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void pushCleanup(CleanupKind Kind) {
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void *Buffer = pushCleanup(Kind, sizeof(T));
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Cleanup *Obj = new(Buffer) T();
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(void) Obj;
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}
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/// Push a lazily-created cleanup on the stack.
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template <class T, class A0>
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void pushCleanup(CleanupKind Kind, A0 a0) {
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void *Buffer = pushCleanup(Kind, sizeof(T));
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Cleanup *Obj = new(Buffer) T(a0);
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(void) Obj;
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}
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/// Push a lazily-created cleanup on the stack.
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template <class T, class A0, class A1>
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void pushCleanup(CleanupKind Kind, A0 a0, A1 a1) {
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void *Buffer = pushCleanup(Kind, sizeof(T));
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Cleanup *Obj = new(Buffer) T(a0, a1);
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(void) Obj;
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}
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/// Push a lazily-created cleanup on the stack.
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template <class T, class A0, class A1, class A2>
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void pushCleanup(CleanupKind Kind, A0 a0, A1 a1, A2 a2) {
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void *Buffer = pushCleanup(Kind, sizeof(T));
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Cleanup *Obj = new(Buffer) T(a0, a1, a2);
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(void) Obj;
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}
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/// Push a lazily-created cleanup on the stack.
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template <class T, class A0, class A1, class A2, class A3>
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void pushCleanup(CleanupKind Kind, A0 a0, A1 a1, A2 a2, A3 a3) {
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void *Buffer = pushCleanup(Kind, sizeof(T));
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Cleanup *Obj = new(Buffer) T(a0, a1, a2, a3);
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(void) Obj;
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}
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/// Push a lazily-created cleanup on the stack.
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template <class T, class A0, class A1, class A2, class A3, class A4>
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void pushCleanup(CleanupKind Kind, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
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void *Buffer = pushCleanup(Kind, sizeof(T));
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Cleanup *Obj = new(Buffer) T(a0, a1, a2, a3, a4);
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(void) Obj;
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}
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// Feel free to add more variants of the following:
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/// Push a cleanup with non-constant storage requirements on the
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/// stack. The cleanup type must provide an additional static method:
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/// static size_t getExtraSize(size_t);
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/// The argument to this method will be the value N, which will also
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/// be passed as the first argument to the constructor.
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///
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/// The data stored in the extra storage must obey the same
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/// restrictions as normal cleanup member data.
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///
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/// The pointer returned from this method is valid until the cleanup
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/// stack is modified.
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template <class T, class A0, class A1, class A2>
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T *pushCleanupWithExtra(CleanupKind Kind, size_t N, A0 a0, A1 a1, A2 a2) {
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void *Buffer = pushCleanup(Kind, sizeof(T) + T::getExtraSize(N));
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return new (Buffer) T(N, a0, a1, a2);
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}
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void pushCopyOfCleanup(CleanupKind Kind, const void *Cleanup, size_t Size) {
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void *Buffer = pushCleanup(Kind, Size);
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std::memcpy(Buffer, Cleanup, Size);
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}
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/// Pops a cleanup scope off the stack. This is private to CGCleanup.cpp.
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void popCleanup();
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/// Push a set of catch handlers on the stack. The catch is
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/// uninitialized and will need to have the given number of handlers
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/// set on it.
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class EHCatchScope *pushCatch(unsigned NumHandlers);
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/// Pops a catch scope off the stack. This is private to CGException.cpp.
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void popCatch();
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/// Push an exceptions filter on the stack.
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class EHFilterScope *pushFilter(unsigned NumFilters);
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/// Pops an exceptions filter off the stack.
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void popFilter();
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/// Push a terminate handler on the stack.
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void pushTerminate();
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/// Pops a terminate handler off the stack.
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void popTerminate();
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/// Determines whether the exception-scopes stack is empty.
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bool empty() const { return StartOfData == EndOfBuffer; }
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bool requiresLandingPad() const {
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return InnermostEHScope != stable_end();
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}
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/// Determines whether there are any normal cleanups on the stack.
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bool hasNormalCleanups() const {
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return InnermostNormalCleanup != stable_end();
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}
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/// Returns the innermost normal cleanup on the stack, or
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/// stable_end() if there are no normal cleanups.
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stable_iterator getInnermostNormalCleanup() const {
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return InnermostNormalCleanup;
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}
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stable_iterator getInnermostActiveNormalCleanup() const;
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stable_iterator getInnermostEHScope() const {
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return InnermostEHScope;
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}
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stable_iterator getInnermostActiveEHScope() const;
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/// An unstable reference to a scope-stack depth. Invalidated by
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/// pushes but not pops.
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class iterator;
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/// Returns an iterator pointing to the innermost EH scope.
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iterator begin() const;
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/// Returns an iterator pointing to the outermost EH scope.
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iterator end() const;
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/// Create a stable reference to the top of the EH stack. The
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/// returned reference is valid until that scope is popped off the
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/// stack.
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stable_iterator stable_begin() const {
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return stable_iterator(EndOfBuffer - StartOfData);
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}
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/// Create a stable reference to the bottom of the EH stack.
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static stable_iterator stable_end() {
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return stable_iterator(0);
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}
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/// Translates an iterator into a stable_iterator.
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stable_iterator stabilize(iterator it) const;
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/// Turn a stable reference to a scope depth into a unstable pointer
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/// to the EH stack.
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iterator find(stable_iterator save) const;
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/// Removes the cleanup pointed to by the given stable_iterator.
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void removeCleanup(stable_iterator save);
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/// Add a branch fixup to the current cleanup scope.
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BranchFixup &addBranchFixup() {
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assert(hasNormalCleanups() && "adding fixup in scope without cleanups");
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BranchFixups.push_back(BranchFixup());
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return BranchFixups.back();
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}
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unsigned getNumBranchFixups() const { return BranchFixups.size(); }
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BranchFixup &getBranchFixup(unsigned I) {
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assert(I < getNumBranchFixups());
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return BranchFixups[I];
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}
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/// Pops lazily-removed fixups from the end of the list. This
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/// should only be called by procedures which have just popped a
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/// cleanup or resolved one or more fixups.
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void popNullFixups();
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/// Clears the branch-fixups list. This should only be called by
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/// ResolveAllBranchFixups.
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void clearFixups() { BranchFixups.clear(); }
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};
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} // namespace CodeGen
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} // namespace clang
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#endif
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