llvm-project/clang/lib/AST/Interp/Pointer.h

354 lines
11 KiB
C++

//===--- Pointer.h - Types for the constexpr VM -----------------*- 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
//
//===----------------------------------------------------------------------===//
//
// Defines the classes responsible for pointer tracking.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_AST_INTERP_POINTER_H
#define LLVM_CLANG_AST_INTERP_POINTER_H
#include "Descriptor.h"
#include "InterpBlock.h"
#include "clang/AST/ComparisonCategories.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/Expr.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/Support/raw_ostream.h"
namespace clang {
namespace interp {
class Block;
class DeadBlock;
class Context;
class InterpState;
class Pointer;
class Function;
enum PrimType : unsigned;
/// A pointer to a memory block, live or dead.
///
/// This object can be allocated into interpreter stack frames. If pointing to
/// a live block, it is a link in the chain of pointers pointing to the block.
class Pointer {
private:
static constexpr unsigned PastEndMark = (unsigned)-1;
static constexpr unsigned RootPtrMark = (unsigned)-1;
public:
Pointer() {}
Pointer(Block *B);
Pointer(const Pointer &P);
Pointer(Pointer &&P);
~Pointer();
void operator=(const Pointer &P);
void operator=(Pointer &&P);
/// Converts the pointer to an APValue.
APValue toAPValue() const;
/// Offsets a pointer inside an array.
Pointer atIndex(unsigned Idx) const {
if (Base == RootPtrMark)
return Pointer(Pointee, RootPtrMark, getDeclDesc()->getSize());
unsigned Off = Idx * elemSize();
if (getFieldDesc()->ElemDesc)
Off += sizeof(InlineDescriptor);
else
Off += sizeof(InitMap *);
return Pointer(Pointee, Base, Base + Off);
}
/// Creates a pointer to a field.
Pointer atField(unsigned Off) const {
unsigned Field = Offset + Off;
return Pointer(Pointee, Field, Field);
}
/// Restricts the scope of an array element pointer.
Pointer narrow() const {
// Null pointers cannot be narrowed.
if (isZero() || isUnknownSizeArray())
return *this;
// Pointer to an array of base types - enter block.
if (Base == RootPtrMark)
return Pointer(Pointee, 0, Offset == 0 ? Offset : PastEndMark);
// Pointer is one past end - magic offset marks that.
if (isOnePastEnd())
return Pointer(Pointee, Base, PastEndMark);
// Primitive arrays are a bit special since they do not have inline
// descriptors. If Offset != Base, then the pointer already points to
// an element and there is nothing to do. Otherwise, the pointer is
// adjusted to the first element of the array.
if (inPrimitiveArray()) {
if (Offset != Base)
return *this;
return Pointer(Pointee, Base, Offset + sizeof(InitMap *));
}
// Pointer is to a field or array element - enter it.
if (Offset != Base)
return Pointer(Pointee, Offset, Offset);
// Enter the first element of an array.
if (!getFieldDesc()->isArray())
return *this;
const unsigned NewBase = Base + sizeof(InlineDescriptor);
return Pointer(Pointee, NewBase, NewBase);
}
/// Expands a pointer to the containing array, undoing narrowing.
Pointer expand() const {
if (isElementPastEnd()) {
// Revert to an outer one-past-end pointer.
unsigned Adjust;
if (inPrimitiveArray())
Adjust = sizeof(InitMap *);
else
Adjust = sizeof(InlineDescriptor);
return Pointer(Pointee, Base, Base + getSize() + Adjust);
}
// Do not step out of array elements.
if (Base != Offset)
return *this;
// If at base, point to an array of base types.
if (Base == 0)
return Pointer(Pointee, RootPtrMark, 0);
// Step into the containing array, if inside one.
unsigned Next = Base - getInlineDesc()->Offset;
Descriptor *Desc = Next == 0 ? getDeclDesc() : getDescriptor(Next)->Desc;
if (!Desc->IsArray)
return *this;
return Pointer(Pointee, Next, Offset);
}
/// Checks if the pointer is null.
bool isZero() const { return Pointee == nullptr; }
/// Checks if the pointer is live.
bool isLive() const { return Pointee && !Pointee->IsDead; }
/// Checks if the item is a field in an object.
bool isField() const { return Base != 0 && Base != RootPtrMark; }
/// Accessor for information about the declaration site.
Descriptor *getDeclDesc() const { return Pointee->Desc; }
SourceLocation getDeclLoc() const { return getDeclDesc()->getLocation(); }
/// Returns a pointer to the object of which this pointer is a field.
Pointer getBase() const {
if (Base == RootPtrMark) {
assert(Offset == PastEndMark && "cannot get base of a block");
return Pointer(Pointee, Base, 0);
}
assert(Offset == Base && "not an inner field");
unsigned NewBase = Base - getInlineDesc()->Offset;
return Pointer(Pointee, NewBase, NewBase);
}
/// Returns the parent array.
Pointer getArray() const {
if (Base == RootPtrMark) {
assert(Offset != 0 && Offset != PastEndMark && "not an array element");
return Pointer(Pointee, Base, 0);
}
assert(Offset != Base && "not an array element");
return Pointer(Pointee, Base, Base);
}
/// Accessors for information about the innermost field.
Descriptor *getFieldDesc() const {
if (Base == 0 || Base == RootPtrMark)
return getDeclDesc();
return getInlineDesc()->Desc;
}
/// Returns the type of the innermost field.
QualType getType() const { return getFieldDesc()->getType(); }
/// Returns the element size of the innermost field.
size_t elemSize() const {
if (Base == RootPtrMark)
return getDeclDesc()->getSize();
return getFieldDesc()->getElemSize();
}
/// Returns the total size of the innermost field.
size_t getSize() const { return getFieldDesc()->getSize(); }
/// Returns the offset into an array.
unsigned getOffset() const {
assert(Offset != PastEndMark && "invalid offset");
if (Base == RootPtrMark)
return Offset;
unsigned Adjust = 0;
if (Offset != Base) {
if (getFieldDesc()->ElemDesc)
Adjust = sizeof(InlineDescriptor);
else
Adjust = sizeof(InitMap *);
}
return Offset - Base - Adjust;
}
/// Checks if the innermost field is an array.
bool inArray() const { return getFieldDesc()->IsArray; }
/// Checks if the structure is a primitive array.
bool inPrimitiveArray() const { return getFieldDesc()->isPrimitiveArray(); }
/// Checks if the structure is an array of unknown size.
bool isUnknownSizeArray() const {
return getFieldDesc()->isUnknownSizeArray();
}
/// Checks if the pointer points to an array.
bool isArrayElement() const { return Base != Offset; }
/// Pointer points directly to a block.
bool isRoot() const {
return (Base == 0 || Base == RootPtrMark) && Offset == 0;
}
/// Returns the record descriptor of a class.
Record *getRecord() const { return getFieldDesc()->ElemRecord; }
/// Returns the field information.
const FieldDecl *getField() const { return getFieldDesc()->asFieldDecl(); }
/// Checks if the object is a union.
bool isUnion() const;
/// Checks if the storage is extern.
bool isExtern() const { return Pointee->isExtern(); }
/// Checks if the storage is static.
bool isStatic() const { return Pointee->isStatic(); }
/// Checks if the storage is temporary.
bool isTemporary() const { return Pointee->isTemporary(); }
/// Checks if the storage is a static temporary.
bool isStaticTemporary() const { return isStatic() && isTemporary(); }
/// Checks if the field is mutable.
bool isMutable() const { return Base != 0 && getInlineDesc()->IsMutable; }
/// Checks if an object was initialized.
bool isInitialized() const;
/// Checks if the object is active.
bool isActive() const { return Base == 0 || getInlineDesc()->IsActive; }
/// Checks if a structure is a base class.
bool isBaseClass() const { return isField() && getInlineDesc()->IsBase; }
/// Checks if an object or a subfield is mutable.
bool isConst() const {
return Base == 0 ? getDeclDesc()->IsConst : getInlineDesc()->IsConst;
}
/// Returns the declaration ID.
llvm::Optional<unsigned> getDeclID() const { return Pointee->getDeclID(); }
/// Returns the byte offset from the start.
unsigned getByteOffset() const {
return Offset;
}
/// Returns the number of elements.
unsigned getNumElems() const { return getSize() / elemSize(); }
/// Returns the index into an array.
int64_t getIndex() const {
if (isElementPastEnd())
return 1;
if (auto ElemSize = elemSize())
return getOffset() / ElemSize;
return 0;
}
/// Checks if the index is one past end.
bool isOnePastEnd() const {
return isElementPastEnd() || getSize() == getOffset();
}
/// Checks if the pointer is an out-of-bounds element pointer.
bool isElementPastEnd() const { return Offset == PastEndMark; }
/// Dereferences the pointer, if it's live.
template <typename T> T &deref() const {
assert(isLive() && "Invalid pointer");
return *reinterpret_cast<T *>(Pointee->data() + Offset);
}
/// Dereferences a primitive element.
template <typename T> T &elem(unsigned I) const {
return reinterpret_cast<T *>(Pointee->data())[I];
}
/// Initializes a field.
void initialize() const;
/// Activats a field.
void activate() const;
/// Deactivates an entire strurcutre.
void deactivate() const;
/// Checks if two pointers are comparable.
static bool hasSameBase(const Pointer &A, const Pointer &B);
/// Checks if two pointers can be subtracted.
static bool hasSameArray(const Pointer &A, const Pointer &B);
/// Prints the pointer.
void print(llvm::raw_ostream &OS) const {
OS << "{" << Base << ", " << Offset << ", ";
if (Pointee)
OS << Pointee->getSize();
else
OS << "nullptr";
OS << "}";
}
private:
friend class Block;
friend class DeadBlock;
Pointer(Block *Pointee, unsigned Base, unsigned Offset);
/// Returns the embedded descriptor preceding a field.
InlineDescriptor *getInlineDesc() const { return getDescriptor(Base); }
/// Returns a descriptor at a given offset.
InlineDescriptor *getDescriptor(unsigned Offset) const {
assert(Offset != 0 && "Not a nested pointer");
return reinterpret_cast<InlineDescriptor *>(Pointee->data() + Offset) - 1;
}
/// Returns a reference to the pointer which stores the initialization map.
InitMap *&getInitMap() const {
return *reinterpret_cast<InitMap **>(Pointee->data() + Base);
}
/// The block the pointer is pointing to.
Block *Pointee = nullptr;
/// Start of the current subfield.
unsigned Base = 0;
/// Offset into the block.
unsigned Offset = 0;
/// Previous link in the pointer chain.
Pointer *Prev = nullptr;
/// Next link in the pointer chain.
Pointer *Next = nullptr;
};
inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Pointer &P) {
P.print(OS);
return OS;
}
} // namespace interp
} // namespace clang
#endif