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+//===--- 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 "Block.h"
+#include "Descriptor.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ComparisonCategories.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