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Diffstat (limited to 'clang/lib/AST/Interp/Descriptor.h')
| -rw-r--r-- | clang/lib/AST/Interp/Descriptor.h | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/clang/lib/AST/Interp/Descriptor.h b/clang/lib/AST/Interp/Descriptor.h new file mode 100644 index 000000000000..b260b7600974 --- /dev/null +++ b/clang/lib/AST/Interp/Descriptor.h @@ -0,0 +1,220 @@ +//===--- Descriptor.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 descriptors which characterise allocations. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_CLANG_AST_INTERP_DESCRIPTOR_H +#define LLVM_CLANG_AST_INTERP_DESCRIPTOR_H + +#include "clang/AST/Decl.h" +#include "clang/AST/Expr.h" + +namespace clang { +namespace interp { +class Block; +class Record; +struct Descriptor; +enum PrimType : unsigned; + +using DeclTy = llvm::PointerUnion<const Decl *, const Expr *>; + +/// Invoked whenever a block is created. The constructor method fills in the +/// inline descriptors of all fields and array elements. It also initializes +/// all the fields which contain non-trivial types. +using BlockCtorFn = void (*)(Block *Storage, char *FieldPtr, bool IsConst, + bool IsMutable, bool IsActive, + Descriptor *FieldDesc); + +/// Invoked when a block is destroyed. Invokes the destructors of all +/// non-trivial nested fields of arrays and records. +using BlockDtorFn = void (*)(Block *Storage, char *FieldPtr, + Descriptor *FieldDesc); + +/// Invoked when a block with pointers referencing it goes out of scope. Such +/// blocks are persisted: the move function copies all inline descriptors and +/// non-trivial fields, as existing pointers might need to reference those +/// descriptors. Data is not copied since it cannot be legally read. +using BlockMoveFn = void (*)(Block *Storage, char *SrcFieldPtr, + char *DstFieldPtr, Descriptor *FieldDesc); + +/// Object size as used by the interpreter. +using InterpSize = unsigned; + +/// Describes a memory block created by an allocation site. +struct Descriptor { +private: + /// Original declaration, used to emit the error message. + const DeclTy Source; + /// Size of an element, in host bytes. + const InterpSize ElemSize; + /// Size of the storage, in host bytes. + const InterpSize Size; + /// Size of the allocation (storage + metadata), in host bytes. + const InterpSize AllocSize; + + /// Value to denote arrays of unknown size. + static constexpr unsigned UnknownSizeMark = (unsigned)-1; + +public: + /// Token to denote structures of unknown size. + struct UnknownSize {}; + + /// Pointer to the record, if block contains records. + Record *const ElemRecord = nullptr; + /// Descriptor of the array element. + Descriptor *const ElemDesc = nullptr; + /// Flag indicating if the block is mutable. + const bool IsConst = false; + /// Flag indicating if a field is mutable. + const bool IsMutable = false; + /// Flag indicating if the block is a temporary. + const bool IsTemporary = false; + /// Flag indicating if the block is an array. + const bool IsArray = false; + + /// Storage management methods. + const BlockCtorFn CtorFn = nullptr; + const BlockDtorFn DtorFn = nullptr; + const BlockMoveFn MoveFn = nullptr; + + /// Allocates a descriptor for a primitive. + Descriptor(const DeclTy &D, PrimType Type, bool IsConst, bool IsTemporary, + bool IsMutable); + + /// Allocates a descriptor for an array of primitives. + Descriptor(const DeclTy &D, PrimType Type, size_t NumElems, bool IsConst, + bool IsTemporary, bool IsMutable); + + /// Allocates a descriptor for an array of primitives of unknown size. + Descriptor(const DeclTy &D, PrimType Type, bool IsTemporary, UnknownSize); + + /// Allocates a descriptor for an array of composites. + Descriptor(const DeclTy &D, Descriptor *Elem, unsigned NumElems, bool IsConst, + bool IsTemporary, bool IsMutable); + + /// Allocates a descriptor for an array of composites of unknown size. + Descriptor(const DeclTy &D, Descriptor *Elem, bool IsTemporary, UnknownSize); + + /// Allocates a descriptor for a record. + Descriptor(const DeclTy &D, Record *R, bool IsConst, bool IsTemporary, + bool IsMutable); + + QualType getType() const; + SourceLocation getLocation() const; + + const Decl *asDecl() const { return Source.dyn_cast<const Decl *>(); } + const Expr *asExpr() const { return Source.dyn_cast<const Expr *>(); } + + const ValueDecl *asValueDecl() const { + return dyn_cast_or_null<ValueDecl>(asDecl()); + } + + const FieldDecl *asFieldDecl() const { + return dyn_cast_or_null<FieldDecl>(asDecl()); + } + + const RecordDecl *asRecordDecl() const { + return dyn_cast_or_null<RecordDecl>(asDecl()); + } + + /// Returns the size of the object without metadata. + unsigned getSize() const { + assert(!isUnknownSizeArray() && "Array of unknown size"); + return Size; + } + + /// Returns the allocated size, including metadata. + unsigned getAllocSize() const { return AllocSize; } + /// returns the size of an element when the structure is viewed as an array. + unsigned getElemSize() const { return ElemSize; } + + /// Returns the number of elements stored in the block. + unsigned getNumElems() const { + return Size == UnknownSizeMark ? 0 : (getSize() / getElemSize()); + } + + /// Checks if the descriptor is of an array of primitives. + bool isPrimitiveArray() const { return IsArray && !ElemDesc; } + /// Checks if the descriptor is of an array of zero size. + bool isZeroSizeArray() const { return Size == 0; } + /// Checks if the descriptor is of an array of unknown size. + bool isUnknownSizeArray() const { return Size == UnknownSizeMark; } + + /// Checks if the descriptor is of a primitive. + bool isPrimitive() const { return !IsArray && !ElemRecord; } + + /// Checks if the descriptor is of an array. + bool isArray() const { return IsArray; } +}; + +/// Inline descriptor embedded in structures and arrays. +/// +/// Such descriptors precede all composite array elements and structure fields. +/// If the base of a pointer is not zero, the base points to the end of this +/// structure. The offset field is used to traverse the pointer chain up +/// to the root structure which allocated the object. +struct InlineDescriptor { + /// Offset inside the structure/array. + unsigned Offset; + + /// Flag indicating if the storage is constant or not. + /// Relevant for primitive fields. + unsigned IsConst : 1; + /// For primitive fields, it indicates if the field was initialized. + /// Primitive fields in static storage are always initialized. + /// Arrays are always initialized, even though their elements might not be. + /// Base classes are initialized after the constructor is invoked. + unsigned IsInitialized : 1; + /// Flag indicating if the field is an embedded base class. + unsigned IsBase : 1; + /// Flag indicating if the field is the active member of a union. + unsigned IsActive : 1; + /// Flag indicating if the field is mutable (if in a record). + unsigned IsMutable : 1; + + Descriptor *Desc; +}; + +/// Bitfield tracking the initialisation status of elements of primitive arrays. +/// A pointer to this is embedded at the end of all primitive arrays. +/// If the map was not yet created and nothing was initialied, the pointer to +/// this structure is 0. If the object was fully initialized, the pointer is -1. +struct InitMap { +private: + /// Type packing bits. + using T = uint64_t; + /// Bits stored in a single field. + static constexpr uint64_t PER_FIELD = sizeof(T) * CHAR_BIT; + + /// Initializes the map with no fields set. + InitMap(unsigned N); + + /// Returns a pointer to storage. + T *data(); + +public: + /// Initializes an element. Returns true when object if fully initialized. + bool initialize(unsigned I); + + /// Checks if an element was initialized. + bool isInitialized(unsigned I); + + /// Allocates a map holding N elements. + static InitMap *allocate(unsigned N); + +private: + /// Number of fields initialized. + unsigned UninitFields; +}; + +} // namespace interp +} // namespace clang + +#endif |