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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#if !V8_ENABLE_WEBASSEMBLY
#error This header should only be included if WebAssembly is enabled.
#endif // !V8_ENABLE_WEBASSEMBLY
#ifndef V8_WASM_WASM_SUBTYPING_H_
#define V8_WASM_WASM_SUBTYPING_H_
#include "src/wasm/value-type.h"
namespace v8 {
namespace internal {
namespace wasm {
struct WasmModule;
V8_NOINLINE V8_EXPORT_PRIVATE bool IsSubtypeOfImpl(
ValueType subtype, ValueType supertype, const WasmModule* sub_module,
const WasmModule* super_module);
V8_NOINLINE V8_EXPORT_PRIVATE bool IsHeapSubtypeOfImpl(
HeapType sub_heap, HeapType super_heap, const WasmModule* sub_module,
const WasmModule* super_module);
// Checks if type1, defined in module1, is equivalent with type2, defined in
// module2.
// Type equivalence (~) is described by the following rules:
// - Two numeric types are equivalent iff they are equal.
// - T(ht1) ~ T(ht2) iff ht1 ~ ht2 for T in {ref, ref null, rtt}.
// Equivalence of heap types ht1 ~ ht2 is defined as follows:
// - Two non-index heap types are equivalent iff they are equal.
// - Two indexed heap types are equivalent iff they are iso-recursive
// equivalent.
V8_NOINLINE V8_EXPORT_PRIVATE bool EquivalentTypes(ValueType type1,
ValueType type2,
const WasmModule* module1,
const WasmModule* module2);
// Checks if {subtype}, defined in {module1}, is a subtype of {supertype},
// defined in {module2}.
// Subtyping between value types is described by the following rules
// (structural subtyping):
// - numeric types are subtype-related iff they are equal.
// - (ref null ht1) <: (ref null ht2) iff ht1 <: ht2.
// - (ref ht1) <: (ref null? ht2) iff ht1 <: ht2.
// - rtt1 <: rtt2 iff rtt1 ~ rtt2.
// For heap types, the following subtyping rules hold:
// - The abstract heap types form the following type hierarchies:
//
// any func extern
// / \ | |
// eq \ nofunc noextern
// / | \ \
// i31 array struct string
// \___|______|_____/
// |
// none
//
// - All functions are subtypes of func.
// - All structs are subtypes of struct.
// - All arrays are subtypes of array.
// - An indexed heap type h1 is a subtype of indexed heap type h2 if h2 is
// transitively an explicit canonical supertype of h1.
// Note that {any} includes references introduced by the host which belong to
// none of any's subtypes (e.g. JS objects).
V8_INLINE bool IsSubtypeOf(ValueType subtype, ValueType supertype,
const WasmModule* sub_module,
const WasmModule* super_module) {
if (subtype == supertype && sub_module == super_module) return true;
return IsSubtypeOfImpl(subtype, supertype, sub_module, super_module);
}
// Checks if {subtype} is a subtype of {supertype} (both defined in {module}).
V8_INLINE bool IsSubtypeOf(ValueType subtype, ValueType supertype,
const WasmModule* module) {
// If the types are trivially identical, exit early.
if (V8_LIKELY(subtype == supertype)) return true;
return IsSubtypeOfImpl(subtype, supertype, module, module);
}
V8_INLINE bool TypesUnrelated(ValueType type1, ValueType type2,
const WasmModule* module1,
const WasmModule* module2) {
return !IsSubtypeOf(type1, type2, module1, module2) &&
!IsSubtypeOf(type2, type1, module2, module1);
}
V8_INLINE bool IsHeapSubtypeOf(HeapType subtype, HeapType supertype,
const WasmModule* sub_module,
const WasmModule* super_module) {
if (subtype == supertype && sub_module == super_module) return true;
return IsHeapSubtypeOfImpl(subtype, supertype, sub_module, super_module);
}
// Checks if {subtype} is a subtype of {supertype} (both defined in {module}).
V8_INLINE bool IsHeapSubtypeOf(HeapType subtype, HeapType supertype,
const WasmModule* module) {
// If the types are trivially identical, exit early.
if (V8_LIKELY(subtype == supertype)) return true;
return IsHeapSubtypeOfImpl(subtype, supertype, module, module);
}
V8_INLINE bool HeapTypesUnrelated(HeapType heap1, HeapType heap2,
const WasmModule* module1,
const WasmModule* module2) {
return !IsHeapSubtypeOf(heap1, heap2, module1, module2) &&
!IsHeapSubtypeOf(heap2, heap1, module2, module1);
}
// Checks whether {subtype_index} is valid as a declared subtype of
// {supertype_index}.
// - Both type must be of the same kind (function, struct, or array).
// - Structs: Subtype must have at least as many fields as supertype,
// covariance for respective immutable fields, equivalence for respective
// mutable fields.
// - Arrays: subtyping of respective element types for immutable arrays,
// equivalence of element types for mutable arrays.
// - Functions: equal number of parameter and return types. Contravariance for
// respective parameter types, covariance for respective return types.
V8_EXPORT_PRIVATE bool ValidSubtypeDefinition(uint32_t subtype_index,
uint32_t supertype_index,
const WasmModule* sub_module,
const WasmModule* super_module);
struct TypeInModule {
ValueType type;
const WasmModule* module;
TypeInModule(ValueType type, const WasmModule* module)
: type(type), module(module) {}
TypeInModule() : TypeInModule(kWasmBottom, nullptr) {}
bool operator==(const TypeInModule& other) const {
return type == other.type && module == other.module;
}
bool operator!=(const TypeInModule& other) const {
return type != other.type || module != other.module;
}
};
inline std::ostream& operator<<(std::ostream& oss, TypeInModule type) {
return oss << type.type.name() << "@"
<< reinterpret_cast<intptr_t>(type.module);
}
// Returns {kWasmBottom} if the union of {type1} and {type2} is not defined.
V8_EXPORT_PRIVATE TypeInModule Union(ValueType type1, ValueType type2,
const WasmModule* module1,
const WasmModule* module2);
V8_INLINE V8_EXPORT_PRIVATE TypeInModule Union(TypeInModule type1,
TypeInModule type2) {
return Union(type1.type, type2.type, type1.module, type2.module);
}
V8_EXPORT_PRIVATE TypeInModule Intersection(ValueType type1, ValueType type2,
const WasmModule* module1,
const WasmModule* module2);
V8_INLINE V8_EXPORT_PRIVATE TypeInModule Intersection(TypeInModule type1,
TypeInModule type2) {
return Intersection(type1.type, type2.type, type1.module, type2.module);
}
// Returns the matching abstract null type (none, nofunc, noextern).
ValueType ToNullSentinel(TypeInModule type);
// Returns if two types share the same type hierarchy (any, extern, funcref).
bool IsSameTypeHierarchy(HeapType type1, HeapType type2,
const WasmModule* module);
} // namespace wasm
} // namespace internal
} // namespace v8
#endif // V8_WASM_WASM_SUBTYPING_H_
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