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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
*
* Copyright 2021 Mozilla Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef wasm_initexpr_h
#define wasm_initexpr_h
#include "wasm/WasmConstants.h"
#include "wasm/WasmSerialize.h"
#include "wasm/WasmTypeDecls.h"
#include "wasm/WasmValType.h"
#include "wasm/WasmValue.h"
namespace js {
namespace wasm {
class Decoder;
struct ModuleEnvironment;
enum class InitExprKind {
None,
Literal,
Variable,
};
// A InitExpr describes a deferred initializer expression, used to initialize
// a global or a table element offset. Such expressions are created during
// decoding and actually executed on module instantiation.
class InitExpr {
InitExprKind kind_;
// The bytecode for this constant expression if this is not a literal.
Bytes bytecode_;
// The value if this is a literal.
LitVal literal_;
// The value type of this constant expression in either case.
ValType type_;
public:
InitExpr() : kind_(InitExprKind::None) {}
explicit InitExpr(LitVal literal)
: kind_(InitExprKind::Literal),
literal_(literal),
type_(literal.type()) {}
// Decode and validate a constant expression given at the current
// position of the decoder. Upon failure, the decoder contains the failure
// message or else the failure was an OOM.
static bool decodeAndValidate(Decoder& d, ModuleEnvironment* env,
ValType expected, InitExpr* expr);
// Evaluate the constant expresssion with the given context. This may only
// fail due to an OOM, as all InitExpr's are required to have been validated.
bool evaluate(JSContext* cx, const ValVector& globalImportValues,
HandleWasmInstanceObject instanceObj,
MutableHandleVal result) const;
bool isLiteral() const { return kind_ == InitExprKind::Literal; }
// Gets the result of this expression if it was determined to be a literal.
LitVal literal() const {
MOZ_ASSERT(isLiteral());
return literal_;
}
// Get the type of the resulting value of this expression.
ValType type() const { return type_; }
// Allow moving, but not implicit copying
InitExpr(const InitExpr&) = delete;
InitExpr& operator=(const InitExpr&) = delete;
InitExpr(InitExpr&&) = default;
InitExpr& operator=(InitExpr&&) = default;
// Allow explicit cloning
[[nodiscard]] bool clone(const InitExpr& src);
size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
WASM_DECLARE_FRIEND_SERIALIZE(InitExpr);
};
} // namespace wasm
} // namespace js
#endif // wasm_initexpr_h