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12cbefbee7
This speeds up expressions such as `BigInt.asIntN(0x4000000000000, 1n)` (#3615). And those involving very large bigints.
113 lines
3.8 KiB
C++
113 lines
3.8 KiB
C++
/*
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* Copyright (c) 2020-2023, Linus Groh <linusg@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibJS/Runtime/AbstractOperations.h>
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#include <LibJS/Runtime/BigInt.h>
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#include <LibJS/Runtime/BigIntConstructor.h>
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#include <LibJS/Runtime/BigIntObject.h>
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#include <LibJS/Runtime/Error.h>
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#include <LibJS/Runtime/GlobalObject.h>
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#include <LibJS/Runtime/VM.h>
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#include <LibJS/Runtime/ValueInlines.h>
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namespace JS {
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GC_DEFINE_ALLOCATOR(BigIntConstructor);
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static Crypto::SignedBigInteger const BIGINT_ONE { 1 };
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static Crypto::SignedBigInteger const BIGINT_ZERO { 0 };
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BigIntConstructor::BigIntConstructor(Realm& realm)
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: NativeFunction(realm.vm().names.BigInt.as_string(), realm.intrinsics().function_prototype())
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{
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}
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void BigIntConstructor::initialize(Realm& realm)
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{
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auto& vm = this->vm();
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Base::initialize(realm);
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// 21.2.2.3 BigInt.prototype, https://tc39.es/ecma262/#sec-bigint.prototype
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define_direct_property(vm.names.prototype, realm.intrinsics().bigint_prototype(), 0);
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u8 attr = Attribute::Writable | Attribute::Configurable;
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define_native_function(realm, vm.names.asIntN, as_int_n, 2, attr);
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define_native_function(realm, vm.names.asUintN, as_uint_n, 2, attr);
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define_direct_property(vm.names.length, Value(1), Attribute::Configurable);
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}
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// 21.2.1.1 BigInt ( value ), https://tc39.es/ecma262/#sec-bigint-constructor-number-value
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ThrowCompletionOr<Value> BigIntConstructor::call()
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{
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auto& vm = this->vm();
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auto value = vm.argument(0);
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// 2. Let prim be ? ToPrimitive(value, number).
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auto primitive = TRY(value.to_primitive(vm, Value::PreferredType::Number));
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// 3. If Type(prim) is Number, return ? NumberToBigInt(prim).
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if (primitive.is_number())
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return TRY(number_to_bigint(vm, primitive));
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// 4. Otherwise, return ? ToBigInt(prim).
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return TRY(primitive.to_bigint(vm));
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}
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// 21.2.1.1 BigInt ( value ), https://tc39.es/ecma262/#sec-bigint-constructor-number-value
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ThrowCompletionOr<GC::Ref<Object>> BigIntConstructor::construct(FunctionObject&)
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{
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return vm().throw_completion<TypeError>(ErrorType::NotAConstructor, "BigInt");
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}
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// 21.2.2.1 BigInt.asIntN ( bits, bigint ), https://tc39.es/ecma262/#sec-bigint.asintn
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JS_DEFINE_NATIVE_FUNCTION(BigIntConstructor::as_int_n)
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{
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// 1. Set bits to ? ToIndex(bits).
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auto bits = TRY(vm.argument(0).to_index(vm));
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// 2. Set bigint to ? ToBigInt(bigint).
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auto bigint = TRY(vm.argument(1).to_bigint(vm));
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// OPTIMIZATION: mod = bigint (mod 2^0) = 0 < 2^(0-1) = 0.5
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if (bits == 0)
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return BigInt::create(vm, BIGINT_ZERO);
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// 3. Let mod be ℝ(bigint) modulo 2^bits.
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auto const mod = TRY_OR_THROW_OOM(vm, bigint->big_integer().mod_power_of_two(bits));
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// OPTIMIZATION: mod < 2^(bits-1)
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if (mod.is_zero())
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return BigInt::create(vm, BIGINT_ZERO);
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// 4. If mod ≥ 2^(bits-1), return ℤ(mod - 2^bits); ...
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if (auto top_bit_index = mod.unsigned_value().one_based_index_of_highest_set_bit(); top_bit_index >= bits) {
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// twos complement decode
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auto decoded = TRY_OR_THROW_OOM(vm, mod.unsigned_value().try_bitwise_not_fill_to_one_based_index(bits)).plus(1);
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return BigInt::create(vm, Crypto::SignedBigInteger { std::move(decoded), true });
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}
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// ... otherwise, return ℤ(mod).
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return BigInt::create(vm, mod);
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}
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// 21.2.2.2 BigInt.asUintN ( bits, bigint ), https://tc39.es/ecma262/#sec-bigint.asuintn
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JS_DEFINE_NATIVE_FUNCTION(BigIntConstructor::as_uint_n)
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{
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// 1. Set bits to ? ToIndex(bits).
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auto bits = TRY(vm.argument(0).to_index(vm));
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// 2. Set bigint to ? ToBigInt(bigint).
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auto bigint = TRY(vm.argument(1).to_bigint(vm));
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// 3. Return the BigInt value that represents ℝ(bigint) modulo 2^bits.
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auto const mod = TRY_OR_THROW_OOM(vm, bigint->big_integer().mod_power_of_two(bits));
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return BigInt::create(vm, mod);
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}
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}
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