TypeCollectionAnalyzer.swift

// Copyright 2020 Google LLC
//
// 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
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// 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.

// Determine what variable types we should collect given instruction
struct TypeCollectionAnalyzer {
    // Special properties which significantly change variable type
    // We should recollect type if we change them
    let specialProperties = ["__proto__"]

    func analyze(_ instr: Instruction) -> [Variable] {
        switch instr.op {
            case is LoadInteger, is LoadBigInt, is LoadFloat, is LoadBoolean, is LoadNull, is LoadUndefined,
                 is TypeOf, is InstanceOf, is In, is Dup, is Reassign, is Compare, is BeginForIn:
                // No need to collect types for instructions interpreter can handle
                return []
            case is BeginAnyFunctionDefinition:
                // No type collection on function definitions for now
                return []
            case let op as StoreProperty where specialProperties.contains(op.propertyName):
                // Recollect type of this variable, because major change happened
                return [instr.input(0)]
            default:
                // By default, collect types for all outputs of an instruction
                return Array(instr.allOutputs)
        }
    }
}