org.jetbrains.kotlin.js.inline.clean.ReferenceTracker.kt Maven / Gradle / Ivy

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/*
 * Copyright 2010-2016 JetBrains s.r.o.
 *
 * 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
 *
 * http://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.
 */

package org.jetbrains.kotlin.js.inline.clean

import org.jetbrains.kotlin.js.backend.ast.JsNode
import org.jetbrains.kotlin.js.inline.util.IdentitySet
import java.util.*

internal class ReferenceTracker {
    private val reachable = IdentityHashMap()
    private val removableCandidates = IdentityHashMap()
    private val referenceFromTo = IdentityHashMap>()
    private val visited = IdentitySet()

    val removable: List
        get() {
            return reachable
                        .filter { !it.value }
                        .map { removableCandidates[it.key]!! }
        }

    fun addCandidateForRemoval(reference: Reference, candidate: RemoveCandidate) {
        assert(!isReferenceToRemovableCandidate(reference)) { "Candidate for removal cannot be reassigned: $candidate" }

        removableCandidates.put(reference, candidate)
        reachable.put(reference, false)
    }

    fun addRemovableReference(referrer: Reference, referenced: Reference) {
        if (!isReferenceToRemovableCandidate(referenced)) return

        getReferencedBy(referrer).add(referenced)

        if (isReachable(referrer)) {
            markReachable(referenced)
        }
    }

    fun markReachable(reference: Reference) {
        if (!isReferenceToRemovableCandidate(reference)) return

        visited.add(reference)
        getReferencedBy(reference)
                .filterNot { it in visited }
                .filter { isReferenceToRemovableCandidate(it) && !isReachable(it) }
                .forEach { markReachable(it) }

        visited.remove(reference)
        reachable[reference] = true
    }

    private fun getReferencedBy(referrer: Reference): MutableSet {
        return referenceFromTo.getOrPut(referrer, { IdentitySet() })
    }

    fun isReferenceToRemovableCandidate(ref: Reference): Boolean {
        return removableCandidates.containsKey(ref)
    }

    private fun isReachable(ref: Reference): Boolean {
        return reachable[ref] ?: false
    }
}