.kotlin.kotlin-compiler.1.3.11.source-code.RedundantNopsCleanupMethodTransformer.kt Maven / Gradle / Ivy
/*
* Copyright 2010-2017 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.codegen.optimization
import org.jetbrains.kotlin.codegen.optimization.common.InsnSequence
import org.jetbrains.kotlin.codegen.optimization.common.findNextOrNull
import org.jetbrains.kotlin.codegen.optimization.common.isMeaningful
import org.jetbrains.kotlin.codegen.optimization.transformer.MethodTransformer
import org.jetbrains.kotlin.utils.addIfNotNull
import org.jetbrains.org.objectweb.asm.Opcodes
import org.jetbrains.org.objectweb.asm.tree.AbstractInsnNode
import org.jetbrains.org.objectweb.asm.tree.LabelNode
import org.jetbrains.org.objectweb.asm.tree.LineNumberNode
import org.jetbrains.org.objectweb.asm.tree.MethodNode
import java.util.*
class RedundantNopsCleanupMethodTransformer : MethodTransformer() {
override fun transform(internalClassName: String, methodNode: MethodNode) {
LabelNormalizationMethodTransformer().transform(internalClassName, methodNode)
val requiredNops = HashSet()
// NOP instruction is required, if it is a sole bytecode instruction in a try-catch block (TCB)
recordNopsRequiredForTryCatchBlocks(methodNode, requiredNops)
// NOP instruction is required, if it is a sole bytecode instruction in a debugger stepping interval
recordNopsRequiredForDebugger(methodNode, requiredNops)
var current: AbstractInsnNode? = methodNode.instructions.first
while (current != null) {
if (current.opcode == Opcodes.NOP && !requiredNops.contains(current)) {
val toRemove = current
current = current.next
methodNode.instructions.remove(toRemove)
} else {
current = current.next
}
}
}
private fun recordNopsRequiredForDebugger(methodNode: MethodNode, requiredNops: MutableSet) {
// We two subsets of labels that are "special" for the debugger:
// 1) Labels for line numbers.
// 2) Labels for observable local variables lifetimes.
// NB this includes synthetic variables denoting inlined function bodies and arguments
// (see JvmAbi.LOCAL_VARIABLE_NAME_PREFIX_INLINE_FUNCTION, JvmAbi.LOCAL_VARIABLE_NAME_PREFIX_INLINE_ARGUMENT).
//
// If we enumerate labels in a given subset in order of occurrence in the method code:
// L[0], L[1], ..., L[n-1], L[n]
// then for each k, 1 <= k <= n-1:
// an instruction interval I[k] = [L[k]; L[k+1]) should contain at least one bytecode instruction (which can be a NOP).
for (insn in methodNode.instructions) {
if (insn is LineNumberNode) {
val nextLineNumber = insn.findNextOrNull { it is LineNumberNode && it.line != insn.line }
requiredNops.addIfNotNull(getRequiredNopInRange(insn, nextLineNumber))
}
}
val localVariableLabels = run {
val labels = hashSetOf().apply {
for (localVariable in methodNode.localVariables) {
add(localVariable.start)
add(localVariable.end)
}
}
methodNode.instructions.toArray().filter { labels.contains(it) }
}
for (i in 0..localVariableLabels.size - 2) {
val begin = localVariableLabels[i]
val end = localVariableLabels[i + 1]
if (InsnSequence(begin, end).any { it in requiredNops }) continue
requiredNops.addIfNotNull(getRequiredNopInRange(begin, end))
}
}
private fun recordNopsRequiredForTryCatchBlocks(methodNode: MethodNode, requiredNops: MutableSet) {
for (tcb in methodNode.tryCatchBlocks) {
val nop = tcb.start.findNextOrNull { it.isMeaningful }
if (nop?.opcode == Opcodes.NOP) {
requiredNops.add(nop)
}
}
}
}
internal fun getRequiredNopInRange(firstInclusive: AbstractInsnNode, lastExclusive: AbstractInsnNode?): AbstractInsnNode? {
var lastNop: AbstractInsnNode? = null
var current: AbstractInsnNode? = firstInclusive
while (current != null && current != lastExclusive) {
if (current.isMeaningful && current.opcode != Opcodes.NOP) {
return null
} else if (current.opcode == Opcodes.NOP) {
lastNop = current
}
current = current.next
}
return lastNop
}