org.jetbrains.kotlin.codegen.optimization.boxing.FastPopBackwardPropagationTransformer.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.boxing
import org.jetbrains.kotlin.codegen.optimization.transformer.MethodTransformer
import org.jetbrains.org.objectweb.asm.Opcodes
import org.jetbrains.org.objectweb.asm.tree.AbstractInsnNode
import org.jetbrains.org.objectweb.asm.tree.InsnNode
import org.jetbrains.org.objectweb.asm.tree.MethodNode
class FastPopBackwardPropagationTransformer : MethodTransformer() {
override fun transform(internalClassName: String, methodNode: MethodNode) {
while (transformOnce(methodNode)) {
}
}
private fun transformOnce(methodNode: MethodNode): Boolean {
val toRemove = ArrayList()
val toReplaceWithNop = ArrayList()
val insns = methodNode.instructions.toArray()
for (i in 1 until insns.size) {
val insn = insns[i]
val prev = insns[i - 1]
when (insn.opcode) {
Opcodes.POP -> {
if (prev.isEliminatedByPop()) {
toReplaceWithNop.add(insn)
toRemove.add(prev)
}
}
Opcodes.POP2 -> {
if (prev.isEliminatedByPop2()) {
toReplaceWithNop.add(insn)
toRemove.add(prev)
}
else if (i > 1) {
val prev2 = insns[i - 2]
if (prev.isEliminatedByPop() && prev2.isEliminatedByPop()) {
toReplaceWithNop.add(insn)
toRemove.add(prev)
toRemove.add(prev2)
}
}
}
}
}
toReplaceWithNop.forEach { methodNode.instructions.set(it, InsnNode(Opcodes.NOP)) }
toRemove.forEach { methodNode.instructions.remove(it) }
return toReplaceWithNop.isNotEmpty() &&
toRemove.isNotEmpty()
}
private fun AbstractInsnNode.isEliminatedByPop() =
opcode in Opcodes.ACONST_NULL..Opcodes.FCONST_2 ||
opcode in Opcodes.BIPUSH..Opcodes.ILOAD ||
opcode == Opcodes.FLOAD ||
opcode == Opcodes.ALOAD ||
isUnitInstance() ||
opcode == Opcodes.DUP
private fun AbstractInsnNode.isEliminatedByPop2() =
opcode == Opcodes.LCONST_0 || opcode == Opcodes.LCONST_1 ||
opcode == Opcodes.DCONST_0 || opcode == Opcodes.DCONST_1 ||
opcode == Opcodes.LLOAD ||
opcode == Opcodes.DLOAD ||
opcode == Opcodes.DUP2
}