/* NSC -- new Scala compiler
* Copyright 2005-2014 LAMP/EPFL
* @author Martin Odersky
*/
package scala.tools.nsc
package backend.jvm
package opt
import scala.tools.asm
import asm.tree._
import scala.collection.convert.decorateAsScala._
import scala.tools.asm.Attribute
import scala.tools.nsc.io.AbstractFile
import scala.tools.nsc.util.ClassFileLookup
import OptimizerReporting._
import BytecodeUtils._
import ByteCodeRepository._
import BTypes.InternalName
import java.util.concurrent.atomic.AtomicLong
/**
* The ByteCodeRepository provides utilities to read the bytecode of classfiles from the compilation
* classpath. Parsed classes are cached in the `classes` map.
*
* @param classPath The compiler classpath where classfiles are searched and read from.
* @param classes Cache for parsed ClassNodes. Also stores the source of the bytecode:
* [[Classfile]] if read from `classPath`, [[CompilationUnit]] if the bytecode
* corresponds to a class being compiled.
* The `Long` field encodes the age of the node in the map, which allows removing
* old entries when the map grows too large.
* For Java classes in mixed compilation, the map contains `None`: there is no
* ClassNode generated by the backend and also no classfile that could be parsed.
*/
class ByteCodeRepository(val classPath: ClassFileLookup[AbstractFile], val classes: collection.concurrent.Map[InternalName, Option[(ClassNode, Source, Long)]]) {
private val maxCacheSize = 1500
private val targetSize = 500
private val idCounter = new AtomicLong(0)
/**
* Prevent the code repository from growing too large. Profiling reveals that the average size
* of a ClassNode is about 30 kb. I observed having 17k+ classes in the cache, i.e., 500 mb.
*
* We can only remove classes with `Source == Classfile`, those can be parsed again if requested.
*/
private def limitCacheSize(): Unit = {
if (classes.count(c => c._2.isDefined && c._2.get._2 == Classfile) > maxCacheSize) {
val removeId = idCounter.get - targetSize
val toRemove = classes.iterator.collect({
case (name, Some((_, Classfile, id))) if id < removeId => name
}).toList
toRemove foreach classes.remove
}
}
def add(classNode: ClassNode, source: Source) = {
classes(classNode.name) = Some((classNode, source, idCounter.incrementAndGet()))
}
/**
* The class node and source for an internal name. If the class node is not yet available, it is
* parsed from the classfile on the compile classpath.
*/
def classNodeAndSource(internalName: InternalName): Option[(ClassNode, Source)] = {
val r = classes.getOrElseUpdate(internalName, {
limitCacheSize()
parseClass(internalName).map((_, Classfile, idCounter.incrementAndGet()))
})
r.map(v => (v._1, v._2))
}
/**
* The class node for an internal name. If the class node is not yet available, it is parsed from
* the classfile on the compile classpath.
*/
def classNode(internalName: InternalName): Option[ClassNode] = classNodeAndSource(internalName).map(_._1)
/**
* The field node for a field matching `name` and `descriptor`, accessed in class `classInternalName`.
* The declaration of the field may be in one of the superclasses.
*
* @return The [[FieldNode]] of the requested field and the [[InternalName]] of its declaring class.
*/
def fieldNode(classInternalName: InternalName, name: String, descriptor: String): Option[(FieldNode, InternalName)] = {
classNode(classInternalName).flatMap(c =>
c.fields.asScala.find(f => f.name == name && f.desc == descriptor).map((_, classInternalName)) orElse {
Option(c.superName).flatMap(n => fieldNode(n, name, descriptor))
})
}
/**
* The method node for a method matching `name` and `descriptor`, accessed in class `classInternalName`.
* The declaration of the method may be in one of the parents.
*
* @return The [[MethodNode]] of the requested method and the [[InternalName]] of its declaring class.
*/
def methodNode(ownerInternalNameOrArrayDescriptor: String, name: String, descriptor: String): Option[(MethodNode, InternalName)] = {
// In a MethodInsnNode, the `owner` field may be an array descriptor, for exmple when invoking `clone`.
// We don't inline array methods (they are native anyway), so just return None.
if (ownerInternalNameOrArrayDescriptor.charAt(0) == '[') None
else {
classNode(ownerInternalNameOrArrayDescriptor).flatMap(c =>
c.methods.asScala.find(m => m.name == name && m.desc == descriptor).map((_, ownerInternalNameOrArrayDescriptor)) orElse {
val parents = Option(c.superName) ++ c.interfaces.asScala
// `view` to stop at the first result
parents.view.flatMap(methodNode(_, name, descriptor)).headOption
})
}
}
private def parseClass(internalName: InternalName): Option[ClassNode] = {
val fullName = internalName.replace('/', '.')
classPath.findClassFile(fullName) map { classFile =>
val classNode = new asm.tree.ClassNode()
val classReader = new asm.ClassReader(classFile.toByteArray)
// Passing the InlineInfoAttributePrototype makes the ClassReader invoke the specific `read`
// method of the InlineInfoAttribute class, instead of putting the byte array into a generic
// Attribute.
// We don't need frames when inlining, but we want to keep the local variable table, so we
// don't use SKIP_DEBUG.
classReader.accept(classNode, Array[Attribute](InlineInfoAttributePrototype), asm.ClassReader.SKIP_FRAMES)
// SKIP_FRAMES leaves line number nodes. Remove them because they are not correct after
// inlining.
// TODO: we need to remove them also for classes that are not parsed from classfiles, why not simplify and do it once when inlining?
// OR: instead of skipping line numbers for inlined code, use write a SourceDebugExtension
// attribute that contains JSR-45 data that encodes debugging info.
// http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.11
// https://jcp.org/aboutJava/communityprocess/final/jsr045/index.html
removeLineNumberNodes(classNode)
classNode
}
}
}
object ByteCodeRepository {
/**
* The source of a ClassNode in the ByteCodeRepository. Can be either [[CompilationUnit]] if the
* class is being compiled or [[Classfile]] if the class was parsed from the compilation classpath.
*/
sealed trait Source
object CompilationUnit extends Source
object Classfile extends Source
}
