diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/backend/jvm/opt/ByteCodeRepository.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/backend/jvm/opt/ByteCodeRepository.scala | 148 |
1 files changed, 122 insertions, 26 deletions
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/opt/ByteCodeRepository.scala b/src/compiler/scala/tools/nsc/backend/jvm/opt/ByteCodeRepository.scala index eaf82f5c65..16590ec75c 100644 --- a/src/compiler/scala/tools/nsc/backend/jvm/opt/ByteCodeRepository.scala +++ b/src/compiler/scala/tools/nsc/backend/jvm/opt/ByteCodeRepository.scala @@ -10,11 +10,10 @@ package opt import scala.tools.asm import asm.tree._ import scala.collection.JavaConverters._ -import scala.collection.concurrent +import scala.collection.{concurrent, mutable} import scala.tools.asm.Attribute import scala.tools.nsc.backend.jvm.BackendReporting._ -import scala.tools.nsc.io.AbstractFile -import scala.tools.nsc.util.ClassFileLookup +import scala.tools.nsc.util.ClassPath import BytecodeUtils._ import ByteCodeRepository._ import BTypes.InternalName @@ -26,7 +25,7 @@ import java.util.concurrent.atomic.AtomicLong * * @param classPath The compiler classpath where classfiles are searched and read from. */ -class ByteCodeRepository[BT <: BTypes](val classPath: ClassFileLookup[AbstractFile], val btypes: BT) { +class ByteCodeRepository[BT <: BTypes](val classPath: ClassPath, val btypes: BT) { import btypes._ /** @@ -132,38 +131,135 @@ class ByteCodeRepository[BT <: BTypes](val classPath: ClassFileLookup[AbstractFi * The method node for a method matching `name` and `descriptor`, accessed in class `ownerInternalNameOrArrayDescriptor`. * The declaration of the method may be in one of the parents. * - * TODO: make sure we always return the right method, the one being invoked. write tests. - * - if there's an abstract and a concrete one. could possibly somehow the abstract be returned? - * - with traits and default methods, if there is more than one default method inherited and - * no override: what should be returned? We should not just inline one of the two. + * Note that the JVM spec performs method lookup in two steps: resolution and selection. + * + * Method resolution, defined in jvms-5.4.3.3 and jvms-5.4.3.4, is the first step and is identical + * for all invocation styles (virtual, interface, special, static). If C is the receiver class + * in the invocation instruction: + * 1 find a matching method (name and descriptor) in C + * 2 then in C's superclasses + * 3 then find the maximally-specific matching superinterface methods, succeed if there's a + * single non-abstract one. static and private methods in superinterfaces are not considered. + * 4 then pick a random non-static, non-private superinterface method. + * 5 then fail. + * + * Note that for an `invokestatic` instruction, a method reference `B.m` may resolve to `A.m`, if + * class `B` doesn't specify a matching method `m`, but the parent `A` does. + * + * Selection depends on the invocation style and is defined in jvms-6.5. + * - invokestatic: invokes the resolved method + * - invokevirtual / invokeinterface: searches for an override of the resolved method starting + * at the dynamic receiver type. the search procedure is basically the same as in resolution, + * but it fails at 4 instead of picking a superinterface method at random. + * - invokespecial: if C is the receiver in the invocation instruction, searches for an override + * of the resolved method starting at + * - the superclass of the current class, if C is a superclass of the current class + * - C otherwise + * again, the search procedure is the same. + * + * In the method here we implement method *resolution*. Whether or not the returned method is + * actually invoked at runtime depends on the invocation instruction and the class hierarchy, so + * the users (e.g. the inliner) have to be aware of method selection. + * + * Note that the returned method may be abstract (ACC_ABSTRACT), native (ACC_NATIVE) or signature + * polymorphic (methods `invoke` and `invokeExact` in class `MehtodHandles`). * * @return The [[MethodNode]] of the requested method and the [[InternalName]] of its declaring - * class, or an error message if the method could not be found. + * class, or an error message if the method could not be found. An error message is also + * returned if method resolution results in multiple default methods. */ def methodNode(ownerInternalNameOrArrayDescriptor: String, name: String, descriptor: String): Either[MethodNotFound, (MethodNode, InternalName)] = { - // on failure, returns a list of class names that could not be found on the classpath - def methodNodeImpl(ownerInternalName: InternalName): Either[List[ClassNotFound], (MethodNode, InternalName)] = { - classNode(ownerInternalName) match { - case Left(e) => Left(List(e)) - case Right(c) => - c.methods.asScala.find(m => m.name == name && m.desc == descriptor) match { - case Some(m) => Right((m, ownerInternalName)) - case None => findInParents(Option(c.superName) ++: c.interfaces.asScala.toList, Nil) - } + def findMethod(c: ClassNode): Option[MethodNode] = c.methods.asScala.find(m => m.name == name && m.desc == descriptor) + + // https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-2.html#jvms-2.9: "In Java SE 8, the only + // signature polymorphic methods are the invoke and invokeExact methods of the class MethodHandle. + def isSignaturePolymorphic(owner: InternalName) = owner == coreBTypes.jliMethodHandleRef.internalName && (name == "invoke" || name == "invokeExact") + + // Note: if `owner` is an interface, in the first iteration we search for a matching member in the interface itself. + // If that fails, the recursive invocation checks in the superclass (which is Object) with `publicInstanceOnly == true`. + // This is specified in jvms-5.4.3.4: interface method resolution only returns public, non-static methods of Object. + def findInSuperClasses(owner: ClassNode, publicInstanceOnly: Boolean = false): Either[ClassNotFound, Option[(MethodNode, InternalName)]] = { + findMethod(owner) match { + case Some(m) if !publicInstanceOnly || (isPublicMethod(m) && !isStaticMethod(m)) => Right(Some((m, owner.name))) + case None => + if (isSignaturePolymorphic(owner.name)) Right(Some((owner.methods.asScala.find(_.name == name).get, owner.name))) + else if (owner.superName == null) Right(None) + else classNode(owner.superName).flatMap(findInSuperClasses(_, isInterface(owner))) } } - // find the MethodNode in one of the parent classes - def findInParents(parents: List[InternalName], failedClasses: List[ClassNotFound]): Either[List[ClassNotFound], (MethodNode, InternalName)] = parents match { - case x :: xs => methodNodeImpl(x).left.flatMap(failed => findInParents(xs, failed ::: failedClasses)) - case Nil => Left(failedClasses) + def findInInterfaces(initialOwner: ClassNode): Either[ClassNotFound, Option[(MethodNode, InternalName)]] = { + val visited = mutable.Set.empty[InternalName] + val found = mutable.ListBuffer.empty[(MethodNode, ClassNode)] + + def findIn(owner: ClassNode): Option[ClassNotFound] = { + for (i <- owner.interfaces.asScala if !visited(i)) classNode(i) match { + case Left(e) => return Some(e) + case Right(c) => + visited += i + // abstract and static methods are excluded, see jvms-5.4.3.3 + for (m <- findMethod(c) if !isPrivateMethod(m) && !isStaticMethod(m)) found += ((m, c)) + val recusionResult = findIn(c) + if (recusionResult.isDefined) return recusionResult + } + None + } + + findIn(initialOwner) + + val result = + if (found.size <= 1) found.headOption + else { + val maxSpecific = found.filterNot({ + case (method, owner) => + isAbstractMethod(method) || { + val ownerTp = classBTypeFromClassNode(owner) + found exists { + case (other, otherOwner) => + (other ne method) && { + val otherTp = classBTypeFromClassNode(otherOwner) + otherTp.isSubtypeOf(ownerTp).get + } + } + } + }) + // (*) note that if there's no single, non-abstract, maximally-specific method, the jvm + // method resolution (jvms-5.4.3.3) returns any of the non-private, non-static parent + // methods at random (abstract or concrete). + // we chose not to do this here, to prevent the inliner from potentially inlining the + // wrong method. in other words, we guarantee that a concrete method is only returned if + // it resolves deterministically. + // however, there may be multiple abstract methods inherited. in this case we *do* want + // to return a result to allow performing accessibility checks in the inliner. note that + // for accessibility it does not matter which of these methods is return, as they are all + // non-private (i.e., public, protected is not possible, jvms-4.1). + // the remaining case (when there's no max-specific method, but some non-abstract one) + // does not occur in bytecode generated by scalac or javac. we return no result in this + // case. this may at worst prevent some optimizations from happening. + if (maxSpecific.size == 1) maxSpecific.headOption + else if (found.forall(p => isAbstractMethod(p._1))) found.headOption // (*) + else None + } + Right(result.map(p => (p._1, p._2.name))) } // In a MethodInsnNode, the `owner` field may be an array descriptor, for example when invoking `clone`. We don't have a method node to return in this case. - if (ownerInternalNameOrArrayDescriptor.charAt(0) == '[') - Left(MethodNotFound(name, descriptor, ownerInternalNameOrArrayDescriptor, Nil)) - else - methodNodeImpl(ownerInternalNameOrArrayDescriptor).left.map(MethodNotFound(name, descriptor, ownerInternalNameOrArrayDescriptor, _)) + if (ownerInternalNameOrArrayDescriptor.charAt(0) == '[') { + Left(MethodNotFound(name, descriptor, ownerInternalNameOrArrayDescriptor, None)) + } else { + def notFound(cnf: Option[ClassNotFound]) = Left(MethodNotFound(name, descriptor, ownerInternalNameOrArrayDescriptor, cnf)) + val res: Either[ClassNotFound, Option[(MethodNode, InternalName)]] = classNode(ownerInternalNameOrArrayDescriptor).flatMap(c => + findInSuperClasses(c) flatMap { + case None => findInInterfaces(c) + case res => Right(res) + } + ) + res match { + case Left(e) => notFound(Some(e)) + case Right(None) => notFound(None) + case Right(Some(res)) => Right(res) + } + } } private def parseClass(internalName: InternalName): Either[ClassNotFound, ClassNode] = { |