diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/backend/jvm/opt/LocalOpt.scala')
-rw-r--r-- | src/compiler/scala/tools/nsc/backend/jvm/opt/LocalOpt.scala | 53 |
1 files changed, 26 insertions, 27 deletions
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/opt/LocalOpt.scala b/src/compiler/scala/tools/nsc/backend/jvm/opt/LocalOpt.scala index f6cfc5598b..fb5cfeb167 100644 --- a/src/compiler/scala/tools/nsc/backend/jvm/opt/LocalOpt.scala +++ b/src/compiler/scala/tools/nsc/backend/jvm/opt/LocalOpt.scala @@ -47,44 +47,37 @@ import scala.tools.nsc.settings.ScalaSettings * stale labels * - eliminate labels that are not referenced, merge sequences of label definitions. */ -class LocalOpt(settings: ScalaSettings) { - /** - * Remove unreachable code from all methods of `classNode`. See of its overload. - * - * @param classNode The class to optimize - * @return `true` if unreachable code was removed from any method - */ - def minimalRemoveUnreachableCode(classNode: ClassNode): Boolean = { - classNode.methods.asScala.foldLeft(false) { - case (changed, method) => minimalRemoveUnreachableCode(method, classNode.name) || changed - } - } - +class LocalOpt(settings: ScalaSettings, unreachableCodeEliminated: collection.mutable.Set[MethodNode]) { /** * Remove unreachable code from a method. * * This implementation only removes instructions that are unreachable for an ASM analyzer / * interpreter. This ensures that future analyses will not produce `null` frames. The inliner * and call graph builder depend on this property. + * + * @return A set containing the eliminated instructions */ - def minimalRemoveUnreachableCode(method: MethodNode, ownerClassName: InternalName): Boolean = { - if (method.instructions.size == 0) return false // fast path for abstract methods + def minimalRemoveUnreachableCode(method: MethodNode, ownerClassName: InternalName): Set[AbstractInsnNode] = { + if (method.instructions.size == 0) return Set.empty // fast path for abstract methods + if (unreachableCodeEliminated(method)) return Set.empty // we know there is no unreachable code // For correctness, after removing unreachable code, we have to eliminate empty exception // handlers, see scaladoc of def methodOptimizations. Removing an live handler may render more // code unreachable and therefore requires running another round. - def removalRound(): Boolean = { - val (codeRemoved, liveLabels) = removeUnreachableCodeImpl(method, ownerClassName) - if (codeRemoved) { + def removalRound(): Set[AbstractInsnNode] = { + val (removedInstructions, liveLabels) = removeUnreachableCodeImpl(method, ownerClassName) + val removedRecursively = if (removedInstructions.nonEmpty) { val liveHandlerRemoved = removeEmptyExceptionHandlers(method).exists(h => liveLabels(h.start)) if (liveHandlerRemoved) removalRound() - } - codeRemoved + else Set.empty + } else Set.empty + removedInstructions ++ removedRecursively } - val codeRemoved = removalRound() - if (codeRemoved) removeUnusedLocalVariableNodes(method)() - codeRemoved + val removedInstructions = removalRound() + if (removedInstructions.nonEmpty) removeUnusedLocalVariableNodes(method)() + unreachableCodeEliminated += method + removedInstructions } /** @@ -145,9 +138,9 @@ class LocalOpt(settings: ScalaSettings) { def removalRound(): Boolean = { // unreachable-code, empty-handlers and simplify-jumps run until reaching a fixpoint (see doc on class LocalOpt) val (codeRemoved, handlersRemoved, liveHandlerRemoved) = if (settings.YoptUnreachableCode) { - val (codeRemoved, liveLabels) = removeUnreachableCodeImpl(method, ownerClassName) + val (removedInstructions, liveLabels) = removeUnreachableCodeImpl(method, ownerClassName) val removedHandlers = removeEmptyExceptionHandlers(method) - (codeRemoved, removedHandlers.nonEmpty, removedHandlers.exists(h => liveLabels(h.start))) + (removedInstructions.nonEmpty, removedHandlers.nonEmpty, removedHandlers.exists(h => liveLabels(h.start))) } else { (false, false, false) } @@ -179,6 +172,8 @@ class LocalOpt(settings: ScalaSettings) { assert(nullOrEmpty(method.visibleLocalVariableAnnotations), method.visibleLocalVariableAnnotations) assert(nullOrEmpty(method.invisibleLocalVariableAnnotations), method.invisibleLocalVariableAnnotations) + unreachableCodeEliminated += method + codeHandlersOrJumpsChanged || localsRemoved || lineNumbersRemoved || labelsRemoved } @@ -186,8 +181,10 @@ class LocalOpt(settings: ScalaSettings) { * Removes unreachable basic blocks. * * TODO: rewrite, don't use computeMaxLocalsMaxStack (runs a ClassWriter) / Analyzer. Too slow. + * + * @return A set containing eliminated instructions, and a set containing all live label nodes. */ - def removeUnreachableCodeImpl(method: MethodNode, ownerClassName: InternalName): (Boolean, Set[LabelNode]) = { + def removeUnreachableCodeImpl(method: MethodNode, ownerClassName: InternalName): (Set[AbstractInsnNode], Set[LabelNode]) = { // The data flow analysis requires the maxLocals / maxStack fields of the method to be computed. computeMaxLocalsMaxStack(method) val a = new Analyzer(new BasicInterpreter) @@ -197,6 +194,7 @@ class LocalOpt(settings: ScalaSettings) { val initialSize = method.instructions.size var i = 0 var liveLabels = Set.empty[LabelNode] + var removedInstructions = Set.empty[AbstractInsnNode] val itr = method.instructions.iterator() while (itr.hasNext) { itr.next() match { @@ -209,11 +207,12 @@ class LocalOpt(settings: ScalaSettings) { // Instruction iterators allow removing during iteration. // Removing is O(1): instructions are doubly linked list elements. itr.remove() + removedInstructions += ins } } i += 1 } - (method.instructions.size != initialSize, liveLabels) + (removedInstructions, liveLabels) } /** |