path: root/src/compiler/scala/tools/nsc/backend/jvm/opt/CallGraph.scala

/* NSC -- new Scala compiler
 * Copyright 2005-2014 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc
package backend.jvm
package opt

import scala.collection.immutable.IntMap
import scala.reflect.internal.util.{NoPosition, Position}
import scala.tools.asm.tree.analysis.{Value, Analyzer, BasicInterpreter}
import scala.tools.asm.{Opcodes, Type, Handle}
import scala.tools.asm.tree._
import scala.collection.{concurrent, mutable}
import scala.collection.convert.decorateAsScala._
import scala.tools.nsc.backend.jvm.BTypes.InternalName
import scala.tools.nsc.backend.jvm.BackendReporting._
import scala.tools.nsc.backend.jvm.analysis.{ParameterProducer, ProdConsAnalyzer, NotNull, NullnessAnalyzer}
import ByteCodeRepository.{Source, CompilationUnit}
import BytecodeUtils._

class CallGraph[BT <: BTypes](val btypes: BT) {
  import btypes._

  /**
   * The call graph contains the callsites in the program being compiled.
   *
   * Indexing the call graph by the containing MethodNode and the invocation MethodInsnNode allows
   * finding callsites efficiently. For example, an inlining heuristic might want to know all
   * callsites withing a callee method.
   *
   * Note that call graph entries (Callsite instances) keep a reference to the invocation
   * MethodInsnNode, which keeps all AbstractInsnNodes of the method reachable. Adding classes
   * from the classpath to the call graph (in addition to classes being compiled) may prevent
   * method instruction nodes from being GCd. The ByteCodeRepository has a fixed size cache for
   * parsed ClassNodes - keeping all ClassNodes alive consumed too much memory.
   * The call graph is less problematic because only methods being called are kept alive, not entire
   * classes. But we should keep an eye on this.
   */
  val callsites: mutable.Map[MethodNode, Map[MethodInsnNode, Callsite]] = recordPerRunCache(concurrent.TrieMap.empty withDefaultValue Map.empty)

  /**
   * Closure instantiations in the program being compiled.
   *
   * Indexing closure instantiations by the containing MethodNode is beneficial for the closure
   * optimizer: finding callsites to re-write requires running a producers-consumers analysis on
   * the method. Here the closure instantiations are already grouped by method.
   */
  val closureInstantiations: mutable.Map[MethodNode, Map[InvokeDynamicInsnNode, ClosureInstantiation]] = recordPerRunCache(concurrent.TrieMap.empty withDefaultValue Map.empty)

  def removeCallsite(invocation: MethodInsnNode, methodNode: MethodNode): Option[Callsite] = {
    val methodCallsites = callsites(methodNode)
    val newCallsites = methodCallsites - invocation
    if (newCallsites.isEmpty) callsites.remove(methodNode)
    else callsites(methodNode) = newCallsites
    methodCallsites.get(invocation)
  }

  def addCallsite(callsite: Callsite): Unit = {
    val methodCallsites = callsites(callsite.callsiteMethod)
    callsites(callsite.callsiteMethod) = methodCallsites + (callsite.callsiteInstruction -> callsite)
  }

  def removeClosureInstantiation(indy: InvokeDynamicInsnNode, methodNode: MethodNode): Option[ClosureInstantiation] = {
    val methodClosureInits = closureInstantiations(methodNode)
    val newClosureInits = methodClosureInits - indy
    if (newClosureInits.isEmpty) closureInstantiations.remove(methodNode)
    else closureInstantiations(methodNode) = newClosureInits
    methodClosureInits.get(indy)
  }

  def addClosureInstantiation(closureInit: ClosureInstantiation) = {
    val methodClosureInits = closureInstantiations(closureInit.ownerMethod)
    closureInstantiations(closureInit.ownerMethod) = methodClosureInits + (closureInit.lambdaMetaFactoryCall.indy -> closureInit)
  }

  def addClass(classNode: ClassNode): Unit = {
    val classType = classBTypeFromClassNode(classNode)
    classNode.methods.asScala.foreach(addMethod(_, classType))
  }

  def addIfMissing(methodNode: MethodNode, definingClass: ClassBType): Unit = {
    if (!callsites.contains(methodNode)) addMethod(methodNode, definingClass)
  }

  /**
   * Returns a list of callsites in the method, plus a list of closure instantiation indy instructions.
   */
  def addMethod(methodNode: MethodNode, definingClass: ClassBType): Unit = {
    // TODO: run dataflow analyses to make the call graph more precise
    //  - producers to get forwarded parameters (ForwardedParam)
    //  - typeAnalysis for more precise argument types, more precise callee

    // For now we run a NullnessAnalyzer. It is used to determine if the receiver of an instance
    // call is known to be not-null, in which case we don't have to emit a null check when inlining.
    // It is also used to get the stack height at the call site.
    localOpt.minimalRemoveUnreachableCode(methodNode, definingClass.internalName)

    val analyzer: Analyzer[_ <: Value] = {
      if (compilerSettings.YoptNullnessTracking) new NullnessAnalyzer
      else new Analyzer(new BasicInterpreter)
    }
    analyzer.analyze(definingClass.internalName, methodNode)

    def receiverNotNullByAnalysis(call: MethodInsnNode, numArgs: Int) = analyzer match {
      case nullnessAnalyzer: NullnessAnalyzer =>
        val frame = nullnessAnalyzer.frameAt(call, methodNode)
        frame.getStack(frame.getStackSize - 1 - numArgs).nullness == NotNull

      case _ => false
    }

    var methodCallsites = Map.empty[MethodInsnNode, Callsite]
    var methodClosureInstantiations = Map.empty[InvokeDynamicInsnNode, ClosureInstantiation]

    // lazy so it is only computed if actually used by computeArgInfos
    lazy val prodCons = new ProdConsAnalyzer(methodNode, definingClass.internalName)

    methodNode.instructions.iterator.asScala foreach {
      case call: MethodInsnNode =>
        val callee: Either[OptimizerWarning, Callee] = for {
          (method, declarationClass)     <- byteCodeRepository.methodNode(call.owner, call.name, call.desc): Either[OptimizerWarning, (MethodNode, InternalName)]
          (declarationClassNode, source) <- byteCodeRepository.classNodeAndSource(declarationClass): Either[OptimizerWarning, (ClassNode, Source)]
          declarationClassBType          =  classBTypeFromClassNode(declarationClassNode)
        } yield {
          val CallsiteInfo(safeToInline, safeToRewrite, annotatedInline, annotatedNoInline, higherOrderParams, warning) = analyzeCallsite(method, declarationClassBType, call.owner, source)
          Callee(
            callee = method,
            calleeDeclarationClass = declarationClassBType,
            safeToInline = safeToInline,
            safeToRewrite = safeToRewrite,
            annotatedInline = annotatedInline,
            annotatedNoInline = annotatedNoInline,
            higherOrderParams = higherOrderParams,
            calleeInfoWarning = warning)
        }

        val argInfos = computeArgInfos(callee, call, methodNode, definingClass, Some(prodCons))

        val receiverNotNull = call.getOpcode == Opcodes.INVOKESTATIC || {
          val numArgs = Type.getArgumentTypes(call.desc).length
          receiverNotNullByAnalysis(call, numArgs)
        }

        methodCallsites += call -> Callsite(
          callsiteInstruction = call,
          callsiteMethod = methodNode,
          callsiteClass = definingClass,
          callee = callee,
          argInfos = argInfos,
          callsiteStackHeight = analyzer.frameAt(call, methodNode).getStackSize,
          receiverKnownNotNull = receiverNotNull,
          callsitePosition = callsitePositions.getOrElse(call, NoPosition)
        )

      case LambdaMetaFactoryCall(indy, samMethodType, implMethod, instantiatedMethodType) =>
        methodClosureInstantiations += indy -> ClosureInstantiation(
          LambdaMetaFactoryCall(indy, samMethodType, implMethod, instantiatedMethodType),
          methodNode,
          definingClass)

      case _ =>
    }

    callsites(methodNode) = methodCallsites
    closureInstantiations(methodNode) = methodClosureInstantiations
  }
  
  def computeArgInfos(
                       callee: Either[OptimizerWarning, Callee],
                       callsiteInsn: MethodInsnNode, callsiteMethod: MethodNode, callsiteClass: ClassBType,
                       methodProdCons: => Option[ProdConsAnalyzer] = None): IntMap[ArgInfo] = {
    if (callee.isLeft) IntMap.empty
    else {
      if (callee.get.higherOrderParams.nonEmpty) {

        val prodCons = methodProdCons.getOrElse({
          localOpt.minimalRemoveUnreachableCode(callsiteMethod, callsiteClass.internalName)
          new ProdConsAnalyzer(callsiteMethod, callsiteClass.internalName)
        })

        // TODO: use type analysis instead - should be more efficient than prodCons
        // some random thoughts:
        //  - assign special types to parameters and indy-lambda-functions to track them
        //  - upcast should not change type flow analysis: don't lose information.
        //  - can we do something about factory calls? Foo(x) for case class foo gives a Foo.
        //    inline the factory? analysis across method boundry?

        lazy val callFrame = prodCons.frameAt(callsiteInsn)
        val receiverOrFirstArgSlot = {
          val numArgs = Type.getArgumentTypes(callsiteInsn.desc).length + (if (callsiteInsn.getOpcode == Opcodes.INVOKESTATIC) 0 else 1)
          callFrame.stackTop - numArgs + 1
        }
        callee.get.higherOrderParams flatMap {
          case (index, paramType) =>
            val prods = prodCons.initialProducersForValueAt(callsiteInsn, receiverOrFirstArgSlot + index)
            if (prods.size != 1) None
            else {
              val argInfo = prods.head match {
                case LambdaMetaFactoryCall(_, _, _, _) => Some(FunctionLiteral)
                case ParameterProducer(local)          => Some(ForwardedParam(local))
                case _                                 => None
              }
              argInfo.map((index, _))
            }
        }
      } else {
        IntMap.empty
      }
    }
  }

  /**
   * Just a named tuple used as return type of `analyzeCallsite`.
   */
  private case class CallsiteInfo(safeToInline: Boolean, safeToRewrite: Boolean,
                                  annotatedInline: Boolean, annotatedNoInline: Boolean,
                                  higherOrderParams: IntMap[ClassBType],
                                  warning: Option[CalleeInfoWarning])

  /**
   * Analyze a callsite and gather meta-data that can be used for inlining decisions.
   */
  private def analyzeCallsite(calleeMethodNode: MethodNode, calleeDeclarationClassBType: ClassBType, receiverTypeInternalName: InternalName, calleeSource: Source): CallsiteInfo = {
    val methodSignature = calleeMethodNode.name + calleeMethodNode.desc

    try {
      // The inlineInfo.methodInfos of a ClassBType holds an InlineInfo for each method *declared*
      // within a class (not for inherited methods). Since we already have the  classBType of the
      // callee, we only check there for the methodInlineInfo, we should find it there.
      calleeDeclarationClassBType.info.orThrow.inlineInfo.methodInfos.get(methodSignature) match {
        case Some(methodInlineInfo) =>
          val canInlineFromSource = compilerSettings.YoptInlineGlobal || calleeSource == CompilationUnit

          val isAbstract = BytecodeUtils.isAbstractMethod(calleeMethodNode)

          val receiverType = classBTypeFromParsedClassfile(receiverTypeInternalName)
          // (1) A non-final method can be safe to inline if the receiver type is a final subclass. Example:
          //   class A { @inline def f = 1 }; object B extends A; B.f  // can be inlined
          //
          // TODO: (1) doesn't cover the following example:
          //   trait TravLike { def map = ... }
          //   sealed trait List extends TravLike { ... } // assume map is not overridden
          //   final case class :: / final case object Nil
          //   (l: List).map // can be inlined
          // we need to know that
          //   - the recevier is sealed
          //   - what are the children of the receiver
          //   - all children are final
          //   - none of the children overrides map
          //
          // TODO: type analysis can render more calls statically resolved. Example:
          //   new A.f  // can be inlined, the receiver type is known to be exactly A.
          val isStaticallyResolved: Boolean = {
            methodInlineInfo.effectivelyFinal ||
              receiverType.info.orThrow.inlineInfo.isEffectivelyFinal // (1)
          }

          val isRewritableTraitCall = isStaticallyResolved && methodInlineInfo.traitMethodWithStaticImplementation

          val warning = calleeDeclarationClassBType.info.orThrow.inlineInfo.warning.map(
            MethodInlineInfoIncomplete(calleeDeclarationClassBType.internalName, calleeMethodNode.name, calleeMethodNode.desc, _))

          // (1) For invocations of final trait methods, the callee isStaticallyResolved but also
          //     abstract. Such a callee is not safe to inline - it needs to be re-written to the
          //     static impl method first (safeToRewrite).
          // (2) Final trait methods can be rewritten from the interface to the static implementation
          //     method to enable inlining.
          CallsiteInfo(
            safeToInline      =
              canInlineFromSource &&
                isStaticallyResolved &&  // (1)
                !isAbstract &&
                !BytecodeUtils.isConstructor(calleeMethodNode) &&
                !BytecodeUtils.isNativeMethod(calleeMethodNode),
            safeToRewrite     = canInlineFromSource && isRewritableTraitCall, // (2)
            annotatedInline   = methodInlineInfo.annotatedInline,
            annotatedNoInline = methodInlineInfo.annotatedNoInline,
            higherOrderParams = inliner.heuristics.higherOrderParams(calleeMethodNode, receiverType),
            warning           = warning)

        case None =>
          val warning = MethodInlineInfoMissing(calleeDeclarationClassBType.internalName, calleeMethodNode.name, calleeMethodNode.desc, calleeDeclarationClassBType.info.orThrow.inlineInfo.warning)
          CallsiteInfo(false, false, false, false, IntMap.empty, Some(warning))
      }
    } catch {
      case Invalid(noInfo: NoClassBTypeInfo) =>
        val warning = MethodInlineInfoError(calleeDeclarationClassBType.internalName, calleeMethodNode.name, calleeMethodNode.desc, noInfo)
        CallsiteInfo(false, false, false, false, IntMap.empty, Some(warning))
    }
  }

    /**
   * A callsite in the call graph.
   *
   * @param callsiteInstruction The invocation instruction
   * @param callsiteMethod      The method containing the callsite
   * @param callsiteClass       The class containing the callsite
   * @param callee              The callee, as it appears in the invocation instruction. For virtual
   *                            calls, an override of the callee might be invoked. Also, the callee
   *                            can be abstract. Contains a warning message if the callee MethodNode
   *                            cannot be found in the bytecode repository.
   * @param argInfos            Information about the invocation receiver and arguments
   * @param callsiteStackHeight The stack height at the callsite, required by the inliner
   * @param callsitePosition    The source position of the callsite, used for inliner warnings.
   */
  final case class Callsite(callsiteInstruction: MethodInsnNode, callsiteMethod: MethodNode, callsiteClass: ClassBType,
                            callee: Either[OptimizerWarning, Callee], argInfos: IntMap[ArgInfo],
                            callsiteStackHeight: Int, receiverKnownNotNull: Boolean, callsitePosition: Position) {
    override def toString =
      "Invocation of" +
        s" ${callee.map(_.calleeDeclarationClass.internalName).getOrElse("?")}.${callsiteInstruction.name + callsiteInstruction.desc}" +
        s"@${callsiteMethod.instructions.indexOf(callsiteInstruction)}" +
        s" in ${callsiteClass.internalName}.${callsiteMethod.name}"
  }

  /**
   * Information about invocation arguments, obtained through data flow analysis of the callsite method.
   */
  sealed trait ArgInfo
  case object FunctionLiteral extends ArgInfo
  final case class ForwardedParam(index: Int) extends ArgInfo
  //  final case class ArgTypeInfo(argType: BType, isPrecise: Boolean, knownNotNull: Boolean) extends ArgInfo
  // can be extended, e.g., with constant types

  /**
   * A callee in the call graph.
   *
   * @param callee                 The callee, as it appears in the invocation instruction. For
   *                               virtual calls, an override of the callee might be invoked. Also,
   *                               the callee can be abstract.
   * @param calleeDeclarationClass The class in which the callee is declared
   * @param safeToInline           True if the callee can be safely inlined: it cannot be overridden,
   *                               and the inliner settings (project / global) allow inlining it.
   * @param safeToRewrite          True if the callee is the interface method of a concrete trait method
   *                               that can be safely re-written to the static implementation method.
   * @param annotatedInline        True if the callee is annotated @inline
   * @param annotatedNoInline      True if the callee is annotated @noinline
   * @param higherOrderParams      A map from parameter positions to SAM parameter types
   * @param calleeInfoWarning      An inliner warning if some information was not available while
   *                               gathering the information about this callee.
   */
  final case class Callee(callee: MethodNode, calleeDeclarationClass: ClassBType,
                          safeToInline: Boolean, safeToRewrite: Boolean,
                          annotatedInline: Boolean, annotatedNoInline: Boolean,
                          higherOrderParams: IntMap[ClassBType],
                          calleeInfoWarning: Option[CalleeInfoWarning]) {
    assert(!(safeToInline && safeToRewrite), s"A callee of ${callee.name} can be either safeToInline or safeToRewrite, but not both.")
    override def toString = s"Callee($calleeDeclarationClass.${callee.name})"
  }

  final case class ClosureInstantiation(lambdaMetaFactoryCall: LambdaMetaFactoryCall, ownerMethod: MethodNode, ownerClass: ClassBType) {
    override def toString = s"ClosureInstantiation($lambdaMetaFactoryCall, ${ownerMethod.name + ownerMethod.desc}, $ownerClass)"
  }
  final case class LambdaMetaFactoryCall(indy: InvokeDynamicInsnNode, samMethodType: Type, implMethod: Handle, instantiatedMethodType: Type)

  object LambdaMetaFactoryCall {
    private val lambdaMetaFactoryInternalName: InternalName = "java/lang/invoke/LambdaMetafactory"

    private val metafactoryHandle = {
      val metafactoryMethodName: String = "metafactory"
      val metafactoryDesc: String       = "(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;"
      new Handle(Opcodes.H_INVOKESTATIC, lambdaMetaFactoryInternalName, metafactoryMethodName, metafactoryDesc)
    }

    private val altMetafactoryHandle = {
      val altMetafactoryMethodName: String = "altMetafactory"
      val altMetafactoryDesc: String       = "(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;[Ljava/lang/Object;)Ljava/lang/invoke/CallSite;"
      new Handle(Opcodes.H_INVOKESTATIC, lambdaMetaFactoryInternalName, altMetafactoryMethodName, altMetafactoryDesc)
    }

    def unapply(insn: AbstractInsnNode): Option[(InvokeDynamicInsnNode, Type, Handle, Type)] = insn match {
      case indy: InvokeDynamicInsnNode if indy.bsm == metafactoryHandle || indy.bsm == altMetafactoryHandle =>
        indy.bsmArgs match {
          case Array(samMethodType: Type, implMethod: Handle, instantiatedMethodType: Type, xs@_*) => // xs binding because IntelliJ gets confused about _@_*
            // LambdaMetaFactory performs a number of automatic adaptations when invoking the lambda
            // implementation method (casting, boxing, unboxing, and primitive widening, see Javadoc).
            //
            // The closure optimizer supports only one of those adaptations: it will cast arguments
            // to the correct type when re-writing a closure call to the body method. Example:
            //
            //   val fun: String => String = l => l
            //   val l = List("")
            //   fun(l.head)
            //
            // The samMethodType of Function1 is `(Object)Object`, while the instantiatedMethodType
            // is `(String)String`. The return type of `List.head` is `Object`.
            //
            // The implMethod has the signature `C$anonfun(String)String`.
            //
            // At the closure callsite, we have an `INVOKEINTERFACE Function1.apply (Object)Object`,
            // so the object returned by `List.head` can be directly passed into the call (no cast).
            //
            // The closure object will cast the object to String before passing it to the implMethod.
            //
            // When re-writing the closure callsite to the implMethod, we have to insert a cast.
            //
            // The check below ensures that
            //   (1) the implMethod type has the expected singature (captured types plus argument types
            //       from instantiatedMethodType)
            //   (2) the receiver of the implMethod matches the first captured type
            //   (3) all parameters that are not the same in samMethodType and instantiatedMethodType
            //       are reference types, so that we can insert casts to perform the same adaptation
            //       that the closure object would.

            val isStatic                   = implMethod.getTag == Opcodes.H_INVOKESTATIC
            val indyParamTypes             = Type.getArgumentTypes(indy.desc)
            val instantiatedMethodArgTypes = instantiatedMethodType.getArgumentTypes
            val expectedImplMethodType     = {
              val paramTypes = (if (isStatic) indyParamTypes else indyParamTypes.tail) ++ instantiatedMethodArgTypes
              Type.getMethodType(instantiatedMethodType.getReturnType, paramTypes: _*)
            }

            val isIndyLambda = (
                 Type.getType(implMethod.getDesc) == expectedImplMethodType              // (1)
              && (isStatic || implMethod.getOwner == indyParamTypes(0).getInternalName)  // (2)
              && samMethodType.getArgumentTypes.corresponds(instantiatedMethodArgTypes)((samArgType, instArgType) =>
                   samArgType == instArgType || isReference(samArgType) && isReference(instArgType)) // (3)
            )

            if (isIndyLambda) Some((indy, samMethodType, implMethod, instantiatedMethodType))
            else None

          case _ => None
        }
      case _ => None
    }
  }
}