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Scala example source code file (GenICode.scala)

This example Scala source code file (GenICode.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

apply, context, context, int, list, long, select, symbol, tree, tree, typekind, typekind, unit, unit

The Scala GenICode.scala source code

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author  Martin Odersky
 */


package scala.tools.nsc
package backend
package icode

import scala.collection.{ mutable, immutable }
import scala.collection.mutable.{ ListBuffer, Buffer }
import scala.tools.nsc.symtab._
import scala.annotation.switch
import PartialFunction._

/** This class ...
 *
 *  @author  Iulian Dragos
 *  @version 1.0
 */
abstract class GenICode extends SubComponent  {
  import global._
  import icodes._
  import icodes.opcodes._
  import definitions.{
    ArrayClass, ObjectClass, ThrowableClass, StringClass, StringModule, NothingClass, NullClass, AnyRefClass,
    Object_equals, Object_isInstanceOf, Object_asInstanceOf, ScalaRunTimeModule,
    BoxedNumberClass, BoxedCharacterClass,
    getMember
  }
  import scalaPrimitives.{
    isArrayOp, isComparisonOp, isLogicalOp,
    isUniversalEqualityOp, isReferenceEqualityOp
  }
  import platform.isMaybeBoxed

  val phaseName = "icode"

  override def newPhase(prev: Phase) = new ICodePhase(prev)
  
  private def debugLog(msg: => String): Unit =
    if (settings.debug.value) log(msg)

  class ICodePhase(prev: Phase) extends StdPhase(prev) {

    override def description = "Generate ICode from the AST"

    var unit: CompilationUnit = _

    override def run() {
      scalaPrimitives.init
      classes.clear
      super.run
    }

    override def apply(unit: CompilationUnit): Unit = {
      this.unit = unit
      unit.icode.clear
      informProgress("Generating icode for " + unit)
      gen(unit.body)
      this.unit = null
    }

    def gen(tree: Tree): Context = gen(tree, new Context())

    def gen(trees: List[Tree], ctx: Context): Context = {
      var ctx1 = ctx
      for (t <- trees) ctx1 = gen(t, ctx1)
      ctx1
    }

    /////////////////// Code generation ///////////////////////

    def gen(tree: Tree, ctx: Context): Context = tree match {
      case EmptyTree => ctx

      case PackageDef(pid, stats) =>
        gen(stats, ctx setPackage pid.name)

      case ClassDef(mods, name, _, impl) =>
        log("Generating class: " + tree.symbol.fullName)
        val outerClass = ctx.clazz
        ctx setClass (new IClass(tree.symbol) setCompilationUnit unit)
        addClassFields(ctx, tree.symbol);
        classes += (tree.symbol -> ctx.clazz)
        unit.icode += ctx.clazz
        gen(impl, ctx)
        ctx.clazz.methods = ctx.clazz.methods.reverse // preserve textual order
        ctx.clazz.fields  = ctx.clazz.fields.reverse  // preserve textual order
        ctx setClass outerClass

      // !! modules should be eliminated by refcheck... or not?
      case ModuleDef(mods, name, impl) =>
        abort("Modules should not reach backend!")

      case ValDef(mods, name, tpt, rhs) =>
        ctx // we use the symbol to add fields

      case DefDef(mods, name, tparams, vparamss, tpt, rhs) =>
        if (settings.debug.value)
          log("Entering method " + name)
        val m = new IMethod(tree.symbol)
        m.sourceFile = unit.source.toString()
        m.returnType = if (tree.symbol.isConstructor) UNIT
                       else toTypeKind(tree.symbol.info.resultType)
        ctx.clazz.addMethod(m)

        var ctx1 = ctx.enterMethod(m, tree.asInstanceOf[DefDef])
        addMethodParams(ctx1, vparamss)
        m.native = m.symbol.hasAnnotation(definitions.NativeAttr)

        if (!m.isAbstractMethod && !m.native) {
          ctx1 = genLoad(rhs, ctx1, m.returnType);

          // reverse the order of the local variables, to match the source-order
          m.locals = m.locals.reverse

          rhs match {
            case Block(_, Return(_)) => ()
            case Return(_) => ()
            case EmptyTree => 
              globalError("Concrete method has no definition: " + tree)
            case _ => if (ctx1.bb.isEmpty)
              ctx1.bb.closeWith(RETURN(m.returnType), rhs.pos)
            else
              ctx1.bb.closeWith(RETURN(m.returnType))
          }
          if (!ctx1.bb.closed) ctx1.bb.close
          prune(ctx1.method)
        } else
          ctx1.method.setCode(null)
        ctx1

      case Template(_, _, body) =>
        gen(body, ctx)

      case _ =>
        abort("Illegal tree in gen: " + tree)
    }

    private def genStat(trees: List[Tree], ctx: Context): Context = 
      trees.foldLeft(ctx)((currentCtx, t) => genStat(t, currentCtx))

    /**
     * Generate code for the given tree. The trees should contain statements
     * and not produce any value. Use genLoad for expressions which leave
     * a value on top of the stack.
     *
     * @param tree ...
     * @param ctx  ...
     * @return a new context. This is necessary for control flow instructions
     *         which may change the current basic block.
     */
    private def genStat(tree: Tree, ctx: Context): Context = tree match {
      case Assign(lhs @ Select(_, _), rhs) =>
        val isStatic = lhs.symbol.isStaticMember
        var ctx1 = if (isStatic) ctx
                   else if (forMSIL && msil_IsValuetypeInstField(lhs.symbol))
                     msil_genLoadQualifierAddress(lhs, ctx)
                   else genLoadQualifier(lhs, ctx)
        
        ctx1 = genLoad(rhs, ctx1, toTypeKind(lhs.symbol.info))
        ctx1.bb.emit(STORE_FIELD(lhs.symbol, isStatic), tree.pos)
        ctx1

      case Assign(lhs, rhs) =>
        val ctx1 = genLoad(rhs, ctx, toTypeKind(lhs.symbol.info))
        val Some(l) = ctx.method.lookupLocal(lhs.symbol)
        ctx1.bb.emit(STORE_LOCAL(l), tree.pos)
        ctx1

      case _ =>
        genLoad(tree, ctx, UNIT)
    }
    
    private def genThrow(expr: Tree, ctx: Context): (Context, TypeKind) = {
      require(expr.tpe <:< ThrowableClass.tpe)
    
      val thrownKind = toTypeKind(expr.tpe)
      val ctx1       = genLoad(expr, ctx, thrownKind)
      ctx1.bb.emit(THROW(expr.tpe.typeSymbol), expr.pos)
      ctx1.bb.enterIgnoreMode

      (ctx1, NothingReference)
    }

    /**
     * Generate code for primitive arithmetic operations.
     * Returns (Context, Generated Type)
     */
    private def genArithmeticOp(tree: Tree, ctx: Context, code: Int): (Context, TypeKind) = {
      val Apply(fun @ Select(larg, _), args) = tree
      var ctx1 = ctx
      var resKind = toTypeKind(larg.tpe)

      if (settings.debug.value) {
        assert(args.length <= 1,
               "Too many arguments for primitive function: " + fun.symbol)
        assert(resKind.isNumericType | resKind == BOOL,
               resKind.toString() + " is not a numeric or boolean type " +
               "[operation: " + fun.symbol + "]")
      }

      args match {
        // unary operation
        case Nil =>
          ctx1 = genLoad(larg, ctx1, resKind)
          code match {
            case scalaPrimitives.POS =>
              () // nothing 
            case scalaPrimitives.NEG =>
              ctx1.bb.emit(CALL_PRIMITIVE(Negation(resKind)), larg.pos)
            case scalaPrimitives.NOT =>
              ctx1.bb.emit(CALL_PRIMITIVE(Arithmetic(NOT, resKind)), larg.pos)
            case _ =>
              abort("Unknown unary operation: " + fun.symbol.fullName +
                    " code: " + code)
          }

        // binary operation
        case rarg :: Nil =>
          resKind = getMaxType(larg.tpe :: rarg.tpe :: Nil);
          if (scalaPrimitives.isShiftOp(code) || scalaPrimitives.isBitwiseOp(code))
            assert(resKind.isIntegralType | resKind == BOOL,
                 resKind.toString() + " incompatible with arithmetic modulo operation: " + ctx1);
                 
          ctx1 = genLoad(larg, ctx1, resKind)
          ctx1 = genLoad(rarg,
                         ctx1, // check .NET size of shift arguments!
                         if (scalaPrimitives.isShiftOp(code)) INT else resKind)
                         
          val primitiveOp = code match {
            case scalaPrimitives.ADD    => Arithmetic(ADD, resKind)
            case scalaPrimitives.SUB    => Arithmetic(SUB, resKind)
            case scalaPrimitives.MUL    => Arithmetic(MUL, resKind)
            case scalaPrimitives.DIV    => Arithmetic(DIV, resKind)
            case scalaPrimitives.MOD    => Arithmetic(REM, resKind)
            case scalaPrimitives.OR     => Logical(OR, resKind)
            case scalaPrimitives.XOR    => Logical(XOR, resKind)
            case scalaPrimitives.AND    => Logical(AND, resKind)
            case scalaPrimitives.LSL    => Shift(LSL, resKind)
            case scalaPrimitives.LSR    => Shift(LSR, resKind)
            case scalaPrimitives.ASR    => Shift(ASR, resKind)
            case _                      => abort("Unknown primitive: " + fun.symbol + "[" + code + "]")
          }
          ctx1.bb.emit(CALL_PRIMITIVE(primitiveOp), tree.pos)

        case _ =>
          abort("Too many arguments for primitive function: " + tree)
      }
      (ctx1, resKind)
    }
    
    /** Generate primitive array operations.
     *
     *  @param tree ...
     *  @param ctx  ...
     *  @param code ...
     *  @return     ...
     */
    private def genArrayOp(tree: Tree, ctx: Context, code: Int, expectedType: TypeKind): (Context, TypeKind) = {
      import scalaPrimitives._
      val Apply(Select(arrayObj, _), args) = tree
      val k = toTypeKind(arrayObj.tpe)
      val ARRAY(elem) = k
      var ctx1 = genLoad(arrayObj, ctx, k)
      val elementType = typeOfArrayOp.getOrElse(code, abort("Unknown operation on arrays: " + tree + " code: " + code))

      var generatedType = expectedType

      if (scalaPrimitives.isArrayGet(code)) {
        // load argument on stack
        if (settings.debug.value)
          assert(args.length == 1,
                 "Too many arguments for array get operation: " + tree);
        ctx1 = genLoad(args.head, ctx1, INT)
        generatedType = elem
        ctx1.bb.emit(LOAD_ARRAY_ITEM(elementType), tree.pos)
      }
      else if (scalaPrimitives.isArraySet(code)) {
        if (settings.debug.value)
          assert(args.length == 2,
                 "Too many arguments for array set operation: " + tree);
        ctx1 = genLoad(args.head, ctx1, INT)
        ctx1 = genLoad(args.tail.head, ctx1, toTypeKind(args.tail.head.tpe))
        // the following line should really be here, but because of bugs in erasure
        // we pretend we generate whatever type is expected from us.
        //generatedType = UNIT

        ctx1.bb.emit(STORE_ARRAY_ITEM(elementType), tree.pos)
      }
      else {
        generatedType = INT
        ctx1.bb.emit(CALL_PRIMITIVE(ArrayLength(elementType)), tree.pos)
      }

      (ctx1, generatedType)
    }
    private def genSynchronized(tree: Apply, ctx: Context, expectedType: TypeKind): (Context, TypeKind) = {
      val Apply(fun, args) = tree
      val monitor = ctx.makeLocal(tree.pos, ObjectClass.tpe, "monitor")
      var monitorResult: Local = null

      // if the synchronized block returns a result, store it in a local variable. just leaving
      // it on the stack is not valid in MSIL (stack is cleaned when leaving try-blocks)
      val argTpe = args.head.tpe
      val hasResult = expectedType != UNIT
      if (hasResult)
        monitorResult = ctx.makeLocal(tree.pos, argTpe, "monitorResult")

      var ctx1 = genLoadQualifier(fun, ctx)
      ctx1.bb.emit(Seq(
        DUP(ObjectReference),
        STORE_LOCAL(monitor),
        MONITOR_ENTER() setPos tree.pos
      ))
      ctx1.enterSynchronized(monitor)
      debugLog("synchronized block start")

      ctx1 = ctx1.Try(
        bodyCtx => {
          val ctx2 = genLoad(args.head, bodyCtx, expectedType /* toTypeKind(tree.tpe.resultType) */)
          if (hasResult)
            ctx2.bb.emit(STORE_LOCAL(monitorResult))
          ctx2.bb.emit(Seq(
            LOAD_LOCAL(monitor),
            MONITOR_EXIT() setPos tree.pos
          ))
          ctx2
        }, List(
          // tree.tpe / fun.tpe is object, which is no longer true after this transformation
          (ThrowableClass, expectedType, exhCtx => {
            exhCtx.bb.emit(Seq(
              LOAD_LOCAL(monitor),
              MONITOR_EXIT() setPos tree.pos,
              THROW(ThrowableClass)
            ))
            exhCtx.bb.enterIgnoreMode
            exhCtx
          })), EmptyTree, tree)
          
      debugLog("synchronized block end with block %s closed=%s".format(ctx1.bb, ctx1.bb.closed))
      ctx1.exitSynchronized(monitor)
      if (hasResult)
        ctx1.bb.emit(LOAD_LOCAL(monitorResult))
      (ctx1, expectedType)
    } 
    
    private def genLoadIf(tree: If, ctx: Context, expectedType: TypeKind): (Context, TypeKind) = {
      val If(cond, thenp, elsep) = tree
      
      var thenCtx = ctx.newBlock
      var elseCtx = ctx.newBlock
      val contCtx = ctx.newBlock
      
      genCond(cond, ctx, thenCtx, elseCtx)
      
      val ifKind = toTypeKind(tree.tpe)
      val thenKind = toTypeKind(thenp.tpe)
      val elseKind = if (elsep == EmptyTree) UNIT else toTypeKind(elsep.tpe)

      // we need to drop unneeded results, if one branch gives
      // unit and the other gives something on the stack, because
      // the type of 'if' is scala.Any, and its erasure would be Object.
      // But unboxed units are not Objects...
      def hasUnitBranch = thenKind == UNIT || elseKind == UNIT
      val resKind = if (hasUnitBranch) UNIT else ifKind

      if (hasUnitBranch)
        debugLog("Will drop result from an if branch")

      thenCtx = genLoad(thenp, thenCtx, resKind)
      elseCtx = genLoad(elsep, elseCtx, resKind)
      
      assert(!settings.debug.value || !(hasUnitBranch && expectedType != UNIT),
        "I produce UNIT in a context where " + expectedType + " is expected!")

      // alternatives may be already closed by a tail-recursive jump
      thenCtx.bb.closeWith(JUMP(contCtx.bb))
      elseCtx.bb.closeWith(
          if (elsep == EmptyTree) JUMP(contCtx.bb)
          else JUMP(contCtx.bb) setPos tree.pos
        )

      (contCtx, resKind)
    }
    private def genLoadTry(tree: Try, ctx: Context, setGeneratedType: TypeKind => Unit): Context = {
      val Try(block, catches, finalizer) = tree
      val kind = toTypeKind(tree.tpe)

      val caseHandlers =
        for (CaseDef(pat, _, body) <- catches.reverse) yield {
          def genWildcardHandler(sym: Symbol): (Symbol, TypeKind, Context => Context) = 
            (sym, kind, ctx => { 
              ctx.bb.emit(DROP(REFERENCE(sym)))
              genLoad(body, ctx, kind)
            })
          
          pat match {            
            case Typed(Ident(nme.WILDCARD), tpt)  => genWildcardHandler(tpt.tpe.typeSymbol)
            case Ident(nme.WILDCARD)              => genWildcardHandler(ThrowableClass)
            case Bind(name, _)                    =>
              val exception = ctx.method addLocal new Local(pat.symbol, toTypeKind(pat.symbol.tpe), false)

              (pat.symbol.tpe.typeSymbol, kind, {
                ctx: Context =>
                  ctx.bb.emit(STORE_LOCAL(exception), pat.pos);
                  genLoad(body, ctx, kind);
              })
          }
        }

      ctx.Try(
        bodyCtx => {
          setGeneratedType(kind)
          genLoad(block, bodyCtx, kind)
        },
        caseHandlers,
        finalizer,
        tree)
    }
    
    private def genPrimitiveOp(tree: Apply, ctx: Context, expectedType: TypeKind): (Context, TypeKind) = {
      val sym = tree.symbol
      val Apply(fun @ Select(receiver, _), args) = tree
      val code = scalaPrimitives.getPrimitive(sym, receiver.tpe)

      if (scalaPrimitives.isArithmeticOp(code))
        genArithmeticOp(tree, ctx, code)
      else if (code == scalaPrimitives.CONCAT)
        (genStringConcat(tree, ctx), StringReference)
      else if (code == scalaPrimitives.HASH)
        (genScalaHash(receiver, ctx), INT)
      else if (isArrayOp(code))
        genArrayOp(tree, ctx, code, expectedType)
      else if (isLogicalOp(code) || isComparisonOp(code)) {
        val trueCtx = ctx.newBlock
        val falseCtx = ctx.newBlock
        val afterCtx = ctx.newBlock
        genCond(tree, ctx, trueCtx, falseCtx)
        trueCtx.bb.emitOnly(
          CONSTANT(Constant(true)) setPos tree.pos,
          JUMP(afterCtx.bb)
        )
        falseCtx.bb.emitOnly(
          CONSTANT(Constant(false)) setPos tree.pos,
          JUMP(afterCtx.bb)
        )
        (afterCtx, BOOL)
      }
      else if (code == scalaPrimitives.SYNCHRONIZED)
        genSynchronized(tree, ctx, expectedType)
      else if (scalaPrimitives.isCoercion(code)) {
        val ctx1 = genLoad(receiver, ctx, toTypeKind(receiver.tpe))
        genCoercion(tree, ctx1, code)
        (ctx1, scalaPrimitives.generatedKind(code))
      }
      else abort("Primitive operation not handled yet: " + sym.fullName + "(" +
                  fun.symbol.simpleName + ") " + " at: " + (tree.pos))
    }

    /**
     * forMSIL
     */
   private def msil_IsValuetypeInstMethod(msym: Symbol) = {
     val mMSILOpt = loaders.clrTypes.methods.get(msym)
     if (mMSILOpt.isEmpty) false
     else {
       val mMSIL = mMSILOpt.get
       val res = mMSIL.IsInstance && mMSIL.DeclaringType.IsValueType
       res
     }
   }

    /**
     * forMSIL
     */
    private def msil_IsValuetypeInstField(fsym: Symbol) = {
     val fMSILOpt = loaders.clrTypes.fields.get(fsym)
     if (fMSILOpt.isEmpty) false
     else {
       val fMSIL = fMSILOpt.get
       val res = !fMSIL.IsStatic && fMSIL.DeclaringType.IsValueType
       res
     }
   }

    /**
     * forMSIL: Adds a local var, the emitted code requires one more slot on the stack as on entry
     */
    private def msil_genLoadZeroOfNonEnumValuetype(ctx: Context, kind: TypeKind, pos: Position, leaveAddressOnStackInstead: Boolean) {
      val REFERENCE(clssym) = kind
      assert(loaders.clrTypes.isNonEnumValuetype(clssym))
      val local = ctx.makeLocal(pos, clssym.tpe, "tmp")
      ctx.method.addLocal(local)
      ctx.bb.emit(CIL_LOAD_LOCAL_ADDRESS(local), pos)
      ctx.bb.emit(CIL_INITOBJ(kind), pos)
      val instr = if (leaveAddressOnStackInstead)
                    CIL_LOAD_LOCAL_ADDRESS(local)
                  else
                    LOAD_LOCAL(local)
      ctx.bb.emit(instr, pos)
    }

    /**
     * forMSIL
     */
    private def msil_genLoadAddressOf(tree: Tree, ctx: Context, expectedType: TypeKind, butRawValueIsAlsoGoodEnough: Boolean): Context = {
      var generatedType = expectedType
      var addressTaken = false
      if (settings.debug.value)
        log("at line: " + (if (tree.pos.isDefined) tree.pos.line else tree.pos))

      var resCtx: Context = tree match {

        // emits CIL_LOAD_FIELD_ADDRESS
        case Select(qualifier, selector) if (!tree.symbol.isModule) =>
          addressTaken = true
          val sym = tree.symbol
          generatedType = toTypeKind(sym.info)

          if (sym.isStaticMember) {
            ctx.bb.emit(CIL_LOAD_FIELD_ADDRESS(sym, true), tree.pos)
            ctx
          } else {
            val ctx1 = genLoadQualifier(tree, ctx)
            ctx1.bb.emit(CIL_LOAD_FIELD_ADDRESS(sym, false), tree.pos)
            ctx1
          }

        // emits CIL_LOAD_LOCAL_ADDRESS
        case Ident(name) if (!tree.symbol.isPackage && !tree.symbol.isModule)=>
          addressTaken = true
          val sym = tree.symbol
          try {
            val Some(l) = ctx.method.lookupLocal(sym)
            ctx.bb.emit(CIL_LOAD_LOCAL_ADDRESS(l), tree.pos)
            generatedType = l.kind // actually, should be "V&" but the callsite is aware of this
          } catch {
            case ex: MatchError =>
              abort("symbol " + sym + " does not exist in " + ctx.method)
          }
          ctx

        // emits CIL_LOAD_ARRAY_ITEM_ADDRESS
        case Apply(fun, args) =>
          if (isPrimitive(fun.symbol)) {

            val sym = tree.symbol
            val Apply(fun @ Select(receiver, _), args) = tree
            val code = scalaPrimitives.getPrimitive(sym, receiver.tpe)

            if (isArrayOp(code)) {
              val arrayObj = receiver
              val k = toTypeKind(arrayObj.tpe)
              val ARRAY(elementType) = k
              if (scalaPrimitives.isArrayGet(code)) {
                var ctx1 = genLoad(arrayObj, ctx, k)
                // load argument on stack
                if (settings.debug.value)
                  assert(args.length == 1, "Too many arguments for array get operation: " + tree);
                ctx1 = genLoad(args.head, ctx1, INT)
                generatedType = elementType // actually "managed pointer to element type" but the callsite is aware of this
                ctx1.bb.emit(CIL_LOAD_ARRAY_ITEM_ADDRESS(elementType), tree.pos)
                addressTaken = true
                ctx1
              } else null
            } else null
          } else null

        case This(qual) =>
          /* TODO: this case handler is a placeholder for the time when Level 2 support for valuetypes is in place,
             in particular when invoking other methods on this where this is a valuetype value (boxed or not).
             As receiver, a managed pointer is expected, and a plain ldarg.0 achieves just that. */
          addressTaken = true
          genLoad(tree, ctx, expectedType)

        case _ =>
          null /* A method returning ByRef won't pass peverify, so I guess this case handler is dead code.
                  Even if it's not, the code below to handler !addressTaken below. */
      }

      if(!addressTaken) {
        resCtx = genLoad(tree, ctx, expectedType)
        if (!butRawValueIsAlsoGoodEnough) {
          // raw value on stack (must be an intermediate result, e.g. returned by method call), take address
          addressTaken = true
          val boxType = expectedType // toTypeKind(expectedType /* TODO FIXME */)
          resCtx.bb.emit(BOX(boxType), tree.pos)
          resCtx.bb.emit(CIL_UNBOX(boxType), tree.pos)
        }
      }

      // emit conversion
      if (generatedType != expectedType)
        abort("Unexpected tree in msil_genLoadAddressOf: " + tree + " at: " + tree.pos)

      resCtx
    }


    /**
     * Generate code for trees that produce values on the stack
     *
     * @param tree The tree to be translated
     * @param ctx  The current context
     * @param expectedType The type of the value to be generated on top of the
     *                     stack.
     * @return The new context. The only thing that may change is the current 
     *         basic block (as the labels map is mutable).
     */
    private def genLoad(tree: Tree, ctx: Context, expectedType: TypeKind): Context = {
      var generatedType = expectedType
      if (settings.debug.value)
        log("at line: " + (if (tree.pos.isDefined) tree.pos.line else tree.pos))

      val resCtx: Context = tree match {
        case LabelDef(name, params, rhs) =>
          val ctx1 = ctx.newBlock
          if (nme.isLoopHeaderLabel(name))
            ctx1.bb.loopHeader = true

          ctx1.labels.get(tree.symbol) match {
            case Some(label) =>
              log("Found existing label for " + tree.symbol)
              label.anchor(ctx1.bb)
              label.patch(ctx.method.code)

            case None =>
              val pair = (tree.symbol -> (new Label(tree.symbol) anchor ctx1.bb setParams (params map (_.symbol))))
              log("Adding label " + tree.symbol + " in genLoad.")
              ctx1.labels += pair
              ctx.method.addLocals(params map (p => new Local(p.symbol, toTypeKind(p.symbol.info), false)));
          }

          ctx.bb.closeWith(JUMP(ctx1.bb), tree.pos)
          genLoad(rhs, ctx1, expectedType /*toTypeKind(tree.symbol.info.resultType)*/)

        case ValDef(_, nme.THIS, _, _) =>
          if (settings.debug.value) log("skipping trivial assign to _$this: " + tree)
          ctx

        case ValDef(_, _, _, rhs) =>
          val sym = tree.symbol
          val local = ctx.method.addLocal(new Local(sym, toTypeKind(sym.info), false))

          if (rhs == EmptyTree) {
            if (settings.debug.value)
              log("Uninitialized variable " + tree + " at: " + (tree.pos));
            ctx.bb.emit(getZeroOf(local.kind))
          }

          var ctx1 = ctx
          if (rhs != EmptyTree)
            ctx1 = genLoad(rhs, ctx, local.kind);

          ctx1.bb.emit(STORE_LOCAL(local), tree.pos)
          ctx1.scope.add(local)
          ctx1.bb.emit(SCOPE_ENTER(local))
          generatedType = UNIT
          ctx1

        case t @ If(cond, thenp, elsep) =>
          val (newCtx, resKind) = genLoadIf(t, ctx, expectedType)
          generatedType = resKind
          newCtx
        
        case Return(expr) =>
          val returnedKind = toTypeKind(expr.tpe)
          log("Return(" + expr + ") with returnedKind = " + returnedKind)
          
          var ctx1         = genLoad(expr, ctx, returnedKind)
          lazy val tmp     = ctx1.makeLocal(tree.pos, expr.tpe, "tmp")
          val saved        = savingCleanups(ctx1) {
            var saved = false
            ctx1.cleanups foreach {
              case MonitorRelease(m) =>
                if (settings.debug.value)
                  log("removing " + m + " from cleanups: " + ctx1.cleanups)
                ctx1.bb.emit(Seq(LOAD_LOCAL(m), MONITOR_EXIT()))
                ctx1.exitSynchronized(m)

              case Finalizer(f, finalizerCtx) =>
                if (settings.debug.value)
                  log("removing " + f + " from cleanups: " + ctx1.cleanups)
                 
                if (returnedKind != UNIT && mayCleanStack(f)) {
                  log("Emitting STORE_LOCAL for " + tmp + " to save finalizer.")
                  ctx1.bb.emit(STORE_LOCAL(tmp))
                  saved = true
                }
                
                // duplicate finalizer (takes care of anchored labels) 
                val f1 = duplicateFinalizer(Set.empty ++ ctx1.labels.keySet, ctx1, f)

                // we have to run this without the same finalizer in
                // the list, otherwise infinite recursion happens for
                // finalizers that contain 'return'
                val fctx = finalizerCtx.newBlock
                ctx1.bb.closeWith(JUMP(fctx.bb))
                ctx1 = genLoad(f1, fctx, UNIT)
            }
            saved
          }

          if (saved) {
            log("Emitting LOAD_LOCAL for " + tmp + " after saving finalizer.")
            ctx1.bb.emit(LOAD_LOCAL(tmp))
          }
          adapt(returnedKind, ctx1.method.returnType, ctx1, tree.pos)
          ctx1.bb.emit(RETURN(ctx.method.returnType), tree.pos)
          ctx1.bb.enterIgnoreMode
          generatedType = expectedType
          ctx1

        case t @ Try(_, _, _) => genLoadTry(t, ctx, (x: TypeKind) => generatedType = x)

        case Throw(expr) =>
          val (ctx1, expectedType) = genThrow(expr, ctx)
          generatedType = expectedType
          ctx1

        case New(tpt) =>
          abort("Unexpected New")

        case Apply(TypeApply(fun, targs), _) =>
          val sym = fun.symbol
          val cast = sym match {
            case Object_isInstanceOf  => false
            case Object_asInstanceOf  => true
            case _                    => abort("Unexpected type application " + fun + "[sym: " + sym.fullName + "]" + " in: " + tree)
          }

          val Select(obj, _) = fun
          val l = toTypeKind(obj.tpe)
          val r = toTypeKind(targs.head.tpe)
          val ctx1 = genLoadQualifier(fun, ctx)

          if (l.isValueType && r.isValueType)
            genConversion(l, r, ctx1, cast)
          else if (l.isValueType) {            
            ctx1.bb.emit(DROP(l), fun.pos)
            if (cast) {
              ctx1.bb.emit(Seq(
                NEW(REFERENCE(definitions.ClassCastExceptionClass)),
                DUP(ObjectReference),
                THROW(definitions.ClassCastExceptionClass)
              ))
            } else
              ctx1.bb.emit(CONSTANT(Constant(false)))
          }
          else if (r.isValueType && cast) {
            assert(false, tree) /* Erasure should have added an unboxing operation to prevent that. */
          }
          else if (r.isValueType)
            ctx.bb.emit(IS_INSTANCE(REFERENCE(definitions.boxedClass(r.toType.typeSymbol))))
          else
            genCast(l, r, ctx1, cast);

          generatedType = if (cast) r else BOOL;
          ctx1

        // 'super' call: Note: since constructors are supposed to 
        // return an instance of what they construct, we have to take
        // special care. On JVM they are 'void', and Scala forbids (syntactically)
        // to call super constructors explicitly and/or use their 'returned' value.
        // therefore, we can ignore this fact, and generate code that leaves nothing
        // on the stack (contrary to what the type in the AST says).
        case Apply(fun @ Select(Super(_, mix), _), args) =>
          if (settings.debug.value)
            log("Call to super: " + tree);
          val invokeStyle = SuperCall(mix)
//            if (fun.symbol.isConstructor) Static(true) else SuperCall(mix);

          ctx.bb.emit(THIS(ctx.clazz.symbol), tree.pos)
          val ctx1 = genLoadArguments(args, fun.symbol.info.paramTypes, ctx)

          ctx1.bb.emit(CALL_METHOD(fun.symbol, invokeStyle), tree.pos)
          generatedType =
            if (fun.symbol.isConstructor) UNIT
            else toTypeKind(fun.symbol.info.resultType)
          ctx1

        // 'new' constructor call: Note: since constructors are
        // thought to return an instance of what they construct,
        // we have to 'simulate' it by DUPlicating the freshly created
        // instance (on JVM, <init> methods return VOID).
        case Apply(fun @ Select(New(tpt), nme.CONSTRUCTOR), args) =>
          val ctor = fun.symbol
          if (settings.debug.value)
            assert(ctor.isClassConstructor,
                   "'new' call to non-constructor: " + ctor.name)

          generatedType = toTypeKind(tpt.tpe)
          if (settings.debug.value)
            assert(generatedType.isReferenceType || generatedType.isArrayType,
                 "Non reference type cannot be instantiated: " + generatedType)

          generatedType match {
            case arr @ ARRAY(elem) =>
              val ctx1 = genLoadArguments(args, ctor.info.paramTypes, ctx)
              val dims = arr.dimensions
              var elemKind = arr.elementKind
              if (args.length > dims)
                unit.error(tree.pos, "too many arguments for array constructor: found " + args.length + 
                  " but array has only " + dims + " dimension(s)")
              if (args.length != dims)
                for (i <- args.length until dims) elemKind = ARRAY(elemKind)
              ctx1.bb.emit(CREATE_ARRAY(elemKind, args.length), tree.pos)
              ctx1

            case rt @ REFERENCE(cls) =>
              if (settings.debug.value)
                assert(ctor.owner == cls,
                       "Symbol " + ctor.owner.fullName + " is different than " + tpt)

              val ctx2 = if (forMSIL && loaders.clrTypes.isNonEnumValuetype(cls)) {
                /* parameterful constructors are the only possible custom constructors,
                   a default constructor can't be defined for valuetypes, CLR dixit */
                val isDefaultConstructor = args.isEmpty
                if (isDefaultConstructor) {
                  msil_genLoadZeroOfNonEnumValuetype(ctx, rt, tree.pos, leaveAddressOnStackInstead = false)
                  ctx
                } else {
                  val ctx1 = genLoadArguments(args, ctor.info.paramTypes, ctx)
                  ctx1.bb.emit(CIL_NEWOBJ(ctor), tree.pos)
                  ctx1
                }
              } else {
                val nw = NEW(rt)
                ctx.bb.emit(nw, tree.pos)
                ctx.bb.emit(DUP(generatedType))
                val ctx1 = genLoadArguments(args, ctor.info.paramTypes, ctx)

                val init = CALL_METHOD(ctor, Static(true))
                nw.init = init
                ctx1.bb.emit(init, tree.pos)
                ctx1
              }
              ctx2

            case _ =>
              abort("Cannot instantiate " + tpt + "of kind: " + generatedType)
          }

        case Apply(fun @ _, List(expr)) if (definitions.isBox(fun.symbol)) =>
          if (settings.debug.value)
            log("BOX : " + fun.symbol.fullName);
          val ctx1 = genLoad(expr, ctx, toTypeKind(expr.tpe))
          val nativeKind = toTypeKind(expr.tpe)
          if (settings.Xdce.value) {
            // we store this boxed value to a local, even if not really needed.
            // boxing optimization might use it, and dead code elimination will 
            // take care of unnecessary stores
            var loc1 = ctx.makeLocal(tree.pos, expr.tpe, "boxed")
            ctx1.bb.emit(STORE_LOCAL(loc1))
            ctx1.bb.emit(LOAD_LOCAL(loc1))
          }
          ctx1.bb.emit(BOX(nativeKind), expr.pos)
          generatedType = toTypeKind(fun.symbol.tpe.resultType)
          ctx1

        case Apply(fun @ _, List(expr)) if (definitions.isUnbox(fun.symbol)) =>
          if (settings.debug.value)
            log("UNBOX : " + fun.symbol.fullName)
          val ctx1 = genLoad(expr, ctx, toTypeKind(expr.tpe))
          val boxType = toTypeKind(fun.symbol.owner.linkedClassOfClass.tpe)
          generatedType = boxType
          ctx1.bb.emit(UNBOX(boxType), expr.pos)
          ctx1

        case Apply(fun @ _, List(expr)) if (forMSIL && loaders.clrTypes.isAddressOf(fun.symbol)) =>
          if (settings.debug.value)
            log("ADDRESSOF : " + fun.symbol.fullName);
          val ctx1 = msil_genLoadAddressOf(expr, ctx, toTypeKind(expr.tpe), butRawValueIsAlsoGoodEnough = false)
          generatedType = toTypeKind(fun.symbol.tpe.resultType)
          ctx1

        case app @ Apply(fun, args) =>
          val sym = fun.symbol

          if (sym.isLabel) {  // jump to a label
            val label = ctx.labels.getOrElse(sym, {
              // it is a forward jump, scan for labels
              log("Performing scan for label because of forward jump.")
              scanForLabels(ctx.defdef, ctx)
              ctx.labels.get(sym) match {
                case Some(l) => 
                  log("Found label: " + l)
                  l
                case _       =>
                  abort("Unknown label target: " + sym +
                        " at: " + (fun.pos) + ": ctx: " + ctx)
              }
            })
            val ctx1 = genLoadLabelArguments(args, label, ctx)
            ctx1.bb.emitOnly(if (label.anchored) JUMP(label.block) else PJUMP(label))
            ctx1.bb.enterIgnoreMode
            ctx1
          } else if (isPrimitive(sym)) { // primitive method call
            val (newCtx, resKind) = genPrimitiveOp(app, ctx, expectedType)
            generatedType = resKind
            newCtx            
          } else {  // normal method call
            if (settings.debug.value)
              log("Gen CALL_METHOD with sym: " + sym + " isStaticSymbol: " + sym.isStaticMember);
            val invokeStyle =
              if (sym.isStaticMember)
                Static(false)
              else if (sym.isPrivate || sym.isClassConstructor)
                Static(true)
              else
                Dynamic

            var ctx1 =
              if (invokeStyle.hasInstance) {
                if (forMSIL && !(invokeStyle.isInstanceOf[SuperCall]) && msil_IsValuetypeInstMethod(sym))
                  msil_genLoadQualifierAddress(fun, ctx)
                else
                  genLoadQualifier(fun, ctx)
              } else ctx

            ctx1 = genLoadArguments(args, sym.info.paramTypes, ctx1)
            val cm = CALL_METHOD(sym, invokeStyle)
            
            /** In a couple cases, squirrel away a little extra information in the
             *  CALL_METHOD for use by GenJVM.
             */
            fun match {
              case Select(qual, _) =>
                val qualSym = qual.tpe.typeSymbol
                if (qualSym == ArrayClass) cm setTargetTypeKind toTypeKind(qual.tpe)
                else cm setHostClass qualSym
                  
                if (settings.debug.value) log(
                  if (qualSym == ArrayClass) "Stored target type kind " + toTypeKind(qual.tpe) + " for " + sym.fullName
                  else "Set more precise host class for " + sym.fullName + " host: " + qualSym
                )
              case _ =>
            }
            ctx1.bb.emit(cm, tree.pos)
            
            if (sym == ctx1.method.symbol) {
              ctx1.method.recursive = true
            }
            generatedType =
              if (sym.isClassConstructor) UNIT
              else toTypeKind(sym.info.resultType);
            ctx1
          }

        case ApplyDynamic(qual, args) =>
          assert(!forMSIL)
          ctx.clazz.bootstrapClass = Some("scala.runtime.DynamicDispatch")
          val ctx1 = genLoad(qual, ctx, ObjectReference)
          genLoadArguments(args, tree.symbol.info.paramTypes, ctx1)
          ctx1.bb.emit(CALL_METHOD(tree.symbol, InvokeDynamic), tree.pos)
          ctx1
          
        case This(qual) =>
          assert(tree.symbol == ctx.clazz.symbol || tree.symbol.isModuleClass,
                 "Trying to access the this of another class: " +
                 "tree.symbol = " + tree.symbol + ", ctx.clazz.symbol = " + ctx.clazz.symbol + " compilation unit:"+unit)
          if (tree.symbol.isModuleClass && tree.symbol != ctx.clazz.symbol) {
            if (settings.debug.value)
              log("LOAD_MODULE from 'This': " + tree.symbol);
            assert(!tree.symbol.isPackageClass, "Cannot use package as value: " + tree)
            genLoadModule(ctx, tree.symbol, tree.pos)
            generatedType = REFERENCE(tree.symbol)
          } else {
            ctx.bb.emit(THIS(ctx.clazz.symbol), tree.pos)
            generatedType = REFERENCE(
              if (tree.symbol == ArrayClass) ObjectClass else ctx.clazz.symbol
            )
          }
          ctx

        case Select(Ident(nme.EMPTY_PACKAGE_NAME), module) =>
          if (settings.debug.value) {
            assert(tree.symbol.isModule,
                   "Selection of non-module from empty package: " + tree.toString() +
                   " sym: " + tree.symbol +
                   " at: " + (tree.pos))
            log("LOAD_MODULE from Select(<emptypackage>): " + tree.symbol);
          }
          assert(!tree.symbol.isPackageClass, "Cannot use package as value: " + tree)
          genLoadModule(ctx, tree.symbol, tree.pos)
          ctx

        case Select(qualifier, selector) =>
          val sym = tree.symbol
          generatedType = toTypeKind(sym.info)
          val hostClass = qualifier.tpe.typeSymbol.orElse(sym.owner)

          if (sym.isModule) {
            if (settings.debug.value)
              log("LOAD_MODULE from Select(qualifier, selector): " + sym)
            assert(!tree.symbol.isPackageClass, "Cannot use package as value: " + tree)
            genLoadModule(ctx, sym, tree.pos)
            ctx
          } else if (sym.isStaticMember) {
            ctx.bb.emit(LOAD_FIELD(sym, true)  setHostClass hostClass, tree.pos)
            ctx
          } else {
            val ctx1 = genLoadQualifier(tree, ctx)
            ctx1.bb.emit(LOAD_FIELD(sym, false) setHostClass hostClass, tree.pos)
            ctx1
          }

        case Ident(name) =>
          val sym = tree.symbol
          if (!sym.isPackage) {
            if (sym.isModule) {
              if (settings.debug.value)
                log("LOAD_MODULE from Ident(name): " + sym)
              assert(!sym.isPackageClass, "Cannot use package as value: " + tree)
              genLoadModule(ctx, sym, tree.pos)
              generatedType = toTypeKind(sym.info)
            } else {
              try {
                val Some(l) = ctx.method.lookupLocal(sym)
                ctx.bb.emit(LOAD_LOCAL(l), tree.pos)
                generatedType = l.kind
              } catch {
                case ex: MatchError => 
                  abort("symbol " + sym + " does not exist in " + ctx.method)
              }
            }
          }
          ctx

        case Literal(value) =>
          if (value.tag != UnitTag) (value.tag, expectedType) match {
            case (IntTag, LONG) =>
              ctx.bb.emit(CONSTANT(Constant(value.longValue)), tree.pos);
              generatedType = LONG
            case (FloatTag, DOUBLE) =>
              ctx.bb.emit(CONSTANT(Constant(value.doubleValue)), tree.pos);
              generatedType = DOUBLE
            case (NullTag, _) =>
              ctx.bb.emit(CONSTANT(value), tree.pos);
              generatedType = NullReference
            case _ =>
              ctx.bb.emit(CONSTANT(value), tree.pos);
              generatedType = toTypeKind(tree.tpe)
          }
          ctx

        case Block(stats, expr) =>
          ctx.enterScope
          var ctx1 = genStat(stats, ctx)
          ctx1 = genLoad(expr, ctx1, expectedType)
          ctx1.exitScope
          ctx1

        case Typed(Super(_, _), _) =>
          genLoad(This(ctx.clazz.symbol), ctx, expectedType)

        case Typed(expr, _) =>
          genLoad(expr, ctx, expectedType)

        case Assign(_, _) =>
          generatedType = UNIT
          genStat(tree, ctx)

        case ArrayValue(tpt @ TypeTree(), _elems) =>
          var ctx1 = ctx
          val elmKind = toTypeKind(tpt.tpe)
          generatedType = ARRAY(elmKind)
          val elems = _elems.toIndexedSeq

          ctx1.bb.emit(CONSTANT(new Constant(elems.length)), tree.pos)
          ctx1.bb.emit(CREATE_ARRAY(elmKind, 1))
          // inline array literals
          var i = 0
          while (i < elems.length) {
            ctx1.bb.emit(DUP(generatedType), tree.pos)
            ctx1.bb.emit(CONSTANT(new Constant(i)))
            ctx1 = genLoad(elems(i), ctx1, elmKind)
            ctx1.bb.emit(STORE_ARRAY_ITEM(elmKind))
            i = i + 1
          }
          ctx1

        case Match(selector, cases) =>
          if (settings.debug.value)
            log("Generating SWITCH statement.");
          var ctx1 = genLoad(selector, ctx, INT)
          val afterCtx = ctx1.newBlock
          var caseCtx: Context  = null
          generatedType = toTypeKind(tree.tpe)

          var targets: List[BasicBlock] = Nil
          var tags: List[Int] = Nil
          var default: BasicBlock = afterCtx.bb

          for (caze @ CaseDef(pat, guard, body) <- cases) {
            assert(guard == EmptyTree)
            val tmpCtx = ctx1.newBlock
            pat match {
              case Literal(value) =>
                tags = value.intValue :: tags
                targets = tmpCtx.bb :: targets                
              case Ident(nme.WILDCARD) =>
                default = tmpCtx.bb
              case _ =>
                abort("Invalid case statement in switch-like pattern match: " +
                      tree + " at: " + (tree.pos))
            }

            caseCtx = genLoad(body, tmpCtx, generatedType)
            caseCtx.bb.closeWith(JUMP(afterCtx.bb) setPos caze.pos)
          }
          ctx1.bb.emitOnly(
            SWITCH(tags.reverse map (x => List(x)), (default :: targets).reverse) setPos tree.pos
          )
          afterCtx

        case EmptyTree => 
          if (expectedType != UNIT)
            ctx.bb.emit(getZeroOf(expectedType))
          ctx

        case _ =>
          abort("Unexpected tree in genLoad: " + tree + "/" + tree.getClass + " at: " + tree.pos)
      }

      // emit conversion
      if (generatedType != expectedType)
        adapt(generatedType, expectedType, resCtx, tree.pos)

      resCtx
    }

    private def adapt(from: TypeKind, to: TypeKind, ctx: Context, pos: Position): Unit = {
      if (!(from <:< to) && !(from == NullReference && to == NothingReference)) {
        to match {
          case UNIT =>
            ctx.bb.emit(DROP(from), pos)
            if (settings.debug.value)
              log("Dropped an " + from);

          case _ =>
            if (settings.debug.value) {
              assert(from != UNIT,
                  "Can't convert from UNIT to " + to + " at: " + pos)
            }
            assert(!from.isReferenceType && !to.isReferenceType,
              "type error: can't convert from " + from + " to " + to +" in unit " + unit.source + " at " + pos)
              
            ctx.bb.emit(CALL_PRIMITIVE(Conversion(from, to)), pos)
        }
      } else if (from == NothingReference) {
        ctx.bb.emit(THROW(ThrowableClass))
        ctx.bb.enterIgnoreMode
      } else if (from == NullReference) {
        ctx.bb.emit(DROP(from))
        ctx.bb.emit(CONSTANT(Constant(null)))
      } 
      else if (from == ThrowableReference && !(ThrowableClass.tpe <:< to.toType)) {
        log("Inserted check-cast on throwable to " + to + " at " + pos)
        ctx.bb.emit(CHECK_CAST(to))
      }
      else (from, to) match  {
        case (BYTE, LONG) | (SHORT, LONG) | (CHAR, LONG) | (INT, LONG) => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, LONG)))
        case _ => ()
      }
    }

    /** Load the qualifier of `tree' on top of the stack. */
    private def genLoadQualifier(tree: Tree, ctx: Context): Context =
      tree match {
        case Select(qualifier, _) =>
          genLoad(qualifier, ctx, toTypeKind(qualifier.tpe)) 
        case _ =>
          abort("Unknown qualifier " + tree)
      }

    /** forMSIL */
    private def msil_genLoadQualifierAddress(tree: Tree, ctx: Context): Context =
      tree match {
        case Select(qualifier, _) =>
          msil_genLoadAddressOf(qualifier, ctx, toTypeKind(qualifier.tpe), butRawValueIsAlsoGoodEnough = false)
        case _ =>
          abort("Unknown qualifier " + tree)
      }

    /**
     * Generate code that loads args into label parameters.
     */
    private def genLoadLabelArguments(args: List[Tree], label: Label, ctx: Context): Context = {
      if (settings.debug.value) {
        assert(args.length == label.params.length, 
               "Wrong number of arguments in call to label " + label.symbol)
      }
      
      var ctx1 = ctx

      def isTrivial(kv: (Tree, Symbol)) = kv match {
        case (This(_), p) if p.name == nme.THIS     => true
        case (arg @ Ident(_), p) if arg.symbol == p => true
        case _                                      => false
      }
      
      val stores = args zip label.params filterNot isTrivial map {
        case (arg, param) =>
          val local = ctx.method.lookupLocal(param).get
          ctx1 = genLoad(arg, ctx1, local.kind)
        
          val store =
            if (param.name == nme.THIS) STORE_THIS(toTypeKind(ctx1.clazz.symbol.tpe))
            else STORE_LOCAL(local)
          
          store setPos arg.pos
      }
      
      // store arguments in reverse order on the stack
      ctx1.bb.emit(stores.reverse)
      ctx1
    }

    private def genLoadArguments(args: List[Tree], tpes: List[Type], ctx: Context): Context =
      (args zip tpes).foldLeft(ctx) {
        case (res, (arg, tpe)) =>
          genLoad(arg, res, toTypeKind(tpe))
      }

    private def genLoadModule(ctx: Context, sym: Symbol, pos: Position) {
      ctx.bb.emit(LOAD_MODULE(sym), pos)
    }

    def genConversion(from: TypeKind, to: TypeKind, ctx: Context, cast: Boolean) = {
      if (cast) 
        ctx.bb.emit(CALL_PRIMITIVE(Conversion(from, to)))
      else {
        ctx.bb.emit(DROP(from))
        ctx.bb.emit(CONSTANT(Constant(from == to)))
      }
    }

    def genCast(from: TypeKind, to: TypeKind, ctx: Context, cast: Boolean) =
      ctx.bb.emit(if (cast) CHECK_CAST(to) else IS_INSTANCE(to))

    def getZeroOf(k: TypeKind): Instruction = k match {
      case UNIT            => CONSTANT(Constant(()))
      case BOOL            => CONSTANT(Constant(false))
      case BYTE            => CONSTANT(Constant(0: Byte))
      case SHORT           => CONSTANT(Constant(0: Short))
      case CHAR            => CONSTANT(Constant(0: Char))
      case INT             => CONSTANT(Constant(0: Int))
      case LONG            => CONSTANT(Constant(0: Long))
      case FLOAT           => CONSTANT(Constant(0.0f))
      case DOUBLE          => CONSTANT(Constant(0.0d))
      case REFERENCE(cls)  => CONSTANT(Constant(null: Any))
      case ARRAY(elem)     => CONSTANT(Constant(null: Any))
      case BOXED(_)        => CONSTANT(Constant(null: Any))
      case ConcatClass     => abort("no zero of ConcatClass")
    }


    /** Is the given symbol a primitive operation? */
    def isPrimitive(fun: Symbol): Boolean = scalaPrimitives.isPrimitive(fun)

    /** Generate coercion denoted by "code"
     */
    def genCoercion(tree: Tree, ctx: Context, code: Int) = {
      import scalaPrimitives._
      (code: @switch) match {
        case B2B => ()
        case B2C => ctx.bb.emit(CALL_PRIMITIVE(Conversion(BYTE, CHAR)), tree.pos)
        case B2S => ctx.bb.emit(CALL_PRIMITIVE(Conversion(BYTE, SHORT)), tree.pos)
        case B2I => ctx.bb.emit(CALL_PRIMITIVE(Conversion(BYTE, INT)), tree.pos)
        case B2L => ctx.bb.emit(CALL_PRIMITIVE(Conversion(BYTE, LONG)), tree.pos)
        case B2F => ctx.bb.emit(CALL_PRIMITIVE(Conversion(BYTE, FLOAT)), tree.pos)
        case B2D => ctx.bb.emit(CALL_PRIMITIVE(Conversion(BYTE, DOUBLE)), tree.pos)

        case S2B => ctx.bb.emit(CALL_PRIMITIVE(Conversion(SHORT, BYTE)), tree.pos)
        case S2S => ()
        case S2C => ctx.bb.emit(CALL_PRIMITIVE(Conversion(SHORT, CHAR)), tree.pos)
        case S2I => ctx.bb.emit(CALL_PRIMITIVE(Conversion(SHORT, INT)), tree.pos)
        case S2L => ctx.bb.emit(CALL_PRIMITIVE(Conversion(SHORT, LONG)), tree.pos)
        case S2F => ctx.bb.emit(CALL_PRIMITIVE(Conversion(SHORT, FLOAT)), tree.pos)
        case S2D => ctx.bb.emit(CALL_PRIMITIVE(Conversion(SHORT, DOUBLE)), tree.pos)

        case C2B => ctx.bb.emit(CALL_PRIMITIVE(Conversion(CHAR, BYTE)), tree.pos)
        case C2S => ctx.bb.emit(CALL_PRIMITIVE(Conversion(CHAR, SHORT)), tree.pos)
        case C2C => ()
        case C2I => ctx.bb.emit(CALL_PRIMITIVE(Conversion(CHAR, INT)), tree.pos)
        case C2L => ctx.bb.emit(CALL_PRIMITIVE(Conversion(CHAR, LONG)), tree.pos)
        case C2F => ctx.bb.emit(CALL_PRIMITIVE(Conversion(CHAR, FLOAT)), tree.pos)
        case C2D => ctx.bb.emit(CALL_PRIMITIVE(Conversion(CHAR, DOUBLE)), tree.pos)

        case I2B => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, BYTE)), tree.pos)
        case I2S => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, SHORT)), tree.pos)
        case I2C => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, CHAR)), tree.pos)
        case I2I => ()
        case I2L => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, LONG)), tree.pos)
        case I2F => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, FLOAT)), tree.pos)
        case I2D => ctx.bb.emit(CALL_PRIMITIVE(Conversion(INT, DOUBLE)), tree.pos)

        case L2B => ctx.bb.emit(CALL_PRIMITIVE(Conversion(LONG, BYTE)), tree.pos)
        case L2S => ctx.bb.emit(CALL_PRIMITIVE(Conversion(LONG, SHORT)), tree.pos)
        case L2C => ctx.bb.emit(CALL_PRIMITIVE(Conversion(LONG, CHAR)), tree.pos)
        case L2I => ctx.bb.emit(CALL_PRIMITIVE(Conversion(LONG, INT)), tree.pos)
        case L2L => ()
        case L2F => ctx.bb.emit(CALL_PRIMITIVE(Conversion(LONG, FLOAT)), tree.pos)
        case L2D => ctx.bb.emit(CALL_PRIMITIVE(Conversion(LONG, DOUBLE)), tree.pos)

        case F2B => ctx.bb.emit(CALL_PRIMITIVE(Conversion(FLOAT, BYTE)), tree.pos)
        case F2S => ctx.bb.emit(CALL_PRIMITIVE(Conversion(FLOAT, SHORT)), tree.pos)
        case F2C => ctx.bb.emit(CALL_PRIMITIVE(Conversion(FLOAT, CHAR)), tree.pos)
        case F2I => ctx.bb.emit(CALL_PRIMITIVE(Conversion(FLOAT, INT)), tree.pos)
        case F2L => ctx.bb.emit(CALL_PRIMITIVE(Conversion(FLOAT, LONG)), tree.pos)
        case F2F => ()
        case F2D => ctx.bb.emit(CALL_PRIMITIVE(Conversion(FLOAT, DOUBLE)), tree.pos)

        case D2B => ctx.bb.emit(CALL_PRIMITIVE(Conversion(DOUBLE, BYTE)), tree.pos)
        case D2S => ctx.bb.emit(CALL_PRIMITIVE(Conversion(DOUBLE, SHORT)), tree.pos)
        case D2C => ctx.bb.emit(CALL_PRIMITIVE(Conversion(DOUBLE, CHAR)), tree.pos)
        case D2I => ctx.bb.emit(CALL_PRIMITIVE(Conversion(DOUBLE, INT)), tree.pos)
        case D2L => ctx.bb.emit(CALL_PRIMITIVE(Conversion(DOUBLE, LONG)), tree.pos)
        case D2F => ctx.bb.emit(CALL_PRIMITIVE(Conversion(DOUBLE, FLOAT)), tree.pos)
        case D2D => ()

        case _ => abort("Unknown coercion primitive: " + code)
      }
    }
    
    /** The Object => String overload.
     */
    private lazy val String_valueOf: Symbol = getMember(StringModule, "valueOf") filter (sym =>
      sym.info.paramTypes match {
        case List(pt) => pt.typeSymbol == ObjectClass
        case _        => false
      }
    )
    
    // I wrote it this way before I realized all the primitive types are
    // boxed at this point, so I'd have to unbox them.  Keeping it around in
    // case we want to get more precise.
    //
    // private def valueOfForType(tp: Type): Symbol = {
    //   val xs = getMember(StringModule, "valueOf") filter (sym =>
    //     // We always exclude the Array[Char] overload because java throws an NPE if 
    //     // you pass it a null.  It will instead find the Object one, which doesn't.
    //     sym.info.paramTypes match {
    //       case List(pt) => pt.typeSymbol != ArrayClass && (tp <:< pt)
    //       case _        => false
    //     }
    //   )
    //   xs.alternatives match {
    //     case List(sym)  => sym
    //     case _          => NoSymbol
    //   }
    // }

    /** Generate string concatenation.
     *
     *  @param tree ...
     *  @param ctx  ...
     *  @return     ...
     */
    def genStringConcat(tree: Tree, ctx: Context): Context = {
      liftStringConcat(tree) match {
        // Optimization for expressions of the form "" + x.  We can avoid the StringBuilder.
        case List(Literal(Constant("")), arg) if !forMSIL =>
          if (settings.debug.value) log("Rewriting \"\" + x as String.valueOf(x) for: " + arg)
          val ctx1 = genLoad(arg, ctx, ObjectReference)
          ctx1.bb.emit(CALL_METHOD(String_valueOf, Static(false)), arg.pos)
          ctx1 
        case concatenations =>
          if (settings.debug.value) log("Lifted string concatenations for " + tree + "\n to: " + concatenations)
          var ctx1 = ctx
          ctx1.bb.emit(CALL_PRIMITIVE(StartConcat), tree.pos)
          for (elem <- concatenations) {
            val kind = toTypeKind(elem.tpe)
            ctx1 = genLoad(elem, ctx1, kind)
            ctx1.bb.emit(CALL_PRIMITIVE(StringConcat(kind)), elem.pos)
          }
          ctx1.bb.emit(CALL_PRIMITIVE(EndConcat), tree.pos)
          ctx1        
      }
    }
    
    /** Generate the scala ## method.
     */
    def genScalaHash(tree: Tree, ctx: Context): Context = {
      val hashMethod = {
        ctx.bb.emit(LOAD_MODULE(ScalaRunTimeModule))
        getMember(ScalaRunTimeModule, "hash")
      }
      
      val ctx1 = genLoad(tree, ctx, ObjectReference)
      ctx1.bb.emit(CALL_METHOD(hashMethod, Static(false)))
      ctx1
    }

    /**
     * Returns a list of trees that each should be concatenated, from
     * left to right. It turns a chained call like "a".+("b").+("c") into
     * a list of arguments.
     */
    def liftStringConcat(tree: Tree): List[Tree] = tree match {
      case Apply(fun @ Select(larg, method), rarg) =>
        if (isPrimitive(fun.symbol) && 
            scalaPrimitives.getPrimitive(fun.symbol) == scalaPrimitives.CONCAT)
          liftStringConcat(larg) ::: rarg
        else
          List(tree)
      case _ =>
        List(tree)
    }

    /** Some useful equality helpers.
     */
    def isNull(t: Tree) = cond(t) { case Literal(Constant(null)) => true }
    
    /* If l or r is constant null, returns the other ; otherwise null */
    def ifOneIsNull(l: Tree, r: Tree) = if (isNull(l)) r else if (isNull(r)) l else null

    /**
     * Traverse the tree and store label stubs in the context. This is
     * necessary to handle forward jumps, because at a label application
     * with arguments, the symbols of the corresponding LabelDef parameters
     * are not yet known.
     *
     * Since it is expensive to traverse each method twice, this method is called
     * only when forward jumps really happen, and then it re-traverses the whole
     * method, scanning for LabelDefs.
     *
     * TODO: restrict the scanning to smaller subtrees than the whole method.
     *  It is sufficient to scan the trees of the innermost enclosing block.
     */
    //
    private def scanForLabels(tree: Tree, ctx: Context): Unit = tree foreachPartial {
      case t @ LabelDef(_, params, rhs) =>
        ctx.labels.getOrElseUpdate(t.symbol, {
          val locals  = params map (p => new Local(p.symbol, toTypeKind(p.symbol.info), false))
          ctx.method addLocals locals

          new Label(t.symbol) setParams (params map (_.symbol))
        })
        rhs
    }

    /**
     * Generate code for conditional expressions. The two basic blocks
     * represent the continuation in case of success/failure of the
     * test.
     */
    private def genCond(tree: Tree,
                        ctx: Context,
                        thenCtx: Context,
                        elseCtx: Context): Unit =
    {
      def genComparisonOp(l: Tree, r: Tree, code: Int) {          
        val op: TestOp = code match {
          case scalaPrimitives.LT => LT
          case scalaPrimitives.LE => LE
          case scalaPrimitives.GT => GT
          case scalaPrimitives.GE => GE
          case scalaPrimitives.ID | scalaPrimitives.EQ => EQ
          case scalaPrimitives.NI | scalaPrimitives.NE => NE

          case _ => abort("Unknown comparison primitive: " + code)
        }

        // special-case reference (in)equality test for null (null eq x, x eq null)
        lazy val nonNullSide = ifOneIsNull(l, r)
        if (isReferenceEqualityOp(code) && nonNullSide != null) {
          val ctx1 = genLoad(nonNullSide, ctx, ObjectReference)
          ctx1.bb.emitOnly(
            CZJUMP(thenCtx.bb, elseCtx.bb, op, ObjectReference)
          )
        }
        else {
          val kind = getMaxType(l.tpe :: r.tpe :: Nil)
          var ctx1 = genLoad(l, ctx, kind) 
          ctx1 = genLoad(r, ctx1, kind)
          
          ctx1.bb.emitOnly(
            CJUMP(thenCtx.bb, elseCtx.bb, op, kind) setPos r.pos
          )
        }
      }

      if (settings.debug.value)
        log("Entering genCond with tree: " + tree);
      
      // the default emission
      def default() = {
        val ctx1 = genLoad(tree, ctx, BOOL)
        ctx1.bb.closeWith(CZJUMP(thenCtx.bb, elseCtx.bb, NE, BOOL) setPos tree.pos)
      }
      
      tree match {
        // The comparison symbol is in ScalaPrimitives's "primitives" map
        case Apply(fun, args) if isPrimitive(fun.symbol) =>
          import scalaPrimitives.{ ZNOT, ZAND, ZOR, EQ, getPrimitive }
          
          // lhs and rhs of test
          lazy val Select(lhs, _) = fun
          lazy val rhs = args.head

          def genZandOrZor(and: Boolean) = {
            val ctxInterm = ctx.newBlock
            
            if (and) genCond(lhs, ctx, ctxInterm, elseCtx)
            else genCond(lhs, ctx, thenCtx, ctxInterm)
            
            genCond(rhs, ctxInterm, thenCtx, elseCtx)
          }
          def genRefEq(isEq: Boolean) = {
            val f = genEqEqPrimitive(lhs, rhs, ctx) _
            if (isEq) f(thenCtx, elseCtx)
            else f(elseCtx, thenCtx)
          }
          
          getPrimitive(fun.symbol) match {
            case ZNOT   => genCond(lhs, ctx, elseCtx, thenCtx)
            case ZAND   => genZandOrZor(and = true)
            case ZOR    => genZandOrZor(and = false)
            case code   =>
              // x == y where LHS is reference type  
              if (isUniversalEqualityOp(code) && toTypeKind(lhs.tpe).isReferenceType) {
                if (code == EQ) genRefEq(isEq = true)
                else genRefEq(isEq = false)
              }
              else if (isComparisonOp(code))
                genComparisonOp(lhs, rhs, code)
              else
                default
          }

        case _ => default
      }
    }

    /**
     * Generate the "==" code for object references. It is equivalent of
     * if (l eq null) r eq null else l.equals(r);
     *
     * @param l       left-hand side of the '=='
     * @param r       right-hand side of the '=='
     * @param ctx     current context
     * @param thenCtx target context if the comparison yields true
     * @param elseCtx target context if the comparison yields false
     */
    def genEqEqPrimitive(l: Tree, r: Tree, ctx: Context)(thenCtx: Context, elseCtx: Context): Unit = {
      def getTempLocal: Local = ctx.method.lookupLocal(nme.EQEQ_LOCAL_VAR) match {
        case Some(local) => local
        case None =>
          val local = ctx.makeLocal(l.pos, AnyRefClass.typeConstructor, nme.EQEQ_LOCAL_VAR)
          //assert(!l.pos.source.isEmpty, "bad position, unit = "+unit+", tree = "+l+", pos = "+l.pos.source)
          // Note - I commented these out because they were crashing the test case in ticket #2426
          // (and I have also had to comment them out at various times while working on equality.)
          // I don't know what purpose they are serving but it would be nice if they didn't have to
          // crash the compiler.
          // assert(l.pos.source == unit.source)
          // assert(r.pos.source == unit.source)
          local.start = (l.pos).line
          local.end   = (r.pos).line
          local
      }

      /** True if the equality comparison is between values that require the use of the rich equality
        * comparator (scala.runtime.Comparator.equals). This is the case when either side of the
        * comparison might have a run-time type subtype of java.lang.Number or java.lang.Character.
        * When it is statically known that both sides are equal and subtypes of Number of Character,
        * not using the rich equality is possible (their own equals method will do ok.)*/
      def mustUseAnyComparator: Boolean = {
        def areSameFinals = l.tpe.isFinalType && r.tpe.isFinalType && (l.tpe =:= r.tpe)
        !areSameFinals && isMaybeBoxed(l.tpe.typeSymbol) && isMaybeBoxed(r.tpe.typeSymbol)
      }

      if (mustUseAnyComparator) {
        // when -optimise is on we call the @inline-version of equals, found in ScalaRunTime
        val equalsMethod =
          if (!settings.XO.value) {
            def default = platform.externalEquals
            platform match {
              case x: JavaPlatform =>
                import x._
                  if (l.tpe <:< BoxedNumberClass.tpe) {
                    if (r.tpe <:< BoxedNumberClass.tpe) externalEqualsNumNum
                    else if (r.tpe <:< BoxedCharacterClass.tpe) externalEqualsNumChar
                    else externalEqualsNumObject
                  }
                  else default
                
              case _ => default
            }
          }
          else {
            ctx.bb.emit(LOAD_MODULE(ScalaRunTimeModule))
            getMember(ScalaRunTimeModule, nme.inlinedEquals)
          }

        val ctx1 = genLoad(l, ctx, ObjectReference)
        val ctx2 = genLoad(r, ctx1, ObjectReference)
        ctx2.bb.emit(CALL_METHOD(equalsMethod, if (settings.XO.value) Dynamic else Static(false)))
        ctx2.bb.emit(CZJUMP(thenCtx.bb, elseCtx.bb, NE, BOOL))
        ctx2.bb.close
      }
      else {
        if (isNull(l))
          // null == expr -> expr eq null
          genLoad(r, ctx, ObjectReference).bb emitOnly CZJUMP(thenCtx.bb, elseCtx.bb, EQ, ObjectReference)
        else if (isNull(r)) {
          // expr == null -> expr eq null
          genLoad(l, ctx, ObjectReference).bb emitOnly CZJUMP(thenCtx.bb, elseCtx.bb, EQ, ObjectReference)
        } else {
          val eqEqTempLocal = getTempLocal
          var ctx1 = genLoad(l, ctx, ObjectReference)
          
          // dicey refactor section
          lazy val nonNullCtx = ctx1.newBlock
          
          // l == r -> if (l eq null) r eq null else l.equals(r)
          ctx1 = genLoad(r, ctx1, ObjectReference)
          val nullCtx = ctx1.newBlock
          
          ctx1.bb.emitOnly(
            STORE_LOCAL(eqEqTempLocal) setPos l.pos,
            DUP(ObjectReference),
            CZJUMP(nullCtx.bb, nonNullCtx.bb, EQ, ObjectReference)
          )          
          nullCtx.bb.emitOnly(
            DROP(ObjectReference) setPos l.pos, // type of AnyRef
            LOAD_LOCAL(eqEqTempLocal),
            CZJUMP(thenCtx.bb, elseCtx.bb, EQ, ObjectReference)
          )
          nonNullCtx.bb.emitOnly(
            LOAD_LOCAL(eqEqTempLocal) setPos l.pos,
            CALL_METHOD(Object_equals, Dynamic),
            CZJUMP(thenCtx.bb, elseCtx.bb, NE, BOOL)
          )
        }
      }
    }

    /**
     * Add all fields of the given class symbol to the current ICode
     * class.
     */
    private def addClassFields(ctx: Context, cls: Symbol) {
      if (settings.debug.value)
        assert(ctx.clazz.symbol eq cls,
               "Classes are not the same: " + ctx.clazz.symbol + ", " + cls)

      /** Non-method term members are fields, except for module members. Module
       *  members can only happen on .NET (no flatten) for inner traits. There,
       *  a module symbol is generated (transformInfo in mixin) which is used
       *  as owner for the members of the implementation class (so that the
       *  backend emits them as static).
       *  No code is needed for this module symbol.
       */
      for (f <- cls.info.decls ; if !f.isMethod && f.isTerm && !f.isModule)
        ctx.clazz addField new IField(f)
    }

    /**
     * Add parameters to the current ICode method. It is assumed the methods
     * have been uncurried, so the list of lists contains just one list.
     */
    private def addMethodParams(ctx: Context, vparamss: List[List[ValDef]]) {
      vparamss match {
        case Nil => ()

        case vparams :: Nil =>
          for (p <- vparams) {
            val lv = new Local(p.symbol, toTypeKind(p.symbol.info), true)
            ctx.method.addParam(lv)
            ctx.scope.add(lv)
            ctx.bb.varsInScope += lv
          }
          ctx.method.params = ctx.method.params.reverse

        case _ =>
          abort("Malformed parameter list: " + vparamss)
      }
    }

    /** Does this tree have a try-catch block? */
    def mayCleanStack(tree: Tree): Boolean = tree exists {
      case Try(_, _, _) => true
      case _            => false
    }

    /**
     *  If the block consists of a single unconditional jump, prune 
     *  it by replacing the instructions in the predecessor to jump 
     *  directly to the JUMP target of the block.
     *
     *  @param method ...
     */
    def prune(method: IMethod) = {
      var changed = false
      var n = 0

      def prune0(block: BasicBlock): Unit = {
        val optCont = block.lastInstruction match {
          case JUMP(b) if (b != block) => Some(b)
          case _ => None
        }
        if (block.size == 1 && optCont.isDefined) {
          val Some(cont) = optCont;
          val pred = block.predecessors;
          log("Preds: " + pred + " of " + block + " (" + optCont + ")");
          pred foreach { p =>
            changed = true
            p.lastInstruction match {
              case CJUMP(succ, fail, cond, kind) if (succ == block || fail == block) =>
                if (settings.debug.value)
                  log("Pruning empty if branch.");
                p.replaceInstruction(p.lastInstruction,
                                     if (block == succ)
                                       if (block == fail)
                                         CJUMP(cont, cont, cond, kind)
                                       else
                                         CJUMP(cont, fail, cond, kind)
                                     else if (block == fail)
                                       CJUMP(succ, cont, cond, kind)
                                     else
                                       abort("Could not find block in preds: " + method + " " + block + " " + pred + " " + p))

              case CZJUMP(succ, fail, cond, kind) if (succ == block || fail == block) =>
                if (settings.debug.value)
                  log("Pruning empty ifz branch.");
                p.replaceInstruction(p.lastInstruction,
                                     if (block == succ)
                                       if (block == fail)
                                         CZJUMP(cont, cont, cond, kind)
                                       else
                                         CZJUMP(cont, fail, cond, kind)
                                     else if (block == fail)
                                       CZJUMP(succ, cont, cond, kind)
                                     else
                                       abort("Could not find block in preds"))

              case JUMP(b) if (b == block) =>
                if (settings.debug.value)
                  log("Pruning empty JMP branch.");
                val replaced = p.replaceInstruction(p.lastInstruction, JUMP(cont))
                if (settings.debug.value)
                  assert(replaced, "Didn't find p.lastInstruction")

              case SWITCH(tags, labels) if (labels contains block) =>
                if (settings.debug.value)
                  log("Pruning empty SWITCH branch.");
                p.replaceInstruction(p.lastInstruction,
                                     SWITCH(tags, labels map (l => if (l == block) cont else l)))

              // the last instr of the predecessor `p` is not a jump to the block `block`.
              // this happens when `block` is part of an exception handler covering `b`.
              case _ => ()
            }
          }
          if (changed) {
            log("Removing block: " + block)
            method.code.removeBlock(block)
            for (e <- method.exh) {
              e.covered = e.covered filter (_ != block)
              e.blocks  = e.blocks filter (_ != block)
              if (e.startBlock eq block)
                e setStartBlock cont;
            }
          }
        }
      }

      do {
        changed = false
        n += 1
        method.code.blocks foreach prune0
      } while (changed)

      if (settings.debug.value)
        log("Prune fixpoint reached in " + n + " iterations.");
    }

    def getMaxType(ts: List[Type]): TypeKind =
      ts map toTypeKind reduceLeft (_ maxType _)

    /** Tree transformer that duplicates code and at the same time creates
     *  fresh symbols for existing labels. Since labels may be used before
     *  they are defined (forward jumps), all labels found are mapped to fresh
     *  symbols. References to the same label (use or definition) will remain
     *  consistent after this transformation (both the use and the definition of
     *  some label l will be mapped to the same label l').
     *
     *  Note: If the tree fragment passed to the duplicator contains unbound
     *  label names, the bind to the outer labeldef will be lost! That's because
     *  a use of an unbound label l will be transformed to l', and the corresponding
     *  label def, being outside the scope of this transformation, will not be updated.
     *
     *  All LabelDefs are entered into the context label map, since it makes no sense
     *  to delay it any more: they will be used at some point.
     */
    class DuplicateLabels(boundLabels: Set[Symbol]) extends Transformer {
      val labels: mutable.Map[Symbol, Symbol] = new mutable.HashMap
      var method: Symbol = _
      var ctx: Context = _
      
      def apply(ctx: Context, t: Tree) = {
        this.method = ctx.method.symbol
        this.ctx = ctx
        transform(t)
      }
      
      override def transform(t: Tree): Tree = {
        val sym = t.symbol
        def getLabel(pos: Position, name: Name) =
          labels.getOrElseUpdate(sym,
            method.newLabel(sym.pos, unit.freshTermName(name.toString)) setInfo sym.tpe
          )
        
        t match {
          case t @ Apply(_, args) if sym.isLabel && !boundLabels(sym) =>
            val newSym = getLabel(sym.pos, sym.name)
            val tree = Apply(global.gen.mkAttributedRef(newSym), transformTrees(args)) setPos t.pos
            tree.tpe = t.tpe
            tree
            
          case t @ LabelDef(name, params, rhs) =>
            val newSym = getLabel(t.pos, name)
            val tree = treeCopy.LabelDef(t, newSym.name, params, transform(rhs))
            tree.symbol = newSym
            
            val pair = (newSym -> (new Label(newSym) setParams (params map (_.symbol))))
            log("Added " + pair + " to labels.")
            ctx.labels += pair
            ctx.method.addLocals(params map (p => new Local(p.symbol, toTypeKind(p.symbol.info), false)))
            
            tree
            
          case _ => super.transform(t)
        }
      }
    }
    
    /////////////////////// Context ////////////////////////////////

    abstract class Cleanup(val value: AnyRef) {
      def contains(x: AnyRef) = value == x
    }
    case class MonitorRelease(m: Local) extends Cleanup(m) { }
    case class Finalizer(f: Tree, ctx: Context) extends Cleanup (f) { }

    def duplicateFinalizer(boundLabels: Set[Symbol], targetCtx: Context, finalizer: Tree) =  {
      (new DuplicateLabels(boundLabels))(targetCtx, finalizer)
    }

    def savingCleanups[T](ctx: Context)(body: => T): T = {
      val saved = ctx.cleanups
      try body
      finally ctx.cleanups = saved
    }
    
    /**
     * The Context class keeps information relative to the current state
     * in code generation
     */
    class Context {
      /** The current package. */
      var packg: Name = _

      /** The current class. */
      var clazz: IClass = _

      /** The current method. */
      var method: IMethod = _

      /** The current basic block. */
      var bb: BasicBlock = _

      /** Map from label symbols to label objects. */
      var labels = mutable.HashMap[Symbol, Label]()

      /** Current method definition. */
      var defdef: DefDef = _

      /** current exception handlers */
      var handlers: List[ExceptionHandler] = Nil

      /** The current monitors or finalizers, to be cleaned up upon `return'. */
      var cleanups: List[Cleanup] = Nil

      /** The exception handlers we are currently generating code for */
      var currentExceptionHandlers: List[ExceptionHandler] = Nil

      /** The current local variable scope. */
      var scope: Scope = EmptyScope

      var handlerCount = 0

      override def toString(): String = {
        val buf = new StringBuilder()
        buf.append("\tpackage: ").append(packg).append('\n')
        buf.append("\tclazz: ").append(clazz).append('\n')
        buf.append("\tmethod: ").append(method).append('\n')
        buf.append("\tbb: ").append(bb).append('\n')
        buf.append("\tlabels: ").append(labels).append('\n')
        buf.append("\texception handlers: ").append(handlers).append('\n')
        buf.append("\tcleanups: ").append(cleanups).append('\n')
        buf.append("\tscope: ").append(scope).append('\n')
        buf.toString()
      }
      
      def loadException(ctx: Context, exh: ExceptionHandler, pos: Position) = {
        log("Emitting LOAD_EXCEPTION for class: " + exh.loadExceptionClass)
        ctx.bb.emit(LOAD_EXCEPTION(exh.loadExceptionClass) setPos pos, pos)
      }

      def this(other: Context) = {
        this()
        this.packg = other.packg
        this.clazz = other.clazz
        this.method = other.method
        this.bb = other.bb
        this.labels = other.labels
        this.defdef = other.defdef
        this.handlers = other.handlers
        this.handlerCount = other.handlerCount
        this.cleanups = other.cleanups
        this.currentExceptionHandlers = other.currentExceptionHandlers
        this.scope = other.scope
      }
      
      def setPackage(p: Name): this.type = {
        this.packg = p
        this
      }

      def setClass(c: IClass): this.type = {
        this.clazz = c
        this
      }

      def setMethod(m: IMethod): this.type = {
        this.method = m
        this
      }

      def setBasicBlock(b: BasicBlock): this.type = {
        this.bb = b
        this
      }

      def enterSynchronized(monitor: Local): this.type = {
        cleanups = MonitorRelease(monitor) :: cleanups
        this
      }

      def exitSynchronized(monitor: Local): this.type = {
        assert(cleanups.head contains monitor,
               "Bad nesting of cleanup operations: " + cleanups + " trying to exit from monitor: " + monitor)
        cleanups = cleanups.tail
        this
      }

      def addFinalizer(f: Tree, ctx: Context): this.type = {
        cleanups = Finalizer(f, ctx) :: cleanups;
        this
      }

      def removeFinalizer(f: Tree): this.type = {
        assert(cleanups.head contains f,
               "Illegal nesting of cleanup operations: " + cleanups + " while exiting finalizer " + f);
        cleanups = cleanups.tail
        this
      }

      /** Prepare a new context upon entry into a method.
       *
       *  @param m ...
       *  @param d ...
       *  @return  ...
       */
      def enterMethod(m: IMethod, d: DefDef): Context = {
        val ctx1 = new Context(this) setMethod(m)
        ctx1.labels = new mutable.HashMap()
        ctx1.method.code = new Code(m)
        ctx1.bb = ctx1.method.code.startBlock
        ctx1.defdef = d
        ctx1.scope = EmptyScope
        ctx1.enterScope
        ctx1
      }

      /** Return a new context for a new basic block. */
      def newBlock: Context = {
        val block = method.code.newBlock
        handlers foreach (_ addCoveredBlock block)
        currentExceptionHandlers foreach (_ addBlock block)
        block.varsInScope = new mutable.HashSet() ++= scope.varsInScope
        new Context(this) setBasicBlock block
      }

      def enterScope() {
        scope = new Scope(scope)
      }

      def exitScope() {
        if (bb.nonEmpty) {
          scope.locals foreach { lv => bb.emit(SCOPE_EXIT(lv)) }
        }
        scope = scope.outer
      }

      /** Create a new exception handler and adds it in the list
       * of current exception handlers. All new blocks will be
       * 'covered' by this exception handler (in addition to the 
       * previously active handlers).
       */
      private def newExceptionHandler(cls: Symbol, resultKind: TypeKind, pos: Position): ExceptionHandler = {
        handlerCount += 1
        val exh = new ExceptionHandler(method, "" + handlerCount, cls, pos)
        exh.resultKind = resultKind
        method.addHandler(exh)
        handlers = exh :: handlers
        if (settings.debug.value)
          log("added handler: " + exh);

        exh
      }

      /** Add an active exception handler in this context. It will cover all new basic blocks
       *  created from now on. */
      private def addActiveHandler(exh: ExceptionHandler) {
        handlerCount += 1
        handlers = exh :: handlers
        if (settings.debug.value)
          log("added handler: " + exh);
      }
      
      /** Return a new context for generating code for the given
       * exception handler.
       */
      private def enterExceptionHandler(exh: ExceptionHandler): Context = {
        currentExceptionHandlers ::= exh
        val ctx = newBlock
        exh.setStartBlock(ctx.bb)
        ctx
      }

      def endHandler() {
        currentExceptionHandlers = currentExceptionHandlers.tail
      }

      /** Remove the given handler from the list of active exception handlers. */
      def removeActiveHandler(exh: ExceptionHandler): Unit = {
        assert(handlerCount > 0 && handlers.head == exh,
               "Wrong nesting of exception handlers." + this + " for " + exh)
        handlerCount -= 1
        handlers = handlers.tail
        if (settings.debug.value)
          log("removed handler: " + exh);

      }

      /** Clone the current context */
      def dup: Context = new Context(this)

      /** Make a fresh local variable. It ensures the 'name' is unique. */
      def makeLocal(pos: Position, tpe: Type, name: String): Local = {
        val sym = method.symbol.newVariable(pos, unit.freshTermName(name))
          .setInfo(tpe)
          .setFlag(Flags.SYNTHETIC)
        this.method.addLocal(new Local(sym, toTypeKind(tpe), false))
      }

      
      /**
       * Generate exception handlers for the body. Body is evaluated
       * with a context where all the handlers are active. Handlers are 
       * evaluated in the 'outer' context. 
       *
       * It returns the resulting context, with the same active handlers as
       * before the call. Use it like:
       *
       * <code> ctx.Try( ctx => { 
       *   ctx.bb.emit(...) // protected block
       * }, (ThrowableClass,
       *   ctx => { 
       *     ctx.bb.emit(...); // exception handler
       *   }), (AnotherExceptionClass,
       *   ctx => {...
       *   } ))</code>
       */
      def Try(body: Context => Context, 
              handlers: List[(Symbol, TypeKind, Context => Context)],
              finalizer: Tree,
              tree: Tree) = if (forMSIL) TryMsil(body, handlers, finalizer, tree) else {

        val outerCtx = this.dup       // context for generating exception handlers, covered by finalizer
        val finalizerCtx = this.dup   // context for generating finalizer handler
        val afterCtx = outerCtx.newBlock
        var tmp: Local = null
        val kind = toTypeKind(tree.tpe)
        val guardResult = kind != UNIT && mayCleanStack(finalizer)
        // we need to save bound labels before any code generation is performed on
        // the current context (otherwise, any new labels in the finalizer that need to
        // be duplicated would be incorrectly considered bound -- see #2850).
        val boundLabels: Set[Symbol] = Set.empty ++ labels.keySet

        if (guardResult) {
          tmp = this.makeLocal(tree.pos, tree.tpe, "tmp")
        }

        def emitFinalizer(ctx: Context): Context = if (!finalizer.isEmpty) {
          val ctx1 = finalizerCtx.dup.newBlock
          ctx.bb.closeWith(JUMP(ctx1.bb))

          if (guardResult) {
            ctx1.bb.emit(STORE_LOCAL(tmp))
            val ctx2 = genLoad(duplicateFinalizer(boundLabels, ctx1, finalizer), ctx1, UNIT)
            ctx2.bb.emit(LOAD_LOCAL(tmp))
            ctx2
          } else
            genLoad(duplicateFinalizer(boundLabels, ctx1, finalizer), ctx1, UNIT)
        } else ctx


        val finalizerExh = if (finalizer != EmptyTree) Some({
          val exh = outerCtx.newExceptionHandler(NoSymbol, toTypeKind(finalizer.tpe), finalizer.pos) // finalizer covers exception handlers
          this.addActiveHandler(exh)  // .. and body aswell 
          val ctx = finalizerCtx.enterExceptionHandler(exh)
          val exception = ctx.makeLocal(finalizer.pos, ThrowableClass.tpe, "exc")
          loadException(ctx, exh, finalizer.pos)
          ctx.bb.emit(STORE_LOCAL(exception));
          val ctx1 = genLoad(finalizer, ctx, UNIT);
          ctx1.bb.emit(LOAD_LOCAL(exception));
          ctx1.bb.emit(THROW(ThrowableClass));
          ctx1.bb.enterIgnoreMode;
          ctx1.bb.close
          finalizerCtx.endHandler()
          exh
        }) else None
        
        val exhs = handlers.map { handler =>
            val exh = this.newExceptionHandler(handler._1, handler._2, tree.pos)
            var ctx1 = outerCtx.enterExceptionHandler(exh)
            ctx1.addFinalizer(finalizer, finalizerCtx)
            loadException(ctx1, exh, tree.pos)
            ctx1 = handler._3(ctx1)
            // emit finalizer
            val ctx2 = emitFinalizer(ctx1)
            ctx2.bb.closeWith(JUMP(afterCtx.bb))
            outerCtx.endHandler()
            exh
          }
        val bodyCtx = this.newBlock
        if (finalizer != EmptyTree)
          bodyCtx.addFinalizer(finalizer, finalizerCtx)

        var finalCtx = body(bodyCtx)
        finalCtx = emitFinalizer(finalCtx)

        outerCtx.bb.closeWith(JUMP(bodyCtx.bb))

        finalCtx.bb.closeWith(JUMP(afterCtx.bb))

        afterCtx
      }


      /** try-catch-finally blocks are actually simpler to emit in MSIL, because there
       *  is support for `finally` in bytecode.
       *
       *  A
       *    try { .. } catch { .. } finally { .. }
       *  block is de-sugared into
       *    try { try { ..} catch { .. } } finally { .. }
       *
       *  In ICode `finally` block is represented exactly the same as an exception handler,
       *  but with `NoSymbol` as the exception class. The covered blocks are all blocks of
       *  the `try { .. } catch { .. }`.
       *
       *  Also, TryMsil does not enter any Finalizers into the `cleanups', because the
       *  CLI takes care of running the finalizer when seeing a `leave' statement inside
       *  a try / catch.
       */
      def TryMsil(body: Context => Context,
                  handlers: List[(Symbol, TypeKind, (Context => Context))],
                  finalizer: Tree,
                  tree: Tree) = {

        val outerCtx = this.dup       // context for generating exception handlers, covered by finalizer
        val finalizerCtx = this.dup   // context for generating finalizer handler
        val afterCtx = outerCtx.newBlock

        if (finalizer != EmptyTree) {
          // finalizer is covers try and all catch blocks, i.e.
          //   try { try { .. } catch { ..} } finally { .. }
          val exh = outerCtx.newExceptionHandler(NoSymbol, UNIT, tree.pos)
          this.addActiveHandler(exh)
          val ctx = finalizerCtx.enterExceptionHandler(exh)
          loadException(ctx, exh, tree.pos)
          val ctx1 = genLoad(finalizer, ctx, UNIT)
          // need jump for the ICode to be valid. MSIL backend will emit `Endfinally` instead.
          ctx1.bb.closeWith(JUMP(afterCtx.bb))
          finalizerCtx.endHandler()
        }

        for (handler <- handlers) {
          val exh = this.newExceptionHandler(handler._1, handler._2, tree.pos)
          var ctx1 = outerCtx.enterExceptionHandler(exh)
          loadException(ctx1, exh, tree.pos)
          ctx1 = handler._3(ctx1)
          // msil backend will emit `Leave` to jump out of a handler
          ctx1.bb.closeWith(JUMP(afterCtx.bb))
          outerCtx.endHandler()
        }

        val bodyCtx = this.newBlock

        val finalCtx = body(bodyCtx)

        outerCtx.bb.closeWith(JUMP(bodyCtx.bb))

        // msil backend will emit `Leave` to jump out of a try-block
        finalCtx.bb.closeWith(JUMP(afterCtx.bb))

        afterCtx
      }
    }
  }

    /** 
     * Represent a label in the current method code. In order
     * to support forward jumps, labels can be created without
     * having a deisgnated target block. They can later be attached 
     * by calling `anchor'.
     */
    class Label(val symbol: Symbol) {
      var anchored = false
      var block: BasicBlock = _
      var params: List[Symbol] = _

      private var toPatch: List[Instruction] = Nil

      /** Fix this label to the given basic block. */
      def anchor(b: BasicBlock): Label = {
        assert(!anchored, "Cannot anchor an already anchored label!")
        anchored = true
        this.block = b
        this
      }

      def setParams(p: List[Symbol]): Label = {
        assert(params eq null, "Cannot set label parameters twice!")
        params = p
        this
      }

      /** Add an instruction that refers to this label. */
      def addCallingInstruction(i: Instruction) =
        toPatch = i :: toPatch;

      /**
       * Patch the code by replacing pseudo call instructions with
       * jumps to the given basic block.
       */
      def patch(code: Code) {
        val map = toPatch map (i => (i -> patch(i))) toMap;
        code.blocks foreach (_ subst map)
      }

      /** 
       * Return the patched instruction. If the given instruction
       * jumps to this label, replace it with the basic block. Otherwise,
       * return the same instruction. Conditional jumps have more than one
       * label, so they are replaced only if all labels are anchored.
       */
      def patch(instr: Instruction): Instruction = {
        assert(anchored, "Cannot patch until this label is anchored: " + this)

        instr match {
          case PJUMP(self)
          if (self == this) => JUMP(block)

          case PCJUMP(self, failure, cond, kind)
          if (self == this && failure.anchored) =>
            CJUMP(block, failure.block, cond, kind)

          case PCJUMP(success, self, cond, kind)
          if (self == this && success.anchored) =>
            CJUMP(success.block, block, cond, kind)

          case PCZJUMP(self, failure, cond, kind)
          if (self == this && failure.anchored) =>
            CZJUMP(block, failure.block, cond, kind)

          case PCZJUMP(success, self, cond, kind)
          if (self == this && success.anchored) =>
            CZJUMP(success.block, block, cond, kind)

          case _ => instr
        }
      }

      override def toString() = symbol.toString()
    }

    ///////////////// Fake instructions //////////////////////////

    /**
     * Pseudo jump: it takes a Label instead of a basic block.
     * It is used temporarily during code generation. It is replaced
     * by a real JUMP instruction when all labels are resolved.
     */
    abstract class PseudoJUMP(label: Label) extends Instruction {
      override def toString(): String = "PJUMP " + label.symbol

      override def consumed = 0
      override def produced = 0

      // register with the given label
      if (!label.anchored)
        label.addCallingInstruction(this);
    }

    case class PJUMP(whereto: Label) extends PseudoJUMP(whereto)

    case class PCJUMP(success: Label, failure: Label, cond: TestOp, kind: TypeKind)
    extends PseudoJUMP(success) {
      override def toString(): String =
        "PCJUMP (" + kind + ") " + success.symbol.simpleName +
        " : " + failure.symbol.simpleName

      if (!failure.anchored)
        failure.addCallingInstruction(this)
    }

    case class PCZJUMP(success: Label, failure: Label, cond: TestOp, kind: TypeKind)
    extends PseudoJUMP(success) {
      override def toString(): String =
        "PCZJUMP (" + kind + ") " + success.symbol.simpleName +
        " : " + failure.symbol.simpleName

      if (!failure.anchored)
        failure.addCallingInstruction(this)
    }

  /** Local variable scopes. Keep track of line numbers for debugging info. */
  class Scope(val outer: Scope) {
    val locals: ListBuffer[Local] = new ListBuffer

    def add(l: Local)     = locals += l
    def remove(l: Local)  = locals -= l
      
    /** Return all locals that are in scope. */
    def varsInScope: Buffer[Local] = outer.varsInScope.clone() ++= locals
    
    override def toString() = locals.mkString(outer.toString + "[", ", ", "]")
  }

  object EmptyScope extends Scope(null) {
    override def toString() = "[]"
    override def varsInScope: Buffer[Local] = new ListBuffer
  }
}

Other Scala examples (source code examples)

Here is a short list of links related to this Scala GenICode.scala source code file:

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