members.scala

JAVA 语言的函数式编程扩展

/* NSC -- new scala compiler
 * Copyright 2005-2008 LAMP/EPFL
 * @author  Martin Odersky
 */

// $Id: Members.scala 13784 2008-01-23 10:54:00Z michelou $

package scala.tools.nsc.backend.icode

import java.io.PrintWriter

import scala.collection.mutable.HashMap
import scala.collection.mutable.{Set, HashSet, ListBuffer}
import scala.{Symbol => scala_Symbol}

import scala.tools.nsc.symtab.Flags

trait Members { self: ICodes =>
  import global._

  /** 
   * This class represents the intermediate code of a method or
   * other multi-block piece of code, like exception handlers.
   */
  class Code(label: String, method: IMethod) {

    /** The set of all blocks */
    val blocks: ListBuffer[BasicBlock] = new ListBuffer

    /** The start block of the method */
    var startBlock: BasicBlock = null

    /** The stack produced by this method */
    var producedStack: TypeStack = null
    
    private var currentLabel: Int = 0

    // Constructor code
    startBlock = newBlock

    def removeBlock(b: BasicBlock) {
      if (settings.debug.value) {
        assert(blocks.forall(p => !(p.successors.contains(b))),
               "Removing block that is still referenced in method code " + b + "preds: " + b.predecessors);
        if (b == startBlock)
          assert(b.successors.length == 1,
                 "Removing start block with more than one successor.");
      }
      
      if (b == startBlock)
        startBlock = b.successors.head;
      blocks -= b
    }

    /** 
     * Apply a function to all basic blocks, for side-effects. It starts at
     * the given startBlock and checks that are no predecessors of the given node.
     * Only blocks that are reachable via a path from startBlock are ever visited.
     */
    def traverseFrom(startBlock: BasicBlock, f: BasicBlock => Unit) = {
      val visited: Set[BasicBlock] = new HashSet();

      def traverse0(toVisit: List[BasicBlock]): Unit = toVisit match {
        case Nil => ();
        case b :: bs => if (!visited.contains(b)) {
          f(b); 
          visited += b;
          traverse0(bs ::: b.successors);
        } else
          traverse0(bs);
      }
      assert(startBlock.predecessors == Nil,
             "Starting traverse from a block with predecessors: " + this);
      traverse0(startBlock :: Nil)
    }

    def traverse(f: BasicBlock => Unit) = blocks.toList foreach f;

    /* This method applies the given function to each basic block. */
    def traverseFeedBack(f: (BasicBlock, HashMap[BasicBlock, Boolean]) => Unit) = {
      val visited : HashMap[BasicBlock, Boolean] = new HashMap;
      visited ++= blocks.elements.map(x => (x, false));
      
      var blockToVisit: List[BasicBlock] = List(startBlock)
      
      while (!blockToVisit.isEmpty) {
        blockToVisit match {
	  case b::xs => 
	    if (!visited(b)) {
	      f(b, visited); 
	      blockToVisit = b.successors ::: xs;
	      visited += (b -> true)
	    } else
	      blockToVisit = xs
          case _ => 
            error("impossible match")
	}
      }
    }
    
    /** This methods returns a string representation of the ICode */
    override def toString() : String = "ICode '" + label + "'";
    
    /* Compute a unique new label */
    def nextLabel: Int = {
      currentLabel += 1
      currentLabel
    }

    /* Create a new block and append it to the list
     */
    def newBlock: BasicBlock = {
      val block = new BasicBlock(nextLabel, method);
      blocks += block;
      block
    }    
  }

  /** Represent a class in ICode */
  class IClass(val symbol: Symbol) {
    var fields: List[IField] = Nil
    var methods: List[IMethod] = Nil
    var cunit: CompilationUnit = _

    def addField(f: IField): this.type = {
      fields = f :: fields;
      this
    }

    def addMethod(m: IMethod): this.type = {
      methods = m :: methods;
      this
    }

    def setCompilationUnit(unit: CompilationUnit): this.type = {
      this.cunit = unit;
      this
    }

    override def toString() = symbol.fullNameString;

    def lookupField(s: Symbol) = fields find ((f) => f.symbol == s);
    def lookupMethod(s: Symbol) = methods find ((m) => m.symbol == s);
    def lookupMethod(s: Name) = methods find ((m) => m.symbol.name == s);
  }

  /** Represent a field in ICode */
  class IField(val symbol: Symbol) {
  }

  /** 
   * Represents a method in ICode. Local variables contain
   * both locals and parameters, similar to the way the JVM 
   * 'sees' them.
   * 
   * Locals and parameters are added in reverse order, as they
   * are kept in cons-lists. The 'builder' is responsible for
   * reversing them and putting them back, when the generation is
   * finished (GenICode does that).
   */
  class IMethod(val symbol: Symbol) {
    var code: Code = null
    var native = false

    /** The list of exception handlers, ordered from innermost to outermost. */
    var exh: List[ExceptionHandler] = Nil
    var sourceFile: String = _
    var returnType: TypeKind = _

    var recursive: Boolean = false

    /** local variables and method parameters */
    var locals: List[Local] = Nil

    /** method parameters */
    var params: List[Local] = Nil

    def setCode(code: Code): IMethod = {
      this.code = code;
      this
    }

    def addLocal(l: Local): Local =
      locals find (l.==) match {
        case Some(loc) => loc
        case None =>
          locals = l :: locals;
          l
      }

    def addLocals(ls: List[Local]) {
      ls foreach addLocal
    }

    def addParam(p: Local) {
      if (!(params contains p)) {
        params = p :: params;
        locals = p :: locals;
      }
    }

    def addParams(as: List[Local]) {
      as foreach addParam
    }

    def lookupLocal(n: Name): Option[Local] = 
      locals find ((l) => l.sym.name == n);

    def lookupLocal(sym: Symbol): Option[Local] =
      locals find ((l) => l.sym == sym);

    def addHandler(e: ExceptionHandler) {
      exh = e :: exh
    }

    /** Is this method deferred ('abstract' in Java sense) */
    def isDeferred = (
      symbol.hasFlag(Flags.DEFERRED) ||
      symbol.owner.hasFlag(Flags.INTERFACE) ||
      native
    );

    def isStatic: Boolean =
      symbol.hasFlag(Flags.STATIC) || symbol.hasFlag(Flags.STATICMEMBER) || symbol.owner.isImplClass;
    
    override def toString() = symbol.fullNameString
    
    import opcodes._
    def checkLocals: Unit = if (code ne null) {
      Console.println("[checking locals of " + this + "]")
      for (bb <- code.blocks; i <- bb.toList) i match {
        case LOAD_LOCAL(l) =>
          if (!this.locals.contains(l)) 
            Console.println("Local " + l + " is not declared in " + this)
        case STORE_LOCAL(l) =>
          if (!this.locals.contains(l)) 
            Console.println("Local " + l + " is not declared in " + this)            
        case _ => ()
      }
    }
    
    /** Merge together blocks that have a single successor which has a 
     * single predecessor. Exception handlers are taken into account (they
     * might force to break a block of straight line code like that).
     *
     * This method should be most effective after heavy inlining.
     */
    def normalize: Unit = if (this.code ne null) {
      import scala.collection.mutable.{Map, HashMap}      
      val nextBlock: Map[BasicBlock, BasicBlock] = HashMap.empty
      for (val b <- code.blocks.toList;
        b.successors.length == 1; 
        val succ = b.successors.head; 
        succ ne b;
        succ.predecessors.length == 1;
        succ.predecessors.head eq b;
        !(exh.exists { (e: ExceptionHandler) => 
            (e.covers(succ) && !e.covers(b)) || (e.covers(b) && !e.covers(succ)) })) {
          nextBlock(b) = succ
      }
          
      var bb = code.startBlock
      while (!nextBlock.isEmpty) {
        if (nextBlock.isDefinedAt(bb)) {
          bb.open
          var succ = bb
          do {
            succ = nextBlock(succ);
            bb.removeLastInstruction
            succ.toList foreach { i => bb.emit(i, i.pos) }
            code.removeBlock(succ)
            nextBlock -= bb
            exh foreach { e => e.covered = e.covered.remove { b1 => b1 == succ } }
          } while (nextBlock.isDefinedAt(succ))
          bb.close
        } else 
          bb = nextBlock.keys.next
      }
    }
    
    def dump {
      val printer = new TextPrinter(new PrintWriter(Console.out, true),
                                    new DumpLinearizer)
      printer.printMethod(this)
    }    
  }

  /** Represent local variables and parameters */
  class Local(val sym: Symbol, val kind: TypeKind, val arg: Boolean) {
    var index: Int = -1

    /** Starting PC for this local's visbility range. */
    var start: Int = _
    
    /** Ending PC for this local's visbility range. */
    var end: Int = _
    
    /** PC-based ranges for this local variable's visibility */
    var ranges: List[(Int, Int)] = Nil

    override def equals(other: Any): Boolean = (
      other.isInstanceOf[Local] &&
      other.asInstanceOf[Local].sym == this.sym
    );

    override def toString(): String = sym.toString()
  }
}