Scala example source code file (Opcodes.scala)

This example Scala source code file (Opcodes.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, instruction, int, nil, objectreference, reflection, string, symbol, test, typekind, unit, utilities

The Opcodes.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala
package tools.nsc
package backend
package icode

import scala.reflect.internal.util.{Position,NoPosition}

/*
  A pattern match

  // locals
    case THIS(clasz) =>
    case STORE_THIS(kind) =>
    case LOAD_LOCAL(local) =>
    case STORE_LOCAL(local) =>
    case SCOPE_ENTER(lv) =>
    case SCOPE_EXIT(lv) =>
  // stack
    case LOAD_MODULE(module) =>
    case LOAD_EXCEPTION(clasz) =>
    case DROP(kind) =>
    case DUP(kind) =>
  // constants
    case CONSTANT(const) =>
  // arithlogic
    case CALL_PRIMITIVE(primitive) =>
  // casts
    case IS_INSTANCE(tpe) =>
    case CHECK_CAST(tpe) =>
  // objs
    case NEW(kind) =>
    case MONITOR_ENTER() =>
    case MONITOR_EXIT() =>
    case BOX(boxType) =>
    case UNBOX(tpe) =>
  // flds
    case LOAD_FIELD(field, isStatic) =>
    case STORE_FIELD(field, isStatic) =>
  // mthds
    case CALL_METHOD(method, style) =>
  // arrays
    case LOAD_ARRAY_ITEM(kind) =>
    case STORE_ARRAY_ITEM(kind) =>
    case CREATE_ARRAY(elem, dims) =>
  // jumps
    case SWITCH(tags, labels) =>
    case JUMP(whereto) =>
    case CJUMP(success, failure, cond, kind) =>
    case CZJUMP(success, failure, cond, kind) =>
  // ret
    case RETURN(kind) =>
    case THROW(clasz) =>
*/


/**
 * The ICode intermediate representation. It is a stack-based
 * representation, very close to the JVM and .NET. It uses the
 * erased types of Scala and references Symbols to refer named entities
 * in the source files.
 */
trait Opcodes { self: ICodes =>
  import global.{Symbol, NoSymbol, Name, Constant}

  // categories of ICode instructions
  final val localsCat =  1
  final val stackCat  =  2
  final val constCat  =  3
  final val arilogCat =  4
  final val castsCat  =  5
  final val objsCat   =  6
  final val fldsCat   =  7
  final val mthdsCat  =  8
  final val arraysCat =  9
  final val jumpsCat  = 10
  final val retCat    = 11

  private lazy val ObjectReferenceList = ObjectReference :: Nil

  /** This class represents an instruction of the intermediate code.
   *  Each case subclass will represent a specific operation.
   */
  abstract class Instruction extends Cloneable {
    // Vlad: I used these for checking the quality of the implementation, and we should regularely run a build with them
    // enabled. But for production these should definitely be disabled, unless we enjoy getting angry emails from Greg :)
    //if (!this.isInstanceOf[opcodes.LOAD_EXCEPTION])
    //  assert(consumed == consumedTypes.length)
    //assert(produced == producedTypes.length)

    def category: Int = 0 // undefined

    /** This abstract method returns the number of used elements on the stack */
    def consumed : Int = 0

    /** This abstract method returns the number of produced elements on the stack */
    def produced : Int = 0

    /** This instruction consumes these types from the top of the stack, the first
     *  element in the list is the deepest element on the stack.
     */
    def consumedTypes: List[TypeKind] = Nil

    /** This instruction produces these types on top of the stack. */
    // Vlad: I wonder why we keep producedTypes around -- it looks like an useless thing to have
    def producedTypes: List[TypeKind] = Nil

    /** The corresponding position in the source file */
    private var _pos: Position = NoPosition

    def pos: Position = _pos

    def setPos(p: Position): this.type = {
      _pos = p
      this
    }

    /** Clone this instruction. */
    override def clone(): Instruction =
      super.clone.asInstanceOf[Instruction]
  }

  object opcodes {
    /** Loads "this" on top of the stack.
     * Stack: ...
     *    ->: ...:ref
     */
    case class THIS(clasz: Symbol) extends Instruction {
      /** Returns a string representation of this constant */
      override def toString = "THIS(" + clasz.name + ")"

      override def consumed = 0
      override def produced = 1

      override def producedTypes =
        // we're not allowed to have REFERENCE(Array), but what about compiling the Array class? Well, we use object for it.
        if (clasz != global.definitions.ArrayClass)
          REFERENCE(clasz) :: Nil
        else
          ObjectReference :: Nil

      override def category = localsCat
    }

    /** Loads a constant on the stack.
     * Stack: ...
     *    ->: ...:constant
     */
    case class CONSTANT(constant: Constant) extends Instruction {
      override def toString = "CONSTANT(" + constant.escapedStringValue + ")"
      override def consumed = 0
      override def produced = 1

      override def producedTypes = toTypeKind(constant.tpe) :: Nil

      override def category = constCat
    }

    /** Loads an element of an array. The array and the index should
     * be on top of the stack.
     * Stack: ...:array[a](Ref):index(Int)
     *    ->: ...:element(a)
     */
    case class LOAD_ARRAY_ITEM(kind: TypeKind) extends Instruction {
      override def consumed = 2
      override def produced = 1

      override def consumedTypes = ARRAY(kind) :: INT :: Nil
      override def producedTypes = kind :: Nil

      override def category = arraysCat
    }

    /** Load a local variable on the stack. It can be a method argument.
     * Stack: ...
     *    ->: ...:value
     */
    case class LOAD_LOCAL(local: Local) extends Instruction {
      override def consumed = 0
      override def produced = 1

      override def producedTypes = local.kind :: Nil

      override def category = localsCat
    }

    /** Load a field on the stack. The object to which it refers should be
     * on the stack.
     * Stack: ...:ref       (assuming isStatic = false)
     *    ->: ...:value
     */
    case class LOAD_FIELD(field: Symbol, isStatic: Boolean) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String =
        "LOAD_FIELD " + (if (isStatic) field.fullName else field.toString())

      override def consumed = if (isStatic) 0 else 1
      override def produced = 1

      override def consumedTypes = if (isStatic) Nil else REFERENCE(field.owner) :: Nil
      override def producedTypes = toTypeKind(field.tpe) :: Nil

      // more precise information about how to load this field
      // see #4283
      var hostClass: Symbol = field.owner
      def setHostClass(cls: Symbol): this.type = { hostClass = cls; this }

      override def category = fldsCat
    }

    case class LOAD_MODULE(module: Symbol) extends Instruction {
      assert(module != NoSymbol, "Invalid module symbol")
      /** Returns a string representation of this instruction */
      override def toString(): String = "LOAD_MODULE " + module

      override def consumed = 0
      override def produced = 1

      override def producedTypes = REFERENCE(module) :: Nil

      override def category = stackCat
    }

    /** Store a value into an array at a specified index.
     * Stack: ...:array[a](Ref):index(Int):value(a)
     *    ->: ...
     */
    case class STORE_ARRAY_ITEM(kind: TypeKind) extends Instruction {
      override def consumed = 3
      override def produced = 0

      override def consumedTypes = ARRAY(kind) :: INT :: kind :: Nil

      override def category = arraysCat
    }

    /** Store a value into a local variable. It can be an argument.
     * Stack: ...:value
     *    ->: ...
     */
    case class STORE_LOCAL(local: Local) extends Instruction {
      override def consumed = 1
      override def produced = 0

      override def consumedTypes = local.kind :: Nil

      override def category = localsCat
    }

    /** Store a value into a field.
     * Stack: ...:ref:value   (assuming isStatic=false)
     *    ->: ...
     */
    case class STORE_FIELD(field: Symbol, isStatic: Boolean) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String =
        "STORE_FIELD "+field + (if (isStatic) " (static)" else " (dynamic)")

      override def consumed = if(isStatic) 1 else 2

      override def produced = 0

      override def consumedTypes =
        if (isStatic)
          toTypeKind(field.tpe) :: Nil
        else
          REFERENCE(field.owner) :: toTypeKind(field.tpe) :: Nil

      override def category = fldsCat
    }

    /** Store a value into the 'this' pointer.
       * Stack: ...:ref
       *    ->: ...
       */
    case class STORE_THIS(kind: TypeKind) extends Instruction {
      override def consumed = 1
      override def produced = 0
      override def consumedTypes = kind :: Nil
      override def category = localsCat
    }

    /** Call a primitive function.
     * Stack: ...:arg1:arg2:...:argn
     *    ->: ...:result
     */
    case class CALL_PRIMITIVE(primitive: Primitive) extends Instruction {
      override def consumed = primitive match {
        case Negation(_)       => 1
        case Test(_,_, true)   => 1
        case Test(_,_, false)  => 2
        case Comparison(_,_)   => 2
        case Arithmetic(NOT,_) => 1
        case Arithmetic(_,_)   => 2
        case Logical(_,_)      => 2
        case Shift(_,_)        => 2
        case Conversion(_,_)   => 1
        case ArrayLength(_)    => 1
        case StringConcat(_)   => 2
        case StartConcat       => 0
        case EndConcat         => 1
      }
      override def produced = 1

      override def consumedTypes = primitive match {
        case Negation(kind)        => kind :: Nil
        case Test(_, kind, true)   => kind :: Nil
        case Test(_, kind, false)  => kind :: kind :: Nil
        case Comparison(_, kind)   => kind :: kind :: Nil
        case Arithmetic(NOT, kind) => kind :: Nil
        case Arithmetic(_, kind)   => kind :: kind :: Nil
        case Logical(_, kind)      => kind :: kind :: Nil
        case Shift(_, kind)        => kind :: INT :: Nil
        case Conversion(from, _)   => from :: Nil
        case ArrayLength(kind)     => ARRAY(kind) :: Nil
        case StringConcat(kind)    => ConcatClass :: kind :: Nil
        case StartConcat           => Nil
        case EndConcat             => ConcatClass :: Nil
      }

      override def producedTypes = primitive match {
        case Negation(kind)      => kind :: Nil
        case Test(_, _, true)    => BOOL :: Nil
        case Test(_, _, false)   => BOOL :: Nil
        case Comparison(_, _)    => INT :: Nil
        case Arithmetic(_, kind) => kind :: Nil
        case Logical(_, kind)    => kind :: Nil
        case Shift(_, kind)      => kind :: Nil
        case Conversion(_, to)   => to :: Nil
        case ArrayLength(_)      => INT :: Nil
        case StringConcat(_)     => ConcatClass :: Nil
        case StartConcat         => ConcatClass :: Nil
        case EndConcat           => REFERENCE(global.definitions.StringClass) :: Nil
      }

      override def category = arilogCat
   }

    /** This class represents a CALL_METHOD instruction
     * STYLE: dynamic / static(StaticInstance)
     * Stack: ...:ref:arg1:arg2:...:argn
     *    ->: ...:result
     *
     * STYLE: static(StaticClass)
     * Stack: ...:arg1:arg2:...:argn
     *    ->: ...:result
     *
     */
    case class CALL_METHOD(method: Symbol, style: InvokeStyle) extends Instruction with ReferenceEquality {
      def toShortString =
        "CALL_METHOD " + method.name +" ("+style+")"

      /** Returns a string representation of this instruction */
      override def toString(): String =
        "CALL_METHOD " + method.fullName +" ("+style+")"

      var hostClass: Symbol = method.owner
      def setHostClass(cls: Symbol): this.type = { hostClass = cls; this }

      /** This is specifically for preserving the target native Array type long
       *  enough that clone() can generate the right call.
       */
      var targetTypeKind: TypeKind = UNIT // the default should never be used, so UNIT should fail fast.
      def setTargetTypeKind(tk: TypeKind) = targetTypeKind = tk

      private def params = method.info.paramTypes
      private def consumesInstance = style match {
        case Static(false)  => 0
        case _              => 1
      }

      override def consumed = params.length + consumesInstance
      override def consumedTypes = {
        val args = params map toTypeKind
        if (consumesInstance > 0) ObjectReference :: args
        else args
      }

      private val producedList = toTypeKind(method.info.resultType) match {
        case UNIT                      => Nil
        case _ if method.isConstructor => Nil
        case kind                      => kind :: Nil
      }
      override def produced = producedList.size
      override def producedTypes = producedList

      /** object identity is equality for CALL_METHODs. Needed for
       *  being able to store such instructions into maps, when more
       *  than one CALL_METHOD to the same method might exist.
       */

      override def category = mthdsCat
    }

    /**
     * A place holder entry that allows us to parse class files with invoke dynamic
     * instructions. Because the compiler doesn't yet really understand the
     * behavior of invokeDynamic, this op acts as a poison pill. Any attempt to analyze
     * this instruction will cause a failure. The only optimization that
     * should ever look at non-Scala generated icode is the inliner, and it
     * has been modified to not examine any method with invokeDynamic
     * instructions. So if this poison pill ever causes problems then
     * there's been a serious misunderstanding
     */
    // TODO do the real thing
    case class INVOKE_DYNAMIC(poolEntry: Int) extends Instruction {
      private def error = sys.error("INVOKE_DYNAMIC is not fully implemented and should not be analyzed")
      override def consumed = error
      override def produced = error
      override def producedTypes = error
      override def category = error
    }

    case class BOX(boxType: TypeKind) extends Instruction {
      assert(boxType.isValueType && (boxType ne UNIT)) // documentation
      override def toString(): String = "BOX " + boxType
      override def consumed = 1
      override def consumedTypes = boxType :: Nil
      override def produced = 1
      override def producedTypes = BOXED(boxType) :: Nil
      override def category = objsCat
    }

    case class UNBOX(boxType: TypeKind) extends Instruction {
      assert(boxType.isValueType && !boxType.isInstanceOf[BOXED] && (boxType ne UNIT)) // documentation
      override def toString(): String = "UNBOX " + boxType
      override def consumed = 1
      override def consumedTypes = ObjectReferenceList
      override def produced = 1
      override def producedTypes = boxType :: Nil
      override def category = objsCat
    }

    /** Create a new instance of a class through the specified constructor
     * Stack: ...:arg1:arg2:...:argn
     *    ->: ...:ref
     */
    case class NEW(kind: REFERENCE) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String = "NEW "+ kind

      override def consumed = 0

      override def produced = 1

      override def producedTypes = kind :: Nil

      /** The corresponding constructor call. */
      var init: CALL_METHOD = _

      override def category = objsCat
    }


    /** This class represents a CREATE_ARRAY instruction
     * Stack: ...:size_1:size_2:..:size_n
     *    ->: ...:arrayref
     */
    case class CREATE_ARRAY(elem: TypeKind, dims: Int) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="CREATE_ARRAY "+elem + " x " + dims

      override def consumed = dims

      override def consumedTypes = List.fill(dims)(INT)
      override def produced = 1

      override def producedTypes = ARRAY(elem) :: Nil

      override def category = arraysCat
    }

    /** This class represents a IS_INSTANCE instruction
     * Stack: ...:ref
     *    ->: ...:result(boolean)
     */
    case class IS_INSTANCE(typ: TypeKind) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="IS_INSTANCE "+typ

      override def consumed = 1
      override def produced = 1
      override def consumedTypes = ObjectReferenceList
      override def producedTypes = BOOL :: Nil

      override def category = castsCat
    }

    /** This class represents a CHECK_CAST instruction
     * Stack: ...:ref(oldtype)
     *    ->: ...:ref(typ <=: oldtype)
     */
    case class CHECK_CAST(typ: TypeKind) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="CHECK_CAST "+typ

      override def consumed = 1
      override def produced = 1
      override def consumedTypes = ObjectReferenceList
      override def producedTypes = typ :: Nil

      override def category = castsCat
    }

    /** This class represents a SWITCH instruction
     * Stack: ...:index(int)
     *    ->: ...:
     *
     * The tags array contains one entry per label, each entry consisting of
     * an array of ints, any of which will trigger the jump to the corresponding label.
     * labels should contain an extra label, which is the 'default' jump.
     */
    case class SWITCH(tags: List[List[Int]], labels: List[BasicBlock]) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="SWITCH ..."

      override def consumed = 1
      override def produced = 0

      override def consumedTypes = INT :: Nil

      def flatTagsCount: Int = { var acc = 0; var rest = tags; while(rest.nonEmpty) { acc += rest.head.length; rest = rest.tail }; acc } // a one-liner

      override def category = jumpsCat
    }

    /** This class represents a JUMP instruction
     * Stack: ...
     *    ->: ...
     */
    case class JUMP(whereto: BasicBlock) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="JUMP "+whereto.label

      override def consumed = 0
      override def produced = 0

      override def category = jumpsCat
    }

    /** This class represents a CJUMP instruction
     * It compares the two values on the stack with the 'cond' test operator
     * Stack: ...:value1:value2
     *    ->: ...
     */
    case class CJUMP(successBlock: BasicBlock,
		     failureBlock: BasicBlock,
		     cond: TestOp,
                     kind: TypeKind) extends Instruction
    {

      /** Returns a string representation of this instruction */
      override def toString(): String = (
        "CJUMP (" + kind + ")" +
        cond + " ? "+successBlock.label+" : "+failureBlock.label
      )

      override def consumed = 2
      override def produced = 0

      override def consumedTypes = kind :: kind :: Nil

      override def category = jumpsCat
    }

    /** This class represents a CZJUMP instruction
     * It compares the one value on the stack and zero with the 'cond' test operator
     * Stack: ...:value:
     *    ->: ...
     */
    case class CZJUMP(successBlock: BasicBlock,
                      failureBlock: BasicBlock,
                      cond: TestOp,
                      kind: TypeKind) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String = (
        "CZJUMP (" + kind + ")" +
        cond + " ? "+successBlock.label+" : "+failureBlock.label
      )

      override def consumed = 1
      override def produced = 0

      override def consumedTypes = kind :: Nil
      override def category = jumpsCat
    }


    /** This class represents a RETURN instruction
     * Stack: ...
     *    ->: ...
     */
    case class RETURN(kind: TypeKind) extends Instruction {
      override def consumed = if (kind == UNIT) 0 else 1
      override def produced = 0

      override def consumedTypes = if (kind == UNIT) Nil else kind :: Nil

      override def category = retCat
    }

    /** This class represents a THROW instruction
     * Stack: ...:Throwable(Ref)
     *    ->: ...:
     */
    case class THROW(clasz: Symbol) extends Instruction {
      /** PP to ID: We discussed parameterizing LOAD_EXCEPTION but
       *  not THROW, which came about organically.  It seems like the
       *  right thing, but can you confirm?
       */
      override def toString = "THROW(" + clasz.name + ")"

      override def consumed = 1
      override def produced = 0

      override def consumedTypes = toTypeKind(clasz.tpe) :: Nil

      override def category = retCat
    }

    /** This class represents a DROP instruction
     * Stack: ...:something
     *    ->: ...
     */
    case class DROP (typ: TypeKind) extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="DROP "+typ

      override def consumed = 1
      override def produced = 0

      override def consumedTypes = typ :: Nil

      override def category = stackCat
    }

    /** This class represents a DUP instruction
     * Stack: ...:something
     *    ->: ...:something:something
     */
    case class DUP (typ: TypeKind) extends Instruction {
      override def consumed = 1
      override def produced = 2
      override def consumedTypes = typ :: Nil
      override def producedTypes = typ :: typ :: Nil
      override def category = stackCat
    }

    /** This class represents a MONITOR_ENTER instruction
     * Stack: ...:object(ref)
     *    ->: ...:
     */
    case class MONITOR_ENTER() extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="MONITOR_ENTER"

      override def consumed = 1
      override def produced = 0

      override def consumedTypes = ObjectReference :: Nil

      override def category = objsCat
    }

    /** This class represents a MONITOR_EXIT instruction
     * Stack: ...:object(ref)
     *    ->: ...:
     */
    case class MONITOR_EXIT() extends Instruction {
      /** Returns a string representation of this instruction */
      override def toString(): String ="MONITOR_EXIT"

      override def consumed = 1

      override def produced = 0

      override def consumedTypes = ObjectReference :: Nil

      override def category = objsCat
    }

    /** A local variable becomes visible at this point in code.
     *  Used only for generating precise local variable tables as
     *  debugging information.
     */
    case class SCOPE_ENTER(lv: Local) extends Instruction {
      override def toString(): String = "SCOPE_ENTER " + lv
      override def consumed = 0
      override def produced = 0
      override def category = localsCat
    }

    /** A local variable leaves its scope at this point in code.
     *  Used only for generating precise local variable tables as
     *  debugging information.
     */
    case class SCOPE_EXIT(lv: Local) extends Instruction {
      override def toString(): String = "SCOPE_EXIT " + lv
      override def consumed = 0
      override def produced = 0
      override def category = localsCat
    }

    /** Fake instruction. It designates the VM who pushes an exception
     *  on top of the /empty/ stack at the beginning of each exception handler.
     *  Note: Unlike other instructions, it consumes all elements on the stack!
     *        then pushes one exception instance.
     */
    case class LOAD_EXCEPTION(clasz: Symbol) extends Instruction {
      override def consumed = sys.error("LOAD_EXCEPTION does clean the whole stack, no idea how many things it consumes!")
      override def produced = 1
      override def producedTypes = REFERENCE(clasz) :: Nil
      override def category = stackCat
    }

    /** This class represents a method invocation style. */
    sealed abstract class InvokeStyle {
      /** Is this a dynamic method call? */
      def isDynamic: Boolean = false

      /** Is this a static method call? */
      def isStatic: Boolean = false

      def isSuper: Boolean = false

      /** Is this an instance method call? */
      def hasInstance: Boolean = true

      /** Returns a string representation of this style. */
      override def toString(): String
    }

    /** Virtual calls.
     *  On JVM, translated to either `invokeinterface` or `invokevirtual`.
     */
    case object Dynamic extends InvokeStyle {
      override def isDynamic = true
      override def toString(): String = "dynamic"
    }

    /**
     * Special invoke:
     *   Static(true)  is used for calls to private members, ie `invokespecial` on JVM.
     *   Static(false) is used for calls to class-level instance-less static methods, ie `invokestatic` on JVM.
     */
    case class Static(onInstance: Boolean) extends InvokeStyle {
      override def isStatic    = true
      override def hasInstance = onInstance
      override def toString(): String = {
        if(onInstance) "static-instance"
        else           "static-class"
      }
    }

    /** Call through super[mix].
     *  On JVM, translated to `invokespecial`.
     */
    case class SuperCall(mix: Name) extends InvokeStyle {
      override def isSuper = true
      override def toString(): String = { "super(" + mix + ")" }
    }
  }
}