/* 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 regularly 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 + ")" }
    }
  }
}