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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Martin Odersky
*/
package scala
package tools.nsc
package typechecker
import java.lang.ArithmeticException
/** This class ...
*
* @author Martin Odersky
* @version 1.0
*/
abstract class ConstantFolder {
val global: Global
import global._
/** If tree is a constant operation, replace with result. */
def apply(tree: Tree): Tree = fold(tree, tree match {
case Apply(Select(Literal(x), op), List(Literal(y))) => foldBinop(op, x, y)
case Select(Literal(x), op) => foldUnop(op, x)
case _ => null
})
/** If tree is a constant value that can be converted to type `pt`, perform
* the conversion.
*/
def apply(tree: Tree, pt: Type): Tree = fold(apply(tree), tree.tpe match {
case ConstantType(x) => x convertTo pt
case _ => null
})
private def fold(tree: Tree, compX: => Constant): Tree =
try {
val x = compX
if ((x ne null) && x.tag != UnitTag) tree setType ConstantType(x)
else tree
} catch {
case _: ArithmeticException => tree // the code will crash at runtime,
// but that is better than the
// compiler itself crashing
}
private def foldUnop(op: Name, x: Constant): Constant = (op, x.tag) match {
case (nme.UNARY_!, BooleanTag) => Constant(!x.booleanValue)
case (nme.UNARY_~ , IntTag ) => Constant(~x.intValue)
case (nme.UNARY_~ , LongTag ) => Constant(~x.longValue)
case (nme.UNARY_+ , IntTag ) => Constant(+x.intValue)
case (nme.UNARY_+ , LongTag ) => Constant(+x.longValue)
case (nme.UNARY_+ , FloatTag ) => Constant(+x.floatValue)
case (nme.UNARY_+ , DoubleTag ) => Constant(+x.doubleValue)
case (nme.UNARY_- , IntTag ) => Constant(-x.intValue)
case (nme.UNARY_- , LongTag ) => Constant(-x.longValue)
case (nme.UNARY_- , FloatTag ) => Constant(-x.floatValue)
case (nme.UNARY_- , DoubleTag ) => Constant(-x.doubleValue)
case _ => null
}
/** These are local helpers to keep foldBinop from overly taxing the
* optimizer.
*/
private def foldBooleanOp(op: Name, x: Constant, y: Constant): Constant = op match {
case nme.ZOR => Constant(x.booleanValue | y.booleanValue)
case nme.OR => Constant(x.booleanValue | y.booleanValue)
case nme.XOR => Constant(x.booleanValue ^ y.booleanValue)
case nme.ZAND => Constant(x.booleanValue & y.booleanValue)
case nme.AND => Constant(x.booleanValue & y.booleanValue)
case nme.EQ => Constant(x.booleanValue == y.booleanValue)
case nme.NE => Constant(x.booleanValue != y.booleanValue)
case _ => null
}
private def foldSubrangeOp(op: Name, x: Constant, y: Constant): Constant = op match {
case nme.OR => Constant(x.intValue | y.intValue)
case nme.XOR => Constant(x.intValue ^ y.intValue)
case nme.AND => Constant(x.intValue & y.intValue)
case nme.LSL => Constant(x.intValue << y.intValue)
case nme.LSR => Constant(x.intValue >>> y.intValue)
case nme.ASR => Constant(x.intValue >> y.intValue)
case nme.EQ => Constant(x.intValue == y.intValue)
case nme.NE => Constant(x.intValue != y.intValue)
case nme.LT => Constant(x.intValue < y.intValue)
case nme.GT => Constant(x.intValue > y.intValue)
case nme.LE => Constant(x.intValue <= y.intValue)
case nme.GE => Constant(x.intValue >= y.intValue)
case nme.ADD => Constant(x.intValue + y.intValue)
case nme.SUB => Constant(x.intValue - y.intValue)
case nme.MUL => Constant(x.intValue * y.intValue)
case nme.DIV => Constant(x.intValue / y.intValue)
case nme.MOD => Constant(x.intValue % y.intValue)
case _ => null
}
private def foldLongOp(op: Name, x: Constant, y: Constant): Constant = op match {
case nme.OR => Constant(x.longValue | y.longValue)
case nme.XOR => Constant(x.longValue ^ y.longValue)
case nme.AND => Constant(x.longValue & y.longValue)
case nme.LSL => Constant(x.longValue << y.longValue)
case nme.LSR => Constant(x.longValue >>> y.longValue)
case nme.ASR => Constant(x.longValue >> y.longValue)
case nme.EQ => Constant(x.longValue == y.longValue)
case nme.NE => Constant(x.longValue != y.longValue)
case nme.LT => Constant(x.longValue < y.longValue)
case nme.GT => Constant(x.longValue > y.longValue)
case nme.LE => Constant(x.longValue <= y.longValue)
case nme.GE => Constant(x.longValue >= y.longValue)
case nme.ADD => Constant(x.longValue + y.longValue)
case nme.SUB => Constant(x.longValue - y.longValue)
case nme.MUL => Constant(x.longValue * y.longValue)
case nme.DIV => Constant(x.longValue / y.longValue)
case nme.MOD => Constant(x.longValue % y.longValue)
case _ => null
}
private def foldFloatOp(op: Name, x: Constant, y: Constant): Constant = op match {
case nme.EQ => Constant(x.floatValue == y.floatValue)
case nme.NE => Constant(x.floatValue != y.floatValue)
case nme.LT => Constant(x.floatValue < y.floatValue)
case nme.GT => Constant(x.floatValue > y.floatValue)
case nme.LE => Constant(x.floatValue <= y.floatValue)
case nme.GE => Constant(x.floatValue >= y.floatValue)
case nme.ADD => Constant(x.floatValue + y.floatValue)
case nme.SUB => Constant(x.floatValue - y.floatValue)
case nme.MUL => Constant(x.floatValue * y.floatValue)
case nme.DIV => Constant(x.floatValue / y.floatValue)
case nme.MOD => Constant(x.floatValue % y.floatValue)
case _ => null
}
private def foldDoubleOp(op: Name, x: Constant, y: Constant): Constant = op match {
case nme.EQ => Constant(x.doubleValue == y.doubleValue)
case nme.NE => Constant(x.doubleValue != y.doubleValue)
case nme.LT => Constant(x.doubleValue < y.doubleValue)
case nme.GT => Constant(x.doubleValue > y.doubleValue)
case nme.LE => Constant(x.doubleValue <= y.doubleValue)
case nme.GE => Constant(x.doubleValue >= y.doubleValue)
case nme.ADD => Constant(x.doubleValue + y.doubleValue)
case nme.SUB => Constant(x.doubleValue - y.doubleValue)
case nme.MUL => Constant(x.doubleValue * y.doubleValue)
case nme.DIV => Constant(x.doubleValue / y.doubleValue)
case nme.MOD => Constant(x.doubleValue % y.doubleValue)
case _ => null
}
private def foldBinop(op: Name, x: Constant, y: Constant): Constant = {
val optag =
if (x.tag == y.tag) x.tag
else if (x.isNumeric && y.isNumeric) math.max(x.tag, y.tag)
else NoTag
try optag match {
case BooleanTag => foldBooleanOp(op, x, y)
case ByteTag | ShortTag | CharTag | IntTag => foldSubrangeOp(op, x, y)
case LongTag => foldLongOp(op, x, y)
case FloatTag => foldFloatOp(op, x, y)
case DoubleTag => foldDoubleOp(op, x, y)
case StringTag if op == nme.ADD => Constant(x.stringValue + y.stringValue)
case _ => null
}
catch {
case ex: ArithmeticException => null
}
}
}
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