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/* NSC -- new Scala compiler
* Copyright 2005-2007 LAMP/EPFL
* @author Iulian Dragos
*/
// $Id$
package scala.tools.nsc.backend.opt;
import scala.collection.mutable.{Map, HashMap};
import scala.tools.nsc.backend.icode.analysis.LubError;
import scala.tools.nsc.symtab._;
/**
* @author Iulian Dragos
*/
abstract class ClosureElimination extends SubComponent {
import global._
import icodes._
import icodes.opcodes._
val phaseName = "closelim"
/** Create a new phase */
override def newPhase(p: Phase) = new ClosureEliminationPhase(p)
/** The Inlining phase.
*/
class ClosureEliminationPhase(prev: Phase) extends ICodePhase(prev) {
def name = phaseName
val closser = new ClosureElim
override def apply(c: IClass): Unit =
closser.analyzeClass(c)
}
/**
* Remove references to the environemnt through fields of a closure object.
* This has to be run after an 'apply' method has been inlined, but it still
* references the closure object.
*
*/
class ClosureElim {
/* fresh name counter */
var count = 0
def freshName(s: String) = {
val ret = s + this.count
this.count += 1
ret
}
/** A simple peephole optimizer. */
val peephole = new PeepholeOpt( (i1, i2) =>
(i1, i2) match {
case (CONSTANT(c), DROP(_)) =>
if (c.tag == UnitTag)
Some(List(i2))
else
Some(Nil);
case (LOAD_LOCAL(x), STORE_LOCAL(y)) =>
if (x eq y) Some(Nil) else None
case (LOAD_LOCAL(_), DROP(_)) =>
Some(Nil)
case (BOX(t1), UNBOX(t2)) if (t1 == t2) =>
Some(Nil)
case (LOAD_FIELD(sym, isStatic), DROP(_)) =>
if (isStatic)
Some(Nil)
else
Some(DROP(REFERENCE(definitions.ObjectClass)) :: Nil);
case _ => None
});
def analyzeClass(cls: IClass): Unit = if (settings.Xcloselim.value) {
cls.methods.foreach { m =>
analyzeMethod(m)
peephole.transformMethod(m);
}}
val cpp = new copyPropagation.CopyAnalysis
import copyPropagation._
/* Some embryonic copy propagation. */
def analyzeMethod(m: IMethod): Unit = try {if (m.code ne null) {
log("Analyzing " + m)
cpp.init(m)
cpp.run
for (bb <- linearizer.linearize(m)) {
var info = cpp.in(bb)
log("Cpp info at entry to block " + bb + ": " + info)
for (i <- bb.toList) {
i match {
case LOAD_LOCAL(l) if (info.bindings.isDefinedAt(LocalVar(l))) =>
val t = info.getBinding(l)
t match {
case Deref(LocalVar(v)) =>
bb.replaceInstruction(i, valueToInstruction(t));
log("replaced " + i + " with " + t)
case Deref(This) =>
bb.replaceInstruction(i, valueToInstruction(t));
log("replaced " + i + " with " + t)
case _ =>
bb.replaceInstruction(i, LOAD_LOCAL(info.getAlias(l)));
log("replaced " + i + " with " + info.getAlias(l))
}
case LOAD_FIELD(f, false) if accessible(f, m.symbol) =>
info.stack(0) match {
case r @ Record(cls, bindings) if bindings.isDefinedAt(f) =>
info.getFieldValue(r, f) match {
case Some(v) =>
bb.replaceInstruction(i,
DROP(REFERENCE(cls)) :: valueToInstruction(v) :: Nil);
log("Replaced " + i + " with " + info.getBinding(r, f));
case None => ();
}
case Deref(LocalVar(l)) =>
info.getBinding(l) match {
case r @ Record(cls, bindings) if bindings.isDefinedAt(f) =>
info.getFieldValue(r, f) match {
case Some(v) =>
bb.replaceInstruction(i,
DROP(REFERENCE(cls)) :: valueToInstruction(v) :: Nil);
log("Replaced " + i + " with " + info.getBinding(r, f));
case None => ();
}
case _ => ();
}
case _ => ();
}
case UNBOX(_) =>
info.stack match {
case Deref(LocalVar(loc1)) :: _ if (info.bindings.isDefinedAt(LocalVar(loc1))) =>
val value = info.getBinding(loc1)
value match {
case Boxed(LocalVar(loc2)) =>
bb.replaceInstruction(i, DROP(icodes.AnyRefReference) :: valueToInstruction(info.getBinding(loc2)) :: Nil)
log("replaced " + i + " with " + info.getBinding(loc2))
case _ =>
()
}
case Boxed(LocalVar(loc1)) :: _ =>
val value = info.getBinding(loc1)
bb.replaceInstruction(i, DROP(icodes.AnyRefReference) :: valueToInstruction(value) :: Nil)
log("replaced " + i + " with " + value)
case _ =>
()
}
case _ => ();
}
info = cpp.interpret(info, i)
}
}
}} catch {
case e: LubError =>
Console.println("In method: " + m)
Console.println(e)
e.printStackTrace
}
/* Partial mapping from values to instructions that load them. */
def valueToInstruction(v: Value): Instruction = (v: @unchecked) match {
case Deref(LocalVar(v)) =>
LOAD_LOCAL(v)
case Const(k) =>
CONSTANT(k)
case Deref(This) =>
THIS(definitions.ObjectClass)
}
/** is field 'f' accessible from method 'm'? */
def accessible(f: Symbol, m: Symbol): Boolean =
f.isPublic || (f.hasFlag(Flags.PROTECTED) && (enclPackage(f) == enclPackage(m)))
private def enclPackage(sym: Symbol): Symbol =
if ((sym == NoSymbol) || sym.isPackageClass) sym else enclPackage(sym.owner)
} /* class ClosureElim */
/** Peephole optimization. */
class PeepholeOpt(peep: (Instruction, Instruction) => Option[List[Instruction]]) {
private var method: IMethod = null
def transformMethod(m: IMethod): Unit = if (m.code ne null) {
method = m
for (b <- m.code.blocks)
transformBlock(b)
}
def transformBlock(b: BasicBlock): Unit = if (b.size >= 2) {
var newInstructions: List[Instruction] = Nil;
newInstructions = b.toList
var redo = false
do {
var h = newInstructions.head;
var t = newInstructions.tail;
var seen: List[Instruction] = Nil;
redo = false;
while (t != Nil) {
peep(h, t.head) match {
case Some(newInstrs) =>
newInstructions = seen.reverse ::: newInstrs ::: t.tail;
redo = true;
case None =>
()
}
seen = h :: seen;
h = t.head;
t = t.tail
}
} while (redo);
b.fromList(newInstructions)
}
}
} /* class ClosureElimination */
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