/* NSC -- new Scala compiler
* Copyright 2005-2007 LAMP/EPFL
* @author Martin Odersky
*/
// $Id$
package scala.tools.nsc.backend.icode.analysis
import scala.collection.mutable.{Map, HashMap}
import scala.tools.nsc.symtab.Flags.DEFERRED
/**
* A modified copy-propagation like analysis. It
* is augmented with a record-like value which is used
* to represent closures.
*/
abstract class CopyPropagation {
val global: Global
import global._
import icodes._
/** Locations can be local variables. */
abstract sealed class Location;
case class LocalVar(l: Local) extends Location
case class Field(r: Record, sym: Symbol) extends Location
/** Values that can be on the stack. */
abstract class Value {
def isRecord = false
}
case class This extends Value
case class Record(cls: Symbol, bindings: Map[Symbol, Value]) extends Value {
override def isRecord = true
}
case class Deref(l: Location) extends Value;
case object Unknown extends Value
object AllRecords extends Record(NoSymbol, new HashMap[Symbol, Value])
/** The lattice for this analysis. */
object copyLattice extends CompleteLattice {
type Bindings = Map[Location, Value]
def emptyBinding = new HashMap[Location, Value]()
class State(val bindings: Bindings, var stack: List[Value]) {
override def equals(that: Any): Boolean =
(this eq that.asInstanceOf[AnyRef]) ||
that.isInstanceOf[State] && {
val other = that.asInstanceOf[State]
/* comparison with bottom is reference equality! */
if ((other eq bottom) || (this eq bottom))
(this eq other)
else {
this.bindings == other.bindings &&
List.forall2(this.stack, other.stack) { (a, b) => a == b }
}
}
/* Return the binding for the given local (another local) */
def getAlias(l: Local): Local = {
var target = l
var stop = false
while (bindings.isDefinedAt(LocalVar(target)) && !stop) {
bindings(LocalVar(target)) match {
case Deref(LocalVar(t)) => target = t
case _ => stop = true
}
}
target
}
/* Return the binding for the given local. */
def getBinding(l: Local): Value = {
var target = l
var stop = false
var value: Value = Deref(LocalVar(target))
while (bindings.isDefinedAt(LocalVar(target)) && !stop) {
// Console.println("finding binding for " + target)
value = bindings(LocalVar(target))
value match {
case Deref(LocalVar(t)) => target = t
case _ => stop = true
}
}
value
}
/* Return the binding for the given field of the given record */
def getBinding(r: Record, f: Symbol): Value = {
assert(r.bindings.isDefinedAt(f),
"Record " + r + " does not contain a field " + f);
var target: Value = r.bindings(f);
target match {
case Deref(LocalVar(sym)) => getBinding(sym)
case _ => target
}
}
/** Return a local which contains the same value as this field, if any. */
def getLocalForField(r: Record, f: Symbol): Option[Value] = {
assert(r.bindings.isDefinedAt(f),
"Record " + r + " does not contain a field " + f);
var target: Value = r.bindings(f)
target match {
case Deref(LocalVar(l)) => Some(Deref(LocalVar(getAlias(l))))
case This() => Some(target)
case _ => None
}
}
override def toString(): String =
"\nBindings: " + bindings + "\nStack: " + stack;
def dup: State = {
val b: Bindings = new HashMap()
b ++= bindings
new State(b, stack)
}
}
type Elem = State
val top = new State(emptyBinding, Nil)
val bottom = new State(emptyBinding, Nil)
def lub2(a: Elem, b: Elem): Elem = {
if (a eq bottom) b
else if (b eq bottom) a
else if (a == b) a
else {
if (a.stack.length != b.stack.length)
throw new LubError(a, b, "Invalid stacks in states: ");
val resStack = List.map2(a.stack, b.stack) { (v1, v2) =>
if (v1 == v2) v1 else Unknown
}
val commonPairs = a.bindings.toList intersect (b.bindings.toList)
val resBindings = new HashMap[Location, Value]
for (val Pair(k, v) <- commonPairs)
resBindings += k -> v;
new State(resBindings, resStack)
}
}
}
final class CopyAnalysis extends DataFlowAnalysis[copyLattice.type] {
type P = BasicBlock
val lattice = copyLattice
var method: IMethod = _
def init(m: IMethod): Unit = {
this.method = m
init {
worklist += m.code.startBlock
worklist ++= (m.exh map (.startBlock))
m.code.blocks.foreach { b =>
in(b) = lattice.bottom
out(b) = lattice.bottom
}
m.exh foreach { e =>
in(e.startBlock) = new copyLattice.State(copyLattice.emptyBinding, Unknown :: Nil);
}
// first block is special: it's not bottom, but a precisely defined state with no bindings
in(m.code.startBlock) = new lattice.State(lattice.emptyBinding, Nil);
}
}
override def run: Unit = {
forwardAnalysis(blockTransfer)
if (settings.debug.value) {
linearizer.linearize(method).foreach(b => if (b != method.code.startBlock)
assert(in(b) != lattice.bottom,
"Block " + b + " in " + this.method + " has input equal to bottom -- not visited?"));
}
}
def blockTransfer(b: BasicBlock, in: lattice.Elem): lattice.Elem =
b.toList.foldLeft(in)(interpret)
import opcodes._
/** Abstract interpretation for one instruction. */
def interpret(in: copyLattice.Elem, i: Instruction): copyLattice.Elem = {
var out = in.dup
if (settings.debug.value) {
log("- " + i)
log("in: " + in)
log("\n")
}
i match {
case THIS(_) =>
out.stack = This :: out.stack
case CONSTANT(k) =>
if (k.tag != UnitTag)
out.stack = Unknown :: out.stack;
case LOAD_ARRAY_ITEM(_) =>
out.stack = (Unknown :: out.stack.drop(2))
case LOAD_LOCAL(local) =>
out.stack = Deref(LocalVar(local)) :: out.stack
case LOAD_FIELD(field, isStatic) =>
if (isStatic)
out.stack = Unknown :: out.stack; /* ignore static fields */
else {
val v1 = in.stack match {
case (r @ Record(cls, bindings)) :: xs =>
Deref(Field(r, field))
case _ => Unknown
}
out.stack = v1 :: out.stack.drop(1)
}
case LOAD_MODULE(module) =>
out.stack = Unknown :: out.stack
case STORE_ARRAY_ITEM(kind) =>
out.stack = out.stack.drop(3)
case STORE_LOCAL(local) =>
cleanReferencesTo(out, LocalVar(local))
in.stack match {
case Unknown :: xs => ()
case v :: vs =>
v match {
case Deref(LocalVar(other)) =>
if (other != local)
out.bindings += LocalVar(local) -> v;
case _ =>
out.bindings += LocalVar(local) -> v;
}
case Nil => error("Incorrect icode. Expecting something on the stack.")
}
out.stack = out.stack drop 1;
case STORE_FIELD(field, isStatic) =>
if (isStatic)
out.stack = out.stack.drop(1);
else {
out.stack = out.stack.drop(2);
cleanReferencesTo(out, Field(AllRecords, field));
in.stack match {
case v :: Record(_, bindings) :: vs =>
bindings += field -> v;
case _ => ();
}
}
case CALL_PRIMITIVE(primitive) =>
out.stack = Unknown :: out.stack.drop(i.consumed)
case CALL_METHOD(method, style) => style match {
case Dynamic =>
out = simulateCall(in, method, false)
case Static(onInstance) =>
if (onInstance) {
val obj = out.stack.drop(method.info.paramTypes.length).head
if (method.isConstructor) {
obj match {
case Record(_, bindings) =>
for (val v <- out.stack.take(method.info.paramTypes.length + 1);
v ne obj) {
bindings ++= getBindingsForClosure(in, method);
}
case _ => ()
}
// put the Record back on the stack and remove the 'returned' value
out.stack = out.stack.drop(1 + method.info.paramTypes.length)
} else
out = simulateCall(in, method, false)
} else
out = simulateCall(in, method, true)
case SuperCall(_) =>
out = simulateCall(in, method, false)
}
case BOX(tpe) =>
out.stack = Unknown :: out.stack.drop(1)
case UNBOX(tpe) =>
out.stack = Unknown :: out.stack.drop(1)
case NEW(kind) =>
val v1 =
kind match {
case REFERENCE(cls) =>
if (isClosureClass(cls))
Record(cls, new HashMap[Symbol, Value])
else Unknown
case _ =>
Unknown
}
out.stack = v1 :: out.stack
case CREATE_ARRAY(elem) =>
out.stack = Unknown :: out.stack.drop(1)
case IS_INSTANCE(tpe) =>
out.stack = Unknown :: out.stack.drop(1)
case CHECK_CAST(tpe) =>
out.stack = Unknown :: out.stack.drop(1)
case SWITCH(tags, labels) =>
out.stack = out.stack.drop(1)
case JUMP(where) =>
()
case CJUMP(success, failure, cond, kind) =>
out.stack = out.stack.drop(2)
case CZJUMP(success, failure, cond, kind) =>
out.stack = out.stack.drop(1)
case RETURN(kind) =>
if (kind != UNIT)
out.stack = out.stack.drop(1)
case THROW() =>
out.stack = out.stack.drop(1)
case DROP(kind) =>
out.stack = out.stack.drop(1)
case DUP(kind) =>
out.stack = out.stack.head :: out.stack
case MONITOR_ENTER() =>
out.stack = out.stack.drop(1);
case MONITOR_EXIT() =>
out.stack = out.stack.drop(1)
case SCOPE_ENTER(_) | SCOPE_EXIT(_) =>
()
case _ =>
dump
abort("Unknown instruction: " + i)
}
out
} /* def interpret */
/** Remove all references to this local variable from both stack
* and bindings. It is called when a new assignment destroys
* previous copy-relations.
*/
final def cleanReferencesTo(s: copyLattice.State, target: Location): Unit = {
def cleanRecord(r: Record): Record = {
r.bindings retain { (loc, value) =>
value match {
case Deref(loc1) if (loc1 == target) => false
case _ => true
}
}
r
}
s.stack = s.stack map { v => v match {
case Record(_, bindings) =>
cleanRecord(v.asInstanceOf[Record])
case _ => v
}}
s.bindings retain { (loc, value) =>
(value match {
case Deref(loc1) if (loc1 == target) => false
case Record(_, _) =>
cleanRecord(value.asInstanceOf[Record]);
true
case _ => true
}) &&
(loc match {
case l: Location if (l == target) => false
case _ => true
})
}
}
/** Update the state <code>s</code> after the call to <code>method</code>.
* The stack elements are dropped and replaced by the result of the call.
* If the method is impure, all bindings to record fields are cleared.
*
* @param state ...
* @param method ...
* @param static ...
* @return ...
*/
final def simulateCall(state: copyLattice.State, method: Symbol, static: Boolean): copyLattice.State = {
val out = new copyLattice.State(state.bindings, state.stack);
out.stack = out.stack.drop(method.info.paramTypes.length + (if (static) 0 else 1));
if (method.info.resultType != definitions.UnitClass.tpe)
out.stack = Unknown :: out.stack;
if (!isPureMethod(method))
invalidateRecords(out);
out
}
/** Drop everything known about record fields.
*
* @param state ...
*/
final def invalidateRecords(state: copyLattice.State): Unit = {
state.stack = state.stack map { v => v match {
case Record(cls, bindings) =>
Record(cls, new HashMap[Symbol, Value])
case _ => v
}}
state.bindings retain {(loc, value) =>
value match {
case Deref(Field(_, _)) => false
case _ => true
}
}
}
/** Return bindings from closure's fields to the values on the stack. This
* method has to find the correct mapping from fields to the order in which
* they are passed on the stack.
*
* @param in ...
* @param ctor ...
* @return ...
*/
private def getBindingsForClosure(in: copyLattice.State, ctor: Symbol): Map[Symbol, Value] = {
val paramAccessors = ctor.owner.constrParamAccessors;
var values = in.stack.take(1 + ctor.info.paramTypes.length).reverse.drop(1);
val bindings = new HashMap[Symbol, Value];
// this relies on having the same order in paramAccessors and
// the arguments on the stack. It should be the same!
for (val p <- paramAccessors) {
bindings += p -> values.head;
values = values.tail;
}
bindings
}
/** Is <code>cls</code> a closure class?
*
* @param cls ...
* @return ...
*/
final def isClosureClass(cls: Symbol): Boolean =
cls.isFinal &&
cls.tpe.parents.exists { t =>
val TypeRef(_, sym, _) = t;
definitions.FunctionClass exists sym.==
}
/** Is symbol <code>m</code> a pure method?
*
* @param m ...
* @return ...
*/
final def isPureMethod(m: Symbol): Boolean =
// MO: I added !m.hasFlag(DEFERRED) in a refactoring where
// getters now can be abstract whereas before they could not.
// Adding the condition thus keeps the old behavior.
// todo: review whether this is correct, or whether abstract getters should be included.
m.isGetter && !m.hasFlag(DEFERRED);
final override def toString(): String = {
var res = ""
for (val b <- this.method.code.blocks.toList)
res = (res + "\nIN(" + b.label + "):\t Bindings: " + in(b).bindings +
"\nIN(" + b.label +"):\t Stack: " + in(b).stack) + "\n";
res
}
} /* class CopyAnalysis */
}