/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Common Public License (CPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/cpl1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.jikesrvm.compilers.opt;
import java.util.Comparator;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.TreeSet;
/**
* Represents a system of Data Flow equations
*
* <p> Implementation Note:
* The set of equations is internally represented as a graph
* (actually a OPT_SpaceEffGraph). Each dataflow equation is a node in the
* graph. If a dataflow equation produces a lattice cell value
* that is used by another equation, the graph has a directed edge
* from the producer to the consumer. Fixed-point iteration proceeds
* in a topological order according to these edges.
*/
public abstract class OPT_DF_System {
static final boolean DEBUG = false;
final boolean EAGER;
OPT_DF_System() {
EAGER = false;
}
OPT_DF_System(boolean eager) {
EAGER = eager;
}
/**
* Solve the set of dataflow equations.
* <p> PRECONDITION: equations are set up
*/
public void solve() {
// addGraphEdges();
numberEquationsTopological();
initializeLatticeCells();
initializeWorkList();
while (!workList.isEmpty()) {
OPT_DF_Equation eq = workList.first();
workList.remove(eq);
boolean change = eq.evaluate();
if (DEBUG) {
System.out.println("After evaluation " + eq);
}
if (change) {
updateWorkList(eq);
}
}
}
/**
* Return the solution of the dataflow equation system.
* This is only valid after calling solve()
*
* @return the solution
*/
public OPT_DF_Solution getSolution() {
return cells;
}
/**
* Return a string representation of the system
* @return a string representation of the system
*/
public String toString() {
String result = "EQUATIONS:\n";
Enumeration<OPT_GraphNode> v = equations.enumerateNodes();
for (int i = 0; i < equations.numberOfNodes(); i++) {
result = result + i + " : " + v.nextElement() + "\n";
}
return result;
}
/**
* Return an Enumeration over the equations in this system.
* @return an Enumeration over the equations in this system
*/
public Enumeration<OPT_DF_Equation> getEquations() {
return new OPT_FilterEnumerator<OPT_GraphNode, OPT_DF_Equation>(equations.enumerateNodes(),
new OPT_FilterEnumerator.Filter<OPT_GraphNode, OPT_DF_Equation>() {
public boolean isElement(OPT_GraphNode x) {
return x instanceof OPT_DF_Equation;
}
});
}
/**
* Get the number of equations in this system
* @return the number of equations in this system
*/
public int getNumberOfEquations() {
return equations.numberOfNodes();
}
/**
* Add an equation to the work list.
* @param eq the equation to add
*/
public void addToWorkList(OPT_DF_Equation eq) {
workList.add(eq);
}
/**
* Add all new equations to the work list.
*/
public void addNewEquationsToWorkList() {
if (DEBUG) {
System.out.println("new equations:");
}
for (OPT_DF_Equation eq : newEquations) {
if (DEBUG) {
System.out.println(eq.toString());
}
addToWorkList(eq);
}
newEquations = new HashSet<OPT_DF_Equation>();
if (DEBUG) {
System.out.println("end of new equations");
}
}
/**
* Add all equations to the work list.
*/
public void addAllEquationsToWorkList() {
for (Enumeration<OPT_DF_Equation> e = getEquations(); e.hasMoreElements();) {
OPT_DF_Equation eq = e.nextElement();
addToWorkList(eq);
}
}
/**
* Call this method when the contents of a lattice cell
* changes. This routine adds all equations using this cell
* to the set of new equations.
* @param cell the lattice cell that has changed
*/
public void changedCell(OPT_DF_LatticeCell cell) {
Iterator<OPT_DF_Equation> e = cell.getUses();
while (e.hasNext()) {
newEquations.add(e.next());
}
}
/**
* Find the cell matching this key. If none found, create one.
*
* @param key the key for the lattice cell.
*/
OPT_DF_LatticeCell findOrCreateCell(Object key) {
OPT_DF_LatticeCell result = cells.get(key);
if (result == null) {
result = makeCell(key);
cells.put(key, result);
}
return result;
}
/**
* Add an equation with one operand on the right-hand side.
*
* @param lhs the lattice cell set by this equation
* @param operator the equation operator
* @param op1 first operand on the rhs
*/
void newEquation(OPT_DF_LatticeCell lhs, OPT_DF_Operator operator, OPT_DF_LatticeCell op1) {
// add to the list of equations
OPT_DF_Equation eq = new OPT_DF_Equation(lhs, operator, op1);
equations.addGraphNode(eq);
equations.addGraphNode(lhs);
equations.addGraphNode(op1);
newEquations.add(eq);
// add lattice cells for the operands to the working solution
// cells.put(lhs.getKey(),lhs);
// cells.put(op1.getKey(),op1);
op1.addUse(eq);
lhs.addDef(eq);
if (EAGER && eq.evaluate()) changedCell(lhs);
}
/**
* Add an equation with two operands on the right-hand side.
*
* @param lhs the lattice cell set by this equation
* @param operator the equation operator
* @param op1 first operand on the rhs
* @param op2 second operand on the rhs
*/
void newEquation(OPT_DF_LatticeCell lhs, OPT_DF_Operator operator, OPT_DF_LatticeCell op1, OPT_DF_LatticeCell op2) {
// add to the list of equations
OPT_DF_Equation eq = new OPT_DF_Equation(lhs, operator, op1, op2);
equations.addGraphNode(eq);
equations.addGraphNode(lhs);
equations.addGraphNode(op1);
equations.addGraphNode(op2);
newEquations.add(eq);
// add lattice cells for the operands to the working solution
// cells.put(lhs.getKey(),lhs);
// cells.put(op1.getKey(),op1);
op1.addUse(eq);
// cells.put(op2.getKey(),op2);
op2.addUse(eq);
lhs.addDef(eq);
if (EAGER && eq.evaluate()) changedCell(lhs);
}
/**
* Add an equation with three operands on the right-hand side.
*
* @param lhs the lattice cell set by this equation
* @param operator the equation operator
* @param op1 first operand on the rhs
* @param op2 second operand on the rhs
* @param op3 third operand on the rhs
*/
void newEquation(OPT_DF_LatticeCell lhs, OPT_DF_Operator operator, OPT_DF_LatticeCell op1, OPT_DF_LatticeCell op2,
OPT_DF_LatticeCell op3) {
// add to the list of equations
OPT_DF_Equation eq = new OPT_DF_Equation(lhs, operator, op1, op2, op3);
equations.addGraphNode(eq);
equations.addGraphNode(lhs);
equations.addGraphNode(op1);
equations.addGraphNode(op2);
equations.addGraphNode(op3);
newEquations.add(eq);
// add lattice cells for the operands to the working solution
// cells.put(lhs.getKey(),lhs);
// cells.put(op1.getKey(),op1);
op1.addUse(eq);
// cells.put(op2.getKey(),op2);
op2.addUse(eq);
// cells.put(op3.getKey(),op3);
op3.addUse(eq);
lhs.addDef(eq);
if (EAGER && eq.evaluate()) changedCell(lhs);
}
/**
* Add an equation to the system with an arbitrary number of operands on
* the right-hand side.
*
* @param lhs lattice cell set by this equation
* @param operator the equation operator
* @param rhs the operands on the rhs
*/
void newEquation(OPT_DF_LatticeCell lhs, OPT_DF_Operator operator, OPT_DF_LatticeCell[] rhs) {
// add to the list of equations
OPT_DF_Equation eq = new OPT_DF_Equation(lhs, operator, rhs);
equations.addGraphNode(eq);
equations.addGraphNode(lhs);
newEquations.add(eq);
// add the operands to the working solution
// cells.put(lhs.getKey(),lhs);
for (OPT_DF_LatticeCell rh : rhs) {
// cells.put(rhs[i].getKey(),rhs[i]);
rh.addUse(eq);
equations.addGraphNode(rh);
}
lhs.addDef(eq);
if (EAGER && eq.evaluate()) changedCell(lhs);
}
/**
* Add an existing equation to the system
*
* @param eq the equation
*/
void addEquation(OPT_DF_Equation eq) {
equations.addGraphNode(eq);
newEquations.add(eq);
OPT_DF_LatticeCell lhs = eq.getLHS();
if (!(lhs.getDefs().hasNext() || lhs.getUses().hasNext())) {
lhs.addDef(eq);
equations.addGraphNode(lhs);
} else {
lhs.addDef(eq);
}
OPT_DF_LatticeCell[] operands = eq.getOperands();
for (int i = 1; i < operands.length; i++) {
OPT_DF_LatticeCell op = operands[i];
if (!(op.getDefs().hasNext() || op.getUses().hasNext())) {
op.addUse(eq);
equations.addGraphNode(op);
} else {
op.addUse(eq);
}
}
if (EAGER && eq.evaluate()) changedCell(lhs);
}
/**
* Return the OPT_DF_LatticeCell corresponding to a key.
*
* @param key the key
* @return the LatticeCell if found. null otherwise
*/
public OPT_DF_LatticeCell getCell(Object key) {
return cells.get(key);
}
/**
* Add all equations which contain a given cell to the work list.
* @param cell the cell in question
*/
public void addCellAppearancesToWorkList(OPT_DF_LatticeCell cell) {
for (Enumeration<OPT_DF_Equation> e = getEquations(); e.hasMoreElements();) {
OPT_DF_Equation eq = e.nextElement();
if (eq.hasCell(cell)) {
addToWorkList(eq);
}
}
}
/**
* The equations that comprise this dataflow system.
*/
final OPT_Graph equations = new OPT_DF_Graph();
private static final Comparator<OPT_DF_Equation> dfComparator = new Comparator<OPT_DF_Equation>() {
public int compare(OPT_DF_Equation o1, OPT_DF_Equation o2) {
OPT_DF_Equation eq1 = o1;
OPT_DF_Equation eq2 = o2;
return (eq1.topologicalNumber - eq2.topologicalNumber);
}
};
/**
* Set of equations pending evaluation
*/
protected final TreeSet<OPT_DF_Equation> workList = new TreeSet<OPT_DF_Equation>(dfComparator);
/**
* Set of equations considered "new"
*/
HashSet<OPT_DF_Equation> newEquations = new HashSet<OPT_DF_Equation>();
/**
* The lattice cells of the system: Mapping from Object to OPT_DF_LatticeCell
*/
protected final OPT_DF_Solution cells = new OPT_DF_Solution();
/**
* Initialize all lattice cells in the system.
*/
protected abstract void initializeLatticeCells();
/**
* Initialize the work list for iteration.j
*/
protected abstract void initializeWorkList();
/**
* Create a new lattice cell, referenced by a given key
* @param key key to look up the new cell with
* @return the newly created lattice cell
*/
protected abstract OPT_DF_LatticeCell makeCell(Object key);
/**
* Update the worklist, assuming that a particular equation
* has been re-evaluated
*
* @param eq the equation that has been re-evaluated.
*/
protected void updateWorkList(OPT_DF_Equation eq) {
// find each equation which uses this lattice cell, and
// add it to the work list
Iterator<OPT_DF_Equation> e = eq.getLHS().getUses();
while (e.hasNext()) {
workList.add(e.next());
}
}
/**
* Number the equations in topological order.
*
* <p> PRECONDITION: Already called addGraphEdges()
*
* <p>Algorithm:
* <ul>
* <li> 1. create a DAG of SCCs
* <li> 2. number this DAG topologically
* <li> 3. walk through the DAG and number nodes as they are
* encountered
* </ul>
*/
private void numberEquationsTopological() {
OPT_GraphNodeEnumeration topOrder = OPT_GraphUtilities.
enumerateTopSort(equations);
Enumeration<OPT_GraphNode> rev = new OPT_ReverseDFSenumerateByFinish(equations, topOrder);
int number = 0;
while (rev.hasMoreElements()) {
OPT_GraphNode elt = rev.nextElement();
if (elt instanceof OPT_DF_Equation) {
OPT_DF_Equation eq = (OPT_DF_Equation) elt;
eq.setTopologicalNumber(number++);
}
}
}
/**
* Debugging aid: print statistics about the dataflow system.
*/
void showGraphStats() {
System.out.println("graph has " + equations.numberOfNodes() + " nodes");
int count = 0;
for (Enumeration<OPT_GraphNode> e = equations.enumerateNodes(); e.hasMoreElements();) {
OPT_GraphNode eq = e.nextElement();
OPT_GraphNodeEnumeration outs = eq.outNodes();
while (outs.hasMoreElements()) {
count++;
outs.next();
}
}
System.out.println("graph has " + count + " edges");
}
}