/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Eclipse Public License (EPL);
* 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/eclipse-1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.jikesrvm.compilers.opt.controlflow;
import org.jikesrvm.compilers.opt.dfsolver.DF_LatticeCell;
import org.jikesrvm.compilers.opt.dfsolver.DF_Operator;
import org.jikesrvm.compilers.opt.ir.BasicBlock;
import org.jikesrvm.compilers.opt.ir.IR;
import org.jikesrvm.util.BitVector;
/**
* This class implements the MEET operation for the
* dataflow equations for the dominator calculation.
*/
class DominatorOperator extends DF_Operator {
/**
* A singleton instance of this class.
*/
static final DominatorOperator MEET = new DominatorOperator();
/**
* Evaluate an equation with the MEET operation
* @param operands the lhs(operands[0]) and rhs(operands[1])
* of the equation.
* @return true if the value of the lhs changes. false otherwise
*/
public boolean evaluate(DF_LatticeCell[] operands) {
DominatorCell lhs = (DominatorCell) operands[0];
IR ir = lhs.ir;
BasicBlock bb = lhs.block;
BitVector oldSet = lhs.dominators.dup();
BitVector newDominators = new BitVector(ir.getMaxBasicBlockNumber() + 1);
if (operands.length > 1) {
if (operands[1] != null) {
newDominators.or(((DominatorCell) operands[1]).dominators);
}
}
for (int i = 2; i < operands.length; i++) {
newDominators.and(((DominatorCell) operands[i]).dominators);
}
newDominators.set(bb.getNumber());
lhs.dominators = newDominators;
return !lhs.dominators.equals(oldSet);
}
/**
* Return a String representation of the operator
* @return "MEET"
*/
public String toString() {
return "MEET";
}
}