/*
* 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 org.jikesrvm.compilers.opt.ir.OPT_BasicBlock;
import org.jikesrvm.compilers.opt.ir.OPT_IR;
/**
* This class implements the MEET operation for the
* dataflow equations for the dominator calculation.
*/
class OPT_DominatorOperator extends OPT_DF_Operator {
/**
* 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
*/
boolean evaluate(OPT_DF_LatticeCell[] operands) {
OPT_DominatorCell lhs = (OPT_DominatorCell) operands[0];
OPT_IR ir = lhs.ir;
OPT_BasicBlock bb = lhs.block;
OPT_BitVector oldSet = lhs.dominators.dup();
OPT_BitVector newDominators = new OPT_BitVector(ir.getMaxBasicBlockNumber() + 1);
if (operands.length > 1) {
if (operands[1] != null) {
newDominators.or(((OPT_DominatorCell) operands[1]).dominators);
}
}
for (int i = 2; i < operands.length; i++) {
newDominators.and(((OPT_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";
}
/**
* A singleton instance of this class.
*/
static final OPT_DominatorOperator MEET = new OPT_DominatorOperator();
}