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package jdk.nashorn.internal.codegen;
import static jdk.nashorn.internal.codegen.Condition.EQ;
import static jdk.nashorn.internal.codegen.Condition.GE;
import static jdk.nashorn.internal.codegen.Condition.GT;
import static jdk.nashorn.internal.codegen.Condition.LE;
import static jdk.nashorn.internal.codegen.Condition.LT;
import static jdk.nashorn.internal.codegen.Condition.NE;
import static jdk.nashorn.internal.parser.TokenType.NOT;
import jdk.nashorn.internal.ir.BinaryNode;
import jdk.nashorn.internal.ir.Expression;
import jdk.nashorn.internal.ir.JoinPredecessorExpression;
import jdk.nashorn.internal.ir.LocalVariableConversion;
import jdk.nashorn.internal.ir.UnaryNode;
/**
* Branch optimizer for CodeGenerator. Given a jump condition this helper
* class attempts to simplify the control flow
*/
final class BranchOptimizer {
private final CodeGenerator codegen;
private final MethodEmitter method;
BranchOptimizer(final CodeGenerator codegen, final MethodEmitter method) {
this.codegen = codegen;
this.method = method;
}
void execute(final Expression node, final Label label, final boolean state) {
branchOptimizer(node, label, state);
}
private void branchOptimizer(final UnaryNode unaryNode, final Label label, final boolean state) {
if (unaryNode.isTokenType(NOT)) {
branchOptimizer(unaryNode.getExpression(), label, !state);
} else {
loadTestAndJump(unaryNode, label, state);
}
}
private void branchOptimizer(final BinaryNode binaryNode, final Label label, final boolean state) {
final Expression lhs = binaryNode.lhs();
final Expression rhs = binaryNode.rhs();
switch (binaryNode.tokenType()) {
case AND:
if (state) {
final Label skip = new Label("skip");
optimizeLogicalOperand(lhs, skip, false, false);
optimizeLogicalOperand(rhs, label, true, true);
method.label(skip);
} else {
optimizeLogicalOperand(lhs, label, false, false);
optimizeLogicalOperand(rhs, label, false, true);
}
return;
case OR:
if (state) {
optimizeLogicalOperand(lhs, label, true, false);
optimizeLogicalOperand(rhs, label, true, true);
} else {
final Label skip = new Label("skip");
optimizeLogicalOperand(lhs, skip, true, false);
optimizeLogicalOperand(rhs, label, false, true);
method.label(skip);
}
return;
case EQ:
case EQ_STRICT:
codegen.loadComparisonOperands(binaryNode);
method.conditionalJump(state ? EQ : NE, true, label);
return;
case NE:
case NE_STRICT:
codegen.loadComparisonOperands(binaryNode);
method.conditionalJump(state ? NE : EQ, true, label);
return;
case GE:
codegen.loadComparisonOperands(binaryNode);
method.conditionalJump(state ? GE : LT, false, label);
return;
case GT:
codegen.loadComparisonOperands(binaryNode);
method.conditionalJump(state ? GT : LE, false, label);
return;
case LE:
codegen.loadComparisonOperands(binaryNode);
method.conditionalJump(state ? LE : GT, true, label);
return;
case LT:
codegen.loadComparisonOperands(binaryNode);
method.conditionalJump(state ? LT : GE, true, label);
return;
default:
break;
}
loadTestAndJump(binaryNode, label, state);
}
private void optimizeLogicalOperand(final Expression expr, final Label label, final boolean state, final boolean isRhs) {
final JoinPredecessorExpression jpexpr = (JoinPredecessorExpression)expr;
if(LocalVariableConversion.hasLiveConversion(jpexpr)) {
final Label after = new Label("after");
branchOptimizer(jpexpr.getExpression(), after, !state);
method.beforeJoinPoint(jpexpr);
method._goto(label);
method.label(after);
if(isRhs) {
method.beforeJoinPoint(jpexpr);
}
} else {
branchOptimizer(jpexpr.getExpression(), label, state);
}
}
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