private void tryReduceOperandsForOp(Node n) {
switch (n.getType()) {
case ADD:
Node left = n.getFirstChild();
Node right = n.getLastChild();
if (!NodeUtil.mayBeString(left, shouldUseTypes)
&& !NodeUtil.mayBeString(right, shouldUseTypes)) {
tryConvertOperandsToNumber(n);
}
break;
case ASSIGN_BITOR:
case ASSIGN_BITXOR:
case ASSIGN_BITAND:
// TODO(johnlenz): convert these to integers.
case ASSIGN_LSH:
case ASSIGN_RSH:
case ASSIGN_URSH:
case ASSIGN_SUB:
case ASSIGN_MUL:
case ASSIGN_MOD:
case ASSIGN_DIV:
tryConvertToNumber(n.getLastChild());
break;
case BITNOT:
case BITOR:
case BITXOR:
case BITAND:
case LSH:
case RSH:
case URSH:
case SUB:
case MUL:
case MOD:
case DIV:
case POS:
case NEG:
tryConvertOperandsToNumber(n);
break;
}
}
private Node tryFoldAdd(Node node, Node left, Node right) {
Preconditions.checkArgument(node.isAdd());
if (NodeUtil.mayBeString(node, shouldUseTypes)) {
if (NodeUtil.isLiteralValue(left, false) && NodeUtil.isLiteralValue(right, false)) {
// '6' + 7
return tryFoldAddConstantString(node, left, right);
} else {
// a + 7 or 6 + a
return tryFoldChildAddString(node, left, right);
}
} else {
// Try arithmetic add
Node result = tryFoldArithmeticOp(node, left, right);
if (result != node) {
return result;
}
return tryFoldLeftChildOp(node, left, right);
}
}
/**
* Expressions such as [foo() * 10 * 20] generate parse trees where no node has two const children
* ((foo() * 10) * 20), so performArithmeticOp() won't fold it -- tryFoldLeftChildOp() will.
* Specifically, it folds associative expressions where: - The left child is also an associative
* expression of the same time. - The right child is a constant NUMBER constant. - The left
* child's right child is a NUMBER constant.
*/
private Node tryFoldLeftChildOp(Node n, Node left, Node right) {
Token opType = n.getType();
Preconditions.checkState(
(NodeUtil.isAssociative(opType) && NodeUtil.isCommutative(opType)) || n.isAdd());
Preconditions.checkState(!n.isAdd() || !NodeUtil.mayBeString(n, shouldUseTypes));
// Use getNumberValue to handle constants like "NaN" and "Infinity"
// other values are converted to numbers elsewhere.
Double rightValObj = NodeUtil.getNumberValue(right, shouldUseTypes);
if (rightValObj != null && left.getType() == opType) {
Preconditions.checkState(left.getChildCount() == 2);
Node ll = left.getFirstChild();
Node lr = ll.getNext();
Node valueToCombine = ll;
Node replacement = performArithmeticOp(opType, valueToCombine, right);
if (replacement == null) {
valueToCombine = lr;
replacement = performArithmeticOp(opType, valueToCombine, right);
}
if (replacement != null) {
// Remove the child that has been combined
left.removeChild(valueToCombine);
// Replace the left op with the remaining child.
n.replaceChild(left, left.removeFirstChild());
// New "-Infinity" node need location info explicitly
// added.
replacement.useSourceInfoIfMissingFromForTree(right);
n.replaceChild(right, replacement);
reportCodeChange();
}
}
return n;
}
/** Try to fold arithmetic binary operators */
private Node performArithmeticOp(Token opType, Node left, Node right) {
// Unlike other operations, ADD operands are not always converted
// to Number.
if (opType == Token.ADD
&& (NodeUtil.mayBeString(left, shouldUseTypes)
|| NodeUtil.mayBeString(right, shouldUseTypes))) {
return null;
}
double result;
// TODO(johnlenz): Handle NaN with unknown value. BIT ops convert NaN
// to zero so this is a little awkward here.
Double lValObj = NodeUtil.getNumberValue(left, shouldUseTypes);
if (lValObj == null) {
return null;
}
Double rValObj = NodeUtil.getNumberValue(right, shouldUseTypes);
if (rValObj == null) {
return null;
}
double lval = lValObj;
double rval = rValObj;
switch (opType) {
case BITAND:
result = NodeUtil.toInt32(lval) & NodeUtil.toInt32(rval);
break;
case BITOR:
result = NodeUtil.toInt32(lval) | NodeUtil.toInt32(rval);
break;
case BITXOR:
result = NodeUtil.toInt32(lval) ^ NodeUtil.toInt32(rval);
break;
case ADD:
result = lval + rval;
break;
case SUB:
result = lval - rval;
break;
case MUL:
result = lval * rval;
break;
case MOD:
if (rval == 0) {
return null;
}
result = lval % rval;
break;
case DIV:
if (rval == 0) {
return null;
}
result = lval / rval;
break;
default:
throw new Error("Unexpected arithmetic operator");
}
// TODO(johnlenz): consider removing the result length check.
// length of the left and right value plus 1 byte for the operator.
if ((String.valueOf(result).length()
<= String.valueOf(lval).length() + String.valueOf(rval).length() + 1
// Do not try to fold arithmetic for numbers > 2^53. After that
// point, fixed-point math starts to break down and become inaccurate.
&& Math.abs(result) <= MAX_FOLD_NUMBER)
|| Double.isNaN(result)
|| result == Double.POSITIVE_INFINITY
|| result == Double.NEGATIVE_INFINITY) {
return NodeUtil.numberNode(result, null);
}
return null;
}