/** http://www.ecma-international.org/ecma-262/6.0/#sec-abstract-relational-comparison */
private static TernaryValue tryAbstractRelationalComparison(
Node left, Node right, boolean useTypes, boolean willNegate) {
// First, try to evaluate based on the general type.
ValueType leftValueType = NodeUtil.getKnownValueType(left);
ValueType rightValueType = NodeUtil.getKnownValueType(right);
if (leftValueType != ValueType.UNDETERMINED && rightValueType != ValueType.UNDETERMINED) {
if (leftValueType == ValueType.STRING && rightValueType == ValueType.STRING) {
String lv = NodeUtil.getStringValue(left);
String rv = NodeUtil.getStringValue(right);
if (lv != null && rv != null) {
// In JS, browsers parse \v differently. So do not compare strings if one contains \v.
if (lv.indexOf('\u000B') != -1 || rv.indexOf('\u000B') != -1) {
return TernaryValue.UNKNOWN;
} else {
return TernaryValue.forBoolean(lv.compareTo(rv) < 0);
}
} else if (left.isTypeOf()
&& right.isTypeOf()
&& left.getFirstChild().isName()
&& right.getFirstChild().isName()
&& left.getFirstChild().getString().equals(right.getFirstChild().getString())) {
// Special case: `typeof a < typeof a` is always false.
return TernaryValue.FALSE;
}
}
}
// Then, try to evaluate based on the value of the node. Try comparing as numbers.
Double lv = NodeUtil.getNumberValue(left, useTypes);
Double rv = NodeUtil.getNumberValue(right, useTypes);
if (lv == null || rv == null) {
// Special case: `x < x` is always false.
//
// TODO(moz): If we knew the named value wouldn't be NaN, it would be nice to handle
// LE and GE. We should use type information if available here.
if (!willNegate && left.isName() && right.isName()) {
if (left.getString().equals(right.getString())) {
return TernaryValue.FALSE;
}
}
return TernaryValue.UNKNOWN;
}
if (Double.isNaN(lv) || Double.isNaN(rv)) {
return TernaryValue.forBoolean(willNegate);
} else {
return TernaryValue.forBoolean(lv.doubleValue() < rv.doubleValue());
}
}
/** http://www.ecma-international.org/ecma-262/6.0/#sec-abstract-equality-comparison */
private static TernaryValue tryAbstractEqualityComparison(
Node left, Node right, boolean useTypes) {
// Evaluate based on the general type.
ValueType leftValueType = NodeUtil.getKnownValueType(left);
ValueType rightValueType = NodeUtil.getKnownValueType(right);
if (leftValueType != ValueType.UNDETERMINED && rightValueType != ValueType.UNDETERMINED) {
// Delegate to strict equality comparison for values of the same type.
if (leftValueType == rightValueType) {
return tryStrictEqualityComparison(left, right, useTypes);
}
if ((leftValueType == ValueType.NULL && rightValueType == ValueType.VOID)
|| (leftValueType == ValueType.VOID && rightValueType == ValueType.NULL)) {
return TernaryValue.TRUE;
}
if ((leftValueType == ValueType.NUMBER && rightValueType == ValueType.STRING)
|| rightValueType == ValueType.BOOLEAN) {
Double rv = NodeUtil.getNumberValue(right, useTypes);
return rv == null
? TernaryValue.UNKNOWN
: tryAbstractEqualityComparison(left, IR.number(rv), useTypes);
}
if ((leftValueType == ValueType.STRING && rightValueType == ValueType.NUMBER)
|| leftValueType == ValueType.BOOLEAN) {
Double lv = NodeUtil.getNumberValue(left, useTypes);
return lv == null
? TernaryValue.UNKNOWN
: tryAbstractEqualityComparison(IR.number(lv), right, useTypes);
}
if ((leftValueType == ValueType.STRING || leftValueType == ValueType.NUMBER)
&& rightValueType == ValueType.OBJECT) {
return TernaryValue.UNKNOWN;
}
if (leftValueType == ValueType.OBJECT
&& (rightValueType == ValueType.STRING || rightValueType == ValueType.NUMBER)) {
return TernaryValue.UNKNOWN;
}
return TernaryValue.FALSE;
}
// In general, the rest of the cases cannot be folded.
return TernaryValue.UNKNOWN;
}
/**
* 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;
}
private void tryConvertToNumber(Node n) {
switch (n.getType()) {
case NUMBER:
// Nothing to do
return;
case AND:
case OR:
case COMMA:
tryConvertToNumber(n.getLastChild());
return;
case HOOK:
tryConvertToNumber(n.getSecondChild());
tryConvertToNumber(n.getLastChild());
return;
case NAME:
if (!NodeUtil.isUndefined(n)) {
return;
}
break;
}
Double result = NodeUtil.getNumberValue(n, shouldUseTypes);
if (result == null) {
return;
}
double value = result;
Node replacement = NodeUtil.numberNode(value, n);
if (replacement.isEquivalentTo(n)) {
return;
}
n.getParent().replaceChild(n, replacement);
reportCodeChange();
}
/** 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;
}
/** http://www.ecma-international.org/ecma-262/6.0/#sec-strict-equality-comparison */
private static TernaryValue tryStrictEqualityComparison(Node left, Node right, boolean useTypes) {
// First, try to evaluate based on the general type.
ValueType leftValueType = NodeUtil.getKnownValueType(left);
ValueType rightValueType = NodeUtil.getKnownValueType(right);
if (leftValueType != ValueType.UNDETERMINED && rightValueType != ValueType.UNDETERMINED) {
// Strict equality can only be true for values of the same type.
if (leftValueType != rightValueType) {
return TernaryValue.FALSE;
}
switch (leftValueType) {
case VOID:
case NULL:
return TernaryValue.TRUE;
case NUMBER:
{
if (NodeUtil.isNaN(left)) {
return TernaryValue.FALSE;
}
if (NodeUtil.isNaN(right)) {
return TernaryValue.FALSE;
}
Double lv = NodeUtil.getNumberValue(left, useTypes);
Double rv = NodeUtil.getNumberValue(right, useTypes);
if (lv != null && rv != null) {
return TernaryValue.forBoolean(lv.doubleValue() == rv.doubleValue());
}
break;
}
case STRING:
{
String lv = NodeUtil.getStringValue(left);
String rv = NodeUtil.getStringValue(right);
if (lv != null && rv != null) {
// In JS, browsers parse \v differently. So do not consider strings
// equal if one contains \v.
if (lv.indexOf('\u000B') != -1 || rv.indexOf('\u000B') != -1) {
return TernaryValue.UNKNOWN;
} else {
return lv.equals(rv) ? TernaryValue.TRUE : TernaryValue.FALSE;
}
} else if (left.isTypeOf()
&& right.isTypeOf()
&& left.getFirstChild().isName()
&& right.getFirstChild().isName()
&& left.getFirstChild().getString().equals(right.getFirstChild().getString())) {
// Special case, typeof a == typeof a is always true.
return TernaryValue.TRUE;
}
break;
}
case BOOLEAN:
{
TernaryValue lv = NodeUtil.getPureBooleanValue(left);
TernaryValue rv = NodeUtil.getPureBooleanValue(right);
return lv.and(rv).or(lv.not().and(rv.not()));
}
default: // Symbol and Object cannot be folded in the general case.
return TernaryValue.UNKNOWN;
}
}
// Then, try to evaluate based on the value of the node. There's only one special case:
// Any strict equality comparison against NaN returns false.
if (NodeUtil.isNaN(left) || NodeUtil.isNaN(right)) {
return TernaryValue.FALSE;
}
return TernaryValue.UNKNOWN;
}
