@Override
public void visit(Node n, Node parent) {
Node value = n.getFirstChild();
if (value.isNumber() && value.getDouble() == 0) {
super.visit(n, parent);
}
}
private Node tryReduceVoid(Node n) {
Node child = n.getFirstChild();
if ((!child.isNumber() || child.getDouble() != 0.0) && !mayHaveSideEffects(n)) {
n.replaceChild(child, IR.number(0));
reportCodeChange();
}
return n;
}
private Node tryFoldArrayAccess(Node n, Node left, Node right) {
// If GETPROP/GETELEM is used as assignment target the array literal is
// acting as a temporary we can't fold it here:
// "[][0] += 1"
if (NodeUtil.isAssignmentTarget(n)) {
return n;
}
if (!right.isNumber()) {
// Sometimes people like to use complex expressions to index into
// arrays, or strings to index into array methods.
return n;
}
double index = right.getDouble();
int intIndex = (int) index;
if (intIndex != index) {
report(INVALID_GETELEM_INDEX_ERROR, right);
return n;
}
if (intIndex < 0) {
report(INDEX_OUT_OF_BOUNDS_ERROR, right);
return n;
}
Node current = left.getFirstChild();
Node elem = null;
for (int i = 0; current != null; i++) {
if (i != intIndex) {
if (mayHaveSideEffects(current)) {
return n;
}
} else {
elem = current;
}
current = current.getNext();
}
if (elem == null) {
report(INDEX_OUT_OF_BOUNDS_ERROR, right);
return n;
}
if (elem.isEmpty()) {
elem = NodeUtil.newUndefinedNode(elem);
} else {
left.removeChild(elem);
}
// Replace the entire GETELEM with the value
n.getParent().replaceChild(n, elem);
reportCodeChange();
return elem;
}
private Node tryFoldStringArrayAccess(Node n, Node left, Node right) {
// If GETPROP/GETELEM is used as assignment target the array literal is
// acting as a temporary we can't fold it here:
// "[][0] += 1"
if (NodeUtil.isAssignmentTarget(n)) {
return n;
}
if (!right.isNumber()) {
// Sometimes people like to use complex expressions to index into
// arrays, or strings to index into array methods.
return n;
}
double index = right.getDouble();
int intIndex = (int) index;
if (intIndex != index) {
report(INVALID_GETELEM_INDEX_ERROR, right);
return n;
}
if (intIndex < 0) {
report(INDEX_OUT_OF_BOUNDS_ERROR, right);
return n;
}
Preconditions.checkState(left.isString());
String value = left.getString();
if (intIndex >= value.length()) {
report(INDEX_OUT_OF_BOUNDS_ERROR, right);
return n;
}
char c = 0;
// Note: For now skip the strings with unicode
// characters as I don't understand the differences
// between Java and JavaScript.
for (int i = 0; i <= intIndex; i++) {
c = value.charAt(i);
if (c < 32 || c > 127) {
return n;
}
}
Node elem = IR.string(Character.toString(c));
// Replace the entire GETELEM with the value
n.getParent().replaceChild(n, elem);
reportCodeChange();
return elem;
}
/**
* Tries to optimize all the arguments array access in this scope by assigning a name to each
* element.
*
* @param scope scope of the function
* @return true if any modification has been done to the AST
*/
private boolean tryReplaceArguments(Scope scope) {
Node parametersList = scope.getRootNode().getSecondChild();
Preconditions.checkState(parametersList.isParamList());
// Keep track of rather this function modified the AST and needs to be
// reported back to the compiler later.
boolean changed = false;
// Number of parameter that can be accessed without using the arguments
// array.
int numNamedParameter = parametersList.getChildCount();
// We want to guess what the highest index that has been access from the
// arguments array. We will guess that it does not use anything index higher
// than the named parameter list first until we see other wise.
int highestIndex = numNamedParameter - 1;
// Iterate through all the references to arguments array in the function to
// determine the real highestIndex.
for (Node ref : currentArgumentsAccess) {
Node getElem = ref.getParent();
// Bail on anything but argument[c] access where c is a constant.
// TODO(user): We might not need to bail out all the time, there might
// be more cases that we can cover.
if (!getElem.isGetElem() || ref != getElem.getFirstChild()) {
return false;
}
Node index = ref.getNext();
// We have something like arguments[x] where x is not a constant. That
// means at least one of the access is not known.
if (!index.isNumber() || index.getDouble() < 0) {
// TODO(user): Its possible not to give up just yet. The type
// inference did a 'semi value propagation'. If we know that string
// is never a subclass of the type of the index. We'd know that
// it is never 'callee'.
return false; // Give up.
}
Node getElemParent = getElem.getParent();
// When we have argument[0](), replacing it with a() is semantically
// different if argument[0] is a function call that refers to 'this'
if (getElemParent.isCall() && getElemParent.getFirstChild() == getElem) {
// TODO(user): We can consider using .call() if aliasing that
// argument allows shorter alias for other arguments.
return false;
}
// Replace the highest index if we see an access that has a higher index
// than all the one we saw before.
int value = (int) index.getDouble();
if (value > highestIndex) {
highestIndex = value;
}
}
// Number of extra arguments we need.
// For example: function() { arguments[3] } access index 3 so
// it will need 4 extra named arguments to changed into:
// function(a,b,c,d) { d }.
int numExtraArgs = highestIndex - numNamedParameter + 1;
// Temporary holds the new names as string for quick access later.
String[] argNames = new String[numExtraArgs];
// Insert the formal parameter to the method's signature.
// Example: function() --> function(r0, r1, r2)
for (int i = 0; i < numExtraArgs; i++) {
String name = getNewName();
argNames[i] = name;
parametersList.addChildToBack(IR.name(name).useSourceInfoIfMissingFrom(parametersList));
changed = true;
}
// This loop performs the replacement of arguments[x] -> a if x is known.
for (Node ref : currentArgumentsAccess) {
Node index = ref.getNext();
// Skip if it is unknown.
if (!index.isNumber()) {
continue;
}
int value = (int) index.getDouble();
// Unnamed parameter.
if (value >= numNamedParameter) {
ref.getGrandparent()
.replaceChild(ref.getParent(), IR.name(argNames[value - numNamedParameter]));
} else {
// Here, for no apparent reason, the user is accessing a named parameter
// with arguments[idx]. We can replace it with the actual name for them.
Node name = parametersList.getFirstChild();
// This is a linear search for the actual name from the signature.
// It is not necessary to make this fast because chances are the user
// will not deliberately write code like this.
for (int i = 0; i < value; i++) {
name = name.getNext();
}
ref.getGrandparent().replaceChild(ref.getParent(), IR.name(name.getString()));
}
changed = true;
}
return changed;
}
/** Try to fold shift operations */
private Node tryFoldShift(Node n, Node left, Node right) {
if (left.isNumber() && right.isNumber()) {
double result;
double lval = left.getDouble();
double rval = right.getDouble();
// check ranges. We do not do anything that would clip the double to
// a 32-bit range, since the user likely does not intend that.
if (lval < Integer.MIN_VALUE) {
report(BITWISE_OPERAND_OUT_OF_RANGE, left);
return n;
}
// only the lower 5 bits are used when shifting, so don't do anything
// if the shift amount is outside [0,32)
if (!(rval >= 0 && rval < 32)) {
report(SHIFT_AMOUNT_OUT_OF_BOUNDS, n);
return n;
}
int rvalInt = (int) rval;
if (rvalInt != rval) {
report(FRACTIONAL_BITWISE_OPERAND, right);
return n;
}
switch (n.getType()) {
case LSH:
case RSH:
// Convert the numbers to ints
if (lval > Integer.MAX_VALUE) {
report(BITWISE_OPERAND_OUT_OF_RANGE, left);
return n;
}
int lvalInt = (int) lval;
if (lvalInt != lval) {
report(FRACTIONAL_BITWISE_OPERAND, left);
return n;
}
if (n.getType() == Token.LSH) {
result = lvalInt << rvalInt;
} else {
result = lvalInt >> rvalInt;
}
break;
case URSH:
// JavaScript handles zero shifts on signed numbers differently than
// Java as an Java int can not represent the unsigned 32-bit number
// where JavaScript can so use a long here.
long maxUint32 = 0xffffffffL;
if (lval > maxUint32) {
report(BITWISE_OPERAND_OUT_OF_RANGE, left);
return n;
}
long lvalLong = (long) lval;
if (lvalLong != lval) {
report(FRACTIONAL_BITWISE_OPERAND, left);
return n;
}
result = (lvalLong & maxUint32) >>> rvalInt;
break;
default:
throw new AssertionError("Unknown shift operator: " + n.getType());
}
Node newNumber = IR.number(result);
n.getParent().replaceChild(n, newNumber);
reportCodeChange();
return newNumber;
}
return n;
}
private Node tryFoldUnaryOperator(Node n) {
Preconditions.checkState(n.hasOneChild(), n);
Node left = n.getFirstChild();
Node parent = n.getParent();
if (left == null) {
return n;
}
TernaryValue leftVal = NodeUtil.getPureBooleanValue(left);
if (leftVal == TernaryValue.UNKNOWN) {
return n;
}
switch (n.getType()) {
case NOT:
// Don't fold !0 and !1 back to false.
if (late && left.isNumber()) {
double numValue = left.getDouble();
if (numValue == 0 || numValue == 1) {
return n;
}
}
Node replacementNode = NodeUtil.booleanNode(!leftVal.toBoolean(true));
parent.replaceChild(n, replacementNode);
reportCodeChange();
return replacementNode;
case POS:
if (NodeUtil.isNumericResult(left)) {
// POS does nothing to numeric values.
parent.replaceChild(n, left.detachFromParent());
reportCodeChange();
return left;
}
return n;
case NEG:
if (left.isName()) {
if (left.getString().equals("Infinity")) {
// "-Infinity" is valid and a literal, don't modify it.
return n;
} else if (left.getString().equals("NaN")) {
// "-NaN" is "NaN".
n.removeChild(left);
parent.replaceChild(n, left);
reportCodeChange();
return left;
}
}
if (left.isNumber()) {
double negNum = -left.getDouble();
Node negNumNode = IR.number(negNum);
parent.replaceChild(n, negNumNode);
reportCodeChange();
return negNumNode;
} else {
// left is not a number node, so do not replace, but warn the
// user because they can't be doing anything good
report(NEGATING_A_NON_NUMBER_ERROR, left);
return n;
}
case BITNOT:
try {
double val = left.getDouble();
if (val >= Integer.MIN_VALUE && val <= Integer.MAX_VALUE) {
int intVal = (int) val;
if (intVal == val) {
Node notIntValNode = IR.number(~intVal);
parent.replaceChild(n, notIntValNode);
reportCodeChange();
return notIntValNode;
} else {
report(FRACTIONAL_BITWISE_OPERAND, left);
return n;
}
} else {
report(BITWISE_OPERAND_OUT_OF_RANGE, left);
return n;
}
} catch (UnsupportedOperationException ex) {
// left is not a number node, so do not replace, but warn the
// user because they can't be doing anything good
report(NEGATING_A_NON_NUMBER_ERROR, left);
return n;
}
default:
return n;
}
}
/**
* Declares global variables to serve as aliases for the values in an object literal, optionally
* removing all of the object literal's keys and values.
*
* @param alias The object literal's flattened name (e.g. "a$b$c")
* @param objlit The OBJLIT node
* @param varNode The VAR node to which new global variables should be added as children
* @param nameToAddAfter The child of {@code varNode} after which new variables should be added
* (may be null)
* @param varParent {@code varNode}'s parent
* @return The number of variables added
*/
private int declareVarsForObjLitValues(
Name objlitName,
String alias,
Node objlit,
Node varNode,
Node nameToAddAfter,
Node varParent) {
int numVars = 0;
int arbitraryNameCounter = 0;
boolean discardKeys = !objlitName.shouldKeepKeys();
for (Node key = objlit.getFirstChild(), nextKey; key != null; key = nextKey) {
Node value = key.getFirstChild();
nextKey = key.getNext();
// A get or a set can not be rewritten as a VAR.
if (key.isGetterDef() || key.isSetterDef()) {
continue;
}
// We generate arbitrary names for keys that aren't valid JavaScript
// identifiers, since those keys are never referenced. (If they were,
// this object literal's child names wouldn't be collapsible.) The only
// reason that we don't eliminate them entirely is the off chance that
// their values are expressions that have side effects.
boolean isJsIdentifier = !key.isNumber() && TokenStream.isJSIdentifier(key.getString());
String propName = isJsIdentifier ? key.getString() : String.valueOf(++arbitraryNameCounter);
// If the name cannot be collapsed, skip it.
String qName = objlitName.getFullName() + '.' + propName;
Name p = nameMap.get(qName);
if (p != null && !p.canCollapse()) {
continue;
}
String propAlias = appendPropForAlias(alias, propName);
Node refNode = null;
if (discardKeys) {
objlit.removeChild(key);
value.detachFromParent();
} else {
// Substitute a reference for the value.
refNode = IR.name(propAlias);
if (key.getBooleanProp(Node.IS_CONSTANT_NAME)) {
refNode.putBooleanProp(Node.IS_CONSTANT_NAME, true);
}
key.replaceChild(value, refNode);
}
// Declare the collapsed name as a variable with the original value.
Node nameNode = IR.name(propAlias);
nameNode.addChildToFront(value);
if (key.getBooleanProp(Node.IS_CONSTANT_NAME)) {
nameNode.putBooleanProp(Node.IS_CONSTANT_NAME, true);
}
Node newVar = IR.var(nameNode).useSourceInfoIfMissingFromForTree(key);
if (nameToAddAfter != null) {
varParent.addChildAfter(newVar, nameToAddAfter);
} else {
varParent.addChildBefore(newVar, varNode);
}
compiler.reportCodeChange();
nameToAddAfter = newVar;
// Update the global name's node ancestry if it hasn't already been
// done. (Duplicate keys in an object literal can bring us here twice
// for the same global name.)
if (isJsIdentifier && p != null) {
if (!discardKeys) {
Ref newAlias = p.getDeclaration().cloneAndReclassify(Ref.Type.ALIASING_GET);
newAlias.node = refNode;
p.addRef(newAlias);
}
p.getDeclaration().node = nameNode;
if (value.isFunction()) {
checkForHosedThisReferences(value, key.getJSDocInfo(), p);
}
}
numVars++;
}
return numVars;
}
