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Closure Compiler is a JavaScript optimizing compiler. It parses your
JavaScript, analyzes it, removes dead code and rewrites and minimizes
what's left. It also checks syntax, variable references, and types, and
warns about common JavaScript pitfalls. It is used in many of Google's
JavaScript apps, including Gmail, Google Web Search, Google Maps, and
Google Docs.
/*
* Copyright 2004 The Closure Compiler Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.javascript.jscomp;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static com.google.javascript.jscomp.base.JSCompDoubles.ecmascriptToInt32;
import static com.google.javascript.jscomp.base.JSCompDoubles.isAtLeastIntegerPrecision;
import static com.google.javascript.jscomp.base.JSCompDoubles.isExactInt32;
import static com.google.javascript.jscomp.base.JSCompDoubles.isExactInt64;
import static com.google.javascript.jscomp.base.JSCompDoubles.isMathematicalInteger;
import static com.google.javascript.jscomp.base.JSCompDoubles.isPositive;
import com.google.javascript.jscomp.NodeUtil.ValueType;
import com.google.javascript.jscomp.base.Tri;
import com.google.javascript.jscomp.colors.StandardColors;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import java.math.BigInteger;
import org.jspecify.nullness.Nullable;
/**
* Peephole optimization to fold constants (e.g. x + 1 + 7 --> x + 8).
*/
class PeepholeFoldConstants extends AbstractPeepholeOptimization {
// TODO(johnlenz): optimizations should not be emiting errors. Move these to
// a check pass.
static final DiagnosticType INVALID_GETELEM_INDEX_ERROR =
DiagnosticType.warning(
"JSC_INVALID_GETELEM_INDEX_ERROR",
"Array index not integer: {0}");
static final DiagnosticType FRACTIONAL_BITWISE_OPERAND =
DiagnosticType.warning(
"JSC_FRACTIONAL_BITWISE_OPERAND",
"Fractional bitwise operand: {0}");
private static final double MAX_FOLD_NUMBER = Math.pow(2, 53);
private final boolean late;
private final boolean shouldUseTypes;
/**
* @param late When late is false, this mean we are currently running before
* most of the other optimizations. In this case we would avoid optimizations
* that would make the code harder to analyze. When this is true, we would
* do anything to minimize for size.
*/
PeepholeFoldConstants(boolean late, boolean shouldUseTypes) {
this.late = late;
this.shouldUseTypes = shouldUseTypes;
}
@Override
Node optimizeSubtree(Node subtree) {
switch (subtree.getToken()) {
case OPTCHAIN_CALL:
case CALL:
return tryFoldCall(subtree);
case NEW:
return tryFoldCtorCall(subtree);
case TYPEOF:
return tryFoldTypeof(subtree);
case ARRAYLIT:
case OBJECTLIT:
return tryFlattenArrayOrObjectLit(subtree);
case NOT:
case POS:
case NEG:
case BITNOT:
tryReduceOperandsForOp(subtree);
return tryFoldUnaryOperator(subtree);
case VOID:
return tryReduceVoid(subtree);
case OPTCHAIN_GETPROP:
case GETPROP:
return tryFoldGetProp(subtree);
default:
tryReduceOperandsForOp(subtree);
return tryFoldBinaryOperator(subtree);
}
}
private Node tryFoldBinaryOperator(Node subtree) {
Node left = subtree.getFirstChild();
if (left == null) {
return subtree;
}
Node right = left.getNext();
if (right == null) {
return subtree;
}
// If we've reached here, node is truly a binary operator.
switch (subtree.getToken()) {
case GETELEM:
case OPTCHAIN_GETELEM:
return tryFoldGetElem(subtree, left, right);
case INSTANCEOF:
return tryFoldInstanceof(subtree, left, right);
case AND:
case OR:
return tryFoldAndOr(subtree, left, right);
case COALESCE:
return tryFoldCoalesce(subtree, left, right);
case LSH:
case RSH:
case URSH:
return tryFoldShift(subtree, left, right);
case ASSIGN:
return tryFoldAssign(subtree, left, right);
case ASSIGN_BITOR:
case ASSIGN_BITXOR:
case ASSIGN_BITAND:
case ASSIGN_LSH:
case ASSIGN_RSH:
case ASSIGN_URSH:
case ASSIGN_ADD:
case ASSIGN_SUB:
case ASSIGN_MUL:
case ASSIGN_DIV:
case ASSIGN_MOD:
case ASSIGN_EXPONENT:
return tryUnfoldAssignOp(subtree, left, right);
case ADD:
return tryFoldAdd(subtree, left, right);
case SUB:
case DIV:
case MOD:
case EXPONENT:
return tryFoldArithmeticOp(subtree, left, right);
case MUL:
case BITAND:
case BITOR:
case BITXOR:
Node result = tryFoldArithmeticOp(subtree, left, right);
if (result != subtree) {
return result;
}
return tryFoldLeftChildOp(subtree, left, right);
case LT:
case GT:
case LE:
case GE:
case EQ:
case NE:
case SHEQ:
case SHNE:
return tryFoldComparison(subtree, left, right);
default:
return subtree;
}
}
private Node tryReduceVoid(Node n) {
Node child = n.getFirstChild();
if ((!child.isNumber() || child.getDouble() != 0.0) && !mayHaveSideEffects(n)) {
child.replaceWith(IR.number(0));
reportChangeToEnclosingScope(n);
}
return n;
}
private void tryReduceOperandsForOp(Node n) {
switch (n.getToken()) {
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:
case EXPONENT:
tryConvertOperandsToNumber(n);
break;
default:
break;
}
}
private void tryConvertOperandsToNumber(Node n) {
Node next;
for (Node c = n.getFirstChild(); c != null; c = next) {
next = c.getNext();
tryConvertToNumber(c);
}
}
private void tryConvertToNumber(Node n) {
switch (n.getToken()) {
case NUMBER:
// Nothing to do
return;
case AND:
case OR:
case COMMA:
case COALESCE:
tryConvertToNumber(n.getLastChild());
return;
case HOOK:
tryConvertToNumber(n.getSecondChild());
tryConvertToNumber(n.getLastChild());
return;
case NAME:
if (!NodeUtil.isUndefined(n)) {
return;
}
break;
default:
break;
}
Double result = getSideEffectFreeNumberValue(n);
if (result == null) {
return;
}
double value = result;
Node replacement = NodeUtil.numberNode(value, n);
if (replacement.isEquivalentTo(n)) {
return;
}
n.replaceWith(replacement);
reportChangeToEnclosingScope(replacement);
}
/**
* Folds 'typeof(foo)' if foo is a literal, e.g.
* typeof("bar") --> "string"
* typeof(6) --> "number"
*/
private Node tryFoldTypeof(Node originalTypeofNode) {
checkArgument(originalTypeofNode.isTypeOf());
Node argumentNode = originalTypeofNode.getFirstChild();
if (argumentNode == null || !NodeUtil.isLiteralValue(argumentNode, true)) {
return originalTypeofNode;
}
String typeNameString = null;
switch (argumentNode.getToken()) {
case FUNCTION:
typeNameString = "function";
break;
case STRINGLIT:
typeNameString = "string";
break;
case NUMBER:
typeNameString = "number";
break;
case TRUE:
case FALSE:
typeNameString = "boolean";
break;
case NULL:
case OBJECTLIT:
case ARRAYLIT:
typeNameString = "object";
break;
case VOID:
typeNameString = "undefined";
break;
case NAME:
// We assume here that programs don't change the value of the
// keyword undefined to something other than the value undefined.
if ("undefined".equals(argumentNode.getString())) {
typeNameString = "undefined";
}
break;
default:
break;
}
if (typeNameString != null) {
Node newNode = IR.string(typeNameString);
reportChangeToEnclosingScope(originalTypeofNode);
originalTypeofNode.replaceWith(newNode);
markFunctionsDeleted(originalTypeofNode);
return newNode;
}
return originalTypeofNode;
}
private Node tryFoldUnaryOperator(Node n) {
checkState(n.hasOneChild(), n);
Node left = n.getFirstChild();
Node parent = n.getParent();
if (left == null) {
return n;
}
Tri leftVal = getSideEffectFreeBooleanValue(left);
if (leftVal == Tri.UNKNOWN) {
return n;
}
switch (n.getToken()) {
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));
n.replaceWith(replacementNode);
reportChangeToEnclosingScope(parent);
return replacementNode;
case POS:
if (NodeUtil.isNumericResult(left)) {
// POS does nothing to numeric values.
n.replaceWith(left.detach());
reportChangeToEnclosingScope(parent);
return left;
}
return n;
case NEG:
{
Node result = null;
if (left.isName() && left.getString().equals("NaN")) {
result = left.detach(); // "-NaN" is "NaN".
} else if (left.isNeg()) {
Node leftLeft = left.getOnlyChild();
if (leftLeft.isBigInt() || leftLeft.isNumber()) {
result = leftLeft.detach(); // `-(-4)` is `4`
}
}
if (result != null) {
n.replaceWith(result);
reportChangeToEnclosingScope(parent);
return result;
}
return n;
}
case BITNOT:
{
Double doubleVal = this.getSideEffectFreeNumberValue(left);
if (doubleVal != null) {
if (isMathematicalInteger(doubleVal)) {
int intVal = ecmascriptToInt32(doubleVal);
Node notIntValNode = NodeUtil.numberNode(~intVal, left);
n.replaceWith(notIntValNode);
reportChangeToEnclosingScope(parent);
return notIntValNode;
} else {
report(FRACTIONAL_BITWISE_OPERAND, left);
return n;
}
}
BigInteger bigintVal = this.getSideEffectFreeBigIntValue(n);
if (bigintVal != null) {
Node bigintNotNode = bigintNode(bigintVal, n);
n.replaceWith(bigintNotNode);
reportChangeToEnclosingScope(parent);
return bigintNotNode;
}
return n;
}
default:
return n;
}
}
private boolean isReasonableDoubleValue(@Nullable Double x) {
return x != null && !x.isInfinite() && !x.isNaN();
}
/**
* Try to fold {@code left instanceof right} into {@code true}
* or {@code false}.
*/
private Node tryFoldInstanceof(Node n, Node left, Node right) {
checkArgument(n.isInstanceOf());
// TODO(johnlenz) Use type information if available to fold
// instanceof.
if (NodeUtil.isLiteralValue(left, true)
&& !mayHaveSideEffects(right)) {
Node replacementNode = null;
if (NodeUtil.isImmutableValue(left)) {
// Non-object types are never instances.
replacementNode = IR.falseNode();
} else if (right.isName()
&& "Object".equals(right.getString())) {
replacementNode = IR.trueNode();
}
if (replacementNode != null) {
n.replaceWith(replacementNode);
reportChangeToEnclosingScope(replacementNode);
markFunctionsDeleted(n);
return replacementNode;
}
}
return n;
}
private Node tryFoldAssign(Node n, Node left, Node right) {
checkArgument(n.isAssign());
if (!late) {
return n;
}
// Tries to convert x = x + y -> x += y;
if (!right.hasChildren() || right.getSecondChild() != right.getLastChild()) {
// RHS must have two children.
return n;
}
if (mayHaveSideEffects(left)) {
return n;
}
Node newRight;
if (areNodesEqualForInlining(left, right.getFirstChild())) {
newRight = right.getLastChild();
} else if (NodeUtil.isCommutative(right.getToken())
&& areNodesEqualForInlining(left, right.getLastChild())) {
newRight = right.getFirstChild();
} else {
return n;
}
Token newType = null;
switch (right.getToken()) {
case ADD:
newType = Token.ASSIGN_ADD;
break;
case BITAND:
newType = Token.ASSIGN_BITAND;
break;
case BITOR:
newType = Token.ASSIGN_BITOR;
break;
case BITXOR:
newType = Token.ASSIGN_BITXOR;
break;
case DIV:
newType = Token.ASSIGN_DIV;
break;
case LSH:
newType = Token.ASSIGN_LSH;
break;
case MOD:
newType = Token.ASSIGN_MOD;
break;
case MUL:
newType = Token.ASSIGN_MUL;
break;
case RSH:
newType = Token.ASSIGN_RSH;
break;
case SUB:
newType = Token.ASSIGN_SUB;
break;
case URSH:
newType = Token.ASSIGN_URSH;
break;
case EXPONENT:
newType = Token.ASSIGN_EXPONENT;
break;
default:
return n;
}
Node newNode = new Node(newType,
left.detach(), newRight.detach());
n.replaceWith(newNode);
reportChangeToEnclosingScope(newNode);
return newNode;
}
private Node tryUnfoldAssignOp(Node n, Node left, Node right) {
if (late) {
return n;
}
if (!n.hasChildren() || n.getSecondChild() != n.getLastChild()) {
return n;
}
if (mayHaveSideEffects(left)) {
return n;
}
// Tries to convert x += y -> x = x + y;
Token op = NodeUtil.getOpFromAssignmentOp(n);
Node replacement = IR.assign(left.detach(),
new Node(op, left.cloneTree(), right.detach())
.srcref(n));
n.replaceWith(replacement);
reportChangeToEnclosingScope(replacement);
return replacement;
}
/**
* Try to fold a AND/OR node.
*/
private Node tryFoldAndOr(Node n, Node left, Node right) {
Node parent = n.getParent();
Node result = null;
Node dropped = null;
Token type = n.getToken();
Tri leftVal = NodeUtil.getBooleanValue(left);
if (leftVal != Tri.UNKNOWN) {
boolean lval = leftVal.toBoolean(true);
// (TRUE || x) => TRUE (also, (3 || x) => 3)
// (FALSE && x) => FALSE
if (lval ? type == Token.OR : type == Token.AND) {
result = left;
dropped = right;
} else if (!mayHaveSideEffects(left)) {
// (FALSE || x) => x
// (TRUE && x) => x
result = right;
dropped = left;
} else {
// Left side may have side effects, but we know its boolean value.
// e.g. true_with_sideeffects || foo() => true_with_sideeffects, foo()
// or: false_with_sideeffects && foo() => false_with_sideeffects, foo()
// This, combined with PeepholeRemoveDeadCode, helps reduce expressions
// like "x() || false || z()".
n.detachChildren();
result = IR.comma(left, right);
dropped = null;
}
} else if (parent.getToken() == type && n == parent.getFirstChild()) {
Tri rightValue = NodeUtil.getBooleanValue(right);
if (!mayHaveSideEffects(right)) {
if ((rightValue == Tri.FALSE && type == Token.OR)
|| (rightValue == Tri.TRUE && type == Token.AND)) {
result = left;
dropped = right;
}
}
}
// Note: Right hand side folding is handled by
// PeepholeMinimizeConditions#tryMinimizeCondition
if (result != null) {
// Fold it!
n.detachChildren();
n.replaceWith(result);
reportChangeToEnclosingScope(result);
if (dropped != null) {
markFunctionsDeleted(dropped);
}
return result;
} else {
return n;
}
}
/** Try to fold a COALESCE node. */
private Node tryFoldCoalesce(Node n, Node left, Node right) {
Node result = null;
ValueType leftVal = NodeUtil.getKnownValueType(left);
switch (leftVal) {
case NULL:
case VOID:
// nullish condition => this expression evaluates to the right side.
if (!mayHaveSideEffects(left)) {
result = right;
markFunctionsDeleted(left);
} else {
// e.g. `(a(), null) ?? 1` => `(a(), null, 1)`
n.detachChildren();
result = IR.comma(left, right);
}
break;
case NUMBER:
case BIGINT:
case STRING:
case BOOLEAN:
case OBJECT:
// non-nullish condition => this expression evaluates to the left side.
result = left;
markFunctionsDeleted(right);
break;
case UNDETERMINED:
break;
}
if (result != null) {
// Fold!
n.detachChildren();
n.replaceWith(result);
reportChangeToEnclosingScope(result);
return result;
} else {
return n;
}
}
/**
* Takes a subtree representing an expression of chained addition between expressions and folds
* adjacent string addition when possible and safe.
*
* @param n root node of ADD expression to be optimized
* @param left left child of n being added
* @param right right child of n being added
* @return AST subtree starting from n that has been optimized to collapse the rightmost left
* child leaf node which must be a string literal and the leftmost right child leaf node if
* possible to do so in a type safe way.
*/
private Node tryFoldAdjacentLiteralLeaves(Node n, Node left, Node right) {
// Find left child's rightmost leaf
Node leftParent = n;
Node rightParent = n;
while (left.isAdd()) {
// This had better be in a chain of '+' operations
leftParent = left;
left = left.getSecondChild();
}
// Find right child's leftmost leaf
while (right.isAdd()) {
// This had better be in a chain of '+' operations
rightParent = right;
right = right.getFirstChild();
}
// Try to fold if of the form:
// ... + +
// ... + + ( + ...)
// aka. when the literal might be collapsible into the string
if (leftParent.isAdd()
&& left.isStringLit()
&& rightParent.isAdd()
&& NodeUtil.isLiteralValue(right, /* includeFunctions= */ false)) {
Node rightGrandparent = rightParent.getParent();
// `rr` is righthand side term that `right` is being added to and is null if right is still
// the second child of `n` being added to `left` and non-null if it is in a nested add expr
Node rr = right.getNext();
boolean foldIsTypeSafe =
// If right.getNext() is already a string, folding won't disturb any typecasting
(rr != null && NodeUtil.isStringResult(rr))
|| (rr != null
// If right.getNext() isn't a string result, right must be a string to be folded
&& right.isStringLit()
// Access the right grandparent safely...
&& rightGrandparent != null
&& rightGrandparent.isAdd()
// The second child of `rightGrandparent` is what `right + rr` is being added to.
// If it exists, `right` can only be safely removed if `rr` is still treated as a
// string in the resulting addition.
&& NodeUtil.isStringResult(rightGrandparent.getSecondChild()))
// Dangling literal term has no typecasting side effects; fold it!
|| (rr == null);
if (foldIsTypeSafe) {
String result = left.getString() + NodeUtil.getStringValue(right);
// If the right parent is the root, shift the left parent up so as not to overwrite the tree
// Otherwise, shift the right parent up
if (rightParent.getSecondChild().equals(right)) {
left.replaceWith(IR.string(result));
replace(rightParent, rightParent.getFirstChild().cloneTree(true));
} else {
left.replaceWith(IR.string(result));
replace(rightParent, rightParent.getSecondChild().cloneTree(true));
}
}
}
return n;
}
/** Try to fold an ADD node with constant operands */
private Node tryFoldAddConstantString(Node n, Node left, Node right) {
if (left.isStringLit() || right.isStringLit() || left.isArrayLit() || right.isArrayLit()) {
// Add strings.
String leftString = getSideEffectFreeStringValue(left);
String rightString = getSideEffectFreeStringValue(right);
if (leftString != null && rightString != null) {
Node newStringNode = IR.string(leftString + rightString);
n.replaceWith(newStringNode);
reportChangeToEnclosingScope(newStringNode);
return newStringNode;
}
}
return n;
}
/**
* Try to fold arithmetic binary operators
*/
private Node tryFoldArithmeticOp(Node n, Node left, Node right) {
Node result = performArithmeticOp(n, left, right);
if (result != null) {
result.srcrefTreeIfMissing(n);
reportChangeToEnclosingScope(n);
n.replaceWith(result);
return result;
}
return n;
}
/** Try to fold arithmetic binary operators */
private @Nullable Node performArithmeticOp(Node n, Node left, Node right) {
// Unlike other operations, ADD operands are not always converted
// to Number.
if (n.isAdd()
&& (NodeUtil.mayBeString(left, shouldUseTypes)
|| NodeUtil.mayBeString(right, shouldUseTypes))) {
return null;
}
if (isBigInt(left) && isBigInt(right)) {
return performBigIntArithmeticOp(n, left, right);
}
double result;
// TODO(johnlenz): Handle NaN with unknown value. BIT ops convert NaN
// to zero so this is a little awkward here.
Double lValObj = getSideEffectFreeNumberValue(left);
Double rValObj = getSideEffectFreeNumberValue(right);
// at least one of the two operands must have a value and both must be numeric
if ((lValObj == null && rValObj == null) || !isNumeric(left) || !isNumeric(right)) {
return null;
}
// handle the operations that have algebraic identities, since we can simplify the tree without
// actually knowing the value statically.
switch (n.getToken()) {
case ADD:
if (lValObj != null && rValObj != null) {
return maybeReplaceBinaryOpWithNumericResult(lValObj + rValObj, lValObj, rValObj);
}
if (lValObj != null && lValObj == 0) {
return right.cloneTree(true);
} else if (rValObj != null && rValObj == 0) {
return left.cloneTree(true);
}
return null;
case SUB:
if (lValObj != null && rValObj != null) {
return maybeReplaceBinaryOpWithNumericResult(lValObj - rValObj, lValObj, rValObj);
}
if (lValObj != null && lValObj == 0) {
// 0 - x -> -x
return IR.neg(right.cloneTree(true));
} else if (rValObj != null && rValObj == 0) {
// x - 0 -> x
return left.cloneTree(true);
}
return null;
case MUL:
if (lValObj != null && rValObj != null) {
return maybeReplaceBinaryOpWithNumericResult(lValObj * rValObj, lValObj, rValObj);
}
// NOTE: 0*x != 0 for all x, if x==0, then it is NaN. So we can't take advantage of that
// without some kind of non-NaN proof. So the special cases here only deal with 1*x
if (lValObj != null) {
if (lValObj == 1) {
return right.cloneTree(true);
}
} else {
if (rValObj == 1) {
return left.cloneTree(true);
}
}
return null;
case DIV:
if (lValObj != null && rValObj != null) {
if (rValObj == 0) {
return null;
}
return maybeReplaceBinaryOpWithNumericResult(lValObj / rValObj, lValObj, rValObj);
}
// NOTE: 0/x != 0 for all x, if x==0, then it is NaN
if (rValObj != null) {
if (rValObj == 1) {
// x/1->x
return left.cloneTree(true);
}
}
return null;
case EXPONENT:
if (lValObj != null && rValObj != null) {
return maybeReplaceBinaryOpWithNumericResult(
Math.pow(lValObj, rValObj), lValObj, rValObj);
}
return null;
default:
// fall-through
}
if (lValObj == null || rValObj == null) {
return null;
}
double lval = lValObj;
double rval = rValObj;
switch (n.getToken()) {
case BITAND:
result = ecmascriptToInt32(lval) & ecmascriptToInt32(rval);
break;
case BITOR:
result = ecmascriptToInt32(lval) | ecmascriptToInt32(rval);
break;
case BITXOR:
result = ecmascriptToInt32(lval) ^ ecmascriptToInt32(rval);
break;
case MOD:
if (rval == 0) {
return null;
}
result = lval % rval;
break;
default:
throw new IllegalStateException("Unexpected arithmetic operator: " + n.getToken());
}
return maybeReplaceBinaryOpWithNumericResult(result, lval, rval);
}
private @Nullable Node performBigIntArithmeticOp(Node n, Node left, Node right) {
BigInteger lVal = getSideEffectFreeBigIntValue(left);
BigInteger rVal = getSideEffectFreeBigIntValue(right);
if (lVal != null && rVal != null) {
switch (n.getToken()) {
case ADD:
return bigintNode(lVal.add(rVal), n);
case SUB:
return bigintNode(lVal.subtract(rVal), n);
case MUL:
return bigintNode(lVal.multiply(rVal), n);
case DIV:
if (!rVal.equals(BigInteger.ZERO)) {
return bigintNode(lVal.divide(rVal), n);
} else {
return null;
}
case EXPONENT:
try {
return bigintNode(lVal.pow(rVal.intValueExact()), n);
} catch (ArithmeticException exception) {
return null;
}
case MOD:
return bigintNode(lVal.mod(rVal), n);
case BITAND:
return bigintNode(lVal.and(rVal), n);
case BITOR:
return bigintNode(lVal.or(rVal), n);
case BITXOR:
return bigintNode(lVal.xor(rVal), n);
default:
return null;
}
}
// handle the operations that have algebraic identities, since we can simplify the tree without
// actually knowing the value statically.
switch (n.getToken()) {
case ADD:
if (lVal != null && lVal.equals(BigInteger.ZERO)) {
return right.cloneTree(/* cloneTypeExprs= */ true);
} else if (rVal != null && rVal.equals(BigInteger.ZERO)) {
return left.cloneTree(/* cloneTypeExprs= */ true);
}
return null;
case SUB:
if (lVal != null && lVal.equals(BigInteger.ZERO)) {
// 0n - x -> -x
return IR.neg(right.cloneTree(/* cloneTypeExprs= */ true));
} else if (rVal != null && rVal.equals(BigInteger.ZERO)) {
// x - 0n -> x
return left.cloneTree(/* cloneTypeExprs= */ true);
}
return null;
case MUL:
if (lVal != null && lVal.equals(BigInteger.ONE)) {
return right.cloneTree(/* cloneTypeExprs= */ true);
} else if (rVal != null && rVal.equals(BigInteger.ONE)) {
return left.cloneTree(/* cloneTypeExprs= */ true);
}
return null;
case DIV:
if (rVal != null && rVal.equals(BigInteger.ONE)) {
return left.cloneTree(/* cloneTypeExprs= */ true);
}
return null;
default:
return null;
}
}
private boolean isNumeric(Node n) {
if (NodeUtil.isNumericResult(n)) {
return true;
}
if (shouldUseTypes) {
return n.getColor() != null && n.getColor().equals(StandardColors.NUMBER);
}
return false;
}
private boolean isBigInt(Node n) {
if (NodeUtil.isBigIntResult(n)) {
return true;
}
if (shouldUseTypes) {
return n.getColor() != null && n.getColor().equals(StandardColors.BIGINT);
}
return false;
}
private @Nullable Node maybeReplaceBinaryOpWithNumericResult(
double result, double lval, double rval) {
// 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;
}
/**
* 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, this folds associative expressions where:
*
*
* - The left child is also an associative expression of the same type.
*
- The right child is a BIGINT or NUMBER constant.
*
- The left child's right child is a BIGINT or NUMBER constant.
*/
private Node tryFoldLeftChildOp(Node n, Node left, Node right) {
Token opType = n.getToken();
checkState((NodeUtil.isAssociative(opType) && NodeUtil.isCommutative(opType)) || n.isAdd());
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 = getSideEffectFreeNumberValue(right);
BigInteger rightBigInt = getSideEffectFreeBigIntValue(right);
if ((rightValObj != null || rightBigInt != null) && left.getToken() == opType) {
checkState(left.hasTwoChildren());
Node ll = left.getFirstChild();
Node lr = ll.getNext();
Node valueToCombine = ll;
Node replacement = performArithmeticOp(n, valueToCombine, right);
if (replacement == null) {
valueToCombine = lr;
replacement = performArithmeticOp(n, valueToCombine, right);
}
if (replacement != null) {
// Remove the child that has been combined
valueToCombine.detach();
// Replace the left op with the remaining child.
left.replaceWith(left.removeFirstChild());
// New "-Infinity" node need location info explicitly
// added.
replacement.srcrefTreeIfMissing(right);
right.replaceWith(replacement);
reportChangeToEnclosingScope(n);
}
}
return n;
}
private Node tryFoldAdd(Node node, Node left, Node right) {
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 {
if (left.isStringLit() && left.getString().isEmpty() && isStringTyped(right)) {
return replace(node, right.cloneTree(true));
} else if (right.isStringLit() && right.getString().isEmpty() && isStringTyped(left)) {
return replace(node, left.cloneTree(true));
}
// a + 7 or 6 + a
return tryFoldAdjacentLiteralLeaves(node, left, right);
}
} else {
// Try arithmetic add
Node result = tryFoldArithmeticOp(node, left, right);
if (result != node) {
return result;
}
return tryFoldLeftChildOp(node, left, right);
}
}
private Node replace(Node oldNode, Node newNode) {
oldNode.replaceWith(newNode);
reportChangeToEnclosingScope(newNode);
return newNode;
}
private boolean isStringTyped(Node n) {
// We could also accept !String, but it is unlikely to be very common.
if (NodeUtil.isStringResult(n)) {
return true;
}
if (shouldUseTypes) {
return n.getColor() != null && n.getColor().equals(StandardColors.STRING);
}
return false;
}
/**
* Try to fold shift operations
*/
private Node tryFoldShift(Node n, Node left, Node right) {
Double leftVal = this.getSideEffectFreeNumberValue(left);
Double rightVal = this.getSideEffectFreeNumberValue(right);
if (!isReasonableDoubleValue(leftVal) || !isReasonableDoubleValue(rightVal)) {
return n;
}
if (!isMathematicalInteger(leftVal)) {
report(FRACTIONAL_BITWISE_OPERAND, left);
return n;
}
if (!isMathematicalInteger(rightVal)) {
report(FRACTIONAL_BITWISE_OPERAND, right);
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 (!(0 <= rightVal && rightVal < 32)) {
return n;
}
int rvalInt = rightVal.intValue();
int bits = ecmascriptToInt32(leftVal);
double result;
switch (n.getToken()) {
case LSH:
result = bits << rvalInt;
break;
case RSH:
result = bits >> rvalInt;
break;
case URSH:
// JavaScript always treats the result of >>> as unsigned.
// We must force Java to do the same here.
result = 0xffffffffL & (bits >>> rvalInt);
break;
default:
throw new AssertionError("Unknown shift operator: " + n.getToken());
}
Node newNumber = NodeUtil.numberNode(result, n);
reportChangeToEnclosingScope(n);
n.replaceWith(newNumber);
return newNumber;
}
/**
* Try to fold comparison nodes, e.g ==
*/
private Node tryFoldComparison(Node n, Node left, Node right) {
Tri result = evaluateComparison(this, n.getToken(), left, right);
if (result == Tri.UNKNOWN) {
return n;
}
Node newNode = NodeUtil.booleanNode(result.toBoolean(true));
reportChangeToEnclosingScope(n);
n.replaceWith(newNode);
markFunctionsDeleted(n);
return newNode;
}
/** https://tc39.es/ecma262/#sec-abstract-relational-comparison */
private static Tri tryAbstractRelationalComparison(
AbstractPeepholeOptimization peepholeOptimization,
Node left,
Node right,
boolean willNegate) {
ValueType leftValueType = NodeUtil.getKnownValueType(left);
ValueType rightValueType = NodeUtil.getKnownValueType(right);
// First, check for a string comparison.
if (leftValueType == ValueType.STRING && rightValueType == ValueType.STRING) {
String lvStr = peepholeOptimization.getSideEffectFreeStringValue(left);
String rvStr = peepholeOptimization.getSideEffectFreeStringValue(right);
if (lvStr != null && rvStr != null) {
// In JS, browsers parse \v differently. So do not compare strings if one contains \v.
if (lvStr.indexOf('\u000B') != -1 || rvStr.indexOf('\u000B') != -1) {
return Tri.UNKNOWN;
} else {
return Tri.forBoolean(lvStr.compareTo(rvStr) < 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 Tri.FALSE;
}
}
// Next, try to evaluate based on the value of the node. Try comparing as BigInts first.
BigInteger lvBig = peepholeOptimization.getSideEffectFreeBigIntValue(left);
BigInteger rvBig = peepholeOptimization.getSideEffectFreeBigIntValue(right);
if (lvBig != null && rvBig != null) {
return Tri.forBoolean(lvBig.compareTo(rvBig) < 0);
}
// Then, try comparing as Numbers.
Double lvNum = peepholeOptimization.getSideEffectFreeNumberValue(left);
Double rvNum = peepholeOptimization.getSideEffectFreeNumberValue(right);
if (lvNum != null && rvNum != null) {
if (Double.isNaN(lvNum) || Double.isNaN(rvNum)) {
return Tri.forBoolean(willNegate);
} else {
return Tri.forBoolean(lvNum.doubleValue() < rvNum.doubleValue());
}
}
// Finally, try comparisons between BigInt and Number.
if (lvBig != null && rvNum != null) {
return bigintLessThanDouble(lvBig, rvNum, Tri.FALSE, willNegate);
}
if (lvNum != null && rvBig != null) {
return bigintLessThanDouble(rvBig, lvNum, Tri.TRUE, willNegate);
}
// 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 Tri.FALSE;
}
}
return Tri.UNKNOWN;
}
private static Tri bigintLessThanDouble(
BigInteger bigint, double number, Tri invert, boolean willNegate) {
// if invert is false, then the number is on the right in tryAbstractRelationalComparison
// if it's true, then the number is on the left
if (Double.isNaN(number)) {
return Tri.forBoolean(willNegate);
} else if (number == Double.POSITIVE_INFINITY) {
return Tri.TRUE.xor(invert);
} else if (number == Double.NEGATIVE_INFINITY) {
return Tri.FALSE.xor(invert);
} else if (!isAtLeastIntegerPrecision(number)) {
return Tri.UNKNOWN;
}
// long can hold all values within [-2^53, 2^53]
BigInteger numberAsBigInt = BigInteger.valueOf((long) number);
int negativeMeansBigintSmaller = bigint.compareTo(numberAsBigInt);
if (negativeMeansBigintSmaller < 0) {
return Tri.TRUE.xor(invert);
} else if (negativeMeansBigintSmaller > 0) {
return Tri.FALSE.xor(invert);
} else if (isExactInt64(number)) {
return Tri.FALSE; // This is the == case, don't invert.
} else {
return Tri.forBoolean(isPositive(number)).xor(invert);
}
}
/** http://www.ecma-international.org/ecma-262/6.0/#sec-abstract-equality-comparison */
private static Tri tryAbstractEqualityComparison(
AbstractPeepholeOptimization peepholeOptimization, Node left, Node right) {
// 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(peepholeOptimization, left, right);
}
if ((leftValueType == ValueType.NULL && rightValueType == ValueType.VOID)
|| (leftValueType == ValueType.VOID && rightValueType == ValueType.NULL)) {
return Tri.TRUE;
}
if ((leftValueType == ValueType.NUMBER && rightValueType == ValueType.STRING)
|| rightValueType == ValueType.BOOLEAN) {
Double rv = peepholeOptimization.getSideEffectFreeNumberValue(right);
return rv == null
? Tri.UNKNOWN
: tryAbstractEqualityComparison(
peepholeOptimization, left, NodeUtil.numberNode(rv, right));
}
if ((leftValueType == ValueType.STRING && rightValueType == ValueType.NUMBER)
|| leftValueType == ValueType.BOOLEAN) {
Double lv = peepholeOptimization.getSideEffectFreeNumberValue(left);
return lv == null
? Tri.UNKNOWN
: tryAbstractEqualityComparison(
peepholeOptimization, NodeUtil.numberNode(lv, left), right);
}
if (leftValueType == ValueType.BIGINT || rightValueType == ValueType.BIGINT) {
BigInteger lv = peepholeOptimization.getSideEffectFreeBigIntValue(left);
BigInteger rv = peepholeOptimization.getSideEffectFreeBigIntValue(right);
if (lv != null && rv != null) {
return Tri.forBoolean(lv.equals(rv));
}
}
if ((leftValueType == ValueType.STRING || leftValueType == ValueType.NUMBER)
&& rightValueType == ValueType.OBJECT) {
return Tri.UNKNOWN;
}
if (leftValueType == ValueType.OBJECT
&& (rightValueType == ValueType.STRING || rightValueType == ValueType.NUMBER)) {
return Tri.UNKNOWN;
}
return Tri.FALSE;
}
// In general, the rest of the cases cannot be folded.
return Tri.UNKNOWN;
}
/** http://www.ecma-international.org/ecma-262/6.0/#sec-strict-equality-comparison */
private static Tri tryStrictEqualityComparison(
AbstractPeepholeOptimization peepholeOptimization, Node left, Node right) {
// 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 Tri.FALSE;
}
switch (leftValueType) {
case VOID:
case NULL:
return Tri.TRUE;
case NUMBER:
{
if (NodeUtil.isNaN(left)) {
return Tri.FALSE;
}
if (NodeUtil.isNaN(right)) {
return Tri.FALSE;
}
Double lv = peepholeOptimization.getSideEffectFreeNumberValue(left);
Double rv = peepholeOptimization.getSideEffectFreeNumberValue(right);
if (lv != null && rv != null) {
return Tri.forBoolean(lv.doubleValue() == rv.doubleValue());
}
break;
}
case STRING:
{
String lv = peepholeOptimization.getSideEffectFreeStringValue(left);
String rv = peepholeOptimization.getSideEffectFreeStringValue(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 Tri.UNKNOWN;
} else {
return lv.equals(rv) ? Tri.TRUE : Tri.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 Tri.TRUE;
}
break;
}
case BOOLEAN:
{
Tri lv = peepholeOptimization.getSideEffectFreeBooleanValue(left);
Tri rv = peepholeOptimization.getSideEffectFreeBooleanValue(right);
return lv.and(rv).or(lv.not().and(rv.not()));
}
case BIGINT:
{
BigInteger lv = peepholeOptimization.getSideEffectFreeBigIntValue(left);
BigInteger rv = peepholeOptimization.getSideEffectFreeBigIntValue(right);
if (lv != null && rv != null) {
return Tri.forBoolean(lv.equals(rv));
}
break;
}
default: // Symbol and Object cannot be folded in the general case.
return Tri.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 Tri.FALSE;
}
return Tri.UNKNOWN;
}
static Tri evaluateComparison(
AbstractPeepholeOptimization peepholeOptimization, Token op, Node left, Node right) {
// Don't try to minimize side-effects here.
if (peepholeOptimization.mayHaveSideEffects(left)
|| peepholeOptimization.mayHaveSideEffects(right)) {
return Tri.UNKNOWN;
}
switch (op) {
case EQ:
return tryAbstractEqualityComparison(peepholeOptimization, left, right);
case NE:
return tryAbstractEqualityComparison(peepholeOptimization, left, right).not();
case SHEQ:
return tryStrictEqualityComparison(peepholeOptimization, left, right);
case SHNE:
return tryStrictEqualityComparison(peepholeOptimization, left, right).not();
case LT:
return tryAbstractRelationalComparison(peepholeOptimization, left, right, false);
case GT:
return tryAbstractRelationalComparison(peepholeOptimization, right, left, false);
case LE:
return tryAbstractRelationalComparison(peepholeOptimization, right, left, true).not();
case GE:
return tryAbstractRelationalComparison(peepholeOptimization, left, right, true).not();
default:
break;
}
throw new IllegalStateException("Unexpected operator for comparison");
}
/**
* Try to fold away unnecessary object instantiation.
* e.g. this[new String('eval')] -> this.eval
*/
private Node tryFoldCtorCall(Node n) {
checkArgument(n.isNew());
// we can remove this for GETELEM calls (anywhere else?)
if (inForcedStringContext(n)) {
return tryFoldInForcedStringContext(n);
}
return n;
}
/**
* Remove useless calls:
* Object.defineProperties(o, {}) -> o
*/
private Node tryFoldCall(Node n) {
checkArgument(n.isCall() || n.isOptChainCall());
if (NodeUtil.isObjectDefinePropertiesDefinition(n)) {
Node srcObj = n.getLastChild();
if (srcObj.isObjectLit() && !srcObj.hasChildren()) {
Node parent = n.getParent();
Node destObj = n.getSecondChild().detach();
n.replaceWith(destObj);
reportChangeToEnclosingScope(parent);
}
}
return n;
}
/** Returns whether this node must be coerced to a string. */
private static boolean inForcedStringContext(Node n) {
if (n.getParent().isGetElem()
&& n.getParent().getLastChild() == n) {
return true;
}
// we can fold in the case "" + new String("")
return n.getParent().isAdd();
}
private Node tryFoldInForcedStringContext(Node n) {
// For now, we only know how to fold ctors.
checkArgument(n.isNew());
Node objectType = n.getFirstChild();
if (!objectType.isName()) {
return n;
}
if (objectType.getString().equals("String")) {
Node value = objectType.getNext();
String stringValue;
if (value == null) {
stringValue = "";
} else {
stringValue = getSideEffectFreeStringValue(value);
}
if (stringValue == null) {
return n;
}
Node parent = n.getParent();
Node newString = IR.string(stringValue);
n.replaceWith(newString);
newString.srcrefIfMissing(parent);
reportChangeToEnclosingScope(parent);
return newString;
}
return n;
}
/**
* For element access using GETLEM/OPTCHAIN_GETELEM on object literals, arrays or strings, tries
* to fold the prop access. e.g. folds array-element [1, 2, 3][1];
*/
private Node tryFoldGetElem(Node n, Node left, Node right) {
checkArgument(n.isGetElem() || n.isOptChainGetElem());
if (left.isObjectLit()) {
if (right.isStringLit()) {
return tryFoldObjectPropAccess(n, left, right.getString());
}
} else if (left.isArrayLit()) {
return tryFoldArrayAccess(n, left, right);
} else if (left.isStringLit()) {
return tryFoldStringArrayAccess(n, left, right);
}
return n;
}
/**
* For prop access using GETPROP/OPTCHAIN_GETPROP on object literals, tries to fold their property
* access. For prop access on arrays, only tries to fold array-length. e.g [1, 2, 3].length ==> 3,
* [x, y].length ==> 2
*/
private Node tryFoldGetProp(Node n) {
checkArgument(n.isGetProp() || n.isOptChainGetProp());
Node left = n.getFirstChild();
String name = n.getString();
if (left.isObjectLit()) {
return tryFoldObjectPropAccess(n, left, name);
}
if (name.equals("length")) {
int knownLength = -1;
switch (left.getToken()) {
case ARRAYLIT:
if (mayHaveSideEffects(left)) {
// Nope, can't fold this, without handling the side-effects.
return n;
}
knownLength = left.getChildCount();
break;
case STRINGLIT:
knownLength = left.getString().length();
break;
default:
// Not a foldable case, forget it.
return n;
}
checkState(knownLength != -1);
Node lengthNode = IR.number(knownLength);
reportChangeToEnclosingScope(n);
n.replaceWith(lengthNode);
return lengthNode;
}
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.isLValue(n)) {
return n;
}
Double index = this.getSideEffectFreeNumberValue(right);
if (!isReasonableDoubleValue(index)) {
// Sometimes people like to use complex expressions to index into
// arrays, or strings to index into array methods.
return n;
}
if (!isExactInt32(index)) {
// Ideally this should be caught in the check passes.
report(INVALID_GETELEM_INDEX_ERROR, right);
return n;
}
int intIndex = index.intValue();
Node current = intIndex >= 0 ? left.getFirstChild() : null;
Node elem = null;
for (int i = 0; current != null; i++) {
if (current.isSpread()) {
// The only time we can fold getelems with spread is for spread arrays literals, and
// `tryFlattenArray` already flattens those.
return n;
}
if (i != intIndex) {
if (mayHaveSideEffects(current)) {
return n;
}
} else {
elem = current;
}
current = current.getNext();
}
if (elem == null) { // If the index was out of bounds
elem = NodeUtil.newUndefinedNode(left);
} else if (elem.isEmpty()) {
elem = NodeUtil.newUndefinedNode(elem);
} else {
elem.detach();
}
// Replace the entire GETELEM with the value
n.replaceWith(elem);
reportChangeToEnclosingScope(elem);
return elem;
}
/**
* Flattens array- or object-literals that contain spreads of other literals.
*
*
Does not recurse into nested spreads because this method is already called as part of a
* postorder traversal and nested spreads will already have been flattened.
*
*
Example: `[0, ...[1, 2, 3], 4, ...[5]]` => `[0, 1, 2, 3, 4, 5]`
*/
private Node tryFlattenArrayOrObjectLit(Node parentLit) {
for (Node child = parentLit.getFirstChild(); child != null; ) {
// We have to store the next element here because nodes may be inserted below.
Node spread = child;
child = child.getNext();
if (!spread.isSpread()) {
continue;
}
Node innerLit = spread.getOnlyChild();
if (!parentLit.getToken().equals(innerLit.getToken())) {
continue; // We only want to inline arrays into arrays and objects into objects.
}
parentLit.addChildrenAfter(innerLit.removeChildren(), spread);
spread.detach();
reportChangeToEnclosingScope(parentLit);
}
return parentLit;
}
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.isLValue(n)) {
return n;
}
Double index = this.getSideEffectFreeNumberValue(right);
if (!isReasonableDoubleValue(index)) {
// Sometimes people like to use complex expressions to index into
// arrays, or strings to index into array methods.
return n;
}
int intIndex = index.intValue();
if (intIndex != index) {
report(INVALID_GETELEM_INDEX_ERROR, right);
return n;
}
checkState(left.isStringLit());
String value = left.getString();
if (intIndex < 0 || intIndex >= value.length()) {
Node undefined = NodeUtil.newUndefinedNode(left);
n.replaceWith(undefined);
reportChangeToEnclosingScope(undefined);
return undefined;
}
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.replaceWith(elem);
reportChangeToEnclosingScope(elem);
return elem;
}
/**
* Tries to fold the node `n` that's accessing an object literal's property. Bails out (skips
* folding and returns the same `n` node) with certainty when any of the following holds true:
*
*
* - the access `n` is L-value
*
- the property references super
*
- the object has side-effects other than those preserved by folding the property
*
- property accessed does not exist on the object (might exist on prototype)
*
*
*
* Examples of folding:
* - `({a() { return 1; }})?.a` ---> `(function() { return 1; })`
*
- `({a() { return 1; }}).a()` ---> `(function() { return 1; }())`
*
*/
private Node tryFoldObjectPropAccess(Node n, Node left, String name) {
checkArgument(NodeUtil.isNormalOrOptChainGet(n));
if (!left.isObjectLit()) {
return n;
}
if (NodeUtil.isLValue(n)) {
// If GETPROP/GETELEM is used as assignment target the object literal is
// acting as a temporary we can't fold it here:
// "{a:x}.a += 1" is not "x += 1"
checkState(!NodeUtil.isOptChainNode(n)); // optional chains can not be targets of assign
return n;
}
// find the last definition in the object literal
Node key = null;
Node value = null;
for (Node c = left.getFirstChild(); c != null; c = c.getNext()) {
switch (c.getToken()) {
case SETTER_DEF:
break;
case OBJECT_SPREAD:
// Reset the search because spread could overwrite any previous result.
key = null;
value = null;
break;
case COMPUTED_PROP:
// don't handle computed properties unless the input is a simple string
Node prop = c.getFirstChild();
if (!prop.isStringLit()) {
return n;
}
if (prop.getString().equals(name)) {
key = c;
value = c.getSecondChild();
}
break;
case GETTER_DEF:
case STRING_KEY:
case MEMBER_FUNCTION_DEF:
if (c.getString().equals(name)) {
key = c;
value = key.getFirstChild();
}
break;
default:
throw new IllegalStateException();
}
}
// Didn't find a definition of the name in the object literal, it might
// be coming from the Object prototype.
if (value == null) {
return n;
}
/** `super` captures a hidden reference to the declaring objectlit, so we can't fold it away. */
if (NodeUtil.referencesSuper(value)) {
return n;
}
/**
* Check to see if there are any side-effects to this object-literal.
*
* We remove the value we're going to use because its side-effects will be preserved.
*/
Node tempValue = IR.nullNode();
value.replaceWith(tempValue);
boolean hasSideEffectBesidesValue = mayHaveSideEffects(left);
tempValue.replaceWith(value);
if (hasSideEffectBesidesValue) {
return n;
}
boolean keyIsGetter = NodeUtil.isGetOrSetKey(key);
boolean nIsInvoked = NodeUtil.isInvocationTarget(n);
if (keyIsGetter || nIsInvoked) {
// When the code looks like:
// {x: f}.x();
// {get x() {...}}.x;
// {get ['x']() {...}}.x;
/**
* It's not safe, in general, to convert that to just a function call, because the receiver
* value will be wrong.
*
*
However, there are some cases where it's ok which we check here.
*/
if (!value.isFunction() || NodeUtil.referencesOwnReceiver(value)) {
return n;
}
}
value.detach();
Node parent = n.getParent();
if (NodeUtil.isOptChainNode(parent)) {
/**
* If the chain continues after `n`, simply doing `n.replaceWith(value)` below would leave the
* subsequent nodes in the current chain segment optional, with their start `n` replaced.
*
*
So, we must ensure that all nodes in the chain's current segment are made non-optional.
*
*
This can happen for e.g.
*
*
* - `({a() { return 1; }})?.a()` ---> `(function() { return 1; })()`. Here, parent
* OPTCHAIN_CALL node must be converted to CALL.
*
- `({a() { return 1; }})?.a().b.c?.d` ---> `(function() { return 1; })().b.c?.d`. Here,
* all nodes upto `({a() { return 1; }})?.a().b.c` must become non-optional
*
*/
Node endOfCurrentChain = NodeUtil.getEndOfOptChainSegment(parent);
NodeUtil.convertToNonOptionalChainSegment(endOfCurrentChain);
}
if (keyIsGetter) {
value = IR.call(value);
value.putBooleanProp(Node.FREE_CALL, true);
} else if (nIsInvoked) {
n.getParent().putBooleanProp(Node.FREE_CALL, true);
}
n.replaceWith(value);
reportChangeToEnclosingScope(value);
markFunctionsDeleted(n);
return n;
}
private static Node bigintNode(BigInteger val, Node srcref) {
Node tree = (val.signum() < 0) ? IR.neg(IR.bigint(val.negate())) : IR.bigint(val);
return tree.srcrefTree(srcref);
}
}