com.google.javascript.jscomp.InlineSimpleMethods Maven / Gradle / Ivy
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/*
* Copyright 2007 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.checkState;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.SetMultimap;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import java.util.HashSet;
import java.util.Set;
import org.jspecify.nullness.Nullable;
/**
* Inlines methods that take no arguments and have only a return statement returning a property.
* Because it works on method names rather than type inference, a method with multiple definitions
* will be inlined if each definition is identical.
*
*
* A.prototype.foo = function() { return this.b; }
* B.prototype.foo = function() { return this.b; }
*
*
* will inline foo, but
*
*
* A.prototype.foo = function() { return this.b; }
* B.prototype.foo = function() { return this.c; }
*
*
* will not.
*
* Declarations are not removed because we do not find all possible call sites. For examples,
* calls of the form foo["bar"] are not detected.
*
*
This pass is not on by default because it is not safe in simple mode. If the prototype method
* is mutated and we don't detect that, inlining it is unsafe. We enable it whenever function
* inlining is enabled.
*/
class InlineSimpleMethods implements CompilerPass {
// List of property names that we know are not safe to inline
// This includes:
// - extern properties (we can't see the actual method definition for externs)
// - non-method properties
// - methods with @noinline
// - methods with multiple, non-equivalent definitions
private final Set nonInlineableProperties = new HashSet<>();
// Use a linked map here to keep the output deterministic. Otherwise,
// the choice of method bodies is random when multiple identical definitions
// are found which causes problems in the source maps.
private final SetMultimap methodDefinitions = LinkedHashMultimap.create();
private final AbstractCompiler compiler;
private final AstAnalyzer astAnalyzer;
InlineSimpleMethods(AbstractCompiler compiler) {
this.compiler = compiler;
astAnalyzer = compiler.getAstAnalyzer();
nonInlineableProperties.addAll(compiler.getExternProperties());
}
@Override
public void process(Node externs, Node root) {
checkState(compiler.getLifeCycleStage().isNormalized(), compiler.getLifeCycleStage());
checkState(methodDefinitions.isEmpty());
checkState(externs != null);
NodeTraversal.traverseRoots(compiler, new GatherSignatures(), externs, root);
NodeTraversal.traverse(compiler, root, new InlineTrivialAccessors());
}
/** For each method call, see if it is a candidate for inlining, and do the inlining if so. */
private class InlineTrivialAccessors extends InvocationsCallback {
@Override
void visit(NodeTraversal t, Node callNode, Node parent, String callName) {
if (nonInlineableProperties.contains(callName)) {
return;
}
Set definitions = methodDefinitions.get(callName);
if (definitions == null || definitions.isEmpty()) {
return;
}
// Exit early if all method definitions are not equivalent, and mark this method as not
// inlineable.
// NOTE: we could also cache the 'good' result of this method having all equivalent
// definitions and avoid recalculating later, but profile data suggests that's not too useful
if (definitions.size() > 1 && !allDefinitionsEquivalent(definitions)) {
nonInlineableProperties.add(callName);
return;
}
// Exit early if any definitions are annotated with @noinline, and mark this method as not
// inlineable.
// NOTE: we could also cache the 'good' result of this method not being marked @noinline and
// avoid recalculating later, but profile data suggests that's not too useful.
if (anyDefinitionsNoInline(definitions)) {
nonInlineableProperties.add(callName);
return;
}
// Do check of arity, complexity, and consistency in what we think is
// the order from least to most complex
Node firstDefinition = definitions.iterator().next();
// Do not inline if the callsite is a derived class calling a base method using `super.`
if (!argsMayHaveSideEffects(callNode) && !NodeUtil.referencesSuper(callNode)) {
// Verify this is a trivial return
Node returned = returnedExpression(firstDefinition);
if (returned != null) {
if (isPropertyTree(returned) && !firstDefinition.isArrowFunction()) {
inlinePropertyReturn(callNode, returned);
} else if (NodeUtil.isLiteralValue(returned, false)
&& !astAnalyzer.mayHaveSideEffects(callNode.getFirstChild())) {
inlineConstReturn(callNode, returned);
}
} else if (isEmptyMethod(firstDefinition)
&& !astAnalyzer.mayHaveSideEffects(callNode.getFirstChild())) {
inlineEmptyMethod(t, parent, callNode);
}
}
}
}
/**
* Returns true if the provided node is a getprop for
* which the left child is this or a valid property tree
* and for which the right side is a string.
*/
private static boolean isPropertyTree(Node expectedGetprop) {
if (!expectedGetprop.isGetProp()) {
return false;
}
Node getpropLhs = expectedGetprop.getFirstChild();
return getpropLhs.isThis() || isPropertyTree(getpropLhs);
}
/**
* Finds the occurrence of "this" in the provided property tree and replaces
* it with replacement
*/
private static void replaceThis(Node expectedGetprop, Node replacement) {
Node leftChild = expectedGetprop.getFirstChild();
if (leftChild.isThis()) {
leftChild.replaceWith(replacement);
} else {
replaceThis(leftChild, replacement);
}
}
/**
* Return the node that represents the expression returned by the method, given a FUNCTION node.
*/
private static @Nullable Node returnedExpression(Node fn) {
Node expectedBlock = NodeUtil.getFunctionBody(fn);
if (!expectedBlock.hasOneChild()) {
return null;
}
Node expectedReturn = expectedBlock.getFirstChild();
if (!expectedReturn.isReturn()) {
return null;
}
if (!expectedReturn.hasOneChild()) {
return null;
}
return expectedReturn.getOnlyChild();
}
/**
* Return whether the given FUNCTION node is an empty method definition.
*
* Must be private, or moved to NodeUtil.
*/
private static boolean isEmptyMethod(Node fn) {
return NodeUtil.isEmptyBlock(NodeUtil.getFunctionBody(fn));
}
/** Given a set of method definitions, verify they are the same. */
private boolean allDefinitionsEquivalent(Set definitions) {
Node first = null;
for (Node n : definitions) {
if (first == null) {
first = n;
} else if (!compiler.areNodesEqualForInlining(first, n)) {
return false;
} // else continue
}
return true;
}
private boolean anyDefinitionsNoInline(Set definitions) {
for (Node n : definitions) {
JSDocInfo jsDocInfo = NodeUtil.getBestJSDocInfo(n.getParent());
if (jsDocInfo != null && jsDocInfo.isNoInline()) {
return true;
}
}
return false;
}
/**
* Replace the provided method call with the tree specified in returnedValue
*
* Parse tree of a call is name call getprop obj string
*/
private void inlinePropertyReturn(Node call, Node returnedValue) {
Node getProp = returnedValue.cloneTree();
replaceThis(getProp, call.getFirstChild().removeFirstChild());
call.replaceWith(getProp);
compiler.reportChangeToEnclosingScope(getProp);
}
/**
* Replace the provided object and its method call with the tree specified in returnedValue.
* Should be called only if the object reference has no side effects.
*/
private void inlineConstReturn(Node call, Node returnedValue) {
Node retValue = returnedValue.cloneTree();
call.replaceWith(retValue);
compiler.reportChangeToEnclosingScope(retValue);
}
/**
* Remove the provided object and its method call.
*/
private void inlineEmptyMethod(NodeTraversal t, Node parent, Node call) {
// If the return value of the method call is read,
// replace it with "void 0". Otherwise, remove the call entirely.
if (NodeUtil.isExprCall(parent)) {
parent.replaceWith(IR.empty());
NodeUtil.markFunctionsDeleted(parent, compiler);
} else {
Node srcLocation = call;
call.replaceWith(NodeUtil.newUndefinedNode(srcLocation));
NodeUtil.markFunctionsDeleted(call, compiler);
}
t.reportCodeChange();
}
/**
* Check whether the given method call's arguments have side effects.
* @param call The call node of a method invocation.
*/
private boolean argsMayHaveSideEffects(Node call) {
for (Node currentChild = call.getSecondChild();
currentChild != null;
currentChild = currentChild.getNext()) {
if (astAnalyzer.mayHaveSideEffects(currentChild)) {
return true;
}
}
return false;
}
/**
* Adds a node that may represent a function signature (if it's a function itself or the name of a
* function).
*/
private void addPossibleSignature(String name, Node node) {
if (node != null && node.isFunction()) {
// The node we're looking at is a function, so we can add it directly
addSignature(name, node);
} else {
nonInlineableProperties.add(name);
}
}
private void addSignature(String name, Node function) {
if (nonInlineableProperties.contains(name)) {
return;
}
methodDefinitions.put(name, function);
}
/** Gather signatures from the source to be compiled. */
private class GatherSignatures extends AbstractPostOrderCallback {
@Override
public void visit(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
// TODO(b/251573710): Handle ES2015+ language features that can reference properties
case GETPROP:
case GETELEM:
String name = getPropName(n);
if (name == null) {
return;
}
if (name.equals("prototype")) {
processPrototypeParent(parent);
} else {
// Static methods of the form Foo.bar = function() {} or
// Static methods of the form Foo.bar = baz (where baz is a
// function name). Parse tree looks like:
// assign <- parent
// getprop <- n
// name Foo
// string bar
// function or name <- n.getNext()
if (parent.isAssign() && n.isFirstChildOf(parent)) {
addPossibleSignature(name, n.getNext());
}
}
break;
case OBJECTLIT:
case CLASS_MEMBERS:
for (Node key = n.getFirstChild(); key != null; key = key.getNext()) {
switch (key.getToken()) {
case MEMBER_FUNCTION_DEF:
case MEMBER_FIELD_DEF:
case STRING_KEY:
addPossibleSignature(key.getString(), key.getFirstChild());
break;
case SETTER_DEF:
case GETTER_DEF:
nonInlineableProperties.add(key.getString());
break;
case COMPUTED_PROP: // complicated
case OBJECT_SPREAD:
case COMPUTED_FIELD_DEF:
break;
default:
throw new IllegalStateException("Unexpected " + n.getToken() + " key: " + key);
}
}
break;
case CALL:
// If a goog.reflect.objectProperty is used for a method's name, we can't assume that the
// method can be safely inlined.
if (compiler.getCodingConvention().isPropertyRenameFunction(n.getFirstChild())) {
// Other code guarantees that getSecondChild() is a STRINGLIT
nonInlineableProperties.add(n.getSecondChild().getString());
}
break;
default:
break;
}
}
/**
* Processes the parent of a GETPROP prototype, which can either be another GETPROP (in the case
* of Foo.prototype.bar), or can be an assignment (in the case of Foo.prototype = ...).
*/
private void processPrototypeParent(Node n) {
switch (n.getToken()) {
// Foo.prototype.getBar = function() { ... } or
// Foo.prototype.getBar = getBaz (where getBaz is a function)
// parse tree looks like:
// assign <- parent
// getprop <- n
// getprop
// name Foo
// string prototype
// string getBar
// function or name <- assignee
case GETPROP:
case GETELEM:
Node grandparent = n.getGrandparent();
String name = getPropName(n);
if (name != null && grandparent.isAssign()) {
Node assignee = grandparent.getSecondChild();
addPossibleSignature(name, assignee);
}
break;
default:
break;
}
}
}
private static @Nullable String getPropName(Node getPropElem) {
if (getPropElem.isGetProp()) {
return getPropElem.getString();
} else if (getPropElem.getSecondChild().isStringLit()) {
return getPropElem.getSecondChild().getString();
} else {
return null;
}
}
}