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/*
* Copyright 2008 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 com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.LinkedHashMultimap;
import com.google.javascript.jscomp.CodingConvention.SubclassRelationship;
import com.google.javascript.jscomp.ReferenceCollector.Behavior;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import org.jspecify.nullness.Nullable;
/**
* Using the infrastructure provided by {@link ReferenceCollector}, identify variables that are used
* in a way that is safe to move, and then inline them.
*
* This pass has two "modes." One mode only inlines variables declared as constants, for legacy
* compiler clients. The second mode inlines any variable that we can provably inline. Note that the
* second mode is a superset of the first mode. We only support the first mode for
* backwards-compatibility with compiler clients that don't want --inline_variables.
*
*
The basic structure of this class is as follows.
*
*
* - {@link ReferenceCollector#process} is invoked on the AST with an instance of {@link
* InliningBehavior}
*
- {@link InliningBehavior#afterExitScope} gets invoked on each scope in DFS order
*
- It iterates through the variables defined in that scope:
*
* - For each variable a {@link VarExpert} is created. This object is responsible for
* determining:
*
* - Can it be inlined?
*
- If so, how should the inlining be done?
*
- If not, is it safe to inline aliases of the variable? (e.g. {@code const b =
* doSomething();} isn't safe to inline due to side-effects, but it should be OK
* to inline {@code const aliasB = b;} in many cases.
*
* - The {@link VarExpert} creates an {@link InlineVarAnalysis} object containing its
* decisions and possibly a method to invoke to do the inlining.
*
- The {@link InlineVarAnalysis} may indicate that a variable is an alias of another
* variable. If so, {@link InliningBehavior} will wait until the aliased variable has
* been analyzed, then pass that analysis back to the {@link VarExpert} for the aliasing
* variable, so it can complete its decision.
*
*
*/
class InlineVariables implements CompilerPass {
private final AbstractCompiler compiler;
enum Mode {
// Only inline things explicitly marked as constant.
CONSTANTS_ONLY(Var::isDeclaredOrInferredConst),
// Locals only
LOCALS_ONLY(Var::isLocal),
ALL(Predicates.alwaysTrue());
@SuppressWarnings("ImmutableEnumChecker")
private final Predicate varPredicate;
private Mode(Predicate varPredicate) {
this.varPredicate = varPredicate;
}
}
private final Mode mode;
InlineVariables(AbstractCompiler compiler, Mode mode) {
this.compiler = compiler;
this.mode = mode;
}
@Override
public void process(Node externs, Node root) {
ReferenceCollector callback =
new ReferenceCollector(
compiler,
new InliningBehavior(),
new SyntacticScopeCreator(compiler),
mode.varPredicate);
callback.process(externs, root);
}
/** Responsible for analyzing a variable to determine if it can be inlined. */
private abstract static class VarExpert {
/** Called to conduct the initial analysis */
abstract InlineVarAnalysis analyze();
/**
* Called for a Var that is an alias after the original variable is handled.
*
* @param aliasedVar The variable that was aliased.
* @param aliasedVarAnalysis The analysis results for the aliased variable
*/
InlineVarAnalysis reanalyzeAfterAliasedVar(
Var aliasedVar, InlineVarAnalysis aliasedVarAnalysis) {
throw new UnsupportedOperationException("not waiting for an aliased variable");
}
}
// Canonical `VarExpert` objects for common cases.
private static final VarExpert NO_INLINE_SELF_OR_ALIASES_EXPERT =
new VarExpert() {
@Override
public InlineVarAnalysis analyze() {
return NO_INLINE_SELF_OR_ALIASES_ANALYSIS;
}
};
private static final VarExpert NO_INLINE_SELF_ALIASES_OK_EXPERT =
new VarExpert() {
@Override
public InlineVarAnalysis analyze() {
return NO_INLINE_SELF_ALIASES_OK_ANALYSIS;
}
};
/**
* The result of analyzing a variable to see if it can be inlined.
*
* Non-abstract classes should be created by extending this class and overriding the methods
* that should return `true` or perform an operation.
*/
private abstract static class InlineVarAnalysis {
/**
* Should we inline this variable?
*
*
Mutually exclusive with `shouldWaitForAliasedVar()`.
*/
public boolean shouldInline() {
return false;
}
/**
* True if this variable is an alias.
*
*
The caller should wait for the aliased variable to be handled, then call the expert's
* `reanalyzeAfterAliasedVar()` method.
*
*
Mutually exclusive with `shouldInline()`
*/
public boolean shouldWaitForAliasedVar() {
return false;
}
/**
* Gets the aliased variable, if this is an alias.
*
* @return The `Var` for which this one is an alias
* @throws `UnsupportedOperationException` if `shouldWaitForAliasedVar()` is `false`.
*/
public Var getAliasedVar() {
throw new UnsupportedOperationException("no aliased Var");
}
/** True if it is safe for aliases of this variable to inline this variable's name. */
public boolean isSafeToInlineAliases() {
return false;
}
/** Performs the inline operation. */
public void performInline() {
throw new UnsupportedOperationException("cannot inline");
}
}
// Canonical `InlineVarAnalysis` values.
// We'll use these instead of creating new objects for each analysis.
private static final InlineVarAnalysis NO_INLINE_SELF_OR_ALIASES_ANALYSIS =
new InlineVarAnalysis() {};
private static final InlineVarAnalysis NO_INLINE_SELF_ALIASES_OK_ANALYSIS =
new InlineVarAnalysis() {
@Override
public boolean isSafeToInlineAliases() {
return true;
}
};
/**
* Builds up information about nodes in each scope. When exiting the scope, inspects all variables
* in that scope, and inlines any that we can.
*/
private class InliningBehavior implements Behavior {
/**
* Records the analyses of variables that have already been handled in the current scope.
*
*
This is necessary in order for aliases of those variables to determine whether they may be
* inlined.
*/
final HashMap currentScopeHandledVarAnalysesMap = new HashMap<>();
/**
* Records alias variables that are waiting for the original variables to be handled.
*
* The value is an object that knows what to do when the original variable is handled.
*/
final LinkedHashMultimap varToAliasRetryHandlersMap =
LinkedHashMultimap.create();
@Override
public void afterExitScope(NodeTraversal t, ReferenceMap referenceMap) {
doInlinesForScope(t, referenceMap);
}
/**
* For all variables in this scope, see if they are only used once. If it looks safe to do so,
* inline them.
*/
private void doInlinesForScope(NodeTraversal t, ReferenceMap referenceMap) {
// Any variables we completed in an earlier scope are now out of scope,
// so we can clear this map.
currentScopeHandledVarAnalysesMap.clear();
boolean mayBeAParameterModifiedViaArguments =
varsInThisScopeMayBeModifiedUsingArguments(t.getScope(), referenceMap);
for (Var v : t.getScope().getVarIterable()) {
ReferenceCollection referenceInfo = referenceMap.getReferences(v);
VarExpert expert = createVarExpert(v, referenceInfo, mayBeAParameterModifiedViaArguments);
final InlineVarAnalysis analysis = expert.analyze();
if (analysis.shouldWaitForAliasedVar()) {
// We need to wait for the aliased variable to be handled.
final AliasInlineRetryHandler retryHandler = new AliasInlineRetryHandler(v, expert);
final Var aliasedVar = analysis.getAliasedVar();
final InlineVarAnalysis aliasedVarAnalysis =
currentScopeHandledVarAnalysesMap.get(aliasedVar);
if (aliasedVarAnalysis != null) {
// We've actually already completed the aliased Var
retryHandler.handleAliasedVarCompletion(aliasedVar, aliasedVarAnalysis);
} else {
// wait for completion of the aliased Var
varToAliasRetryHandlersMap.put(aliasedVar, retryHandler);
}
} else {
if (analysis.shouldInline()) {
analysis.performInline();
}
// Record the results for aliases we may find later
currentScopeHandledVarAnalysesMap.put(v, analysis);
// Retry any aliases we saw before handling this Var
retryAliases(v, analysis);
}
}
}
/**
* Returns true for function scopes (the whole function, not the body), if the function uses
* `arguments` in some way other than a few that are known not to change the values of parameter
* variables.
*
* TODO(bradfordcsmith): In strict mode `arguments` is a copy of the parameters, so modifying
* it cannot change the parameters. Sloppy mode is now so rare, that we should probably just
* ignore the possibility of `arguments` being used to modify a parameter value. We ignore loose
* mode issues or simply don't support them ("with" for instance).
*/
private boolean varsInThisScopeMayBeModifiedUsingArguments(
Scope scope, ReferenceMap referenceMap) {
if (scope.isFunctionScope() && !scope.getRootNode().isArrowFunction()) {
Var arguments = scope.getArgumentsVar();
ReferenceCollection refs = referenceMap.getReferences(arguments);
if (refs != null && !refs.references.isEmpty()) {
for (Reference ref : refs.references) {
if (!isSafeUseOfArguments(ref.getNode())) {
return true;
}
}
}
}
return false;
}
private void retryAliases(Var aliasedVar, InlineVarAnalysis aliasedVarAnalysis) {
for (AliasInlineRetryHandler aliasInlineRetryHandler :
varToAliasRetryHandlersMap.removeAll(aliasedVar)) {
aliasInlineRetryHandler.handleAliasedVarCompletion(aliasedVar, aliasedVarAnalysis);
}
}
/** Retries inlining an alias variable after the original variable has been dealt with. */
private class AliasInlineRetryHandler {
private final Var v;
private final VarExpert expert;
AliasInlineRetryHandler(Var v, VarExpert expert) {
this.v = v;
this.expert = expert;
}
void handleAliasedVarCompletion(Var aliasedVar, InlineVarAnalysis aliasedVarAnalyis) {
InlineVarAnalysis newAnalysis =
expert.reanalyzeAfterAliasedVar(aliasedVar, aliasedVarAnalyis);
checkState(
!newAnalysis.shouldWaitForAliasedVar(), "expert for %s asked to wait a second time", v);
if (newAnalysis.shouldInline()) {
newAnalysis.performInline();
}
currentScopeHandledVarAnalysesMap.put(v, newAnalysis);
retryAliases(v, newAnalysis);
}
}
/**
* Knows how to analyze a variable to determine whether it should be inlined, how to do the
* inlining, and whether it's OK to inline aliases of the variable.
*/
private class StandardVarExpert extends VarExpert {
private final Var v;
private final ReferenceCollection referenceInfo;
private final Reference declaration;
private final boolean isDeclaredOrInferredConstant;
private final boolean mayBeAParameterModifiedViaArguments;
StandardVarExpert(VarExpertInitData initData) {
this.v = initData.v;
this.referenceInfo = initData.referenceInfo;
this.declaration = initData.referenceInfo.references.get(0);
this.isDeclaredOrInferredConstant = initData.isDeclaredOrInferredConstant;
this.mayBeAParameterModifiedViaArguments = initData.mayBeAParameterModifiedViaArguments;
}
private final InitiallyUnknown isNeverAssigned = new InitiallyUnknown<>();
private boolean isNeverAssigned() {
if (isNeverAssigned.isKnown()) {
return isNeverAssigned.getKnownValue();
} else if (initializationReference.isKnownNotNull()
|| isAssignedOnceInLifetime.isKnownToBe(true)) {
return isNeverAssigned.setKnownValueOnce(false);
} else {
return isNeverAssigned.setKnownValueOnce(referenceInfo.isNeverAssigned());
}
}
private final InitiallyUnknown isWellDefined = new InitiallyUnknown<>();
private boolean isWellDefined() {
if (isWellDefined.isKnown()) {
return isWellDefined.getKnownValue();
} else {
return isWellDefined.setKnownValueOnce(referenceInfo.isWellDefined());
}
}
private final InitiallyUnknown isAssignedOnceInLifetime = new InitiallyUnknown<>();
private boolean isAssignedOnceInLifetime() {
if (isAssignedOnceInLifetime.isKnown()) {
return isAssignedOnceInLifetime.getKnownValue();
} else {
return isAssignedOnceInLifetime.setKnownValueOnce(
referenceInfo.isAssignedOnceInLifetime());
}
}
private final InitiallyUnknown isWellDefinedAssignedOnce = new InitiallyUnknown<>();
/**
* A more efficient way to ask if the variable is both well defined and assigned exactly once
* in its lifetime.
*/
private boolean isWellDefinedAssignedOnce() {
if (isWellDefinedAssignedOnce.isKnown()) {
return isWellDefinedAssignedOnce.getKnownValue();
} else {
// Check first to see if either is already known to be false before calculating anything.
return isWellDefinedAssignedOnce.setKnownValueOnce(
!isWellDefined.isKnownToBe(false)
&& !isAssignedOnceInLifetime.isKnownToBe(false)
// isWellDefined is generally less expensive to calculate
&& isWellDefined()
&& isAssignedOnceInLifetime());
}
}
private final InitiallyUnknown initializationReference = new InitiallyUnknown<>();
private Reference getInitialization() {
if (initializationReference.isKnown()) {
return initializationReference.getKnownValue();
} else {
final Reference initRef =
isDeclaredOrInferredConstant
? referenceInfo.getInitializingReferenceForConstants()
: referenceInfo.getInitializingReference();
return initializationReference.setKnownValueOnce(initRef);
}
}
private boolean hasValidDeclaration() {
return isValidDeclaration(declaration);
}
private boolean hasValidInitialization() {
return isValidInitialization(getInitialization());
}
private final InitiallyUnknown allReferencesAreValid = new InitiallyUnknown<>();
private boolean allReferencesAreValid() {
if (allReferencesAreValid.isKnown()) {
return allReferencesAreValid.getKnownValue();
} else {
final boolean hasValidDeclaration = hasValidDeclaration();
final boolean hasValidInitialization = hasValidInitialization();
final boolean neverAssigned = isNeverAssigned();
if (hasValidDeclaration && (hasValidInitialization || neverAssigned)) {
Reference initialization = getInitialization();
for (Reference ref : referenceInfo.references) {
if (ref != declaration && ref != initialization && !isValidReference(ref)) {
return allReferencesAreValid.setKnownValueOnce(false);
}
}
return allReferencesAreValid.setKnownValueOnce(true);
}
return allReferencesAreValid.setKnownValueOnce(false);
}
}
@Override
public InlineVarAnalysis analyze() {
if (hasNoInlineAnnotation(v)) {
return getNegativeInlineVarAnalysis();
}
final Reference initialization = getInitialization();
final Node initValue = initialization == null ? null : initialization.getAssignedValue();
final InitialValueAnalysis initialValueAnalysis = new InitialValueAnalysis(initValue);
if (isDeclaredOrInferredConstant
&& initialValueAnalysis.isImmutableValue()
// isAssignedOnceInLifetime() is much more expensive than the other checks
&& isAssignedOnceInLifetime()) {
return createInlineWellDefinedVarAnalysis(initValue);
}
if (mode == Mode.CONSTANTS_ONLY) {
// If we're in constants-only mode, don't run more aggressive
// inlining heuristics. See InlineConstantsTest.
return getNegativeInlineVarAnalysis();
}
if (initialValueAnalysis.isAlias()) {
return new VarIsAliasAnalysis(initialValueAnalysis.getAliasedVar());
}
return analyzeWithInitialValue(initialization, initValue, initialValueAnalysis);
}
private InlineVarAnalysis analyzeWithInitialValue(
Reference initialization, Node initValue, InitialValueAnalysis initialValueAnalysis) {
final int refCount = referenceInfo.references.size();
// TODO(bradfordcsmith): We could remove the `refCount > 1` here, but:
// 1. That will require some additional logic to handle stuff like named function
// expressions and avoiding the removal of side-effects.
// 2. RemoveUnusedCode will remove those cases anyway.
// 3. The unit tests will have to be more verbose to make sure stuff we don't want to be
// removed is used.
if (refCount > 1 && allReferencesAreValid()) {
if (referenceInfo.isNeverAssigned()) {
return new PositiveInlineVarAnalysis(
() -> {
// Create a new `undefined` node to inline for a variable that is never
// initialized.
Node srcLocation = declaration.getNode();
final Node undefinedNode = NodeUtil.newUndefinedNode(srcLocation);
inlineWellDefinedVariable(v, undefinedNode, referenceInfo.references);
});
}
if (isWellDefined()
&& (initialValueAnalysis.isImmutableValue()
|| (initValue.isThis() && !referenceInfo.isEscaped()))) {
// if the variable is referenced more than once, we can only
// inline it if it's immutable and never defined before referenced.
return createInlineWellDefinedVarAnalysis(initValue);
}
final int firstReadRefIndex = (declaration == initialization ? 1 : 2);
final int numReadRefs = refCount - firstReadRefIndex;
if (numReadRefs == 0) {
// The only reference is the initialization.
// Remove the assignment and the variable declaration.
return createInlineWellDefinedVarAnalysis(initValue);
}
if (numReadRefs == 1) {
// The variable is likely only read once, so we can try some more complex inlining
// heuristics.
final Reference singleReadReference = referenceInfo.references.get(firstReadRefIndex);
if (canInline(declaration, initialization, singleReadReference, initValue)) {
// A custom inline method is needed for this case.
return new PositiveInlineVarAnalysis(
() -> inline(declaration, initialization, singleReadReference));
}
}
}
return getNegativeInlineVarAnalysis();
}
private InlineVarAnalysis getNegativeInlineVarAnalysis() {
// If we already know whether it is safe to inline aliases of this variable,
// use canonical analysis values to save on memory space.
if (mayBeAParameterModifiedViaArguments
|| mode == Mode.CONSTANTS_ONLY
|| isWellDefinedAssignedOnce.isKnownToBe(false)) {
return NO_INLINE_SELF_OR_ALIASES_ANALYSIS;
}
if (isWellDefinedAssignedOnce.isKnownToBe(true)) {
return NO_INLINE_SELF_ALIASES_OK_ANALYSIS;
}
// Delay calculating safety until we're actually asked.
return new InlineVarAnalysis() {
@Override
public boolean isSafeToInlineAliases() {
return isWellDefinedAssignedOnce();
}
};
}
private PositiveInlineVarAnalysis createInlineWellDefinedVarAnalysis(Node initValue) {
return new PositiveInlineVarAnalysis(
() -> inlineWellDefinedVariable(v, initValue, referenceInfo.references));
}
@Override
public InlineVarAnalysis reanalyzeAfterAliasedVar(
Var aliasedVar, InlineVarAnalysis aliasedVarAnalysis) {
final Reference initialization = getInitialization();
final Node initValue = initialization == null ? null : initialization.getAssignedValue();
final InitialValueAnalysis initialValueAnalysis = new InitialValueAnalysis(initValue);
if (isDeclaredOrInferredConstant
&& initialValueAnalysis.isImmutableValue()
// isAssignedOnceInLifetime() is much more expensive than the other checks
&& isAssignedOnceInLifetime()) {
return createInlineWellDefinedVarAnalysis(initValue);
}
if (initialValueAnalysis.isAlias()
&& aliasedVarAnalysis.isSafeToInlineAliases()
&& isWellDefinedAssignedOnce()) {
// The variable we aliased couldn't be inlined itself, or it was an alias for another
// variable that got inlined in its place.
// However, it is safe to inline the name assigned to this variable now.
return createInlineWellDefinedVarAnalysis(initValue);
}
return analyzeWithInitialValue(initialization, initValue, initialValueAnalysis);
}
/** Information about a value used to initialize a variable. */
private class InitialValueAnalysis {
private final Node value;
InitialValueAnalysis(Node value) {
this.value = value;
}
private final InitiallyUnknown isImmutableValue = new InitiallyUnknown<>();
boolean isImmutableValue() {
if (isImmutableValue.isKnown()) {
return isImmutableValue.getKnownValue();
} else {
return isImmutableValue.setKnownValueOnce(
value != null && NodeUtil.isImmutableValue(value));
}
}
private final InitiallyUnknown aliasedVar = new InitiallyUnknown<>();
boolean isAlias() {
return getAliasedVar() != null;
}
Var getAliasedVar() {
if (aliasedVar.isKnown()) {
return aliasedVar.getKnownValue();
} else {
if (value != null && value.isName()) {
String aliasedName = value.getString();
// Never consider this variable to be an alias of itself.
return aliasedVar.setKnownValueOnce(
aliasedName.equals(v.getName()) ? null : v.getScope().getVar(aliasedName));
}
return aliasedVar.setKnownValueOnce(null);
}
}
}
}
/** Indicates that the analyzed variable may be inlined. */
private class PositiveInlineVarAnalysis extends InlineVarAnalysis {
private final Runnable inliner;
private PositiveInlineVarAnalysis(Runnable inliner) {
this.inliner = inliner;
}
@Override
public boolean shouldInline() {
return true;
}
@Override
public void performInline() {
inliner.run();
}
@Override
public boolean isSafeToInlineAliases() {
// If we've inlined this variable, then any aliases of it should definitely try to
// inline themselves with the new value that replaced this variable.
// If for some reason the logic that requested this analysis decided not to actually
// do the inlining, it's still safe to inline the name of this variable.
// If it weren't, we wouldn't have said it was OK to inline its value.
return true;
}
}
/**
* Indicates that the analyzed variable is an alias and the decision about whether to inline it
* must wait until inlining has been done (or not) for the original value it aliases.
*/
private class VarIsAliasAnalysis extends InlineVarAnalysis {
private final Var aliasedVar;
private VarIsAliasAnalysis(Var aliasedVar) {
this.aliasedVar = aliasedVar;
}
@Override
public boolean shouldWaitForAliasedVar() {
return true;
}
@Override
public Var getAliasedVar() {
return aliasedVar;
}
@Override
public boolean isSafeToInlineAliases() {
throw new UnsupportedOperationException("analysis is incomplete");
}
}
/** Creates a VarExpert object appropriate for the given variable. */
private VarExpert createVarExpert(
Var v, ReferenceCollection referenceInfo, boolean mayBeAParameterModifiedViaArguments) {
if (referenceInfo == null) {
// If we couldn't collect any reference info, don't try to inline and assume it's unsafe
// to inline aliases of this variable, too.
return NO_INLINE_SELF_OR_ALIASES_EXPERT;
}
final boolean isDeclaredOrInferredConstant = v.isDeclaredOrInferredConst();
if (!isDeclaredOrInferredConstant && mode == Mode.CONSTANTS_ONLY) {
// If we're only inlining constants, then we shouldn't inline an alias.
return NO_INLINE_SELF_OR_ALIASES_EXPERT;
}
if (v.isExtern()) {
// TODO(bradfordcsmith): Extern variables are generally unsafe to inline.
return NO_INLINE_SELF_OR_ALIASES_EXPERT;
}
if (compiler.getCodingConvention().isExported(v.getName(), /* local= */ v.isLocal())) {
// If the variable is exported, it might be assigned a new value by code we cannot see,
// so aliases to it are creating snapshots of its state.
// We cannot inline this variable or its aliases.
return NO_INLINE_SELF_OR_ALIASES_EXPERT;
}
if (compiler.getCodingConvention().isPropertyRenameFunction(v.getNameNode())) {
// It's not terribly likely that anything creates an alias of our special property rename
// function, but its value never changes, so it should be safe to inline aliases to it.
return NO_INLINE_SELF_ALIASES_OK_EXPERT;
}
final VarExpertInitData initData = new VarExpertInitData();
initData.v = v;
initData.referenceInfo = referenceInfo;
initData.isDeclaredOrInferredConstant = isDeclaredOrInferredConstant;
initData.mayBeAParameterModifiedViaArguments = mayBeAParameterModifiedViaArguments;
return new StandardVarExpert(initData);
}
/** Used to initialize fields in a `StandardVarExpert` object. */
private class VarExpertInitData {
Var v;
ReferenceCollection referenceInfo;
boolean isDeclaredOrInferredConstant;
boolean mayBeAParameterModifiedViaArguments;
}
/**
* True if `argumentsNode` is a use of `arguments` we know won't modify any parameter values.
*
* In sloppy mode it is possible to change the value of a function parameter by assigning to
* the corresponding entry in {@code arguments}.
*
*
This method checks for just a few common uses that are known to be safe. However, we may
* soon remove this check entirely because unsafe uses aren't worth worrying about. See the
* comment on {@link #varsInThisScopeMayBeModifiedUsingArguments}.
*/
boolean isSafeUseOfArguments(Node argumentsNode) {
checkArgument(argumentsNode.matchesName("arguments"));
// `arguments[i]` that is only read, not assigned
// or `fn.apply(thisArg, arguments)`
return isTargetOfPropertyRead(argumentsNode)
|| isSecondArgumentToDotApplyMethod(argumentsNode);
}
/**
* True if `n` is the object in a property access expression (`obj[prop]` or `obj.prop` or an
* optional chain version of one of those) and the property is only being read, not modified.
*/
boolean isTargetOfPropertyRead(Node n) {
Node getNode = n.getParent();
return n.isFirstChildOf(getNode)
&& NodeUtil.isNormalOrOptChainGet(getNode)
&& !NodeUtil.isLValue(getNode);
}
/** True if `n` is being used in a call like this: `fn.apply(thisArg, n)`. */
boolean isSecondArgumentToDotApplyMethod(Node n) {
Node callNode = n.getParent();
if (NodeUtil.isNormalOrOptChainCall(callNode)) {
Node calleeNode = callNode.getFirstChild();
if (NodeUtil.isNormalOrOptChainGetProp(calleeNode)) {
if (calleeNode.getString().equals("apply")) {
Node thisArgNode = calleeNode.getNext();
if (thisArgNode != null) {
return thisArgNode.getNext() == n;
}
}
}
}
return false;
}
/** Do the actual work of inlining a single declaration into a single reference. */
private void inline(Reference decl, Reference init, Reference ref) {
Node value = init.getAssignedValue();
checkState(value != null);
// Check for function declarations before the value is moved in the AST.
boolean isFunctionDeclaration = NodeUtil.isFunctionDeclaration(value);
if (isFunctionDeclaration) {
// In addition to changing the containing scope, inlining function declarations also changes
// the function name scope from the containing scope to the inner scope.
compiler.reportChangeToChangeScope(value);
compiler.reportChangeToEnclosingScope(value.getParent());
}
inlineValue(ref.getNode(), value.detach());
if (decl != init) {
Node expressRoot = init.getGrandparent();
checkState(expressRoot.isExprResult());
NodeUtil.removeChild(expressRoot.getParent(), expressRoot);
}
// Function declarations have already been removed.
if (!isFunctionDeclaration) {
removeDeclaration(decl);
}
}
/** Inline an immutable variable into all of its references. */
private void inlineWellDefinedVariable(Var v, Node value, List refSet) {
for (Reference r : refSet) {
if (r.getNode() == v.getNameNode()) {
removeDeclaration(r);
} else if (r.isSimpleAssignmentToName()) {
/**
* This is the initialization.
*
* Replace the entire assignment with just the value, and use the original value node
* in case it contains references to variables that still require inlining.
*/
inlineValue(r.getParent(), value.detach());
} else {
Node clonedValue = value.cloneTree();
NodeUtil.markNewScopesChanged(clonedValue, compiler);
inlineValue(r.getNode(), clonedValue);
}
}
}
/** Remove the given VAR declaration. */
private void removeDeclaration(Reference decl) {
Node varNode = decl.getParent();
checkState(NodeUtil.isNameDeclaration(varNode), varNode);
Node grandparent = decl.getGrandparent();
compiler.reportChangeToEnclosingScope(decl.getNode());
decl.getNode().detach();
// Remove var node if empty
if (!varNode.hasChildren()) {
NodeUtil.removeChild(grandparent, varNode);
}
}
private void inlineValue(Node toRemove, Node toInsert) {
compiler.reportChangeToEnclosingScope(toRemove);
// Help type-based optimizations by propagating more specific types from type assertions
if (toRemove.getColor() != null && toRemove.isColorFromTypeCast()) {
toInsert.setColor(toRemove.getColor());
toInsert.setColorFromTypeCast();
}
toRemove.replaceWith(toInsert);
NodeUtil.markFunctionsDeleted(toRemove, compiler);
}
/**
* @return true if the provided reference and declaration can be safely inlined according to our
* criteria
*/
private boolean canInline(
Reference declaration, Reference initialization, Reference reference, Node initValue) {
// If the value is read more than once, skip it.
// VAR declarations and EXPR_RESULT don't need the value, but other
// ASSIGN expressions parents do.
if (declaration != initialization && !initialization.getGrandparent().isExprResult()) {
return false;
}
// Be very conservative and do not cross control structures or scope boundaries
if (declaration.getBasicBlock() != initialization.getBasicBlock()
|| declaration.getBasicBlock() != reference.getBasicBlock()) {
return false;
}
// Do not inline into a call node. This would change
// the context in which it was being called. For example,
// var a = b.c;
// a();
// should not be inlined, because it calls a in the context of b
// rather than the context of the window.
// var a = b.c;
// f(a)
// is OK.
checkState(initValue != null);
if (initValue.isGetProp()
&& reference.getParent().isCall()
&& reference.getParent().getFirstChild() == reference.getNode()) {
return false;
}
if (initValue.isFunction()) {
Node callNode = reference.getParent();
if (reference.getParent().isCall()) {
CodingConvention convention = compiler.getCodingConvention();
// Bug 2388531: Don't inline subclass definitions into class defining
// calls as this confused class removing logic.
SubclassRelationship relationship = convention.getClassesDefinedByCall(callNode);
if (relationship != null) {
return false;
}
// issue 668: Don't inline singleton getter methods
// calls as this confused class removing logic.
if (convention.getSingletonGetterClassName(callNode) != null) {
return false;
}
}
}
if (initialization.getScope() != declaration.getScope()
|| !initialization.getScope().contains(reference.getScope())) {
return false;
}
return canMoveAggressively(initValue) || canMoveModerately(initialization, reference);
}
/** If the value is a literal, we can cross more boundaries to inline it. */
private boolean canMoveAggressively(Node value) {
// Function expressions and other mutable objects can move within
// the same basic block.
return NodeUtil.isLiteralValue(value, true) || value.isFunction();
}
/**
* If the value of a variable is not constant, then it may read or modify state. Therefore it
* cannot be moved past anything else that may modify the value being read or read values that
* are modified.
*/
private boolean canMoveModerately(Reference initialization, Reference reference) {
// Check if declaration can be inlined without passing
// any side-effect causing nodes.
Iterator it;
if (NodeUtil.isNameDeclaration(initialization.getParent())) {
it =
NodeIterators.LocalVarMotion.forVar(
compiler,
initialization.getNode(), // NAME
initialization.getParent(), // VAR/LET/CONST
initialization.getGrandparent()); // VAR/LET/CONST container
} else if (initialization.getParent().isAssign()) {
checkState(initialization.getGrandparent().isExprResult());
it =
NodeIterators.LocalVarMotion.forAssign(
compiler,
initialization.getNode(), // NAME
initialization.getParent(), // ASSIGN
initialization.getGrandparent(), // EXPR_RESULT
initialization.getGrandparent().getParent()); // EXPR container
} else {
throw new IllegalStateException(
"Unexpected initialization parent\n" + initialization.getParent().toStringTree());
}
Node targetName = reference.getNode();
while (it.hasNext()) {
Node curNode = it.next();
if (curNode == targetName) {
return true;
}
}
return false;
}
/**
* @return true if the reference is a normal VAR or FUNCTION declaration.
*/
private boolean isValidDeclaration(Reference declaration) {
return (NodeUtil.isNameDeclaration(declaration.getParent())
&& !NodeUtil.isLoopStructure(declaration.getGrandparent()))
|| NodeUtil.isFunctionDeclaration(declaration.getParent());
}
/**
* @return Whether there is a initial value.
*/
private boolean isValidInitialization(Reference initialization) {
if (initialization == null) {
return false;
} else if (initialization.isDeclaration()) {
// The reference is a FUNCTION declaration or normal VAR declaration
// with a value.
if (!NodeUtil.isFunctionDeclaration(initialization.getParent())
&& !initialization.getNode().hasChildren()) {
return false;
}
} else {
Node parent = initialization.getParent();
checkState(parent.isAssign() && parent.getFirstChild() == initialization.getNode());
}
return true;
}
/**
* @return true if the reference is a candidate for inlining
*/
private boolean isValidReference(Reference reference) {
return !reference.isDeclaration() && !reference.isLvalue();
}
}
private static boolean hasNoInlineAnnotation(Var var) {
JSDocInfo jsDocInfo = var.getJSDocInfo();
return jsDocInfo != null && jsDocInfo.isNoInline();
}
private static class InitiallyUnknown {
protected boolean isKnown = false;
protected @Nullable T value = null;
boolean isKnown() {
return isKnown;
}
boolean isKnownNotNull() {
return isKnownNotToBe(null);
}
boolean isKnownToBe(T other) {
return isKnown && value == other;
}
boolean isKnownNotToBe(T other) {
return isKnown && value != other;
}
T setKnownValueOnce(T value) {
checkState(!isKnown, "already known");
this.value = value;
isKnown = true;
return value;
}
T getKnownValue() {
checkState(isKnown, "not yet known");
return value;
}
}
}