/*
* 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 com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.base.Supplier;
import com.google.javascript.jscomp.ExpressionDecomposer.DecompositionType;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import com.google.javascript.rhino.TypeI;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* A set of utility functions that replaces CALL with a specified
* FUNCTION body, replacing and aliasing function parameters as
* necessary.
*
* @author johnlenz@google.com (John Lenz)
*/
class FunctionInjector {
private final AbstractCompiler compiler;
private final boolean allowDecomposition;
private Set<String> knownConstants = new HashSet<>();
private final boolean assumeStrictThis;
private final boolean assumeMinimumCapture;
private final Supplier<String> safeNameIdSupplier;
private final Supplier<String> throwawayNameSupplier =
new Supplier<String>() {
private int nextId = 0;
@Override
public String get() {
return String.valueOf(nextId++);
}
};
/**
* @param allowDecomposition Whether an effort should be made to break down
* expressions into simpler expressions to allow functions to be injected
* where they would otherwise be disallowed.
*/
public FunctionInjector(
AbstractCompiler compiler,
Supplier<String> safeNameIdSupplier,
boolean allowDecomposition,
boolean assumeStrictThis,
boolean assumeMinimumCapture) {
Preconditions.checkNotNull(compiler);
Preconditions.checkNotNull(safeNameIdSupplier);
this.compiler = compiler;
this.safeNameIdSupplier = safeNameIdSupplier;
this.allowDecomposition = allowDecomposition;
this.assumeStrictThis = assumeStrictThis;
this.assumeMinimumCapture = assumeMinimumCapture;
}
/** The type of inlining to perform. */
enum InliningMode {
/**
* Directly replace the call expression. Only functions of meeting
* strict preconditions can be inlined.
*/
DIRECT,
/**
* Replaces the call expression with a block of statements. Conditions
* on the function are looser in mode, but stricter on the call site.
*/
BLOCK
}
/** Holds a reference to the call node of a function call */
static class Reference {
final Node callNode;
final Scope scope;
final JSModule module;
final InliningMode mode;
Reference(Node callNode, Scope scope, JSModule module, InliningMode mode) {
this.callNode = callNode;
this.scope = scope;
this.module = module;
this.mode = mode;
}
}
/**
* In order to estimate the cost of lining, we make the assumption that
* Identifiers are reduced 2 characters. For the call arguments, the important
* thing is that the cost is assumed to be the same in the call and the
* function, so the actual length doesn't matter in most cases.
*/
private static final int NAME_COST_ESTIMATE =
InlineCostEstimator.ESTIMATED_IDENTIFIER_COST;
/** The cost of a argument separator (a comma). */
private static final int COMMA_COST = 1;
/** The cost of the parentheses needed to make a call.*/
private static final int PAREN_COST = 2;
/**
* @param fnName The name of this function. This either the name of the
* variable to which the function is assigned or the name from the FUNCTION
* node.
* @param fnNode The FUNCTION node of the function to inspect.
* @return Whether the function node meets the minimum requirements for
* inlining.
*/
boolean doesFunctionMeetMinimumRequirements(
final String fnName, Node fnNode) {
Node block = NodeUtil.getFunctionBody(fnNode);
// Basic restrictions on functions that can be inlined:
// 0) The function is inlinable by convention
// 1) It contains a reference to itself.
// 2) It uses its parameters indirectly using "arguments" (it isn't
// handled yet.
// 3) It references "eval". Inline a function containing eval can have
// large performance implications.
if (!compiler.getCodingConvention().isInlinableFunction(fnNode)) {
return false;
}
final String fnRecursionName = fnNode.getFirstChild().getString();
Preconditions.checkState(fnRecursionName != null);
// If the function references "arguments" directly in the function
boolean referencesArguments = NodeUtil.isNameReferenced(
block, "arguments", NodeUtil.MATCH_NOT_FUNCTION);
// or it references "eval" or one of its names anywhere.
Predicate<Node> p = new Predicate<Node>(){
@Override
public boolean apply(Node n) {
if (n.isName()) {
return n.getString().equals("eval")
|| (!fnName.isEmpty()
&& n.getString().equals(fnName))
|| (!fnRecursionName.isEmpty()
&& n.getString().equals(fnRecursionName));
}
return false;
}
};
return !referencesArguments
&& !NodeUtil.has(block, p, Predicates.<Node>alwaysTrue());
}
/**
* @param fnNode The function to evaluate for inlining.
* @param needAliases A set of function parameter names that can not be
* used without aliasing. Returned by getUnsafeParameterNames().
* @param referencesThis Whether fnNode contains references to its this
* object.
* @param containsFunctions Whether fnNode contains inner functions.
* @return Whether the inlining can occur.
*/
CanInlineResult canInlineReferenceToFunction(
Reference ref, Node fnNode, Set<String> needAliases,
boolean referencesThis, boolean containsFunctions) {
// TODO(johnlenz): This function takes too many parameter, without
// context. Modify the API to take a structure describing the function.
// Allow direct function calls or "fn.call" style calls.
Node callNode = ref.callNode;
if (!isSupportedCallType(callNode)) {
return CanInlineResult.NO;
}
// Limit where functions that contain functions can be inline. Introducing
// an inner function into another function can capture a variable and cause
// a memory leak. This isn't a problem in the global scope as those values
// last until explicitly cleared.
if (containsFunctions) {
if (!assumeMinimumCapture && !ref.scope.isGlobal()) {
// TODO(johnlenz): Allow inlining into any scope without local names or
// inner functions.
return CanInlineResult.NO;
} else if (NodeUtil.isWithinLoop(callNode)) {
// An inner closure maybe relying on a local value holding a value for a
// single iteration through a loop.
return CanInlineResult.NO;
}
}
// TODO(johnlenz): Add support for 'apply'
if (referencesThis && !NodeUtil.isFunctionObjectCall(callNode)) {
// TODO(johnlenz): Allow 'this' references to be replaced with a
// global 'this' object.
return CanInlineResult.NO;
}
if (ref.mode == InliningMode.DIRECT) {
return canInlineReferenceDirectly(ref, fnNode, needAliases);
} else {
return canInlineReferenceAsStatementBlock(
ref, fnNode, needAliases);
}
}
/**
* Only ".call" calls and direct calls to functions are supported.
* @param callNode The call evaluate.
* @return Whether the call is of a type that is supported.
*/
private boolean isSupportedCallType(Node callNode) {
if (!callNode.getFirstChild().isName()) {
if (NodeUtil.isFunctionObjectCall(callNode)) {
if (!assumeStrictThis) {
Node thisValue = callNode.getSecondChild();
if (thisValue == null || !thisValue.isThis()) {
return false;
}
}
} else if (NodeUtil.isFunctionObjectApply(callNode)) {
return false;
}
}
return true;
}
/**
* Inline a function into the call site.
*/
Node inline(Reference ref, String fnName, Node fnNode) {
Preconditions.checkState(compiler.getLifeCycleStage().isNormalized());
if (ref.mode == InliningMode.DIRECT) {
return inlineReturnValue(ref, fnNode);
} else {
return inlineFunction(ref, fnNode, fnName);
}
}
/**
* Inline a function that fulfills the requirements of
* canInlineReferenceDirectly into the call site, replacing only the CALL
* node.
*/
private Node inlineReturnValue(Reference ref, Node fnNode) {
Node callNode = ref.callNode;
Node block = fnNode.getLastChild();
Node callParentNode = callNode.getParent();
// NOTE: As the normalize pass guarantees globals aren't being
// shadowed and an expression can't introduce new names, there is
// no need to check for conflicts.
// Create an argName -> expression map, checking for side effects.
Map<String, Node> argMap =
FunctionArgumentInjector.getFunctionCallParameterMap(
fnNode, callNode, this.safeNameIdSupplier);
Node newExpression;
if (!block.hasChildren()) {
Node srcLocation = block;
newExpression = NodeUtil.newUndefinedNode(srcLocation);
} else {
Node returnNode = block.getFirstChild();
Preconditions.checkArgument(returnNode.isReturn());
// Clone the return node first.
Node safeReturnNode = returnNode.cloneTree();
NodeUtil.markNewScopesChanged(safeReturnNode, compiler);
Node inlineResult = FunctionArgumentInjector.inject(
null, safeReturnNode, null, argMap);
Preconditions.checkArgument(safeReturnNode == inlineResult);
newExpression = safeReturnNode.removeFirstChild();
}
// If the call site had a cast ensure it's persisted to the new expression that replaces it.
TypeI typeBeforeCast = callNode.getTypeIBeforeCast();
if (typeBeforeCast != null) {
newExpression.putProp(Node.TYPE_BEFORE_CAST, typeBeforeCast);
newExpression.setTypeI(callNode.getTypeI());
}
callParentNode.replaceChild(callNode, newExpression);
return newExpression;
}
/**
* Supported call site types.
*/
private static enum CallSiteType {
/**
* Used for a call site for which there does not exist a method
* to inline it.
*/
UNSUPPORTED() {
@Override
public void prepare(FunctionInjector injector, Reference ref) {
throw new IllegalStateException("unexpected");
}
},
/**
* A call as a statement. For example: "foo();".
* EXPR_RESULT
* CALL
*/
SIMPLE_CALL() {
@Override
public void prepare(FunctionInjector injector, Reference ref) {
// Nothing to do.
}
},
/**
* An assignment, where the result of the call is assigned to a simple
* name. For example: "a = foo();".
* EXPR_RESULT
* NAME A
* CALL
* FOO
*/
SIMPLE_ASSIGNMENT() {
@Override
public void prepare(FunctionInjector injector, Reference ref) {
// Nothing to do.
}
},
/**
* An var declaration and initialization, where the result of the call is
* assigned to the declared name
* name. For example: "a = foo();".
* VAR
* NAME A
* CALL
* FOO
*/
VAR_DECL_SIMPLE_ASSIGNMENT() {
@Override
public void prepare(FunctionInjector injector, Reference ref) {
// Nothing to do.
}
},
/**
* An arbitrary expression, the root of which is a EXPR_RESULT, IF,
* RETURN, SWITCH or VAR. The call must be the first side-effect in
* the expression.
*
* Examples include:
* "if (foo()) {..."
* "return foo();"
* "var a = 1 + foo();"
* "a = 1 + foo()"
* "foo() ? 1:0"
* "foo() && x"
*/
EXPRESSION() {
@Override
public void prepare(FunctionInjector injector, Reference ref) {
Node callNode = ref.callNode;
injector.getDecomposer(ref.scope).moveExpression(callNode);
// Reclassify after move
CallSiteType callSiteType = injector.classifyCallSite(ref);
Preconditions.checkState(this != callSiteType);
callSiteType.prepare(injector, ref);
}
},
/**
* An arbitrary expression, the root of which is a EXPR_RESULT, IF,
* RETURN, SWITCH or VAR. Where the call is not the first side-effect in
* the expression.
*/
DECOMPOSABLE_EXPRESSION() {
@Override
public void prepare(FunctionInjector injector, Reference ref) {
Node callNode = ref.callNode;
injector.getDecomposer(ref.scope).maybeExposeExpression(callNode);
// Reclassify after decomposition
CallSiteType callSiteType = injector.classifyCallSite(ref);
Preconditions.checkState(this != callSiteType);
callSiteType.prepare(injector, ref);
}
};
public abstract void prepare(FunctionInjector injector, Reference ref);
}
/**
* Determine which, if any, of the supported types the call site is.
*
* Constant vars are treated differently so that we don't break their
* const-ness when we decompose the expression. Once the CONSTANT_VAR
* annotation is used everywhere instead of coding conventions, we should just
* teach this pass how to remove the annotation.
*/
private CallSiteType classifyCallSite(Reference ref) {
Node callNode = ref.callNode;
Node parent = callNode.getParent();
Node grandParent = parent.getParent();
// Verify the call site:
if (NodeUtil.isExprCall(parent)) {
// This is a simple call? Example: "foo();".
return CallSiteType.SIMPLE_CALL;
} else if (NodeUtil.isExprAssign(grandParent)
&& !NodeUtil.isVarOrSimpleAssignLhs(callNode, parent)
&& parent.getFirstChild().isName()
// TODO(nicksantos): Remove this once everyone is using
// the CONSTANT_VAR annotation. We know how to remove that.
&& !NodeUtil.isConstantName(parent.getFirstChild())) {
// This is a simple assignment. Example: "x = foo();"
return CallSiteType.SIMPLE_ASSIGNMENT;
} else if (parent.isName()
// TODO(nicksantos): Remove this once everyone is using
// the CONSTANT_VAR annotation.
&& !NodeUtil.isConstantName(parent)
&& grandParent.isVar()
&& grandParent.hasOneChild()) {
// This is a var declaration. Example: "var x = foo();"
// TODO(johnlenz): Should we be checking for constants on the
// left-hand-side of the assignments and handling them as EXPRESSION?
return CallSiteType.VAR_DECL_SIMPLE_ASSIGNMENT;
} else {
Node expressionRoot = ExpressionDecomposer.findExpressionRoot(callNode);
if (expressionRoot != null) {
ExpressionDecomposer decomposer = new ExpressionDecomposer(
compiler, safeNameIdSupplier, knownConstants, ref.scope);
DecompositionType type = decomposer.canExposeExpression(
callNode);
if (type == DecompositionType.MOVABLE) {
return CallSiteType.EXPRESSION;
} else if (type == DecompositionType.DECOMPOSABLE) {
return CallSiteType.DECOMPOSABLE_EXPRESSION;
} else {
Preconditions.checkState(type == DecompositionType.UNDECOMPOSABLE);
}
}
}
return CallSiteType.UNSUPPORTED;
}
private ExpressionDecomposer getDecomposer(Scope scope) {
return new ExpressionDecomposer(
compiler, safeNameIdSupplier, knownConstants, scope);
}
/**
* If required, rewrite the statement containing the call expression.
* @see ExpressionDecomposer#canExposeExpression
*/
void maybePrepareCall(Reference ref) {
CallSiteType callSiteType = classifyCallSite(ref);
callSiteType.prepare(this, ref);
}
/**
* Inline a function which fulfills the requirements of
* canInlineReferenceAsStatementBlock into the call site, replacing the
* parent expression.
*/
private Node inlineFunction(
Reference ref, Node fnNode, String fnName) {
Node callNode = ref.callNode;
Node parent = callNode.getParent();
Node grandParent = parent.getParent();
// TODO(johnlenz): Consider storing the callSite classification in the
// reference object and passing it in here.
CallSiteType callSiteType = classifyCallSite(ref);
Preconditions.checkArgument(callSiteType != CallSiteType.UNSUPPORTED);
// Store the name for the result. This will be used to
// replace "return expr" statements with "resultName = expr"
// to replace
String resultName = null;
boolean needsDefaultReturnResult = true;
switch (callSiteType) {
case SIMPLE_ASSIGNMENT:
resultName = parent.getFirstChild().getString();
removeConstantVarAnnotation(ref.scope, resultName);
break;
case VAR_DECL_SIMPLE_ASSIGNMENT:
resultName = parent.getString();
removeConstantVarAnnotation(ref.scope, resultName);
break;
case SIMPLE_CALL:
resultName = null; // "foo()" doesn't need a result.
needsDefaultReturnResult = false;
break;
case EXPRESSION:
throw new IllegalStateException(
"Movable expressions must be moved before inlining.");
case DECOMPOSABLE_EXPRESSION:
throw new IllegalStateException(
"Decomposable expressions must be decomposed before inlining.");
default:
throw new IllegalStateException("Unexpected call site type.");
}
FunctionToBlockMutator mutator = new FunctionToBlockMutator(
compiler, this.safeNameIdSupplier);
boolean isCallInLoop = NodeUtil.isWithinLoop(callNode);
Node newBlock = mutator.mutate(
fnName, fnNode, callNode, resultName,
needsDefaultReturnResult, isCallInLoop);
NodeUtil.markNewScopesChanged(newBlock, compiler);
// TODO(nicksantos): Create a common mutation function that
// can replace either a VAR name assignment, assignment expression or
// a EXPR_RESULT.
Node greatGrandParent = grandParent.getParent();
switch (callSiteType) {
case VAR_DECL_SIMPLE_ASSIGNMENT:
// Remove the call from the name node.
parent.removeFirstChild();
Preconditions.checkState(parent.getFirstChild() == null);
// Add the call, after the VAR.
greatGrandParent.addChildAfter(newBlock, grandParent);
break;
case SIMPLE_ASSIGNMENT:
// The assignment is now part of the inline function so
// replace it completely.
Preconditions.checkState(grandParent.isExprResult());
greatGrandParent.replaceChild(grandParent, newBlock);
break;
case SIMPLE_CALL:
// If nothing is looking at the result just replace the call.
Preconditions.checkState(parent.isExprResult());
grandParent.replaceChild(parent, newBlock);
break;
default:
throw new IllegalStateException("Unexpected call site type.");
}
return newBlock;
}
private static void removeConstantVarAnnotation(Scope scope, String name) {
Var var = scope.getVar(name);
Node nameNode = var == null ? null : var.getNameNode();
if (nameNode == null) {
return;
}
if (nameNode.getBooleanProp(Node.IS_CONSTANT_VAR)) {
nameNode.removeProp(Node.IS_CONSTANT_VAR);
}
}
/**
* Checks if the given function matches the criteria for an inlinable
* function, and if so, adds it to our set of inlinable functions.
*/
static boolean isDirectCallNodeReplacementPossible(Node fnNode) {
// Only inline single-statement functions
Node block = NodeUtil.getFunctionBody(fnNode);
// Check if this function is suitable for direct replacement of a CALL node:
// a function that consists of single return that returns an expression.
if (!block.hasChildren()) {
// special case empty functions.
return true;
} else if (block.hasOneChild()) {
// Only inline functions that return something.
if (block.getFirstChild().isReturn()
&& block.getFirstFirstChild() != null) {
return true;
}
}
return false;
}
enum CanInlineResult {
YES,
AFTER_PREPARATION,
NO
}
/**
* Determines whether a function can be inlined at a particular call site.
* There are several criteria that the function and reference must hold in
* order for the functions to be inlined:
* - It must be a simple call, or assignment, or var initialization.
* <pre>
* f();
* a = foo();
* var a = foo();
* </pre>
*/
private CanInlineResult canInlineReferenceAsStatementBlock(
Reference ref, Node fnNode, Set<String> namesToAlias) {
CallSiteType callSiteType = classifyCallSite(ref);
if (callSiteType == CallSiteType.UNSUPPORTED) {
return CanInlineResult.NO;
}
if (!allowDecomposition
&& (callSiteType == CallSiteType.DECOMPOSABLE_EXPRESSION
|| callSiteType == CallSiteType.EXPRESSION)) {
return CanInlineResult.NO;
}
if (!callMeetsBlockInliningRequirements(
ref, fnNode, namesToAlias)) {
return CanInlineResult.NO;
}
if (callSiteType == CallSiteType.DECOMPOSABLE_EXPRESSION
|| callSiteType == CallSiteType.EXPRESSION) {
return CanInlineResult.AFTER_PREPARATION;
} else {
return CanInlineResult.YES;
}
}
/**
* Determines whether a function can be inlined at a particular call site.
* - Don't inline if the calling function contains an inner function and
* inlining would introduce new globals.
*/
private boolean callMeetsBlockInliningRequirements(
Reference ref, final Node fnNode,
Set<String> namesToAlias) {
final boolean assumeMinimumCapture = this.assumeMinimumCapture;
// Note: functions that contain function definitions are filtered out
// in isCandidateFunction.
// TODO(johnlenz): Determining if the called function contains VARs
// or if the caller contains inner functions accounts for 20% of the
// run-time cost of this pass.
// Don't inline functions with var declarations into a scope with inner
// functions as the new vars would leak into the inner function and
// cause memory leaks.
boolean fnContainsVars = NodeUtil.has(
NodeUtil.getFunctionBody(fnNode),
new NodeUtil.MatchDeclaration(),
new NodeUtil.MatchShallowStatement());
boolean forbidTemps = false;
if (!ref.scope.getClosestHoistScope().isGlobal()) {
Node fnCallerBody = ref.scope.getClosestHoistScope().getRootNode();
// Don't allow any new vars into a scope that contains eval or one
// that contains functions (excluding the function being inlined).
Predicate<Node> match = new Predicate<Node>(){
@Override
public boolean apply(Node n) {
if (n.isName()) {
return n.getString().equals("eval");
}
if (!assumeMinimumCapture && n.isFunction()) {
return n != fnNode;
}
return false;
}
};
forbidTemps = NodeUtil.has(fnCallerBody, match, NodeUtil.MATCH_NOT_FUNCTION);
}
if (fnContainsVars && forbidTemps) {
return false;
}
// If the caller contains functions or evals, verify we aren't adding any
// additional VAR declarations because aliasing is needed.
if (forbidTemps) {
Map<String, Node> args =
FunctionArgumentInjector.getFunctionCallParameterMap(
fnNode, ref.callNode, this.safeNameIdSupplier);
boolean hasArgs = !args.isEmpty();
if (hasArgs) {
// Limit the inlining
Set<String> allNamesToAlias = new HashSet<>(namesToAlias);
FunctionArgumentInjector.maybeAddTempsForCallArguments(
fnNode, args, allNamesToAlias, compiler.getCodingConvention());
if (!allNamesToAlias.isEmpty()) {
return false;
}
}
}
return true;
}
/**
* Determines whether a function can be inlined at a particular call site.
* There are several criteria that the function and reference must hold in
* order for the functions to be inlined:
* 1) If a call's arguments have side effects,
* the corresponding argument in the function must only be referenced once.
* For instance, this will not be inlined:
* <pre>
* function foo(a) { return a + a }
* x = foo(i++);
* </pre>
*/
private CanInlineResult canInlineReferenceDirectly(
Reference ref, Node fnNode, Set<String> namesToAlias) {
if (!isDirectCallNodeReplacementPossible(fnNode)) {
return CanInlineResult.NO;
}
// CALL NODE: [ NAME, ARG1, ARG2, ... ]
Node callNode = ref.callNode;
Node cArg = callNode.getSecondChild();
// Functions called via 'call' and 'apply' have a this-object as
// the first parameter, but this is not part of the called function's
// parameter list.
if (!callNode.getFirstChild().isName()) {
if (NodeUtil.isFunctionObjectCall(callNode)) {
// TODO(johnlenz): Support replace this with a value.
if (cArg == null || !cArg.isThis()) {
return CanInlineResult.NO;
}
cArg = cArg.getNext();
} else {
// ".apply" call should be filtered before this.
Preconditions.checkState(!NodeUtil.isFunctionObjectApply(callNode));
}
}
Map<String, Node> args =
FunctionArgumentInjector.getFunctionCallParameterMap(
fnNode, callNode, this.throwawayNameSupplier);
boolean hasArgs = !args.isEmpty();
if (hasArgs) {
// Limit the inlining
Set<String> allNamesToAlias = new HashSet<>(namesToAlias);
FunctionArgumentInjector.maybeAddTempsForCallArguments(
fnNode, args, allNamesToAlias, compiler.getCodingConvention());
if (!allNamesToAlias.isEmpty()) {
return CanInlineResult.NO;
}
}
return CanInlineResult.YES;
}
/**
* Determine if inlining the function is likely to reduce the code size.
* @param namesToAlias
*/
boolean inliningLowersCost(
JSModule fnModule, Node fnNode, Collection<? extends Reference> refs,
Set<String> namesToAlias, boolean isRemovable, boolean referencesThis) {
int referenceCount = refs.size();
if (referenceCount == 0) {
return true;
}
int referencesUsingBlockInlining = 0;
boolean checkModules = isRemovable && fnModule != null;
JSModuleGraph moduleGraph = compiler.getModuleGraph();
for (Reference ref : refs) {
if (ref.mode == InliningMode.BLOCK) {
referencesUsingBlockInlining++;
}
// Check if any of the references cross the module boundaries.
if (checkModules && ref.module != null) {
if (ref.module != fnModule &&
!moduleGraph.dependsOn(ref.module, fnModule)) {
// Calculate the cost as if the function were non-removable,
// if it still lowers the cost inline it.
isRemovable = false;
checkModules = false; // no need to check additional modules.
}
}
}
int referencesUsingDirectInlining = referenceCount -
referencesUsingBlockInlining;
// Don't bother calculating the cost of function for simple functions where
// possible.
// However, when inlining a complex function, even a single reference may be
// larger than the original function if there are many returns (resulting
// in additional assignments) or many parameters that need to be aliased
// so use the cost estimating.
if (referenceCount == 1 && isRemovable &&
referencesUsingDirectInlining == 1) {
return true;
}
int callCost = estimateCallCost(fnNode, referencesThis);
int overallCallCost = callCost * referenceCount;
int costDeltaDirect = inlineCostDelta(
fnNode, namesToAlias, InliningMode.DIRECT);
int costDeltaBlock = inlineCostDelta(
fnNode, namesToAlias, InliningMode.BLOCK);
return doesLowerCost(fnNode, overallCallCost,
referencesUsingDirectInlining, costDeltaDirect,
referencesUsingBlockInlining, costDeltaBlock,
isRemovable);
}
/**
* @return Whether inlining will lower cost.
*/
private static boolean doesLowerCost(
Node fnNode, int callCost,
int directInlines, int costDeltaDirect,
int blockInlines, int costDeltaBlock,
boolean removable) {
// Determine the threshold value for this inequality:
// inline_cost < call_cost
// But solve it for the function declaration size so the size of it
// is only calculated once and terminated early if possible.
int fnInstanceCount = directInlines + blockInlines - (removable ? 1 : 0);
// Prevent division by zero.
if (fnInstanceCount == 0) {
// Special case single reference function that are being block inlined:
// If the cost of the inline is greater than the function definition size,
// don't inline.
return blockInlines <= 0 || costDeltaBlock <= 0;
}
int costDelta = (directInlines * -costDeltaDirect) + (blockInlines * -costDeltaBlock);
int threshold = (callCost + costDelta) / fnInstanceCount;
return InlineCostEstimator.getCost(fnNode, threshold + 1) <= threshold;
}
/**
* Gets an estimate of the cost in characters of making the function call:
* the sum of the identifiers and the separators.
* @param referencesThis
*/
private static int estimateCallCost(Node fnNode, boolean referencesThis) {
Node argsNode = NodeUtil.getFunctionParameters(fnNode);
int numArgs = argsNode.getChildCount();
int callCost = NAME_COST_ESTIMATE + PAREN_COST;
if (numArgs > 0) {
callCost += (numArgs * NAME_COST_ESTIMATE) + ((numArgs - 1) * COMMA_COST);
}
if (referencesThis) {
// TODO(johnlenz): Update this if we start supporting inlining
// other functions that reference this.
// The only functions that reference this that are currently inlined
// are those that are called via ".call" with an explicit "this".
callCost += 5 + 5; // ".call" + "this,"
}
return callCost;
}
/**
* @return The difference between the function definition cost and
* inline cost.
*/
private static int inlineCostDelta(
Node fnNode, Set<String> namesToAlias, InliningMode mode) {
// The part of the function that is never inlined:
// "function xx(xx,xx){}" (15 + (param count * 3) -1;
int paramCount = NodeUtil.getFunctionParameters(fnNode).getChildCount();
int commaCount = (paramCount > 1) ? paramCount - 1 : 0;
int costDeltaFunctionOverhead = 15 + commaCount +
(paramCount * InlineCostEstimator.ESTIMATED_IDENTIFIER_COST);
Node block = fnNode.getLastChild();
if (!block.hasChildren()) {
// Assume the inline cost is zero for empty functions.
return -costDeltaFunctionOverhead;
}
if (mode == InliningMode.DIRECT) {
// The part of the function that is inlined using direct inlining:
// "return " (7)
return -(costDeltaFunctionOverhead + 7);
} else {
int aliasCount = namesToAlias.size();
// Originally, we estimated purely base on the function code size, relying
// on later optimizations. But that did not produce good results, so here
// we try to estimate the something closer to the actual inlined coded.
// NOTE 1: Result overhead is only if there is an assignment, but
// getting that information would require some refactoring.
// NOTE 2: The aliasing overhead is currently an under-estimate,
// as some parameters are aliased because of the parameters used.
// Perhaps we should just assume all parameters will be aliased?
final int inlineBlockOverhead = 4; // "X:{}"
final int perReturnOverhead = 2; // "return" --> "break X"
final int perReturnResultOverhead = 3; // "XX="
final int perAliasOverhead = 3; // "XX="
// TODO(johnlenz): Counting the number of returns is relatively expensive
// this information should be determined during the traversal and
// cached.
int returnCount = NodeUtil.getNodeTypeReferenceCount(
block, Token.RETURN, new NodeUtil.MatchShallowStatement());
int resultCount = (returnCount > 0) ? returnCount - 1 : 0;
int baseOverhead = (returnCount > 0) ? inlineBlockOverhead : 0;
int overhead = baseOverhead
+ returnCount * perReturnOverhead
+ resultCount * perReturnResultOverhead
+ aliasCount * perAliasOverhead;
return (overhead - costDeltaFunctionOverhead);
}
}
/**
* Store the names of known constants to be used when classifying call-sites
* in expressions.
*/
public void setKnownConstants(Set<String> knownConstants) {
// This is only expected to be set once. The same set should be used
// when evaluating call-sites and inlining calls.
Preconditions.checkState(this.knownConstants.isEmpty());
this.knownConstants = knownConstants;
}
}