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/*
* Copyright 2008 Google Inc.
*
* 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.gwt.dev.js;
import com.google.gwt.dev.jjs.HasSourceInfo;
import com.google.gwt.dev.jjs.InternalCompilerException;
import com.google.gwt.dev.jjs.SourceInfo;
import com.google.gwt.dev.jjs.impl.OptimizerStats;
import com.google.gwt.dev.js.ast.JsArrayAccess;
import com.google.gwt.dev.js.ast.JsArrayLiteral;
import com.google.gwt.dev.js.ast.JsBinaryOperation;
import com.google.gwt.dev.js.ast.JsBinaryOperator;
import com.google.gwt.dev.js.ast.JsBlock;
import com.google.gwt.dev.js.ast.JsBooleanLiteral;
import com.google.gwt.dev.js.ast.JsCase;
import com.google.gwt.dev.js.ast.JsCatchScope;
import com.google.gwt.dev.js.ast.JsConditional;
import com.google.gwt.dev.js.ast.JsContext;
import com.google.gwt.dev.js.ast.JsDefault;
import com.google.gwt.dev.js.ast.JsEmpty;
import com.google.gwt.dev.js.ast.JsExprStmt;
import com.google.gwt.dev.js.ast.JsExpression;
import com.google.gwt.dev.js.ast.JsFor;
import com.google.gwt.dev.js.ast.JsForIn;
import com.google.gwt.dev.js.ast.JsFunction;
import com.google.gwt.dev.js.ast.JsIf;
import com.google.gwt.dev.js.ast.JsInvocation;
import com.google.gwt.dev.js.ast.JsModVisitor;
import com.google.gwt.dev.js.ast.JsName;
import com.google.gwt.dev.js.ast.JsNameRef;
import com.google.gwt.dev.js.ast.JsNew;
import com.google.gwt.dev.js.ast.JsNode;
import com.google.gwt.dev.js.ast.JsNullLiteral;
import com.google.gwt.dev.js.ast.JsNumberLiteral;
import com.google.gwt.dev.js.ast.JsObjectLiteral;
import com.google.gwt.dev.js.ast.JsParameter;
import com.google.gwt.dev.js.ast.JsPostfixOperation;
import com.google.gwt.dev.js.ast.JsPrefixOperation;
import com.google.gwt.dev.js.ast.JsProgram;
import com.google.gwt.dev.js.ast.JsRegExp;
import com.google.gwt.dev.js.ast.JsReturn;
import com.google.gwt.dev.js.ast.JsRootScope;
import com.google.gwt.dev.js.ast.JsScope;
import com.google.gwt.dev.js.ast.JsStatement;
import com.google.gwt.dev.js.ast.JsStringLiteral;
import com.google.gwt.dev.js.ast.JsThisRef;
import com.google.gwt.dev.js.ast.JsVars;
import com.google.gwt.dev.js.ast.JsVars.JsVar;
import com.google.gwt.dev.js.ast.JsVisitor;
import com.google.gwt.dev.js.ast.JsWhile;
import com.google.gwt.dev.util.log.speedtracer.CompilerEventType;
import com.google.gwt.dev.util.log.speedtracer.SpeedTracerLogger;
import com.google.gwt.dev.util.log.speedtracer.SpeedTracerLogger.Event;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;
import java.util.Stack;
/**
* Perform inlining optimizations on the JavaScript AST.
*
* TODO(bobv): remove anything that's duplicating work with {@link JsStaticEval}
* migrate other stuff to that class perhaps.
*/
public class JsInliner {
private static final String NAME = JsInliner.class.getSimpleName();
/**
* Determines if the evaluation of a JsNode may be affected by side effects.
*/
private static class AffectedBySideEffectsVisitor extends JsVisitor {
private boolean affectedBySideEffects;
private final JsScope safeScope;
public AffectedBySideEffectsVisitor(JsScope safeScope) {
this.safeScope = safeScope;
}
public boolean affectedBySideEffects() {
return affectedBySideEffects;
}
@Override
public void endVisit(JsArrayLiteral x, JsContext ctx) {
affectedBySideEffects = true;
}
@Override
public void endVisit(JsFunction x, JsContext ctx) {
affectedBySideEffects = true;
}
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
/*
* We could make this more accurate by analyzing the function that's being
* executed, but we'll bank on subsequent passes inlining simple function
* invocations.
*/
affectedBySideEffects = true;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
if (x.getQualifier() == null && x.getName() != null) {
// Special case the undefined literal.
if (x.getName() == JsRootScope.INSTANCE.getUndefined()) {
return;
}
// Locals in a safe scope are unaffected.
if (x.getName().getEnclosing() == safeScope) {
return;
}
}
/*
* We can make this more accurate if we had single-assignment information
* (e.g. static final fields).
*/
affectedBySideEffects = true;
}
@Override
public void endVisit(JsObjectLiteral x, JsContext ctx) {
affectedBySideEffects = true;
}
}
/**
* Make comma binary operations left-nested since commas are naturally
* left-associative. We will define the comma-normal form such that a comma
* expression should never have a comma expression as its RHS and contains no
* side-effect-free expressions save for the outer, right-hand expression.
* This form has a nice side-effect of minimizing the number of generated
* parentheses.
*
*
* (X, b) is unchanged
* (X, (b, c) becomes ((X, b), c); b is guaranteed to have a side-effect
* (X, ((b, c), d)) becomes (((X, b), c), d)
*
*/
private static class CommaNormalizer extends JsModVisitor {
/**
* Returns an expression as a JsBinaryOperation if it is a comma expression.
*/
private static JsBinaryOperation isComma(JsExpression x) {
if (!(x instanceof JsBinaryOperation)) {
return null;
}
JsBinaryOperation op = (JsBinaryOperation) x;
return op.getOperator().equals(JsBinaryOperator.COMMA) ? op : null;
}
private final List localVariableNames;
public CommaNormalizer(List localVariableNames) {
this.localVariableNames = localVariableNames;
}
@Override
public void endVisit(JsBinaryOperation x, JsContext ctx) {
if (isComma(x) == null) {
return;
}
// If (X, a) and X has no side effects, replace with a
if (!x.getArg1().hasSideEffects()) {
ctx.replaceMe(x.getArg2());
return;
}
JsBinaryOperation toUpdate = isComma(x.getArg2());
if (toUpdate == null) {
/*
* We have a JsBinaryOperation that's structurally normal: (X, a). Now
* it may be the case that the inner expression X is a comma expression
* (Y, b). If b creates no side-effects, we can remove it, leaving (Y,
* a) as the expression.
*/
JsBinaryOperation inner = isComma(x.getArg1());
if (inner != null && !inner.getArg2().hasSideEffects()) {
x.setArg1(inner.getArg1());
didChange = true;
}
/*
* Eliminate the pattern (localVar = expr, localVar). This tends to
* occur when a method interacted with pruned fields or had statements
* removed.
*/
JsName assignmentRef = null;
JsExpression expr = null;
JsName returnRef = null;
if (x.getArg1() instanceof JsBinaryOperation) {
JsBinaryOperation op = (JsBinaryOperation) x.getArg1();
if (op.getOperator() == JsBinaryOperator.ASG
&& op.getArg1() instanceof JsNameRef) {
JsNameRef nameRef = (JsNameRef) op.getArg1();
if (nameRef.getQualifier() == null) {
assignmentRef = nameRef.getName();
expr = op.getArg2();
}
}
}
if (x.getArg2() instanceof JsNameRef) {
JsNameRef nameRef = (JsNameRef) x.getArg2();
if (nameRef.getQualifier() == null) {
returnRef = nameRef.getName();
}
}
if (assignmentRef != null && assignmentRef.equals(returnRef)
&& localVariableNames.contains(assignmentRef)) {
assert expr != null;
localVariableNames.remove(assignmentRef);
ctx.replaceMe(expr);
}
return;
}
// Find the left-most, nested comma expression
while (isComma(toUpdate.getArg1()) != null) {
toUpdate = (JsBinaryOperation) toUpdate.getArg1();
}
/*
* Create a new comma expression with the original LHS and the LHS of the
* nested comma expression.
*/
JsBinaryOperation newOp = new JsBinaryOperation(x.getSourceInfo(),
JsBinaryOperator.COMMA);
newOp.setArg1(x.getArg1());
newOp.setArg2(toUpdate.getArg1());
// Set the LHS of the nested comma expression to the new comma expression
toUpdate.setArg1(newOp);
// Replace the original node with its updated RHS
ctx.replaceMe(x.getArg2());
}
}
/**
* Provides a relative metric by which the syntactic complexity of a
* JsExpression can be gauged.
*/
private static class ComplexityEstimator extends JsVisitor {
/**
* The current measure of complexity. This measures the number of
* expressions that have been encountered by the visitor.
*/
private int complexity = 0;
@Override
public void endVisit(JsArrayAccess x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsArrayLiteral x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsBinaryOperation x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsBooleanLiteral x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsConditional x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsFunction x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsNew x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsNullLiteral x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsNumberLiteral x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsObjectLiteral x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsPostfixOperation x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsPrefixOperation x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsRegExp x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsStringLiteral x, JsContext ctx) {
complexity++;
}
@Override
public void endVisit(JsThisRef x, JsContext ctx) {
complexity++;
}
public int getComplexity() {
return complexity;
}
}
/**
* This is used to clean up duplication invocations of functions that should
* only be executed once, such as clinit functions. Whenever there is a
* possible branch in program flow, the remover will create a new instance of
* itself to handle the possible branches.
*
* We don't look at combining branch choices. This will not produce the most
* efficient elimination of duplicated calls, but it handles the general case
* and is simple to verify.
*/
private static class DuplicateXORemover extends JsModVisitor {
/*
* TODO: Most of the special casing below can be removed if complex
* statements always use blocks, rather than plain statements.
*/
/**
* Retains the the functions that we know have been called.
*/
private final Set called;
private final JsProgram program;
public DuplicateXORemover(JsProgram program) {
this.program = program;
called = new HashSet();
}
public DuplicateXORemover(JsProgram program, Set alreadyCalled) {
this.program = program;
called = new HashSet(alreadyCalled);
}
/**
* Look for comma expressions that contain duplicate calls and handle the
* conditional-evaluation case of logical and/or operations.
*/
@Override
public boolean visit(JsBinaryOperation x, JsContext ctx) {
if (x.getOperator() == JsBinaryOperator.COMMA) {
boolean left = isDuplicateCall(x.getArg1());
boolean right = isDuplicateCall(x.getArg2());
if (left && right) {
/*
* (clinit(), clinit()) --> delete or null.
*
* This construct is very unlikely since the InliningVisitor builds
* the comma expressions in a right-nested manner.
*/
if (ctx.canRemove()) {
ctx.removeMe();
return false;
} else {
// The return value from an XO function is never used
ctx.replaceMe(JsNullLiteral.INSTANCE);
return false;
}
} else if (left) {
// (clinit(), xyz) --> xyz
// This is the common case
ctx.replaceMe(accept(x.getArg2()));
return false;
} else if (right) {
// (xyz, clinit()) --> xyz
// Possible if a clinit() were the last element
ctx.replaceMe(accept(x.getArg1()));
return false;
}
} else if (x.getOperator().equals(JsBinaryOperator.AND)
|| x.getOperator().equals(JsBinaryOperator.OR)) {
x.setArg1(accept(x.getArg1()));
// Possibility of conditional evaluation of second parameter
x.setArg2(branch(x.getArg2()));
return false;
}
return true;
}
/**
* Most of the branching statements (as well as JsFunctions) will visit with
* a JsBlock, so we don't need to explicitly enumerate all JsStatement
* subtypes.
*/
@Override
public boolean visit(JsBlock x, JsContext ctx) {
branch(x.getStatements());
return false;
}
@Override
public boolean visit(JsCase x, JsContext ctx) {
x.setCaseExpr(accept(x.getCaseExpr()));
branch(x.getStmts());
return false;
}
@Override
public boolean visit(JsConditional x, JsContext ctx) {
x.setTestExpression(accept(x.getTestExpression()));
x.setThenExpression(branch(x.getThenExpression()));
x.setElseExpression(branch(x.getElseExpression()));
return false;
}
@Override
public boolean visit(JsDefault x, JsContext ctx) {
branch(x.getStmts());
return false;
}
@Override
public boolean visit(JsExprStmt x, JsContext ctx) {
if (isDuplicateCall(x.getExpression())) {
if (ctx.canRemove()) {
ctx.removeMe();
} else {
ctx.replaceMe(new JsEmpty(x.getSourceInfo()));
}
return false;
} else {
return true;
}
}
@Override
public boolean visit(JsFor x, JsContext ctx) {
// The JsFor may have an expression xor a variable declaration.
if (x.getInitExpr() != null) {
x.setInitExpr(accept(x.getInitExpr()));
} else if (x.getInitVars() != null) {
x.setInitVars(accept(x.getInitVars()));
}
// The condition is optional
if (x.getCondition() != null) {
x.setCondition(accept(x.getCondition()));
}
// The increment expression is optional
if (x.getIncrExpr() != null) {
x.setIncrExpr(branch(x.getIncrExpr()));
}
// The body is not guaranteed to be a JsBlock
x.setBody(branch(x.getBody()));
return false;
}
@Override
public boolean visit(JsForIn x, JsContext ctx) {
if (x.getIterExpr() != null) {
x.setIterExpr(accept(x.getIterExpr()));
}
x.setObjExpr(accept(x.getObjExpr()));
// The body is not guaranteed to be a JsBlock
x.setBody(branch(x.getBody()));
return false;
}
@Override
public boolean visit(JsIf x, JsContext ctx) {
x.setIfExpr(accept(x.getIfExpr()));
x.setThenStmt(branch(x.getThenStmt()));
if (x.getElseStmt() != null) {
x.setElseStmt(branch(x.getElseStmt()));
}
return false;
}
/**
* Possibly record that we've seen a call in the current context.
*/
@Override
public boolean visit(JsInvocation x, JsContext ctx) {
JsFunction func = isExecuteOnce(x);
while (func != null) {
called.add(func);
func = func.getImpliedExecute();
}
return true;
}
@Override
public boolean visit(JsWhile x, JsContext ctx) {
x.setCondition(accept(x.getCondition()));
// The body is not guaranteed to be a JsBlock
x.setBody(branch(x.getBody()));
return false;
}
private void branch(List x) {
DuplicateXORemover dup = new DuplicateXORemover(program, called);
dup.acceptWithInsertRemove(x);
didChange |= dup.didChange();
}
private T branch(T x) {
DuplicateXORemover dup = new DuplicateXORemover(program, called);
T toReturn = dup.accept(x);
if ((toReturn != x) && !dup.didChange()) {
throw new InternalCompilerException(
"node replacement should imply didChange()");
}
didChange |= dup.didChange();
return toReturn;
}
private boolean isDuplicateCall(JsExpression x) {
if (!(x instanceof JsInvocation)) {
return false;
}
JsFunction func = isExecuteOnce((JsInvocation) x);
return (func != null && called.contains(func));
}
}
/**
* Determines that a list of names is guaranteed to be evaluated in a
* particular order. Also ensures that all names are evaluated before any
* invocations occur.
*/
private static class EvaluationOrderVisitor extends JsVisitor {
/**
* A dummy name to represent 'this' refs.
*/
public static final JsName THIS_NAME = new JsCatchScope(
JsRootScope.INSTANCE, "this").getAllNames().next();
private boolean maintainsOrder = true;
private final List toEvaluate;
private final List unevaluated;
private final Set paramsOrLocals = new HashSet();
public EvaluationOrderVisitor(List toEvaluate, JsFunction callee) {
this.toEvaluate = toEvaluate;
this.unevaluated = new ArrayList(toEvaluate);
// collect params and locals from callee function
new JsVisitor() {
@Override
public void endVisit(JsParameter x, JsContext ctx) {
paramsOrLocals.add(x.getName());
}
@Override
public boolean visit(JsVar x, JsContext ctx) {
// record this before visiting initializer
paramsOrLocals.add(x.getName());
return true;
}
}.accept(callee);
}
@Override
public void endVisit(JsBinaryOperation x, JsContext ctx) {
JsBinaryOperator op = x.getOperator();
/*
* We don't care about the left-hand expression, because it is guaranteed
* to be evaluated.
*/
boolean rightStrict = refersToRequiredName(x.getArg2());
boolean conditionalEvaluation = JsBinaryOperator.AND.equals(op)
|| JsBinaryOperator.OR.equals(op);
if (rightStrict && conditionalEvaluation) {
maintainsOrder = false;
}
}
/**
* If the condition would cause conditional evaluation of strict parameters,
* don't allow inlining.
*/
@Override
public void endVisit(JsConditional x, JsContext ctx) {
boolean thenStrict = refersToRequiredName(x.getThenExpression());
boolean elseStrict = refersToRequiredName(x.getElseExpression());
if (thenStrict || elseStrict) {
maintainsOrder = false;
}
}
/**
* The statement declares a function closure. This makes actual evaluation
* order of the parameters difficult or impossible to determine, so we'll
* just ignore them.
*/
@Override
public void endVisit(JsFunction x, JsContext ctx) {
maintainsOrder = false;
}
/**
* The innermost invocation we see must consume all presently unevaluated
* parameters to ensure that an exception does not prevent their evaluation.
*
* In the case of a nested invocation, such as
* F(r1, r2, G(r3, r4), f1); the evaluation order is guaranteed
* to be maintained, provided that no required parameters occur after the
* nested invocation.
*/
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
if (unevaluated.size() > 0) {
maintainsOrder = false;
}
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
checkName(x.getName());
}
@Override
public void endVisit(JsNew x, JsContext ctx) {
/*
* Unless all arguments have already been evaluated, assume that invoking
* the new expression might interfere with the evaluation of the argument.
*
* It would be possible to allow this if the invoked function either does
* nothing or does nothing that affects the remaining arguments. However,
* currently there is no analysis of the invoked function.
*/
if (unevaluated.size() > 0) {
maintainsOrder = false;
}
}
@Override
public void endVisit(JsThisRef x, JsContext ctx) {
checkName(THIS_NAME);
}
public boolean maintainsOrder() {
return maintainsOrder && unevaluated.size() == 0;
}
/**
* Check to see if the evaluation of this JsName will break program order assumptions given
* the parameters left to be substituted.
*
* The cases are as follows:
* 1) JsName is a function parameter name which has side effects or is affected by side effects
* (hereafter called 'volatile'), so it will be in 'toEvaluate'
* 2) JsName is a function parameter which is not volatile (not in toEvaluate)
* 3) JsName is a reference to a global variable
* 4) JsName is a reference to a local variable
*
* A reference to a global while there are still parameters left to evaluate / substitute
* implies an order violation.
*
* A reference to a volatile parameter is ok if it is the next parameter in sequence to
* be evaluated (beginning of unevaluated list). Else, it is either being evaluated out of
* order with respect to other parameters, or it is being evaluated more than once.
*/
private void checkName(JsName name) {
if (!toEvaluate.contains(name)) {
// if the name is a non-local/non-parameter (e.g. global) and there are params left to eval
if (!paramsOrLocals.contains(name) && unevaluated.size() > 0) {
maintainsOrder = false;
}
// else this may be a local, or all volatile params have already been evaluated, so it's ok.
return;
}
// either this param is being evaled twice, or out of order
if (unevaluated.size() == 0 || !unevaluated.remove(0).equals(name)) {
maintainsOrder = false;
}
}
/**
* Determine if an expression contains a reference to a strict parameter.
*/
private boolean refersToRequiredName(JsExpression e) {
RefersToNameVisitor v = new RefersToNameVisitor(toEvaluate);
v.accept(e);
return v.refersToName();
}
}
/**
* Collect names in a hoisted statement that are local to the original
* scope. These names will need to be copied to the destination scope
* once the statement becomes hoisted.
*/
private static class HoistedNameVisitor extends JsVisitor {
private final JsScope toScope;
private final JsScope fromScope;
private final List hoistedNames;
public HoistedNameVisitor(JsScope toScope, JsScope fromScope) {
this.toScope = toScope;
this.fromScope = fromScope;
this.hoistedNames = new ArrayList();
}
public List getHoistedNames() {
return hoistedNames;
}
/*
* We need to hoist names that are only visible in fromScope, but not in
* toScope (i.e. we don't want to hoist names that are visible to both
* scopes, such as a global). Also, we don't want to hoist names that have a
* staticRef, which indicates a formal parameter, or a function name.
*/
@Override
public boolean visit(JsNameRef nameRef, JsContext ctx) {
JsName name = nameRef.getName();
JsName fromScopeName = fromScope.findExistingName(name.getIdent());
JsName toScopeName = toScope.findExistingName(name.getIdent());
if (name.getStaticRef() == null
&& name == fromScopeName
&& name != toScopeName
&& !hoistedNames.contains(name)) {
hoistedNames.add(name);
}
return true;
}
}
/**
* Collect all of the idents used in an AST node. The collector can be
* configured to collect idents from qualified xor unqualified JsNameRefs.
*/
private static class IdentCollector extends JsVisitor {
private final boolean collectQualified;
private final Set idents = new HashSet();
public IdentCollector(boolean collectQualified) {
this.collectQualified = collectQualified;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
boolean hasQualifier = x.getQualifier() != null;
if ((collectQualified && !hasQualifier)
|| (!collectQualified && hasQualifier)) {
return;
}
assert x.getIdent() != null;
idents.add(x.getIdent());
}
public Set getIdents() {
return idents;
}
}
/**
* This class looks for function invocations that can be inlined and performs
* the replacement by replacing the JsInvocation with a comma expression
* consisting of the expressions evaluated by the target function. A second
* step may convert the expressions in the comma expression back to multiple
* statements if the context of the invocation would allow this.
*/
private static class InliningVisitor extends JsModVisitor {
private final Set blacklist = new HashSet();
/**
* This reflects the functions that are currently being inlined to prevent
* infinite expansion.
*/
private final Stack inlining = new Stack();
/**
* This reflects which function the visitor is currently visiting.
*/
private final Stack functionStack = new Stack();
private final InvocationCountingVisitor invocationCountingVisitor = new InvocationCountingVisitor();
private final Stack> newLocalVariableStack = new Stack>();
/**
* A map containing the next integer to try as an identifier suffix for a
* given JsScope.
*/
private IdentityHashMap> startIdentForScope = new IdentityHashMap>();
/**
* Not a stack because program fragments aren't nested.
*/
private JsFunction programFunction;
public InliningVisitor(JsProgram program) {
invocationCountingVisitor.accept(program);
}
/**
* Add to the list of JsFunctions that should not be inlined, regardless of
* whether or not they would normally be inlinable.
*/
public void blacklist(Collection functions) {
blacklist.addAll(functions);
}
/**
* This normalizes the comma expressions into multiple statements and
* removes statements with no side-effects.
*/
@Override
public void endVisit(JsExprStmt x, JsContext ctx) {
JsExpression e = x.getExpression();
// We will occasionally create JsExprStmts that have no side-effects.
if (ctx.canRemove() && !x.getExpression().hasSideEffects()) {
ctx.removeMe();
return;
}
List statements = new ArrayList();
/*
* Assemble the expressions back into a list of JsExprStmts. We will
* iteratively disassemble the nested comma expressions, stopping when the
* LHS is not a comma expression.
*/
while (e instanceof JsBinaryOperation) {
JsBinaryOperation op = (JsBinaryOperation) e;
if (!op.getOperator().equals(JsBinaryOperator.COMMA)) {
break;
}
/*
* We can ignore intermediate expressions as long as they have no
* side-effects.
*/
if (op.getArg2().hasSideEffects()) {
statements.add(0, op.getArg2().makeStmt());
}
e = op.getArg1();
}
/*
* We know the return value from the original invocation was ignored, so
* it may be possible to ignore the final expressions as long as it has no
* side-effects.
*/
if (e.hasSideEffects()) {
statements.add(0, e.makeStmt());
}
if (statements.size() == 0) {
// The expression contained no side effects at all.
if (ctx.canRemove()) {
ctx.removeMe();
} else {
ctx.replaceMe(new JsEmpty(x.getSourceInfo()));
}
} else if (x.getExpression() != statements.get(0).getExpression()) {
// Something has changed
if (!ctx.canInsert()) {
/*
* This indicates that the function was attached to a clause of a
* control function and not into an existing block. We'll replace the
* single JsExprStmt with a JsBlock that contains all of the
* statements.
*/
JsBlock b = new JsBlock(x.getSourceInfo());
b.getStatements().addAll(statements);
ctx.replaceMe(b);
return;
} else {
// Insert the new statements into the original context
for (JsStatement s : statements) {
ctx.insertBefore(s);
}
ctx.removeMe();
}
}
}
@Override
public void endVisit(JsFunction x, JsContext ctx) {
if (!functionStack.pop().equals(x)) {
throw new InternalCompilerException("Unexpected function popped");
}
JsBlock body = x.getBody();
List newLocalVariables = newLocalVariableStack.pop();
addVars(x, body, newLocalVariables);
}
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
if (functionStack.isEmpty()) {
return;
}
JsFunction callerFunction = functionStack.peek();
/*
* We only want to look at invocations of things that we statically know
* to be functions. Otherwise, we can't know what statements the
* invocation would actually invoke. The static reference would be null
* when trying operate on references to external functions, or functions
* as arguments to another function.
*/
JsFunction invokedFunction = isFunction(x.getQualifier());
if (invokedFunction == null) {
return;
}
/*
* Don't inline huge functions into huge multi-expressions. Some JS
* engines will blow up.
*/
if (invokedFunction.getBody().getStatements().size() > 50) {
return;
}
// Don't inline blacklisted functions
if (blacklist.contains(invokedFunction)) {
return;
}
/*
* The current function has been mutated so as to be self-recursive. Ban
* it from any future inlining to prevent infinite expansion.
*/
if (invokedFunction == callerFunction) {
blacklist.add(invokedFunction);
return;
}
/*
* We are already in the middle of attempting to inline a call to this
* function. This check prevents infinite expansion across
* mutually-recursive, inlinable functions. Any invocation skipped by this
* logic will be re-visited in the op = accept(op) call in
* the outermost JsInvocation.
*/
if (inlining.contains(invokedFunction)) {
return;
}
inlining.push(invokedFunction);
x = tryToUnravelExplicitCall(x);
JsExpression op = process(x, callerFunction, invokedFunction);
if (x != op) {
/*
* See if any further inlining can be performed in the current context.
* By attempting to maximize the level of inlining now, we can reduce
* the total number of passes required to finalize the AST.
*/
op = accept(op);
ctx.replaceMe(op);
}
if (inlining.pop() != invokedFunction) {
throw new RuntimeException("Unexpected function popped");
}
}
@Override
public void endVisit(JsProgram x, JsContext ctx) {
if (!functionStack.pop().equals(programFunction)) {
throw new InternalCompilerException("Unexpected function popped");
}
assert programFunction.getBody().getStatements().size() == 0 : "Should not have moved statements into program";
List newLocalVariables = newLocalVariableStack.pop();
assert newLocalVariables.size() == 0 : "Should not have tried to create variables in program";
}
@Override
public boolean visit(JsExprStmt x, JsContext ctx) {
if (functionStack.peek() == programFunction) {
/* Don't inline top-level invocations. */
if (x.getExpression() instanceof JsInvocation) {
return false;
}
}
return true;
}
@Override
public boolean visit(JsFunction x, JsContext ctx) {
functionStack.push(x);
newLocalVariableStack.push(new ArrayList());
return true;
}
/**
* Create a synthetic context to attempt to simplify statements in the
* top-level of the program.
*/
@Override
public boolean visit(JsProgram x, JsContext ctx) {
programFunction = new JsFunction(x.getSourceInfo(), x.getScope());
programFunction.setBody(new JsBlock(x.getSourceInfo()));
functionStack.push(programFunction);
newLocalVariableStack.push(new ArrayList());
return true;
}
private void addVars(HasSourceInfo x, JsBlock body,
List newLocalVariables) {
// Nothing to do
if (newLocalVariables.isEmpty()) {
return;
}
List statements = body.getStatements();
// The body can't be empty if we have local variables to create
assert !statements.isEmpty();
// Find or create the JsVars as the first statement
SourceInfo sourceInfo = x.getSourceInfo();
JsVars vars;
if (statements.get(0) instanceof JsVars) {
vars = (JsVars) statements.get(0);
} else {
vars = new JsVars(sourceInfo);
statements.add(0, vars);
}
// Add all variables
for (JsName name : newLocalVariables) {
vars.add(new JsVar(sourceInfo, name));
}
}
private boolean isInvokedMoreThanOnce(JsFunction f) {
Integer count = invocationCountingVisitor.invocationCount(f);
return count == null || count > 1;
}
/**
* Determine if invokedFunction can be inlined into
* callerFunction at callsite x.
*
* @return An expression equivalent to x
*/
private JsExpression process(JsInvocation x, JsFunction callerFunction,
JsFunction invokedFunction) {
List statements;
if (invokedFunction.getBody() != null) {
statements = new ArrayList(
invokedFunction.getBody().getStatements());
} else {
/*
* Will see this with certain classes whose clinits are folded into the
* main JsProgram body.
*/
statements = Collections.emptyList();
}
List hoisted = new ArrayList(statements.size());
JsExpression thisExpr = ((JsNameRef) x.getQualifier()).getQualifier();
HoistedNameVisitor hoistedNameVisitor =
new HoistedNameVisitor(callerFunction.getScope(), invokedFunction.getScope());
boolean sawReturnStatement = false;
for (JsStatement statement : statements) {
if (sawReturnStatement) {
/*
* We've already seen a return statement, but there are still more
* statements. The target is unsafe to inline, so bail. Note: in most
* cases JsStaticEval will have removed any statements following a
* return statement.
*
* The reason we have to bail is that the return statement's
* expression MUST be the last thing evaluated.
*
* TODO(bobv): maybe it could still be inlined with smart
* transformation?
*/
return x;
}
/*
* Create replacement expressions to use in place of the original
* statements. It is important that the replacement is newly-minted and
* therefore not referenced by any other AST nodes. Consider the case of
* a common, delegating function. If the hoisted expressions were not
* distinct objects, it would not be possible to substitute different
* JsNameRefs at different call sites.
*/
JsExpression h = hoistedExpression(statement);
if (h == null) {
return x;
}
/*
* Visit the statement to find names that will be moved to the caller's
* scope from the invoked function.
*/
hoistedNameVisitor.accept(statement);
if (isReturnStatement(statement)) {
sawReturnStatement = true;
hoisted.add(h);
} else if (hasSideEffects(Collections.singletonList(h))) {
hoisted.add(h);
}
}
/*
* Get the referenced names that need to be copied to the caller's scope.
*/
List hoistedNames = hoistedNameVisitor.getHoistedNames();
/*
* If the inlined method has no return statement, synthesize an undefined
* reference. It will be reclaimed if the method call is from a
* JsExprStmt.
*/
if (!sawReturnStatement) {
hoisted.add(new JsNameRef(x.getSourceInfo(),
JsRootScope.INSTANCE.getUndefined()));
}
assert (hoisted.size() > 0);
/*
* Build up the new comma expression from right-to-left; building the
* rightmost comma expressions first. Bootstrapping with i.previous()
* ensures that this logic will function correctly in the case of a single
* expression.
*/
SourceInfo sourceInfo = x.getSourceInfo();
ListIterator i = hoisted.listIterator(hoisted.size());
JsExpression op = i.previous();
while (i.hasPrevious()) {
JsBinaryOperation outerOp = new JsBinaryOperation(sourceInfo,
JsBinaryOperator.COMMA);
outerOp.setArg1(i.previous());
outerOp.setArg2(op);
op = outerOp;
}
// Confirm that the expression conforms to the desired heuristics
if (!isInlinable(callerFunction, invokedFunction, thisExpr,
x.getArguments(), op)) {
return x;
}
// Perform the name replacement
NameRefReplacerVisitor v = new NameRefReplacerVisitor(thisExpr,
x.getArguments(), invokedFunction.getParameters());
for (ListIterator nameIterator = hoistedNames.listIterator(); nameIterator.hasNext();) {
JsName name = nameIterator.next();
/*
* Find an unused identifier in the caller's scope. It's possible that
* the same function has been inlined in multiple places within the
* function so we'll use a counter for disambiguation.
*/
String ident;
String base = invokedFunction.getName() + "_" + name.getIdent();
JsScope scope = callerFunction.getScope();
HashMap startIdent = startIdentForScope.get(scope);
if (startIdent == null) {
startIdent = new HashMap();
startIdentForScope.put(scope, startIdent);
}
Integer s = startIdent.get(base);
int suffix = (s == null) ? 0 : s.intValue();
do {
ident = base + "_" + suffix++;
} while (scope.findExistingName(ident) != null);
startIdent.put(base, suffix);
JsName newName = scope.declareName(ident, name.getShortIdent());
v.setReplacementName(name, newName);
nameIterator.set(newName);
}
op = v.accept(op);
// Normalize any nested comma expressions that we may have generated.
op = (new CommaNormalizer(hoistedNames)).accept(op);
/*
* Compare the relative complexity of the original invocation versus the
* inlined form.
*/
int originalComplexity = complexity(x);
int inlinedComplexity = complexity(op);
double ratio = ((double) inlinedComplexity) / originalComplexity;
if (ratio > MAX_COMPLEXITY_INCREASE
&& isInvokedMoreThanOnce(invokedFunction)) {
return x;
}
if (callerFunction == programFunction && hoistedNames.size() > 0) {
// Don't add additional variables to the top-level program.
return x;
}
// We've committed to the inlining, ensure the vars are created
newLocalVariableStack.peek().addAll(hoistedNames);
// update invocation counts according to this inlining
invocationCountingVisitor.removeCountsFor(x);
invocationCountingVisitor.accept(op);
return op;
}
}
/**
* Counts the number of times a function is invoked. Functions that only have
* a single call site in the whole program are inlined, regardless of
* complexity.
*/
private static class InvocationCountingVisitor extends JsVisitor {
private boolean removingCounts = false;
private final Map invocationCount = new IdentityHashMap();
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
checkFunctionCall(x.getQualifier());
}
@Override
public void endVisit(JsNew x, JsContext ctx) {
checkFunctionCall(x.getConstructorExpression());
}
public Integer invocationCount(JsFunction f) {
return invocationCount.get(f);
}
/**
* Like accept(), but remove counts for all invocations in expr.
*/
public void removeCountsFor(JsExpression expr) {
assert (!removingCounts);
removingCounts = true;
accept(expr);
removingCounts = false;
}
private void checkFunctionCall(JsExpression qualifier) {
JsFunction function = isFunction(qualifier);
if (function != null) {
Integer count = invocationCount.get(function);
if (count == null) {
assert (!removingCounts);
count = 1;
} else {
if (removingCounts) {
count -= 1;
} else {
count += 1;
}
}
invocationCount.put(function, count);
}
}
}
/**
* Replace references to JsNames with the inlined JsExpression.
*/
private static class NameRefReplacerVisitor extends JsModVisitor {
/**
* Set up a map to record name replacements to perform.
*/
final Map nameReplacements = new IdentityHashMap();
/**
* Set up a map of parameter names back to the expressions that will be
* passed in from the outer call site.
*/
final Map paramsToArgsMap = new IdentityHashMap();
/**
* A replacement expression for this references.
*/
private JsExpression thisExpr;
public NameRefReplacerVisitor(JsExpression thisExpr,
List arguments, List parameters) {
this.thisExpr = thisExpr;
if (parameters.size() != arguments.size()) {
// This shouldn't happen if the cloned JsInvocation has been properly
// configured
throw new InternalCompilerException(
"Mismatch on parameters and arguments");
}
for (int i = 0; i < parameters.size(); i++) {
JsParameter p = parameters.get(i);
JsExpression e = arguments.get(i);
paramsToArgsMap.put(p.getName(), e);
}
}
/**
* Replace JsNameRefs that refer to parameters with the expression passed
* into the function invocation.
*/
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
if (x.getQualifier() != null) {
return;
}
JsExpression replacement = tryGetReplacementExpression(x.getSourceInfo(),
x.getName());
if (replacement != null) {
ctx.replaceMe(replacement);
}
}
@Override
public void endVisit(JsThisRef x, JsContext ctx) {
assert thisExpr != null;
ctx.replaceMe(thisExpr);
}
/**
* Set a replacement JsName for all references to a JsName.
*
* @param name the name to replace
* @param newName the new name that should be used in place of references to
* name
* @return the previous JsName the name would have been replaced with or
* null if one was not previously set
*/
public JsName setReplacementName(JsName name, JsName newName) {
return nameReplacements.put(name, newName);
}
/**
* Determine the replacement expression to use in place of a reference to a
* given name. Returns null if no replacement has been set for
* the name.
*/
private JsExpression tryGetReplacementExpression(SourceInfo sourceInfo,
JsName name) {
if (paramsToArgsMap.containsKey(name)) {
/*
* TODO if we ever allow mutable JsExpression types to be considered
* always flexible, then it would be necessary to clone the expression.
*/
return paramsToArgsMap.get(name);
} else if (nameReplacements.containsKey(name)) {
return nameReplacements.get(name).makeRef(sourceInfo);
} else {
return null;
}
}
}
/**
* Detects function declarations.
*/
private static class NestedFunctionVisitor extends JsVisitor {
private boolean containsNestedFunctions = false;
public boolean containsNestedFunctions() {
return containsNestedFunctions;
}
@Override
public void endVisit(JsFunction x, JsContext ctx) {
containsNestedFunctions = true;
}
}
/**
* Detects uses of parameters that would produce incorrect results if inlined.
* Generally speaking, we disallow the use of parameters as lvalues. Also
* detects trying to inline a method which references 'this' where the call
* site has no qualifier.
*/
private static class ParameterUsageVisitor extends JsVisitor {
private final boolean hasThisExpr;
private final Set parameterNames;
private boolean violation = false;
public ParameterUsageVisitor(boolean hasThisExpr, Set parameterNames) {
this.hasThisExpr = hasThisExpr;
this.parameterNames = parameterNames;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
if (ctx.isLvalue() && isParameter(x)) {
violation = true;
}
}
@Override
public void endVisit(JsThisRef x, JsContext ctx) {
if (!hasThisExpr) {
violation = true;
}
}
public boolean hasViolation() {
return violation;
}
/**
* Determine if a JsExpression is a JsNameRef that refers to a parameter.
*/
private boolean isParameter(JsNameRef ref) {
if (ref.getQualifier() != null) {
return false;
}
JsName name = ref.getName();
return parameterNames.contains(name);
}
}
/**
* Collect self-recursive functions. This visitor does not look for
* mutually-recursive functions because inlining one of the functions into the
* other would make the single resultant function self-recursive and not
* eligible for inlining in a subsequent pass.
*/
private static class RecursionCollector extends JsVisitor {
private final Stack functionStack = new Stack();
private final Set recursive = new HashSet();
@Override
public void endVisit(JsFunction x, JsContext ctx) {
if (!functionStack.pop().equals(x)) {
throw new InternalCompilerException("Unexpected function popped");
}
}
@Override
public void endVisit(JsInvocation x, JsContext ctx) {
/*
* Because functions can encapsulate other functions, we look at the
* entire stack and not just the top element. This would prevent inlining
*
* function a() { function b() { a(); } b(); }
*
* in the case that we generally allow nested functions to be inlinable.
*/
JsFunction f = isFunction(x.getQualifier());
if (functionStack.contains(f)) {
recursive.add(f);
}
}
public Set getRecursive() {
return recursive;
}
@Override
public boolean visit(JsFunction x, JsContext ctx) {
functionStack.push(x);
return true;
}
}
/**
* Determine which functions should not be inlined because they are redefined
* during program execution. This would violate the assumption that the
* statements to be executed by any given function invocation are stable over
* the lifetime of the program.
*/
private static class RedefinedFunctionCollector extends JsVisitor {
private final Map nameMap = new IdentityHashMap();
private final Set redefined = new HashSet();
/**
* Look for assignments to JsNames whose static references are JsFunctions.
*/
@Override
public void endVisit(JsBinaryOperation x, JsContext ctx) {
if (!x.getOperator().equals(JsBinaryOperator.ASG)) {
return;
}
JsFunction f = isFunction(x.getArg1());
if (f != null) {
redefined.add(f);
}
}
/**
* Look for the case where a function is declared with the same name as an
* existing function.
*/
@Override
public void endVisit(JsFunction x, JsContext ctx) {
JsName name = x.getName();
if (name == null) {
// Ignore anonymous functions
return;
} else if (nameMap.containsKey(name)) {
/*
* We have to add the current function as well as the original
* JsFunction that was declared to use that name.
*/
redefined.add(nameMap.get(name));
redefined.add(x);
} else {
nameMap.put(name, x);
}
}
public Collection getRedefined() {
return redefined;
}
}
/**
* Given a collection of JsNames, determine if an AST node refers to any of
* those names.
*/
private static class RefersToNameVisitor extends JsVisitor {
private final Collection names;
private boolean refersToName;
public RefersToNameVisitor(Collection names) {
this.names = names;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
JsName name = x.getName();
if (name != null) {
refersToName = refersToName || names.contains(name);
}
}
public boolean refersToName() {
return refersToName;
}
}
/**
* This ensures that changing the scope of an expression from its enclosing
* function into the scope of the call site will not cause unqualified
* identifiers to resolve to different values.
*/
private static class StableNameChecker extends JsVisitor {
private final JsScope calleeScope;
private final JsScope callerScope;
private final Collection parameterNames;
private boolean stable = true;
public StableNameChecker(JsScope callerScope, JsScope calleeScope,
Collection parameterNames) {
this.callerScope = callerScope;
this.calleeScope = calleeScope;
this.parameterNames = parameterNames;
}
@Override
public void endVisit(JsNameRef x, JsContext ctx) {
/*
* We can ignore qualified reference, since their scope is always that of
* the qualifier.
*/
if (x.getQualifier() != null) {
return;
}
/*
* Attempt to resolve the ident in both scopes
*/
JsName callerName = callerScope.findExistingName(x.getIdent());
JsName calleeName = calleeScope.findExistingName(x.getIdent());
if (callerName == null && calleeName == null) {
// They both reference out-of-module names
} else if (parameterNames.contains(calleeName)) {
// A reference to a parameter, which will be replaced by an argument
} else if (callerName != null && callerName.equals(calleeName)) {
// The names are known to us and are the same
} else if (calleeName.getEnclosing().equals(calleeScope)) {
// It's a local variable in the callee
} else {
stable = false;
}
}
public boolean isStable() {
return stable;
}
}
/**
* When attempting to inline an invocation, this constant determines the
* maximum allowable ratio of potential inlined complexity to initial
* complexity. This acts as a brake on very large expansions from bloating the
* the generated output. Increasing this number will allow larger sections of
* code to be inlined, but at a cost of larger JS output.
*/
private static final double MAX_COMPLEXITY_INCREASE = Double.parseDouble(System.getProperty(
"gwt.jsinlinerRatio", "1.7"));
/**
* Static entry point used by JavaToJavaScriptCompiler.
*/
public static OptimizerStats exec(JsProgram program) {
Event optimizeJsEvent = SpeedTracerLogger.start(
CompilerEventType.OPTIMIZE_JS, "optimizer", NAME);
OptimizerStats stats = execImpl(program);
optimizeJsEvent.end("didChange", "" + stats.didChange());
return stats;
}
/**
* Determine whether or not a list of AST nodes are affected by side effects.
* The context parameter provides a scope in which local (and therefore
* immutable) variables are defined.
*/
private static boolean affectedBySideEffects(List list,
JsFunction context) {
/*
* If the caller contains no nested functions, none of its locals can
* possibly be affected by side effects.
*/
JsScope safeScope = null;
if (context != null && !containsNestedFunctions(context)) {
safeScope = context.getScope();
}
AffectedBySideEffectsVisitor v = new AffectedBySideEffectsVisitor(safeScope);
v.acceptList(list);
return v.affectedBySideEffects();
}
/**
* Generate an estimated measure of the syntactic complexity of a JsNode.
*/
private static int complexity(JsNode toEstimate) {
ComplexityEstimator e = new ComplexityEstimator();
e.accept(toEstimate);
return e.getComplexity();
}
/**
* Examine a JsFunction to determine if it contains nested functions.
*/
private static boolean containsNestedFunctions(JsFunction func) {
NestedFunctionVisitor v = new NestedFunctionVisitor();
v.accept(func.getBody());
return v.containsNestedFunctions();
}
/**
* @param program
* @return stats
*/
private static OptimizerStats execImpl(JsProgram program) {
OptimizerStats stats = new OptimizerStats(NAME);
RedefinedFunctionCollector d = new RedefinedFunctionCollector();
d.accept(program);
RecursionCollector rc = new RecursionCollector();
rc.accept(program);
InliningVisitor v = new InliningVisitor(program);
v.blacklist(d.getRedefined());
v.blacklist(rc.getRecursive());
v.accept(program);
if (v.didChange()) {
stats.recordModified();
}
DuplicateXORemover r = new DuplicateXORemover(program);
r.accept(program);
if (r.didChange()) {
stats.recordModified();
}
return stats;
}
/**
* Check to see if the to-be-inlined statement shares any idents with the
* call-side arguments. Two passes are made: the first one looks for qualified
* names; the second pass looks for unqualified names, but ignores identifiers
* that refer to function parameters.
*/
private static boolean hasCommonIdents(List arguments,
JsNode toInline, Collection parameterIdents) {
// This is a fire-twice loop
boolean checkQualified = false;
do {
checkQualified = !checkQualified;
// Collect the idents used in the arguments and the statement
IdentCollector argCollector = new IdentCollector(checkQualified);
argCollector.acceptList(arguments);
IdentCollector statementCollector = new IdentCollector(checkQualified);
statementCollector.accept(toInline);
Set idents = argCollector.getIdents();
// Unqualified idents may be references to parameters, thus ignored
if (!checkQualified) {
idents.removeAll(parameterIdents);
}
// Perform the set difference
idents.retainAll(statementCollector.getIdents());
if (idents.size() > 0) {
return true;
}
} while (checkQualified);
return false;
}
/**
* Determine whether or not a list of AST nodes have side effects.
*/
private static boolean hasSideEffects(List list) {
for (JsExpression expr : list) {
if (expr.hasSideEffects()) {
return true;
}
}
return false;
}
/**
* Given a delegated JsStatement, construct an expression to hoist into the
* outer caller. This does not perform any name replacement, but simply
* constructs a mutable copy of the expression that can be manipulated
* at-will.
*
* @param statement the statement from which to extract the expressions
* @return a JsExpression representing all expressions that would have been
* evaluated by the statement
*/
private static JsExpression hoistedExpression(JsStatement statement) {
JsExpression expression;
if (statement instanceof JsExprStmt) {
// Extract the expression
JsExprStmt exprStmt = (JsExprStmt) statement;
expression = exprStmt.getExpression();
} else if (statement instanceof JsReturn) {
// Extract the return value
JsReturn ret = (JsReturn) statement;
expression = ret.getExpr();
if (expression == null) {
expression = new JsNameRef(ret.getSourceInfo(),
JsRootScope.INSTANCE.getUndefined());
}
} else if (statement instanceof JsVars) {
// Create a comma expression for variable initializers
JsVars vars = (JsVars) statement;
// Rely on comma expression cleanup to remove this later.
expression = JsNullLiteral.INSTANCE;
for (JsVar var : vars) {
// Extract the initialization expression
JsExpression init = var.getInitExpr();
if (init != null) {
SourceInfo sourceInfo = var.getSourceInfo();
JsBinaryOperation assignment = new JsBinaryOperation(sourceInfo,
JsBinaryOperator.ASG);
assignment.setArg1(var.getName().makeRef(sourceInfo));
assignment.setArg2(init);
// Multiple initializers go into a comma expression
JsBinaryOperation comma = new JsBinaryOperation(sourceInfo,
JsBinaryOperator.COMMA);
comma.setArg1(expression);
comma.setArg2(assignment);
expression = comma;
}
}
} else {
return null;
}
assert expression != null;
return JsHoister.hoist(expression);
}
/**
* Given a JsInvocation, determine if it is invoking a JsFunction that is
* specified to be executed only once during the program's lifetime.
*/
private static JsFunction isExecuteOnce(JsInvocation invocation) {
JsFunction f = isFunction(invocation.getQualifier());
if (f != null && f.getExecuteOnce()) {
return f;
}
return null;
}
/**
* Given an expression, determine if it is a JsNameRef that refers to a
* statically-defined JsFunction.
*/
private static JsFunction isFunction(JsExpression e) {
if (e instanceof JsNameRef) {
JsNameRef ref = (JsNameRef) e;
// Unravel foo.call(...).
if (!ref.getName().isObfuscatable() && "call".equals(ref.getIdent())) {
if (ref.getQualifier() instanceof JsNameRef) {
ref = (JsNameRef) ref.getQualifier();
}
}
JsNode staticRef = ref.getName().getStaticRef();
if (staticRef instanceof JsFunction) {
return (JsFunction) staticRef;
}
}
return null;
}
/**
* Determine if a statement can be inlined into a call site.
*/
private static boolean isInlinable(JsFunction caller, JsFunction callee,
JsExpression thisExpr, List arguments, JsNode toInline) {
/*
* This will happen with varargs-style JavaScript functions that rely on the
* "arguments" array. The reference to arguments would be detected in
* BoundedScopeVisitor, but the code below assumes the same number of
* parameters and arguments.
*/
if (arguments.size() != callee.getParameters().size()) {
return false;
}
// Build up a list of all parameter names
Set parameterNames = new HashSet();
Set parameterIdents = new HashSet();
for (JsParameter param : callee.getParameters()) {
parameterNames.add(param.getName());
parameterIdents.add(param.getName().getIdent());
}
/*
* Make sure that inlining won't change the final name of non-parameter
* idents due to the change of scope. The most likely cause would be the use
* of an unqualified variable reference in a JSNI block that happened to
* conflict with a Java-derived identifier.
*/
StableNameChecker detector = new StableNameChecker(caller.getScope(),
callee.getScope(), parameterNames);
detector.accept(toInline);
if (!detector.isStable()) {
return false;
}
/*
* Ensure that the names referred to by the argument list and the statement
* are disjoint. This prevents inlining of the following:
*
* static int i; public void add(int a) { i += a; }; add(i++);
*/
if (hasCommonIdents(arguments, toInline, parameterIdents)) {
return false;
}
List evalArgs;
if (thisExpr == null) {
evalArgs = arguments;
} else {
evalArgs = new ArrayList(1 + arguments.size());
evalArgs.add(thisExpr);
evalArgs.addAll(arguments);
}
/*
* Determine if the evaluation of the invocation's arguments may create side
* effects. This will determine how aggressively the parameters may be
* reordered.
*/
if (isVolatile(evalArgs, caller)) {
/*
* Determine the order in which the parameters must be evaluated. This
* will vary between call sites, based on whether or not the invocation's
* arguments can be repeated without ill effect.
*/
List requiredOrder = new ArrayList();
if (thisExpr != null && isVolatile(thisExpr, callee)) {
requiredOrder.add(EvaluationOrderVisitor.THIS_NAME);
}
for (int i = 0; i < arguments.size(); i++) {
JsExpression e = arguments.get(i);
JsParameter p = callee.getParameters().get(i);
if (isVolatile(e, callee)) {
requiredOrder.add(p.getName());
}
}
// This would indicate that isVolatile changed its output between
// the if statement and the loop.
assert requiredOrder.size() > 0;
/*
* Verify that the non-reorderable arguments are evaluated in the right
* order.
*/
EvaluationOrderVisitor orderVisitor = new EvaluationOrderVisitor(
requiredOrder, callee);
orderVisitor.accept(toInline);
if (!orderVisitor.maintainsOrder()) {
return false;
}
}
// Check that parameters aren't used in such a way as to prohibit inlining
ParameterUsageVisitor v = new ParameterUsageVisitor(thisExpr != null,
parameterNames);
v.accept(toInline);
if (v.hasViolation()) {
return false;
}
// Hooray!
return true;
}
/**
* This is used in combination with {@link #hoistedExpression(JsStatement)} to
* indicate if a given statement would terminate the list of hoisted
* expressions.
*/
private static boolean isReturnStatement(JsStatement statement) {
return statement instanceof JsReturn;
}
/**
* Indicates if an expression would create side effects or possibly be
* affected by side effects when evaluated within a particular function
* context.
*/
private static boolean isVolatile(JsExpression e, JsFunction context) {
return isVolatile(Collections.singletonList(e), context);
}
/**
* Indicates if a list of expressions would create side effects or possibly be
* affected by side effects when evaluated within a particular function
* context.
*/
private static boolean isVolatile(List list, JsFunction context) {
return hasSideEffects(list) || affectedBySideEffects(list, context);
}
/**
* Transforms any foo.call(this) into this.foo() to
* be compatible with our inlining algorithm.
*/
private static JsInvocation tryToUnravelExplicitCall(JsInvocation x) {
if (!(x.getQualifier() instanceof JsNameRef)) {
return x;
}
JsNameRef ref = (JsNameRef) x.getQualifier();
if (ref.getName().isObfuscatable() || !"call".equals(ref.getIdent())) {
return x;
}
List oldArgs = x.getArguments();
if (oldArgs.size() < 1) {
return x;
}
JsNameRef oldTarget = (JsNameRef) ref.getQualifier();
JsNameRef newTarget = new JsNameRef(oldTarget.getSourceInfo(),
oldTarget.getName());
newTarget.setQualifier(oldArgs.get(0));
JsInvocation newCall = new JsInvocation(x.getSourceInfo());
newCall.setQualifier(newTarget);
// Don't have to clone because the returned invocation is transient.
newCall.getArguments().addAll(oldArgs.subList(1, oldArgs.size()));
return newCall;
}
/**
* Utility class.
*/
private JsInliner() {
}
}
