com.google.javascript.jscomp

Class OptimizeReturns

java.lang.Object

com.google.javascript.jscomp.OptimizeReturns

All Implemented Interfaces:

CompilerPass, OptimizeCalls.CallGraphCompilerPass

class OptimizeReturns
extends java.lang.Object
implements OptimizeCalls.CallGraphCompilerPass, CompilerPass

A compiler pass for optimize function return results. Currently this pass looks for results that are complete unused and rewrite then to be: "return x()" -->"x(); return" , but it can easily be expanded to look for use context to avoid unneeded type coercion: - "return x.toString()" --> "return x" - "return !!x" --> "return x"

Field Summary

Fields

Modifier and Type	Field and Description
private AbstractCompiler	compiler

Constructor Summary

Constructors

Constructor and Description
OptimizeReturns(AbstractCompiler compiler)

Method Summary

Modifier and Type	Method and Description
private static boolean	callResultsMaybeUsed(SimpleDefinitionFinder defFinder, DefinitionSite definitionSite) Determines if a function result might be used.
private static boolean	isCall(UseSite site) Determines if the name node acts as the function name in a call expression.
void	process(Node externs, Node root) Process the JS with root node root.
void	process(Node externs, Node root, SimpleDefinitionFinder definitions)
private void	rewriteReturns(SimpleDefinitionFinder defFinder, Node fnNode) For the supplied function node, rewrite all the return expressions so that: return foo(); becomes: foo(); return; Useless return will be removed later by the peephole optimization passes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

compiler

private AbstractCompiler compiler

Constructor Detail

OptimizeReturns

OptimizeReturns(AbstractCompiler compiler)

Method Detail

process

public void process(Node externs,
                    Node root)

Description copied from interface: CompilerPass

Process the JS with root node root. Can modify the contents of each Node tree

Specified by:

process in interface CompilerPass

Parameters:

externs - Top of external JS tree

root - Top of JS tree

process

public void process(Node externs,
                    Node root,
                    SimpleDefinitionFinder definitions)

Specified by:

process in interface OptimizeCalls.CallGraphCompilerPass

callResultsMaybeUsed

private static boolean callResultsMaybeUsed(SimpleDefinitionFinder defFinder,
                                            DefinitionSite definitionSite)

Determines if a function result might be used. A result might be use if: - Function must is exported. - The definition is never accessed outside a function call context.

rewriteReturns

private void rewriteReturns(SimpleDefinitionFinder defFinder,
                            Node fnNode)

For the supplied function node, rewrite all the return expressions so that: return foo(); becomes: foo(); return; Useless return will be removed later by the peephole optimization passes.

isCall

private static boolean isCall(UseSite site)

Determines if the name node acts as the function name in a call expression.