com.google.gwt.dev.jjs.impl

Class Simplifier

java.lang.Object

com.google.gwt.dev.jjs.impl.Simplifier

public class Simplifier
extends Object

Methods that both construct and try to simplify AST nodes. If simplification fails, then the methods will return an original, unmodified version of the node if one is supplied. The routines do not recurse into their arguments; the arguments are assumed to already be simplified as much as possible.

Method Summary

Modifier and Type	Method and Description
static JExpression	cast(JType type, JExpression exp) Simplify cast operations.
static JExpression	simplifyAnd(JBinaryOperation expression) Simplify short circuit AND expressions.
static JExpression	simplifyCast(JCastOperation castExpression) Simplify cast operations.
static JExpression	simplifyConditional(JConditional expression) Simplify conditional expressions.
static JStatement	simplifyIfStatement(JIfStatement ifStatement, JType methodReturnType) Simplifies an if then else statement.
static JExpression	simplifyNot(JPrefixOperation expression) Simplifies an negation expression.
static JExpression	simplifyOr(JBinaryOperation expression) Simplify short circuit OR expressions.

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, toString

Method Detail

cast

public static JExpression cast(JType type,
                               JExpression exp)

Simplify cast operations. Used when creating a cast in DeadCodeElimination. For simplifying casts that are actually in the AST, cast(JCastOperation) is used instead.

 (int) 1 -> 1
 (A) (a,b) -> (a, (A) b)
 

Parameters:

type - the Type to cast the expression exp to.

exp - the current JExpression under the cast as it is being simplified.

Returns:

the simplified expression.

simplifyCast

public static JExpression simplifyCast(JCastOperation castExpression)

Simplify cast operations.

 (int) 1 -> 1
 (A) (a,b) -> (a, (A) b)
 

Parameters:

castExpression - a JCastOperation to be simplified.

Returns:

the simplified expression if a simplification was possible; exp otherwise.

simplifyConditional

public static JExpression simplifyConditional(JConditional expression)

Simplify conditional expressions.

 (a,b,c)?d:e -> a,b,(c?d:e)
 true ? then : else -> then
 false ? then : else -> else
 cond ? true : else) -> cond || else
 cond ? false : else -> !cond && else
 cond ? then : true -> !cond || then
 cond ? then : false -> cond && then
 !cond ? then : else -> cond ? else : then
 

Parameters:

expression - a JCondintional to be simplified.

Returns:

the simplified expression if a simplification was possible; exp otherwise.

simplifyIfStatement

public static JStatement simplifyIfStatement(JIfStatement ifStatement,
                                             JType methodReturnType)

Simplifies an if then else statement.

 if(a,b,c) d [else e] -> {a; b; if(c) d [else e]; }
 if(true) a [else b] -> a
 if(false) a else b -> b
 if(notImpl(c)) a else b -> if(c) b else a
 if(true) ; else b -> true
 if(false) a [else ;] -> false
 if(c) ; [else ;] -> c

Parameters:

ifStatement - the statement to simplify.

methodReturnType - the return type of the method where the statement resides if any

Returns:

the simplified statement if a simplification could be done and ifStatement otherwise.

simplifyNot

public static JExpression simplifyNot(JPrefixOperation expression)

Simplifies an negation expression. !(a > b) => a <= b

Parameters:

expression - the expression to simplify.

Returns:

the simplified expression if a simplification could be done and expr otherwise.

simplifyAnd

public static JExpression simplifyAnd(JBinaryOperation expression)

Simplify short circuit AND expressions.

 true && isWhatever() -> isWhatever()
 false && isWhatever() -> false

 isWhatever() && true -> isWhatever()
 isWhatever() && false -> false, unless side effects

 (a, b) && c -> (a, b && c)
 

Parameters:

expression - an AND JBinaryExpression to be simplified.

Returns:

the simplified expression if a simplification was possible; exp otherwise.

simplifyOr

public static JExpression simplifyOr(JBinaryOperation expression)

Simplify short circuit OR expressions.

 true || isWhatever() -> true
 false || isWhatever() -> isWhatever()

 isWhatever() || false isWhatever()
 isWhatever() || true -> true, unless side effects

 (a, b) || c -> (a, b || c)
 

Parameters:

expression - an OR JBinaryExpression to be simplified.

Returns:

the simplified expression if a simplification was possible; exp otherwise.