Added in a couple of new optimizations:
1) Conditional expressions where the test expression is a boolean literal.
2) Equality tests where both operands are statically null.
Also performed some minor style cleanup.
Review by: mmendez
git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@404 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/dev/core/src/com/google/gwt/dev/jjs/impl/DeadCodeElimination.java b/dev/core/src/com/google/gwt/dev/jjs/impl/DeadCodeElimination.java
index 6c6176d..b2c24a3 100644
--- a/dev/core/src/com/google/gwt/dev/jjs/impl/DeadCodeElimination.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/impl/DeadCodeElimination.java
@@ -21,6 +21,7 @@
import com.google.gwt.dev.jjs.ast.JBlock;
import com.google.gwt.dev.jjs.ast.JBooleanLiteral;
import com.google.gwt.dev.jjs.ast.JBreakStatement;
+import com.google.gwt.dev.jjs.ast.JConditional;
import com.google.gwt.dev.jjs.ast.JContinueStatement;
import com.google.gwt.dev.jjs.ast.JDoStatement;
import com.google.gwt.dev.jjs.ast.JExpression;
@@ -54,45 +55,60 @@
* Short circuit boolean AND or OR expressions when possible.
*/
public void endVisit(JBinaryOperation x, Context ctx) {
- if (x.getOp() == JBinaryOperator.AND) {
+ JBinaryOperator op = x.getOp();
+ JExpression lhs = x.getLhs();
+ JExpression rhs = x.getRhs();
+ if (op == JBinaryOperator.AND) {
// simplify short circuit AND expressions
- if (x.getLhs() instanceof JBooleanLiteral) {
+ if (lhs instanceof JBooleanLiteral) {
// eg: if (false && isWhatever()) -> if (false)
// eg: if (true && isWhatever()) -> if (isWhatever())
- JBooleanLiteral booleanLiteral = (JBooleanLiteral) x.getLhs();
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) lhs;
if (booleanLiteral.getValue()) {
- ctx.replaceMe(x.getRhs());
+ ctx.replaceMe(rhs);
} else {
- ctx.replaceMe(x.getLhs());
+ ctx.replaceMe(lhs);
}
- } else if (x.getRhs() instanceof JBooleanLiteral) {
+ } else if (rhs instanceof JBooleanLiteral) {
// eg: if (isWhatever() && true) -> if (isWhatever())
- JBooleanLiteral booleanLiteral = (JBooleanLiteral) x.getRhs();
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) rhs;
if (booleanLiteral.getValue()) {
- ctx.replaceMe(x.getLhs());
+ ctx.replaceMe(lhs);
}
}
- } else if (x.getOp() == JBinaryOperator.OR) {
+ } else if (op == JBinaryOperator.OR) {
// simplify short circuit OR expressions
- if (x.getLhs() instanceof JBooleanLiteral) {
+ if (lhs instanceof JBooleanLiteral) {
// eg: if (true || isWhatever()) -> if (true)
// eg: if (false || isWhatever()) -> if (isWhatever())
- JBooleanLiteral booleanLiteral = (JBooleanLiteral) x.getLhs();
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) lhs;
if (booleanLiteral.getValue()) {
- ctx.replaceMe(x.getLhs());
+ ctx.replaceMe(lhs);
} else {
- ctx.replaceMe(x.getRhs());
+ ctx.replaceMe(rhs);
}
- } else if (x.getRhs() instanceof JBooleanLiteral) {
+ } else if (rhs instanceof JBooleanLiteral) {
// eg: if (isWhatever() || false) -> if (isWhatever())
- JBooleanLiteral booleanLiteral = (JBooleanLiteral) x.getRhs();
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) rhs;
if (!booleanLiteral.getValue()) {
- ctx.replaceMe(x.getLhs());
+ ctx.replaceMe(lhs);
}
}
+ } else if (op == JBinaryOperator.EQ) {
+ // simplify: null == null -> true
+ if (lhs.getType() == program.getTypeNull()
+ && rhs.getType() == program.getTypeNull()) {
+ ctx.replaceMe(program.getLiteralBoolean(true));
+ }
+ } else if (op == JBinaryOperator.NEQ) {
+ // simplify: null != null -> false
+ if (lhs.getType() == program.getTypeNull()
+ && rhs.getType() == program.getTypeNull()) {
+ ctx.replaceMe(program.getLiteralBoolean(false));
+ }
}
}
@@ -107,13 +123,28 @@
}
}
+ public void endVisit(JConditional x, Context ctx) {
+ JExpression expression = x.getIfTest();
+ if (expression instanceof JBooleanLiteral) {
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
+
+ if (booleanLiteral.getValue()) {
+ // If true, replace myself with then expression
+ ctx.replaceMe(x.getThenExpr());
+ } else {
+ // If false, replace myself with else expression
+ ctx.replaceMe(x.getElseExpr());
+ }
+ }
+ }
+
/**
* Convert do { } while (false); into a block.
*/
public void endVisit(JDoStatement x, Context ctx) {
- final JExpression expression = x.getTestExpr();
+ JExpression expression = x.getTestExpr();
if (expression instanceof JBooleanLiteral) {
- final JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
// If false, replace do with do's body
if (!booleanLiteral.getValue()) {
@@ -131,9 +162,9 @@
* Prune for (X; false; Y) statements, but make sure X is run.
*/
public void endVisit(JForStatement x, Context ctx) {
- final JExpression expression = x.getTestExpr();
+ JExpression expression = x.getTestExpr();
if (expression instanceof JBooleanLiteral) {
- final JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
// If false, replace the for statement with its initializers
if (!booleanLiteral.getValue()) {
@@ -148,9 +179,9 @@
* Prune "if (false)" statements.
*/
public void endVisit(JIfStatement x, Context ctx) {
- final JExpression expression = x.getIfExpr();
+ JExpression expression = x.getIfExpr();
if (expression instanceof JBooleanLiteral) {
- final JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
if (booleanLiteral.getValue()) {
// If true, replace myself with then statement
@@ -219,9 +250,9 @@
* Prune while (false) statements.
*/
public void endVisit(JWhileStatement x, Context ctx) {
- final JExpression expression = x.getTestExpr();
+ JExpression expression = x.getTestExpr();
if (expression instanceof JBooleanLiteral) {
- final JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
+ JBooleanLiteral booleanLiteral = (JBooleanLiteral) expression;
// If false, prune the while statement
if (!booleanLiteral.getValue()) {
