Author: sco...@google.com
Date: Thu Jun 11 12:08:45 2009
New Revision: 5540
Modified:
trunk/dev/core/src/com/google/gwt/dev/js/JsStaticEval.java
trunk/dev/core/test/com/google/gwt/dev/js/JsStaticEvalTest.java
Log:
JsStaticEval now optimizes certain if statements to conditional operators.
if (a()) {b()} else {c()} -> a()?b():c()
if (a()) {b()} -> a()&&b()
if (a()) {} else {b()} -> a()||b()
Patch by: mmastrac
Suggested by: me
Review by: me
Modified: trunk/dev/core/src/com/google/gwt/dev/js/JsStaticEval.java
==============================================================================
--- trunk/dev/core/src/com/google/gwt/dev/js/JsStaticEval.java (original)
+++ trunk/dev/core/src/com/google/gwt/dev/js/JsStaticEval.java Thu Jun 11
12:08:45 2009
@@ -352,32 +352,50 @@
} else {
boolean thenIsEmpty = isEmpty(thenStmt);
boolean elseIsEmpty = isEmpty(elseStmt);
-
+ JsExpression thenExpr = extractExpression(thenStmt);
+ JsExpression elseExpr = extractExpression(elseStmt);
+
if (thenIsEmpty && elseIsEmpty) {
+ // Convert "if (a()) {}" => "a()".
ctx.replaceMe(expr.makeStmt());
+ } else if (thenExpr != null && elseExpr != null) {
+ // Convert "if (a()) {b()} else {c()}" => "a()?b():c()".
+ sourceInfo = x.getSourceInfo().makeChild(StaticEvalVisitor.class,
+ "Replaced if statement with conditional");
+
+ JsConditional cond = new JsConditional(sourceInfo, x.getIfExpr(),
+ thenExpr, elseExpr);
+ ctx.replaceMe(accept(cond.makeStmt()));
+ } else if (thenIsEmpty && elseExpr != null) {
+ // Convert "if (a()) {} else {b()}" => a()||b().
+ sourceInfo = x.getSourceInfo().makeChild(StaticEvalVisitor.class,
+ "Replaced if statement with ||");
+
+ JsBinaryOperation op = new JsBinaryOperation(sourceInfo,
+ JsBinaryOperator.OR, x.getIfExpr(), elseExpr);
+ ctx.replaceMe(accept(op.makeStmt()));
} else if (thenIsEmpty && !elseIsEmpty) {
- /*
- * If the then block is blank, but the else statement has
statements,
- * invert the test
- */
+ // Convert "if (a()) {} else {stuff}" => "if (!a()) {stuff}".
sourceInfo = x.getSourceInfo().makeChild(StaticEvalVisitor.class,
"Simplified if with empty then statement");
JsUnaryOperation negatedOperation = new
JsPrefixOperation(sourceInfo,
JsUnaryOperator.NOT, x.getIfExpr());
JsIf newIf = new JsIf(sourceInfo, negatedOperation, elseStmt,
null);
-
ctx.replaceMe(accept(newIf));
+ } else if (elseIsEmpty && thenExpr != null) {
+ // Convert "if (a()) {b()}" => "a()&&b()".
+ sourceInfo = x.getSourceInfo().makeChild(StaticEvalVisitor.class,
+ "Replaced if statement with &&");
+
+ JsBinaryOperation op = new JsBinaryOperation(sourceInfo,
+ JsBinaryOperator.AND, x.getIfExpr(), thenExpr);
+ ctx.replaceMe(accept(op.makeStmt()));
} else if (elseIsEmpty && elseStmt != null) {
- /*
- * If the else statement is present but has no effective
statements,
- * prune it
- */
+ // Convert "if (a()) {b()} else {}" => "if (a()) {b()}".
sourceInfo = x.getSourceInfo().makeChild(StaticEvalVisitor.class,
"Pruned empty else statement");
-
JsIf newIf = new JsIf(sourceInfo, x.getIfExpr(), thenStmt, null);
-
ctx.replaceMe(accept(newIf));
}
}
@@ -583,6 +601,26 @@
public static boolean exec(JsProgram program) {
return (new JsStaticEval(program)).execImpl();
+ }
+
+ /**
+ * Attempts to extract a single expression from a given statement and
returns
+ * it. If no such expression exists, returns <code>null</code>.
+ */
+ protected static JsExpression extractExpression(JsStatement stmt) {
+ if (stmt == null) {
+ return null;
+ }
+
+ if (stmt instanceof JsExprStmt) {
+ return ((JsExprStmt) stmt).getExpression();
+ }
+
+ if (stmt instanceof JsBlock && ((JsBlock) stmt).getStatements().size()
== 1) {
+ return extractExpression(((JsBlock) stmt).getStatements().get(0));
+ }
+
+ return null;
}
protected static boolean isEmpty(JsStatement stmt) {
Modified: trunk/dev/core/test/com/google/gwt/dev/js/JsStaticEvalTest.java
==============================================================================
--- trunk/dev/core/test/com/google/gwt/dev/js/JsStaticEvalTest.java
(original)
+++ trunk/dev/core/test/com/google/gwt/dev/js/JsStaticEvalTest.java Thu Jun
11 12:08:45 2009
@@ -33,8 +33,13 @@
assertEquals("a();", optimize("if (a()) { }"));
}
+ public void testIfWithEmptyThenAndElseExpression() throws Exception {
+ assertEquals("a()||b();", optimize("if (a()) { } else { b(); }"));
+ }
+
public void testIfWithEmptyThenAndElse() throws Exception {
- assertEquals("if(!a()){b()}", optimize("if (a()) { } else { b(); }"));
+ assertEquals("if(!a()){throw 1}",
+ optimize("if (a()) { } else { throw 1; }"));
}
public void testIfWithEmptyThenAndEmptyElse() throws Exception {
@@ -42,7 +47,21 @@
}
public void testIfWithThenAndEmptyElse() throws Exception {
- assertEquals("if(a()){b()}", optimize("if (a()) { b() } else { }"));
+ assertEquals("if(a()){throw 1}", optimize("if (a()) { throw 1; } else
{ }"));
+ }
+
+ public void testIfWithThenExpressionAndEmptyElse() throws Exception {
+ assertEquals("a()&&b();", optimize("if (a()) { b() } else { }"));
+ }
+
+ public void testIfWithThenExpressionAndElseExpression() throws Exception
{
+ assertEquals("a()?b():c();", optimize("if (a()) { b() } else { c();
}"));
+ }
+
+ public void testIfWithThenExpressionAndElseStatement() throws Exception {
+ // This can't be optimized further
+ assertEquals("if(a()){b()}else{throw 1}",
+ optimize("if (a()) { b() } else { throw 1; }"));
}
public void testLiteralEqNull() throws Exception {
@@ -66,13 +85,13 @@
List<JsStatement> expected = JsParser.parse(SourceOrigin.UNKNOWN,
program.getScope(), new StringReader(js));
program.getGlobalBlock().getStatements().addAll(expected);
-
+
// Run the static evaluation over this new program
JsStaticEval.exec(program);
TextOutput text = new DefaultTextOutput(true);
JsVisitor generator = new JsSourceGenerationVisitor(text);
-
+
generator.accept(program);
return text.toString();
}
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http://groups.google.com/group/Google-Web-Toolkit-Contributors
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