--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Gen.java Mon Oct 13 12:12:06 2014 -0400
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Gen.java Mon Oct 13 17:09:12 2014 -0400
@@ -1220,14 +1220,17 @@
}
// Determine whether to issue a tableswitch or a lookupswitch
- // instruction. The difference in computation cost is
- // proportional to log(#cases), which is negligable, so we only
- // consider the size of the bytecode.
- // A discussion of the metric can be found here:
- // http://mail.openjdk.java.net/pipermail/compiler-dev/2014-September/008987.html
- long table_cost = 4 + ((long)hi - lo + 1); // words
- long lookup_cost = 3 + 2 * (long)nlabels;
- int opcode = table_cost <= lookup_cost ? tableswitch : lookupswitch;
+ // instruction.
+ long table_space_cost = 4 + ((long) hi - lo + 1); // words
+ long table_time_cost = 3; // comparisons
+ long lookup_space_cost = 3 + 2 * (long) nlabels;
+ long lookup_time_cost = nlabels;
+ int opcode =
+ nlabels > 0 &&
+ table_space_cost + 3 * table_time_cost <=
+ lookup_space_cost + 3 * lookup_time_cost
+ ?
+ tableswitch : lookupswitch;
int startpc = code.curCP(); // the position of the selector operation
code.emitop0(opcode);
--- a/langtools/test/tools/javac/SwitchMetricTest.java Mon Oct 13 12:12:06 2014 -0400
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,88 +0,0 @@
-/*
- * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-/*
- * @test
- * @bug 8058243
- * @summary Reduce size of bytecode for large switch statements
- * @library /tools/lib
- * @build ToolBox
- * @run main SwitchMetricTest
- */
-
-import java.net.URL;
-import java.util.List;
-
-public class SwitchMetricTest {
- public static void main(String... args) throws Exception {
- new SwitchMetricTest().run();
- }
-
- // This code should produce a tableswitch
- class Test1 {
- int m(int x) {
- switch (x) {
- case 1:
- case 2:
- case 3:
- case 4:
- case 5: return 1;
- default: return 0;
- }
- }
- }
-
- // This code should produce a lookupswitch
- class Test2 {
- int m(int x) {
- switch (x) {
- case 1:
- case 2:
- case 3:
- case 4:
- case 50: return 1;
- default: return 0;
- }
- }
- }
-
- void check(String classfile, String bytecode) throws Exception {
- ToolBox tb = new ToolBox();
- URL url = SwitchMetricTest.class.getResource(classfile);
- List<String> result = tb.new JavapTask()
- .options("-c")
- .classes(url.getFile())
- .run()
- .write(ToolBox.OutputKind.DIRECT)
- .getOutputLines(ToolBox.OutputKind.DIRECT);
-
- List<String> matches = tb.grep(bytecode, result);
- if (matches.isEmpty())
- throw new Exception(bytecode + " not found");
- }
-
- void run() throws Exception {
- check("SwitchMetricTest$Test1.class", "tableswitch");
- check("SwitchMetricTest$Test2.class", "lookupswitch");
- }
-}