changeset 2666:76b58486b9d5

8060249: Backout fix for JDK-8058243 Reviewed-by: vromero
author pgovereau
date Mon, 13 Oct 2014 17:09:12 -0400
parents 9e6a9d5a3551
children 103d3df93bbd
files src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Gen.java test/tools/javac/SwitchMetricTest.java
diffstat 2 files changed, 11 insertions(+), 96 deletions(-) [+]
line wrap: on
line diff
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/Gen.java	Mon Oct 13 12:12:06 2014 -0400
+++ b/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/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");
-    }
-}