7110586: C2 generates incorrect results

Summary: Exact limit of empty loop calculated incorrectly.
Reviewed-by: iveresov, never

src/share/vm/opto/loopnode.cpp

@@ -715,7 +715,6 @@ Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
     long limit_con = cl->limit()->get_int();
     julong trip_cnt = cl->trip_count();
     long final_con = init_con + trip_cnt*stride_con;
-    final_con -= stride_con;
     int final_int = (int)final_con;
     // The final value should be in integer range since the loop
     // is counted and the limit was checked for overflow.

test/compiler/7110586/Test7110586.java

+/*
+ * Copyright (c) 2011, 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 7110586
+ * @summary C2 generates icorrect results
+ *
+ * @run main/othervm -Xbatch Test7110586
+ */
+
+public class Test7110586 {
+  static int test1() {
+    int i = 0;
+    for ( ; i < 11; i+=1) {}
+    return i;
+  }
+  static int test2() {
+    int i = 0;
+    for ( ; i < 11; i+=2) {}
+    return i;
+  }
+  static int test3() {
+    int i = 0;
+    for ( ; i < 11; i+=3) {}
+    return i;
+  }
+  static int test11() {
+    int i = 0;
+    for ( ; i < 11; i+=11) {}
+    return i;
+  }
+
+  static int testm1() {
+    int i = 0;
+    for ( ; i > -11; i-=1) {}
+    return i;
+  }
+  static int testm2() {
+    int i = 0;
+    for ( ; i > -11; i-=2) {}
+    return i;
+  }
+  static int testm3() {
+    int i = 0;
+    for ( ; i > -11; i-=3) {}
+    return i;
+  }
+  static int testm11() {
+    int i = 0;
+    for ( ; i > -11; i-=11) {}
+    return i;
+  }
+
+  public static void main(String args[]) {
+    int x1  = 0;
+    int x2  = 0;
+    int x3  = 0;
+    int x11 = 0;
+    int m1  = 0;
+    int m2  = 0;
+    int m3  = 0;
+    int m11 = 0;
+    for (int i=0; i<10000; i++) {
+      x1  = test1();
+      x2  = test2();
+      x3  = test3();
+      x11 = test11();
+      m1  = testm1();
+      m2  = testm2();
+      m3  = testm3();
+      m11 = testm11();
+    }
+    boolean failed = false;
+    if (x1 != 11) {
+      System.out.println("ERROR (incr = +1): " + x1 + " != 11");
+      failed = true;
+    }
+    if (x2 != 12) {
+      System.out.println("ERROR (incr = +2): " + x2 + " != 12");
+      failed = true;
+    }
+    if (x3 != 12) {
+      System.out.println("ERROR (incr = +3): " + x3 + " != 12");
+      failed = true;
+    }
+    if (x11 != 11) {
+      System.out.println("ERROR (incr = +11): " + x11 + " != 11");
+      failed = true;
+    }
+    if (m1 != -11) {
+      System.out.println("ERROR (incr = -1): " + m1 + " != -11");
+      failed = true;
+    }
+    if (m2 != -12) {
+      System.out.println("ERROR (incr = -2): " + m2 + " != -12");
+      failed = true;
+    }
+    if (m3 != -12) {
+      System.out.println("ERROR (incr = -3): " + m3 + " != -12");
+      failed = true;
+    }
+    if (m11 != -11) {
+      System.out.println("ERROR (incr = -11): " + m11 + " != -11");
+      failed = true;
+    }
+    if (failed) {
+      System.exit(97);
+    }
+  }
+}