diff --git a/src/share/vm/runtime/sharedRuntime.cpp b/src/share/vm/runtime/sharedRuntime.cpp
index 76067dc8ee1f89f8164c326978ab03cd349ac0dc..cf69631c0bb35ed740c4f91ed3a5be833c58816d 100644
--- a/src/share/vm/runtime/sharedRuntime.cpp
+++ b/src/share/vm/runtime/sharedRuntime.cpp
@@ -192,64 +192,46 @@ JRT_END
 
 
 JRT_LEAF(jint, SharedRuntime::f2i(jfloat  x))
-  if (g_isnan(x)) {return 0;}
-  jlong lltmp = (jlong)x;
-  jint ltmp   = (jint)lltmp;
-  if (ltmp == lltmp) {
-    return ltmp;
-  } else {
-    if (x < 0) {
-      return min_jint;
-    } else {
-      return max_jint;
-    }
-  }
+  if (g_isnan(x))
+    return 0;
+  if (x >= (jfloat) max_jint)
+    return max_jint;
+  if (x <= (jfloat) min_jint)
+    return min_jint;
+  return (jint) x;
 JRT_END
 
 
 JRT_LEAF(jlong, SharedRuntime::f2l(jfloat  x))
-  if (g_isnan(x)) {return 0;}
-  jlong lltmp = (jlong)x;
-  if (lltmp != min_jlong) {
-    return lltmp;
-  } else {
-    if (x < 0) {
-      return min_jlong;
-    } else {
-      return max_jlong;
-    }
-  }
+  if (g_isnan(x))
+    return 0;
+  if (x >= (jfloat) max_jlong)
+    return max_jlong;
+  if (x <= (jfloat) min_jlong)
+    return min_jlong;
+  return (jlong) x;
 JRT_END
 
 
 JRT_LEAF(jint, SharedRuntime::d2i(jdouble x))
-  if (g_isnan(x)) {return 0;}
-  jlong lltmp = (jlong)x;
-  jint ltmp   = (jint)lltmp;
-  if (ltmp == lltmp) {
-    return ltmp;
-  } else {
-    if (x < 0) {
-      return min_jint;
-    } else {
-      return max_jint;
-    }
-  }
+  if (g_isnan(x))
+    return 0;
+  if (x >= (jdouble) max_jint)
+    return max_jint;
+  if (x <= (jdouble) min_jint)
+    return min_jint;
+  return (jint) x;
 JRT_END
 
 
 JRT_LEAF(jlong, SharedRuntime::d2l(jdouble x))
-  if (g_isnan(x)) {return 0;}
-  jlong lltmp = (jlong)x;
-  if (lltmp != min_jlong) {
-    return lltmp;
-  } else {
-    if (x < 0) {
-      return min_jlong;
-    } else {
-      return max_jlong;
-    }
-  }
+  if (g_isnan(x))
+    return 0;
+  if (x >= (jdouble) max_jlong)
+    return max_jlong;
+  if (x <= (jdouble) min_jlong)
+    return min_jlong;
+  return (jlong) x;
 JRT_END
 
 
diff --git a/test/compiler/6778657/Test.java b/test/compiler/6778657/Test.java
new file mode 100644
index 0000000000000000000000000000000000000000..4fdd33e93868fab350c2bc9d2b1f3ddd4afecfcf
--- /dev/null
+++ b/test/compiler/6778657/Test.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+/*
+ * @test
+ * @bug 6778657
+ * @summary Casts in SharedRuntime::f2i, f2l, d2i and d2l rely on undefined C++ behaviour
+ */
+
+public class Test {
+  public static void check_f2i(int expect) {
+    float check = expect;
+    check *= 2;
+    int actual = (int) check;
+    if (actual != expect)
+      throw new RuntimeException("expecting " + expect + ", got " + actual);
+  }
+
+  public static void check_f2l(long expect) {
+    float check = expect;
+    check *= 2;
+    long actual = (long) check;
+    if (actual != expect)
+      throw new RuntimeException("expecting " + expect + ", got " + actual);
+  }
+
+  public static void check_d2i(int expect) {
+    double check = expect;
+    check *= 2;
+    int actual = (int) check;
+    if (actual != expect)
+      throw new RuntimeException("expecting " + expect + ", got " + actual);
+  }
+
+  public static void check_d2l(long expect) {
+    double check = expect;
+    check *= 2;
+    long actual = (long) check;
+    if (actual != expect)
+      throw new RuntimeException("expecting " + expect + ", got " + actual);
+  }
+
+  public static void main(String[] args) {
+    check_f2i(Integer.MAX_VALUE);
+    check_f2i(Integer.MIN_VALUE);
+    check_f2l(Long.MAX_VALUE);
+    check_f2l(Long.MIN_VALUE);
+    check_d2i(Integer.MAX_VALUE);
+    check_d2i(Integer.MIN_VALUE);
+    check_d2l(Long.MAX_VALUE);
+    check_d2l(Long.MIN_VALUE);
+  }
+}
+