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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 *

 * 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.

 *

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 */

/*

 * @test TestIntegerComparison

 * @bug 8043284 8042786

 * @summary "Tests optimizations of signed and unsigned integer comparison."

 * @run main/othervm -Xcomp -XX:CompileOnly=TestIntegerComparison::testSigned,TestIntegerComparison::testUnsigned TestIntegerComparison

 */

public class TestIntegerComparison {

  /**

   * Tests optimization of signed integer comparison (see BoolNode::Ideal).

   * The body of the if statement is unreachable and should not be compiled.

   * @param c Character (value in the integer range [0, 65535])

   */

  public static void testSigned(char c) {

    // The following addition may overflow. The result is in one

    // of the two ranges [IntMax] and [IntMin, IntMin + CharMax - 1].

    int result = c + Integer.MAX_VALUE;

    // CmpINode has to consider both result ranges instead of only

    // the general [IntMin, IntMax] range to be able to prove that

    // result is always unequal to CharMax.

    if (result == Character.MAX_VALUE) {

      // Unreachable

      throw new RuntimeException("Should not reach here!");

    }

  }

  /**

   * Tests optimization of unsigned integer comparison (see CmpUNode::Value).

   * The body of the if statement is unreachable and should not be compiled.

   * @param c Character (value in the integer range [0, 65535])

   */

  public static void testUnsigned(char c) {

    /*

     * The following if statement consisting of two CmpIs is replaced

     * by a CmpU during optimization (see 'IfNode::fold_compares').

     *

     * The signed (lo < i) and (i < hi) are replaced by the unsigned

     * (i - (lo+1) < hi - (lo+1)). In this case the unsigned comparison

     * equals (result - 2) < 98 leading to the following CmpUNode:

     *

     * CmpU (AddI result, -2) 98

     *

     * With the value of result this is simplified to:

     *

     * CmpU (AddI c, -(CharMax - IntMin)) 98

     *

     * The subtraction may underflow. The result is in one of the two

     * ranges [IntMin], [IntMax - CharMax + 1]. Both ranges have to be

     * considered instead of only the general [IntMin, IntMax] to prove

     * that due to the overflow the signed comparison result < 98 is

     * always false.

     */

    int result = c - (Character.MAX_VALUE - Integer.MIN_VALUE) + 2;

    if (1 < result && result < 100) {

      // Unreachable

      throw new RuntimeException("Should not reach here!");

    }

  }

  /**

   * Tests optimizations of signed and unsigned integer comparison.

   */

  public static void main(String[] args) {

    // We use characters to get a limited integer range for free

    for (int i = Character.MIN_VALUE; i <= Character.MAX_VALUE; ++i) {

      testSigned((char) i);

      testUnsigned((char) i);

    }

  }

}