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/*
 * @test TestIntegerComparison
 * @bug 8043284 8042786
 * @summary "Tests optimizations of signed and unsigned integer comparison."
 * @run main/othervm -server -Xcomp -XX:+IgnoreUnrecognizedVMOptions -XX:-TieredCompilation -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);
    }
  }
}