test/compiler/codegen/IntRotateWithImmediate.java

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/*
 * @test
 * @bug 8080190
 * @key regression
 * @summary Test that the rotate distance used in the rotate instruction is properly masked with 0x1f
 * @run main/othervm -Xbatch -XX:-UseOnStackReplacement IntRotateWithImmediate
 * @author volker.simonis@gmail.com
 */

public class IntRotateWithImmediate {

  // This is currently the same as Integer.rotateRight()
  static int rotateRight(int i, int distance) {
    // On some architectures (i.e. x86_64 and ppc64) the following computation is
    // matched in the .ad file into a single MachNode which emmits a single rotate
    // machine instruction. It is important that the shift amount is masked to match
    // corresponding immediate width in the native instruction. On x86_64 the rotate
    // left instruction ('rol') encodes an 8-bit immediate while the corresponding
    // 'rotlwi' instruction on Power only encodes a 5-bit immediate.
    return ((i >>> distance) | (i << -distance));
  }

  static int compute(int x) {
    return rotateRight(x, 3);
  }

  public static void main(String args[]) {
    int val = 4096;

    int firstResult = compute(val);

    for (int i = 0; i < 100000; i++) {
      int newResult = compute(val);
      if (firstResult != newResult) {
        throw new InternalError(firstResult + " != " + newResult);
      }
    }
    System.out.println("OK");
  }

}