The server compiler replaces the expression "(x & -32) / 2" by "x >> 1" which is not correct. Actually it's ok to replace the division by a right shift, but the removal of the "and operation" is not correct.


1) Test program

DivIdealizeAndMinus32FollowedByDivConst2Bug.java:

public class DivIdealizeAndMinus32FollowedByDivConst2Bug {

    public static void main(String[] args) {
        long iteration = 0;
        while (true) {
            iteration++;
            int result = andMinus32FollowedByDivConst2(255);
            if (result != 112) {
                System.out.println("expected 112, but got " + result + " after iteration " + iteration);
                System.exit(-1);
            }
        }
    }

    private static int andMinus32FollowedByDivConst2(int x) {
        return (x & -32) / 2;
    }

}


2) Output of the test program on linux-x86_64

$ bin/java -showversion -classpath tests -server -XX:-UseOnStackReplacement -XX:+PrintCompilation DivIdealizeAndMinus32FollowedByDivConst2Bug

java version "1.6.0_17"
Java(TM) SE Runtime Environment (build 1.6.0_17-b04)
Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01, mixed mode)

  1       DivIdealizeAndMinus32FollowedByDivConst2Bug::andMinus32FollowedByDivConst2 (7 bytes)
expected 112, but got 127 after iteration 171644