(Noticed by Joel Rudsberg during manual code inspection.)

Run the following test with:
$ java -Xcomp -XX:-UseBMI2Instructions -XX:CompileCommand=print,BMI.shift -XX:CompileCommand=dontinline,BMI.shift BMI.java

class BMI {
    static int shift(int a, int b) {
        return a >> b;
    }

    public static void main(String[] args) {
        shift(42, 23);
    }
}

Expected: no BMI2 instructions in the generated code

Actual: the generated code contains the BMI2 instruction sarx eax,esi,edx

I believe the reason is that the definition of sarx and other BMI2 instructions in hotspot/cpu/x86/x86_64.ad is guarded by:

  predicate(VM_Version::supports_bmi2());

which only checks the host CPU's flags. In contrast, BMI1 instructions in the same file are guarded by:

  predicate(UseBMI1Instructions);

I believe the fix is to replace the predicates for BMI2 instructions with the corresponding

  predicate(UseBMI2Instructions);

I can put together a PR if someone can confirm that this would be the correct fix.