java aliasing rules

[Dan Nicolaescu]

Given this code:

class first  {  int i; char a;  char f1;  char f2; double d;};
class second {  char b;  char f2;  int f3;};


public class t
{
    public  void f (first  ps1, second ps2)
    {
        ps1.f1++;
        ps2.f2++;
        ps1.f1++;
        ps2.f2++;
    }
}

can it be assumed that given that "first" and "second" are
incompatible then ps1.f1 and ps2.f2 don't alias and we can generate
code like the following: (SPARC assembly)

        !#PROLOGUE# 0
        !#PROLOGUE# 1
        lduh    [%o1+14], %o0
        lduh    [%o2+10], %o3
        add     %o0, 2, %o0
        add     %o3, 2, %o3
        sth     %o0, [%o1+14]
        retl
        sth     %o3, [%o2+10]

instead of what is generated now: 

        !#PROLOGUE# 0
        !#PROLOGUE# 1
        lduh    [%o1+14], %o3
        add     %o3, 1, %o3
        sth     %o3, [%o1+14]
        lduh    [%o2+10], %o0
        add     %o0, 1, %o0
        sth     %o0, [%o2+10]
        lduh    [%o1+14], %o3
        add     %o3, 1, %o3
        sth     %o3, [%o1+14]
        lduh    [%o2+10], %o0
        add     %o0, 1, %o0
        retl
        sth     %o0, [%o2+10]


The more general question is if 2 COMPONENT_REFs that refer to classes
that are in conflicting alias sets (ie alias_sets_conflict_p) alias in
java. I have a hunch that this might be true, but I don't know enough
about java to be sure.  If the above is not true, is there a
restricted case when it is true?


(for the curious this is related to the patch at
http://gcc.gnu.org/ml/gcc-patches/2002-03/msg00576.html that is not
totally correct for C, but I have a hunch that it might be OK for
java, if that is the case I will change the patch to be language
specific).