Re: [Jamvm-general] Data Alignment of a double precision float

[Donald G. <don...@gm...>]

Hi Rob,

We tested JamVM 1.5.2 on our MIPS box.
But it seems that we still have the trouble on 8-byte-unaligned double data.
It could not be from your JVM.
If you're still interested in any testing on the MIPS box,
we're ready to provide a login onto our development server.
You can access to the MIPS box from the server.

Donald

2008/12/13 Robert Lougher <rob...@gm...>

> Hi Donald,
>
> Yes, there may be other more subtle ones lurking in the code.  I'm
> quite keen to fix the "8-byte aligned double" issues once and for all.
>  I've actually realised I do have a machine -- an old UltraSparc IIi
> -- although it's 64-bit, Ubuntu has a 32-bit userland (the problem
> only occurs on 32-bit machines) but I need to port JamVM to Sparc
> first.  Alternatively, is it possible to provide a login onto your
> MIPS box?
>
> Rob.
>
> but it's difficult without a machine that requires it.
>
> 2008/12/12 Donald Gim <don...@gm...>:
> > Thank you for your reply.
> >
> > I tried the recent Jamvm with the recent Classpath CVS version.
> > I still got the Bus Error from the 'double' data alignment.
> >
> > The following code is from src/jni:798.
> > This has the possibility of causing the alignment exception if
> > 'native_type' is 'double'.
> > Actually I ran into the issue at this part.
> >
> > #define GET_STATIC_FIELD(type, native_type) \
> >  native_type Jam_GetStatic##type##Field(JNIEnv *env, jclass clazz,
> > jfieldID fieldID) { \
> >     FieldBlock *fb = (FieldBlock *) fieldID; \
> >     return *(native_type *)&fb->static_value; \
> >  }
> >
> > So I did a little tweak on the FieldBlock structure like below.
> > And I could avoid the SIGBUS at this part.
> > But I still got the Bus Error messages from other places.
> > Should I continue tracing the source?
> > The case below may be simple. But I guess there could be codes which
> > are difficult to modify structurally.
> > Please give me any hints...
> >
> > thanks,
> > ddgim
> >
> >  512 typedef struct fieldblock {
> >  513    double dummy_align;        <=== added
> >  514    Class *class;
> >  515    char *name;
> >  516    char *type;
> >  517    char *signature;
> >  518    u2 access_flags;
> >  519    u2 constant;
> >  520    int dummy_pad;              <=== added
> >  521    uintptr_t static_value;
> >  522    u4 offset;
> >  523    AnnotationData *annotations;
> >  524 } FieldBlock;
> >
> >
> > 2008/12/12, Robert Lougher <rob...@gm...>:
> >> P.S.  When using source from CVS, you need to run autogen.sh (in the
> >> top level) to generate all the configure stuff.  You can give your
> >> configure arguments to autogen.sh, which will run configure for you,
> >> once all the autconf/automake/libtool stuff has been done.
> >>
> >> Rob.
> >>
> >> 2008/12/11 Robert Lougher <rob...@gm...>:
> >>> Hi Donald,
> >>>
> >>> 2008/12/11 Donald Gim <don...@gm...>:
> >>>> Hello,
> >>>>
> >>>> I'm working on a MIPS SoC with the floating-point coprocessor.
> >>>> It requires an 8-byte aligned address to access to 'double' data.
> >>>> Jamvm includes codes which try to access 'double' data without
> >>>> 8-byte-aligned addresses.
> >>>> They cause 'Bus Error' on the SoC.
> >>>> How could I work around it.
> >>>>
> >>>
> >>> Try the latest development version from CVS.  Instructions to get it
> are
> >>> here:
> >>>
> >>> http://developer.berlios.de/cvs/?group_id=6545
> >>>
> >>> There's been quite a bit of alignment work since 1.5.1, and doubles
> >>> should now always be 8-byte aligned.  However, I can't guarantee it
> >>> will work, as I don't have a machine which requires it...
> >>>
> >>> Rob.
> >>>
> >>>> Thanks,
> >>>> ddgim
> >>>>
> >>>>
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> >>
> >
>