Re: assertion failure in regcache.c

[Elena Zannoni <ezannoni at redhat dot com>]

Kris Warkentin writes:
 > >  > I'd start with the obvious thing - a simple tipo in the SH4 register
 > >  > byte function.  The code was written long before these sanity checks
 > >  > were added and ``the old way'' makes it very hard to notice that the
 > >  > values are skewed.
 > >  >
 > >  > Andrew
 > >  >
 > >
 > >
 > > yes, look at sh_sh4_register_byte. Maybe FV0_REGNUM or FV_LAST_REGNUM
 > > are not set correctly or fv_reg_base_num does something wrong. These
 > > registers with (*1) are pseudo registers, so it's easy that the
 > > calculations could have been screwed up.
 > 
 > Well, I found the disagreement.  It looks to me like
 > regcache->descr->register_offset[] is pointing to an upwardly growing list
 > of registers including the pseudo-registers.  So you get something like dr5
 > being 260 in the register_offset array but sh4_register_byte will return 124
 > which would be the offset of fr10 (taking into account that dr0 is overlaid
 > on top of the fr regs).  I'm inclined to think that the regcache way is
 > wrong since someone who updates dr0 and then reads fr0 will get conflicting
 > values.  We shouldn't be storing extra copies of the same register.

Looking at regcache.c I see that the long term goal is to not allocate
space in the regcache for the PSEUDOs. But in the meantime, 
        descr->register_offset[i] = REGISTER_BYTE (i); 
in the legacy init function, while
	descr->sizeof_register[i] = TYPE_LENGTH (descr->register_type[i]);
	descr->register_offset[i] = offset;
	offset += descr->sizeof_register[i];
in the new version of the function.

So the mismatch seems to come from the TYPE_LENGTH() on the type of a
pseudo, because that's always a positive quantity, while the
REGISTER_BYTE points 'backwards'. Maybe we should be using the legacy
version of the regcache init function? Is that doable?

elena


 > 
 > Where do I go from here?
 > 
 > cheers,
 > 
 > Kris