Re: ARM and virtual/raw registers

[Richard Earnshaw <rearnsha@arm.com>]

> > If, as I understand your previous postings to imply, having pseudo 
> > registers stored in the cache is wrong, why does regcache_read() allow 
> > them?
> > 
> > regcache_read (int rawnum, char *buf)
> > {
> >   gdb_assert (rawnum >= 0 && rawnum < (NUM_REGS + NUM_PSEUDO_REGS));
> 
> Lets just pretend you didn't see that :-)
> Some existing mechanisms store pseudo-register values in the cache.  In 
> addition ``NUM_REGS'' is overloaded - it controls too many aspects of 
> GDB - num regs in G packet, num regs to save across an inferior function 
> call, ...
> 
> Andrew
> 
> 

Argh!  I've just come across another nasty gotcha in this code, if I try 
to make it so that the regcache does not hold any pseudos:  There's an 
implicit assumption that all the physical registers will preceed the 
pseudo registers.

This is a major problem when I want to implement the banked registers for 
the ARM, since then r8 through r14 (which must have regnums 8 through 14 
for stabs debug info to work correctly), need to be pseudo registers (they 
must access the correct physical register for the current processor mode); 
which means they must appear in the middle of the register range.

I can make my arm_register_read function correctly remap the register 
numbers, but then I run into the problem that REGISTER_RAW_SIZE is used 
both above and below the regcache.

Would you be averse to me creating a gdbarch entry for 
REGISTER_REGCACHE_RAW_SIZE (which defaults to REGISTER_RAW_SIZE) and then 
using that when directly accessing the cache?

R.