Re: [wip/cagney_regbuf-20020515-branch] Introduce regcache_move()

Richard Earnshaw
2002-05-19T14:47:49Z

> There is a ``work around'' for this immediate problem.
>
> I'm going to add a register_bytes() method to regcache that makes the [0
> .. NUM_REGS + NUM_PSEUDO_REGS) contigious and returns an offset based on
> that assumption.
>
> write_register_bytes(), with the suggested change, will convert the
> offset back to a regnum and call write_register_gen() with that.

Hmm, so each pseudo would allocate a unique address even though there was
no real regbuf space for it; something like

0 4 4*(n-1) 4*n 4*(n+1) ...
+---------+---------+ +---------+---------+---------+
| Phys r0 | Phys r1 | ... | Phys rn | Pseu r0 | Pseu r1 |
+---------+---------+ +---------+---------+---------+
| REGBUF ... |
+-------------------- ----------+

Then each reg would have a unique address. Provided we always call
through the correct interfaces, and never use

memcpy (grub_around...registers() + REGISTER_BYTE(PseudoN), ...)

then this would work.

> Rock warning: GDB uses the above to handle (with limited success) values
> that cross two registers. For instance a long long in two adjacent long
> registers. See value_from_register().

I've been told ARM's own C compiler can put long longs in non-adjacent
register pairs. At some point I will need to support that... it will
probably mean being able to read from some ordered list of registers, or
some such.

R.