[wip/cagney_regbuf-20020515-branch] Introduce regcache_move()
Richard Earnshaw
rearnsha@arm.com
Sun May 19 07:47:00 GMT 2002
> 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.
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