A reload inheritance bug

[Mark Shinwell]

Bernd Schmidt wrote:
>>  My gut feeling is that this example will work as a consequence.
> 
> ... note that I inserted <some other insn> which could conceivably use
> R9 as an input reload, as the hard reg is dead.  Where would we
> invalidate previous information about R9?  I assume it would be the loop
> at the end of emit_reload_insns, specifically
> 
>               /* First, clear out memory of what used to be in this
> spill reg.
>                  If consecutive registers are used, clear them all.  */
> 
>               for (k = 0; k < nr; k++)
>                 {
>                 CLEAR_HARD_REG_BIT (reg_reloaded_valid, i + k);
>                   CLEAR_HARD_REG_BIT (reg_reloaded_call_part_clobbered,
> i + k);
> 
> Why isn't this triggering?

This code is guarded by

       /* I is nonneg if this reload used a register.
	 If rld[r].reg_rtx is 0, this is an optional reload
	 that we opted to ignore.  */

       if (i >= 0 && rld[r].reg_rtx != 0)

and in this [my original] case, i is negative (see my original patch).

I don't understand the "I is nonneg ..." comment above: the surrounding
code seems to say that i is actually non-negative if the reload used a
_spill_ register (rather than just any register).  Bernd, could you
clarify the precise meaning of "spill register" in this context?  I've
not yet managed to completely pin this down.

Mark