Sorry, reading back in different surroundings made me notice a couple
of silly errors:
Richard Sandiford <rdsandif...@googlemail.com> writes:
> E.g.:
>
> if ((*loc = get_equiv_substitution (reg)) != reg)
> ...as above...
> if (*loc != reg || !in_class_p (reg, cl, &new_class))
> ...as above...
> else if (new_class != NO_REGS && rclass != new_class)
> change_class (regno, new_class, " Change", true);
> return change_p;
>
> (assuming change to in_class_p suggested earlier) seems like it
> covers the same cases.
...but that same in_class_p change means that the "rclass != new_class"
condition isn't needed. I.e.
if ((*loc = get_equiv_substitution (reg)) != reg)
...as above...
if (*loc != reg || !in_class_p (reg, cl, &new_class))
...as above...
else if (new_class != NO_REGS)
change_class (regno, new_class, " Change", true);
return change_p;
>> + if (operand_reg[nop] != NULL_RTX)
>> + {
>> + int last_reload = (lra_reg_info[ORIGINAL_REGNO
>> + (operand_reg[nop])]
>> + .last_reload);
>> +
>> + if (last_reload > bb_reload_num)
>> + reload_sum += last_reload;
>> + else
>> + reload_sum += bb_reload_num;
>
> The comment for reload_sum says:
>
>> +/* Overall number reflecting distances of previous reloading the same
>> + value. It is used to improve inheritance chances. */
>> +static int best_reload_sum;
>
> which made me think of distance from the current instruction. I see
> it's actually something else, effectively a sum of instruction numbers.
>
> I assumed the idea was to prefer registers that were reloaded more
> recently (closer the current instruction). In that case I thought that,
> for a distance-based best_reload_sum, smaller would be better,
> while for an instruction-number-based best_reload_sum, larger would
> be better. It looks like we use instruction-number based best_reload_sums
> but prefer smaller sums:
>
>> + && (reload_nregs < best_reload_nregs
>> + || (reload_nregs == best_reload_nregs
>> + && best_reload_sum < reload_sum))))))))
>
> Is that intentional?
Clearly I can't read. The code _does_ prefer higher numbers. I still
think "distance" is a bit misleading though. :-)
Just for the record, the rest of my question:
> Also, is this value meaningful for output reloads, which aren't really
> going to be able to inherit a value as such? We seem to apply the cost
> regardless of whether it's an input or an output, so probably deserves
> a comment.
>
> Same for matched input operands, which as you say elsewhere aren't
> inherited.
still applies.
Richard
