reload question about unmet constraints

[Ulrich Weigand]

DJ Delorie wrote:

> For such constraints that are memory operands but not
> define_memory_constraint, you need to use '*' to keep reload from
> trying to guess a register class from them (it guesses wrong for
> rl78).
> 
> I.e. use "*Wfr" instead of "Wfr".

Huh?  That seems weird.  It should make no difference for purposes
of register class preferences whether a constraint is marked as
memory constraint or extra constraint: neither contributes to
register class preferences at all.

If the '*' makes any difference, I guess this can only be because
IRA chooses another alternative for the insn to begin with.

Do you have an example that shows the problem?

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com