Re: where are caller-save addresses legitimized?

[Jeff Law <law at redhat dot com>]

On 05/05/10 21:34, Greg McGary wrote:
> On 05/05/10 20:21, Jeff Law wrote:
> > I'm not sure they are ever legitimized -- IIRC caller-save tries to only
> > generate addressing modes which are safe for precisely this reason.
>
> Apparently not so: caller save is quite capable of producing invalid 
> offsets.
> Perhaps my port needs some hook to help GCC produce good addresses?
> I've been looking, but haven't found it yet...

Try != successful :(

You might want to look at his code in init_caller_save:


  /* The following code tries to approximate the conditions under which
     we can easily save and restore a register without scratch registers or
     other complexities.  It will usually work, except under conditions 
where
     the validity of an insn operand is dependent on the address offset.
     No such cases are currently known.

     We first find a typical offset from some BASE_REG_CLASS register.
     This address is chosen by finding the first register in the class
     and by finding the smallest power of two that is a valid offset from
     that register in every mode we will use to save registers.  */