Legitimize address after reload

[Jeff Law]

On 03/14/14 05:52, David Guillen wrote:
> Hello,
>
> I'm writing a simple gcc backend and I'm experiencing a weird thing
> regarding address legitimation process. Two scenarios:
>
> If I only allow addresses to be either a register or symbols my gcc
> works. To do so I add the restrictions into the
> TARGET_LEGITIMATE_ADDRESS_P macro. This makes gcc to force registers
> for all the addresses.
>
> If I allow also a 'PLUS' expression to be a valid address (adding the
> restriction that the two addends are a register and a constant) it
> happens (sometimes) that gcc comes up with an expression like this
> one:
>
>       (plus:SI (plus:SI (reg:SI somereg)
>        (const_int 4))
>       (const_int 8))
>
>
> After taking a look at the 386 backend (and others) I just discovered
> that there is a function called LEGITIMIZE_RELOAD_ADDRESS which is
> responsible for handling this case. My issue is that this function is
> not being called and, from what I saw while debugging, it seems that
> the offending RTX expression is created after the address_reload pass,
> and thus impossible for this pass to legitimize the address.
>
> Looking at other architectures it seems that they are doing more or
> less the same, so I don't know what the issue might be.
LEGITIMIZE_RELOAD_ADDRESS is a hook that allows the target to rewrite 
invalid addresses during the reload pass in such a way that reload can 
generate the address more efficiently than the generic code in reload 
can do.

It should always be safe for LEGITIMIZE_RELOAD_ADDRESS to do nothing. 
For your problem I'm sure it's a total red herring.

Jeff