How to define special requirements for an address operand?

[Georg-Johann Lay]

Setjem Setjem wrote:
> Hi, I'am trying to write a backend for my own target system. The target has
> two pointer registers but only one of them can be used to read data from
> memory and the other one to write data into memory.

What will happen if a frame pointer is needed? Is GCC supposed to work with
such a limited hardware at all?

> How could i tell the compiler to use the correct register for the respective
> operation?
> 
> I have tried to copy the address into the correct register in the
> define_expand "mov<mode>", but this seems to confuse the compiler and not
> working always. I also tried to describe it in the target hook
> TARGET_LEGITIMATE_ADDRESS_P, but there i have no idea how to find out which
> operation is performed (write/read).
> 
> Thanks in advance.
> 
> best regards, Andreas