how to implement pre-dec, post-inc in a new backend?

[Ian Lance Taylor]

Florent DEFAY <spira.inhabitant@gmail.com> writes:

> I looked over AVR backend but I did not understand some things like:
> 'p' and 'r' are codes introduced to mean that operands should be
> pre-dec or post-inc
> ___________________________________________________________
> ;;  p  POST_INC or PRE_DEC address as a pointer (X, Y, Z)
> ;;  r  POST_INC or PRE_DEC address as a register (r26, r28, r30)
> ___________________________________________________________
> but they seem to be never used.

Those are % operands used with PRINT_OPERAND.  They are used in avr.c.
Look at, e.g., out_movhi_r_mr.

              return (AS2 (sbiw,%r1,2)   CR_TAB
                      AS2 (ld,%A0,%p1)  CR_TAB
                      AS2 (ldd,%B0,%p1+1));

Ian