Using an automodified register twice in the same insn

[Paul Brook]

On Wednesday 01 November 2006 17:39, Richard Sandiford wrote:
> Can a register be used more than once in an insn if one of those uses is
> an auto-modification?  I've looked at this several times in the past and
> never come to a conclusion.  doc/rtl.texi says:

We have a related problem on ARM. The ISA does not allow the base of a 
automodify address to be used as a source register. ie.

  (set (mem (post_inc (reg X)) (reg Y))

Is not valid  when X == Y.

Currently there is no way of expressing this, which leads to invalid asm being 
generated in some obscure cases.

Paul