Fix PR 46297

[Richard Guenther]

On Sat, Nov 6, 2010 at 4:53 PM, Jeff Law <law@redhat.com> wrote:
>  The fundamental problem is some ports have embedded auto-inc addressing
> modes without REG_INC nodes.  The improved reload optimizations were not
> accounting for the possibility of embedded auto-inc addressing, particularly
> for argument pushing.
> As a result the new optimization applied, but the offset we generated in the
> MEM was wrong due to the intervening autoinc addressing mode.
>
> While we could track the auto-incs, it's far easier to treat them as an
> unrecordable use/set which disables the optimization across the argument
> pushes.   While we lose a few optimization opportunities, I suspect they
> definitely fall into the unmeasurable category.
>
> Bootstrapped & regression tested on i686-pc-linux-gnu.

Can we detect this in RTL checking and fixup the targets?  Obviously not
for stage3 though.

Richard.