[Bug target/60778] shift not folded into shift on x86-64

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60778

--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Jakub Jelinek from comment #4)
> > > We have 2->2 combine now but it looks like we don't try to split inside a
> > > mem ...
> > 
> > This address looks similar to how Alpha implemented unaligned load. It looks
> > like combine tries to synthesize AND address.
> 
> That is from the (x >> 3) * 8.  Perhaps a combine splitter that will tell
> combine that it should split it at the AND?  Though, not sure if the cost
> will say that it is beneficial.

Maybe we should allow AND addresses and split AND out in
ix86_legitimize_address?