[Bug target/65456] powerpc64le autovectorized copy loop missed optimization

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65456

--- Comment #15 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
That last bit also needs an update to the table in ISA 2.07 II.2, p. 754.

I'm planning to include the change for the vector alignment piece in my P8
unaligned vectors patch, since it seems relevant there.  I think we should
probably fix this other bit separately, as that will likely need some more
extensive testing.