Re: Fix vectorizer conditions on updating alignment

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Jun 12, 2014 at 3:14 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
> Hi,
> while updating vect_can_force_dr_alignment_p for section API I noticed the
> predicate is bit confused about when it can update the alignment.
>
> We need to check that decl_binds_to_current_def_p and in case we compile
> a partition also that the symbol is not homed in other partition.
> Previous code was wrong i.e. for COMDATs, weaks or -fpic.
>
> Also when having an alias, only way to promote the alignment is to bump
> up alignment of target.
>
> On the other hand comment about DECL_IN_CONSTANT_POOL seems confused - we have
> no sharing across partitions. I assume it was old hack and removed it.
>
> I also see no reason for disregarding DECL_PRESERVE - we only update
> alignment that should not disturb whatever magic user does. But I kept
> it.
>
> We probably should separate the logic into symtab predicate - it just checks if
> we can change definition of variable to meet our needs. I can do that
> incrementally.
>
> Bootstrapped/regtested x86_64-linux, comitted.
>
> Honza
>
>         * tree-vect-data-refs.c (vect_can_force_dr_alignment_p): Reorg
>         to use symtab and decl_binds_to_current_def_p
>         * tree-vectorizer.c (increase_alignment): Increase alignment
>         of alias target, too.

It caused:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64024
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64028

H.J.