[Bug target/63679] [5.0 Regression][AArch64] Failure to constant fold.

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63679

--- Comment #12 from rguenther at suse dot de <rguenther at suse dot de> ---
On Fri, 21 Nov 2014, belagod at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63679
> 
> --- Comment #11 from Tejas Belagod <belagod at gcc dot gnu.org> ---
> (In reply to Andrew Pinski from comment #8)
> > (In reply to Tejas Belagod from comment #7)
> > > I tried this, but it still doesn't seem to fold for aarch64.
> > > 
> > > So, here is the DOM trace for aarch64:
> > > 
> > > Optimizing statement a = *.LC0;
> > 
> > Why do we get LC0 in the first place?  It seems like it is happening because
> > of some cost model issue with MOVECOST.
> > 
> 
> Can the cost model affect something as early as gimple?

Through CLEAR_RATIO and can_move_by_pieces (and for complex stuff
initializer_constant_valid_p).  I think it's mostly can_move_by_pieces
here.