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From: "belagod at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/63679] [5.0 Regression][AArch64] Failure to constant fold.
Date: Fri, 21 Nov 2014 10:54:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63679

--- Comment #13 from Tejas Belagod <belagod at gcc dot gnu.org> ---
(In reply to rguenther@suse.de from comment #12)
> 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.

Ah, jgreenhalgh just did some move_by_pieces restructuring recently.