Re: [PATCH][expmed] Calculate mult-by-const cost properly in mult_by_coeff_cost

[Kyrill Tkachov <kyrylo dot tkachov at arm dot com>]

On 17/03/15 19:11, Jeff Law wrote:
> On 03/16/2015 04:12 AM, Kyrill Tkachov wrote:
> > Hi all,
> >
> > Eyeballing the mult_by_coeff_cost function I think it has a typo/bug.
> > It's supposed to return the cost of multiplying by a constant 'coeff'.
> > It calculates that by taking the cost of a MULT rtx by that constant
> > and comparing it to the cost of synthesizing that multiplication, and
> > returning
> > the cheapest. However, in the MULT rtx cost calculations it creates
> > a MULT rtx of two REGs rather than the a REG and the GEN_INT of coeff as
> > I would
> > expect. This patches fixes that in the obvious way.
> >
> > Tested aarch64-none-elf and bootstrapped on x86_64-linux-gnu.
> > I'm guessing this is stage 1 material at this point?
> >
> > Thanks,
> > Kyrill
> >
> > 2015-03-13  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> >
> >       * expmed.c (mult_by_coeff_cost): Pass CONT_INT rtx to MULT cost
> >       calculation rather than fake_reg.
> I'd think stage1, unless you can point to a bug, particularly a regression.

No regression that I know of. I'll queue it up for stage 1 if it's ok 
code-wise.

Thanks,
Kyrill

> Jeff