Re: [RFC] Fix recent popcount change is breaking

[Andrew Pinski <pinskia at gmail dot com>]

On Tue, Jul 10, 2018 at 6:14 PM Kugan Vivekanandarajah
<kugan.vivekanandarajah@linaro.org> wrote:
>
> On 10 July 2018 at 23:17, Richard Biener <richard.guenther@gmail.com> wrote:
> > On Tue, Jul 10, 2018 at 3:06 PM Kugan Vivekanandarajah
> > <kugan.vivekanandarajah@linaro.org> wrote:
> >>
> >> Hi,
> >>
> >> Jeff told me that the recent popcount built-in detection is causing
> >> kernel build issues as
> >> ERROR: "__popcountsi2"
> >> [drivers/net/wireless/broadcom/brcm80211/brcmfmac/brcmfmac.ko] undefined!
> >>
> >> I could also reproduce this. AFIK, we should check if the libfunc is
> >> defined while checking popcount?
> >>
> >> I am testing the attached RFC patch. Is this reasonable?
> >
> > It doesn't work that way, all targets have this libfunc in libgcc.  This means
> > the kernel has to provide it.  The only thing you could do is restrict
> > replacement of CALL_EXPRs (in SCEV cprop) to those the target
> > natively supports.
>
> How about restricting it in expression_expensive_p ? Is that what you
> wanted. Attached patch does this.
> Bootstrap and regression testing progressing.

Seems like that should go into is_inexpensive_builtin  instead which
is just tested right below.

Thanks,
Andrew

>
> Thanks,
> Kugan
>
> >
> > Richard.
> >
> >> Thanks,
> >> Kugan
> >>
> >> gcc/ChangeLog:
> >>
> >> 2018-07-10  Kugan Vivekanandarajah  <kuganv@linaro.org>
> >>
> >>     * tree-ssa-loop-niter.c (number_of_iterations_popcount): Check
> >>     if libfunc for popcount is available.