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Re: [RFC] Fix recent popcount change is breaking


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.

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.


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