Re: [RFC] Fix recent popcount change is breaking

[Kugan Vivekanandarajah <kugan dot vivekanandarajah at linaro dot org>]

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.

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.

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