[Bug target/86677] popcount builtin detection is breaking some kernel build

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86677

--- Comment #10 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #9)
> Taking look at
> ../drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c file:
> 
> The __builtin_popcount is generated from:
> 
> static int brcmf_setup_wiphybands(struct brcmf_cfg80211_info *cfg)
> {
> ...
>  } else {
>   for (nchain = 0; rxchain; nchain++)
>    rxchain = rxchain & (rxchain - 1);
>  }
> ...
> }
> 
> It started from r262486. I would that in this situation it's maybe
> unexpected that a popcount call will be eventually generated. So I'm for an
> option what will disable the pattern recognition.

I'd say this is exactly a case where using a faster popcount instruction helps
- if available of course. 

Is there any reason -fno-builtin-popcount can't also block automatic generation
of popcount?