linux-kernel - Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention

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Message-ID: <20160511124756.GG2180@pd.tnic>
Date:	Wed, 11 May 2016 14:47:56 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Brian Gerst <brgerst@...il.com>, "H. Peter Anvin" <hpa@...or.com>,
	x86-ml <x86@...nel.org>, Denys Vlasenko <dvlasenk@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, zengzhaoxiu@....com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH -v2] x86/hweight: Get rid of the special calling
 convention

On Wed, May 11, 2016 at 01:24:09PM +0200, Peter Zijlstra wrote:
> Yeah, it might save a few cycles on the call, but given that most
> machines should have popcnt these days is it worth the hassle/cost of
> duplicating the lib/hweight.c magic in asm (and remember, twice, once
> for 32bit and once for 64bit) ?

Makes sense to me - we can do the funky cool stuff but considering the
fact that we have all the required bits already, I think we should do
the thunking game and be done with it.

I guess we're older, lazy and more realists now...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--