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

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Date:	Wed, 4 May 2016 13:51:14 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Brian Gerst <brgerst@...il.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>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>,
	Andy Lutomirski <luto@...capital.net>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC PATCH] x86/hweight: Get rid of the special calling
 convention

On 05/04/2016 01:22 PM, Borislav Petkov wrote:
> On Wed, May 04, 2016 at 12:49:17PM -0700, H. Peter Anvin wrote:
>> Sigh.  Doesn't look like -Wa is going to help due to the lack of the
>> equivalent of an -include option in gas.
> 
> So much for the register "freedom" - I'll resurrect the hardcoded insn
> bytes. :-\
> 
> Unless my gcc friends have some other ideas...

There is the option of looking for assembler support for popcnt and only
hard-code the register if not supported.  This is where being able to
insert a macro package would help...

	-hpa