linux-kernel - Re: [PATCH] x86: Optimize variable_test

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Date:	Mon, 04 May 2015 14:07:32 -0400
From:	Vladimir Makarov <vmakarov@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Jakub Jelinek <jakub@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Richard Henderson <rth@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86: Optimize variable_test_bit()



On 02/05/15 08:43 AM, Peter Zijlstra wrote:
> On Fri, May 01, 2015 at 03:02:24PM -0400, Vladimir Makarov wrote:
>>    Currently LRA is used by x86/x86-64, ARM, AARCH64, s390, and MIPS.
>> PPC, SH, and ARC are moving to LRA.  All other targets are still
>> reload based.
>>
>>    So I could implement the output reloads in LRA, probably for the
>> next GCC release.  How to enable and mostly use it for multi-target
>> code like the kernel is another question.
> Pretty much all inline asm is in per arch code; so one arch having
> different asm features than another should not be a problem at all.
Ok, then. I'll try to implement output operands for asm-goto in LRA for 
the next GCC release.

Of course, if nobody objects to changing asm goto semantics from

  An 'asm goto' statement cannot have outputs ...

to

  An 'asm goto' statement cannot have outputs on some targets ...


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