Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752199AbbEAQ4d (ORCPT ); Fri, 1 May 2015 12:56:33 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:34044 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751405AbbEAQ42 (ORCPT ); Fri, 1 May 2015 12:56:28 -0400 Date: Fri, 1 May 2015 18:46:40 +0200 From: Peter Zijlstra To: Jakub Jelinek Cc: Linus Torvalds , Richard Henderson , Vladimir Makarov , Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , Linux Kernel Mailing List , Borislav Petkov Subject: Re: [PATCH] x86: Optimize variable_test_bit() Message-ID: <20150501164639.GA19158@dyad.arnhem.chello.nl> References: <20150501151630.GH5029@twins.programming.kicks-ass.net> <20150501163329.GU1751@tucnak.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150501163329.GU1751@tucnak.redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1120 Lines: 20 On Fri, May 01, 2015 at 06:33:29PM +0200, Jakub Jelinek wrote: > On Fri, May 01, 2015 at 09:03:32AM -0700, Linus Torvalds wrote: > > > PPS. Jakub, I see gcc5.1 still hasn't got output operands for asm goto; > > > is this something we can get 'fixed' ? > > CCing Richard as author of asm goto and Vlad as register allocator > maintainer. There are a few enhancement requests to support this, like > http://gcc.gnu.org/PR59615 and http://gcc.gnu.org/PR52381 , but indeed the > reason why no outputs are allowed is the register allocation issue. > Don't know if LRA would be better suited to handle that case, but it would > indeed be pretty hard. So it would b awesome if we could use these freshly modeled flags as output for regular asm stmts; that would obviate much of the asm goto hackery we now do/have and allow gcc to pick the right branch for likely/unlikely. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/