From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47306) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1THNBg-000773-NS for qemu-devel@nongnu.org; Thu, 27 Sep 2012 19:08:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1THNBf-0004F9-DX for qemu-devel@nongnu.org; Thu, 27 Sep 2012 19:08:08 -0400 Received: from hall.aurel32.net ([88.191.126.93]:55677) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1THNBf-0004Ev-7K for qemu-devel@nongnu.org; Thu, 27 Sep 2012 19:08:07 -0400 Date: Fri, 28 Sep 2012 01:08:05 +0200 From: Aurelien Jarno Message-ID: <20120927230805.GA22257@hall.aurel32.net> References: <1348766113-18373-1-git-send-email-aurelien@aurel32.net> <1348766113-18373-14-git-send-email-aurelien@aurel32.net> <5064AF5B.2050704@twiddle.net> <20120927203711.GO20151@ohm.aurel32.net> <5064CC6F.90806@twiddle.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <5064CC6F.90806@twiddle.net> Sender: Aurelien Jarno Subject: Re: [Qemu-devel] [PATCH 13/13] tcg: rework TCG ops flags List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: qemu-devel@nongnu.org On Thu, Sep 27, 2012 at 03:00:15PM -0700, Richard Henderson wrote: > On 09/27/2012 01:37 PM, Aurelien Jarno wrote: > >> > I don't agree with SIDE_EFFECTS implying exceptions. How can "br" cause an > >> > exception? Or for that matter "st_i32", recalling that we're not storing > >> > to guest memory. > > That's exactly why SIDE_EFFECTS has been removed from this op in the > > previous patch. > > Well, you removed it from br, but not st. Oh correct. st doesn't need one as it has zero output arguments, so it won't be removed. > > I think it implies exception, because I don't see why an op shouldn't be > > removed otherwise (remember ops without outputs are never removed). > > In which case, because the non-qemu store insns cannot raise exceptions, > there ought to be exactly zero instances of TCG_OPF_SIDE_EFFECTS remaining. > At which point we simply ought to remove it. > I don't understand, the qemu/load store still need to keep this TCG_OPF_SIDE_EFFECTS. Even a load to a dead output argument might trigger a TLB miss exception, and thus should be fixed. -- Aurelien Jarno GPG: 1024D/F1BCDB73 aurelien@aurel32.net http://www.aurel32.net