From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 91820 invoked by alias); 13 Sep 2015 16:53:19 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 91807 invoked by uid 89); 13 Sep 2015 16:53:18 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=1.1 required=5.0 tests=AWL,BAYES_40,KAM_LAZY_DOMAIN_SECURITY,RDNS_DYNAMIC,TVD_RCVD_IP autolearn=no version=3.3.2 X-HELO: brightrain.aerifal.cx Received: from 216-12-86-13.cv.mvl.ntelos.net (HELO brightrain.aerifal.cx) (216.12.86.13) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 13 Sep 2015 16:53:17 +0000 Received: from dalias by brightrain.aerifal.cx with local (Exim 3.15 #2) id 1ZbAWV-0005f3-00; Sun, 13 Sep 2015 16:53:03 +0000 Date: Sun, 13 Sep 2015 17:11:00 -0000 From: Rich Felker To: Segher Boessenkool Cc: Joseph Myers , gcc-patches@gcc.gnu.org Subject: Re: Reviving SH FDPIC target Message-ID: <20150913165303.GC17773@brightrain.aerifal.cx> References: <20150902183650.GA16052@brightrain.aerifal.cx> <20150902210535.GM17773@brightrain.aerifal.cx> <20150903005101.GN17773@brightrain.aerifal.cx> <20150903155345.GQ17773@brightrain.aerifal.cx> <20150904201640.GU17773@brightrain.aerifal.cx> <20150904230415.GA23901@gate.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150904230415.GA23901@gate.crashing.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-IsSubscribed: yes X-SW-Source: 2015-09/txt/msg00883.txt.bz2 On Fri, Sep 04, 2015 at 06:04:15PM -0500, Segher Boessenkool wrote: > On Fri, Sep 04, 2015 at 04:16:40PM -0400, Rich Felker wrote: > > One thing I've noticed that's odd is that gcc -mfdpic -fPIC produces > > different (less efficient) code from just gcc -mfdpic, which seems > > wrong, but agrees with sh.c which has a number of checks for flag_pic > > not matched with a TARGET_FDPIC check. > > Generic code tests flag_pic in important places as well. > > > I'm thinking all of these > > should either be flag_pic||TARGET_PIC or flag_pic&&!TARGET_FDPIC, > > depending on whether the code applies to all PIC or is specific to the > > non-FDPIC PIC model where r12 is call-saved. Does this sound correct? > > I think we need spurious -fPIC to work (although it could be handled > > with spec magic) and not pessimize code, since most library builds > > will use -fPIC. > > If you never want -fPIC (or -fpic) if fdpic is enabled, you can disable > it (in sh_option_override)? It turns out that with !flag_pic, gcc is generating broken code and/or ICE, and this happens even after changing all the remaining flag_pic tests in sh.c to flag_pic||TARGET_FDPIC. There are a few more in sh.md I didn't try changing but they did not look relevant; the ICE came via expand_binop in prepare_move_operands. Before I look at it further, is there any reason to expect !flag_pic in the generic code to break things when the target-specific code has PIC-like constraints? For now I just made sh_option_override force flag_pic when TARGET_FDPIC is set. Note that flag_pic by itself is equivalent to -fPIE; -fPIC also sets flag_shlib which affects other things like TLS model and binds_locally interpretation. This seems like a viable solution (and I got rid of the suboptimal codegen by fixing the condition in sh_function_ok_for_sibcall so that flag_pic doesn't preclude sibcalls when TARGET_FDPIC is set) but I'd still like to figure out why gcc is breaking without flag_pic... Rich