From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13594 invoked by alias); 3 Dec 2014 15:01:16 -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 13585 invoked by uid 89); 3 Dec 2014 15:01:15 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.3 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-ob0-f177.google.com Received: from mail-ob0-f177.google.com (HELO mail-ob0-f177.google.com) (209.85.214.177) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-SHA encrypted) ESMTPS; Wed, 03 Dec 2014 15:01:09 +0000 Received: by mail-ob0-f177.google.com with SMTP id va2so1110670obc.8 for ; Wed, 03 Dec 2014 07:01:07 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.182.24.8 with SMTP id q8mr3506175obf.26.1417618867566; Wed, 03 Dec 2014 07:01:07 -0800 (PST) Received: by 10.76.185.7 with HTTP; Wed, 3 Dec 2014 07:01:07 -0800 (PST) In-Reply-To: References: Date: Wed, 03 Dec 2014 15:01:00 -0000 Message-ID: Subject: Re: [PATCH x86_64] Optimize access to globals in "-fpie -pie" builds with copy relocations From: "H.J. Lu" To: Uros Bizjak Cc: "gcc-patches@gcc.gnu.org" , Sriraman Tallam , Jakub Jelinek Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2014-12/txt/msg00284.txt.bz2 On Wed, Dec 3, 2014 at 5:47 AM, H.J. Lu wrote: > On Tue, Dec 2, 2014 at 12:01 PM, Uros Bizjak wrote: >> On Tue, Dec 2, 2014 at 8:40 PM, H.J. Lu wrote: >>> On Tue, Dec 2, 2014 at 11:19 AM, Uros Bizjak wrote: >>>> Hello! >>>> >>>>> Ping. >>>>>> Ping. >>>>>>> Ping. >>>>>>>> Ping. >>>> >>>> It would probably help reviewers if you pointed to actual path >>>> submission [1], which unfortunately contains the explanation in the >>>> patch itself [2], which further explains that this functionality is >>>> currently only supported with gold, patched with [3]. >>>> >>>> [1] https://gcc.gnu.org/ml/gcc-patches/2014-09/msg00645.html >>>> [2] https://gcc.gnu.org/ml/gcc-patches/2014-09/txt2CHtu81P1O.txt >>>> [3] https://sourceware.org/ml/binutils/2014-05/msg00092.html >>>> >>>> After a bit of the above detective work, I think that new gcc option >>>> is not necessary. The configure should detect if new functionality is >>>> supported in the linker, and auto-configure gcc to use it when >>>> appropriate. >>> >>> I think GCC option is needed since one can use -fuse-ld= to >>> change linker. >> >> IMO, nobody will use this highly special x86_64-only option. It would >> be best for gnu-ld to reach feature parity with gold as far as this >> functionality is concerned. In this case, the optimization would be >> auto-configured, and would fire automatically, without any user >> intervention. >> > > Let's do it. I implemented the same feature in bfd linker on both > master and 2.25 branch. > +bool +i386_binds_local_p (const_tree exp) +{ + /* Globals marked extern are treated as local when linker copy relocations + support is available with -f{pie|PIE}. */ + if (TARGET_64BIT && ix86_copyrelocs && flag_pie + && TREE_CODE (exp) == VAR_DECL + && DECL_EXTERNAL (exp) && !DECL_WEAK (exp)) + return true; + return default_binds_local_p (exp); +} + It returns true with -fPIE and false without -fPIE. It is lying to compiler. Maybe legitimate_pic_address_disp_p is a better place. -- H.J.