From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31316 invoked by alias); 4 May 2015 00:32:04 -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 31306 invoked by uid 89); 4 May 2015 00:32:03 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.4 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-ig0-f176.google.com Received: from mail-ig0-f176.google.com (HELO mail-ig0-f176.google.com) (209.85.213.176) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Mon, 04 May 2015 00:32:02 +0000 Received: by igbyr2 with SMTP id yr2so73342145igb.0 for ; Sun, 03 May 2015 17:32:00 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.107.133.225 with SMTP id p94mr25413458ioi.40.1430699520125; Sun, 03 May 2015 17:32:00 -0700 (PDT) Received: by 10.36.108.21 with HTTP; Sun, 3 May 2015 17:32:00 -0700 (PDT) In-Reply-To: <11730594.qrxZLO7yKG@polaris> References: <1633828.L6eKc0dpVU@polaris> <1752984.z0ljzjyPbr@polaris> <11730594.qrxZLO7yKG@polaris> Date: Mon, 04 May 2015 00:32:00 -0000 Message-ID: Subject: Re: [rs6000] Fix compare debug failure on AIX From: David Edelsohn To: Eric Botcazou Cc: GCC Patches , Andrew Pinski Content-Type: text/plain; charset=ISO-8859-1 X-SW-Source: 2015-05/txt/msg00185.txt.bz2 On Sat, May 2, 2015 at 6:04 AM, Eric Botcazou wrote: >> Why should GCC unnecessarily create stack frames to avoid >> compare-debug testcase failures? > > I'm not sure I understand the question... compare-debug failures are failures > (-g is not supposed to change the generated code and this XCOFF-specific bug > was reported to us) so they need to be fixed. > > From there on, as Alan said, there are 2 cases: either AIX needs a frame for > debugging or it doesn't. If the latter, then the lines can simply be deleted. > If the former, we have to draw a line somewhere; Alan suggests always creating > a frame while I suggest creating it only at -O0 and -Og. I believe that AIX does need a frame for debugging. I don't remember the exact reason off hand. I'm sorry that XCOFF debugging changes the generated code (only in the sense of allocating a frame), but that is a system dependency. It's been this way for over 20 years. I see no reason to produce worse code at -O0 when not debugging simply to make testcases happier. By the way, I'm still waiting for the DWARF debugging patches from Adacore compatible with AIX as and ld. DWARF debugging would not require pushing a frame, and would resolve the failure when testing with DWARF. The patch would be adjusted to only push a frame when writing XCOFF debugging. - David