From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 23801 invoked by alias); 12 Apr 2012 10:45:49 -0000 Received: (qmail 23786 invoked by uid 22791); 12 Apr 2012 10:45:46 -0000 X-SWARE-Spam-Status: No, hits=-4.8 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,KHOP_RCVD_TRUST,KHOP_THREADED,RCVD_IN_DNSWL_LOW,RCVD_IN_HOSTKARMA_YE X-Spam-Check-By: sourceware.org Received: from mail-iy0-f175.google.com (HELO mail-iy0-f175.google.com) (209.85.210.175) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 12 Apr 2012 10:45:33 +0000 Received: by iaag37 with SMTP id g37so2778130iaa.20 for ; Thu, 12 Apr 2012 03:45:33 -0700 (PDT) MIME-Version: 1.0 Received: by 10.50.158.202 with SMTP id ww10mr1703410igb.30.1334227533163; Thu, 12 Apr 2012 03:45:33 -0700 (PDT) Received: by 10.42.228.200 with HTTP; Thu, 12 Apr 2012 03:45:33 -0700 (PDT) In-Reply-To: References: Date: Thu, 12 Apr 2012 10:45:00 -0000 Message-ID: Subject: Re: [PATCH] Atom: Scheduler improvements for better imul placement From: Richard Guenther To: Igor Zamyatin Cc: Andi Kleen , gcc-patches@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 X-IsSubscribed: yes 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 X-SW-Source: 2012-04/txt/msg00736.txt.bz2 On Thu, Apr 12, 2012 at 12:20 PM, Igor Zamyatin wrote: > On Wed, Apr 11, 2012 at 6:10 PM, Richard Guenther > wrote: >> On Wed, Apr 11, 2012 at 3:38 PM, Andi Kleen wrote: >>> Igor Zamyatin writes: >>> >>>> Hi All! >>>> >>>> It is known that imul placement is rather critical for Atom processors >>>> and changes try to improve imul scheduling for Atom. >>>> >>>> This gives +5% performance on several tests from new OA 2.0 testsuite >>>> from EEMBC. >>>> >>>> Tested for i386 and x86-64, ok for trunk? >>> >>> Did you measure how much this slows down the compiler when compiling >>> for Atom? The new pass looks rather slow. >> >> Also please explain why adjusting the automaton for Atom is not a way to >> attack this issue. > > If I understand the question correctly - it's a dynamic check and it's > not clear how to describe this adjusting statically in machine > description >From reading the code (the comments are not clear to me) you seem to produce two adjacent IMUL instructions from within the ready list - but first check that there is only a single one. So I fail to see how it can work. Can atom execute two IMUL in parallel? Or what exactly is the pipeline behavior? You miss a testcase that would show the effect of your patch. Richard. >> >> Richard. >> >>> -Andi >>> >>> -- >>> ak@linux.intel.com -- Speaking for myself only