From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 87364 invoked by alias); 14 Oct 2015 01:11:46 -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 87355 invoked by uid 89); 14 Oct 2015 01:11:45 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.8 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,T_RP_MATCHES_RCVD,UNSUBSCRIBE_BODY autolearn=no version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 14 Oct 2015 01:11:44 +0000 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id 538E18C1D5; Wed, 14 Oct 2015 01:11:43 +0000 (UTC) Received: from bigtime.twiddle.net (ovpn-113-208.phx2.redhat.com [10.3.113.208]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t9E1Bdi3007769; Tue, 13 Oct 2015 21:11:40 -0400 Subject: Re: using scratchpads to enhance RTL-level if-conversion: revised patch To: Bernd Schmidt , Abe , "gcc-patches@gcc.gnu.org" , Sebastian Pop , Kyrill Tkachov References: <5615AADE.4030306@yahoo.com> <56166E68.2040004@redhat.com> <561DAA48.60604@redhat.com> From: Richard Henderson Message-ID: <561DABC9.4080309@redhat.com> Date: Wed, 14 Oct 2015 01:11:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <561DAA48.60604@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2015-10/txt/msg01306.txt.bz2 On 10/14/2015 12:05 PM, Richard Henderson wrote: > If you're using one of the switches that checks for stack overflow at the start > of the function, you certainly don't want to do any such stores. Oh, and for a given target the kernel may consider any write to the stack vma below the stack pointer as invalid. The x86 kernels will at least handle "enter $65535, $31", which can write to a bit more than 64k below %esp before %esp gets updated, but that's probably not going to be true of most risc targets. r~