From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 647051F4C0 for ; Tue, 22 Oct 2019 10:25:57 +0000 (UTC) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:references:date:in-reply-to :message-id:mime-version:content-type:content-transfer-encoding; q=dns; s=default; b=Y7PDIvXt8H3sd1fEpGzr2Qn0gbt6xLFY4IOr17J8sUe pW4fIsAzin4rROnvzZAoNLOGHNH6+6KJPpqrWWh93POcqk/NBlbVpDSo089P8chn wC6EsIPrvezdnrWAwGAyvqk+Juae4J1EwnY+zSyBBRwNabI2gqOfcbhOM24jM9l4 = DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:references:date:in-reply-to :message-id:mime-version:content-type:content-transfer-encoding; s=default; bh=xalh/9inZlsdF0TSo3hNPGIfCF8=; b=AWFUCxzZP/Y5EXqXt DdDZS4EU3I5gApu7maA5TbbSKfgLC03NsL93Zpaq6wOkeECIHawWDqGDzxWo7H0G cYjt8nItosmXiSfG5xZITtdgkvQ8Rw6GiCqj5xeFW6YMZ5jHxCV0wH9dPxb8vcWC y+uBmCY9Tn3bnip9ZqtzfuIlDk= Received: (qmail 57616 invoked by alias); 22 Oct 2019 10:25:55 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 57608 invoked by uid 89); 22 Oct 2019 10:25:54 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: us-smtp-1.mimecast.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571739952; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Zeg0TZJdqDTL1Tx8WFWY816dR2WLq1uZyFHXo2KgWR8=; b=ciDS09Uc6jc0+NYi6TuNNdRh9qyrJ+gmWwjBAa69Yo3LULyGR8LgPNRJEW+nElJ1m0Qr6h 39sNgG4tkwI1AnmhVzJjDFHdOxvgVjbjx9cFiJPfKROvWBCGgEnAHj9cyzIv5+ecCoDnTK 9CNYfMMNjGsI/zKZJi1ia9EknCwr3dg= From: Florian Weimer To: Stefan Liebler Cc: GNU C Library Subject: Re: [PATCH] S390: Remove not needed stack frame in syscall function. References: <0e66f775-9669-ff29-e605-195b79382b3e@linux.ibm.com> Date: Tue, 22 Oct 2019 12:25:46 +0200 In-Reply-To: <0e66f775-9669-ff29-e605-195b79382b3e@linux.ibm.com> (Stefan Liebler's message of "Tue, 22 Oct 2019 10:00:04 +0200") Message-ID: <87o8y9krf9.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable * Stefan Liebler: > As an svc invocation does not clobber any user space registers > despite of the return value r2 and it does not need a special > stack frame. This patch gets rid of the extra frame. > We just have to save and restore r6 and r7 as those are > preserved across function calls. Looks okay to me. Would it be possible to save r6 and r7 in caller-saved registers not clobbered by the system call? That might provide another small benefit. Thanks, Florian