From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from beige.elm.relay.mailchannels.net (beige.elm.relay.mailchannels.net [23.83.212.16]) by sourceware.org (Postfix) with ESMTPS id DD3C8385735D for ; Fri, 15 Jul 2022 20:17:49 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DD3C8385735D X-Sender-Id: dreamhost|x-authsender|tuliom@ascii.art.br Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 12F108011CC; Fri, 15 Jul 2022 20:17:47 +0000 (UTC) Received: from pdx1-sub0-mail-a246.dreamhost.com (unknown [127.0.0.6]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id 3C3FB8020A1; Fri, 15 Jul 2022 20:17:46 +0000 (UTC) ARC-Seal: i=1; s=arc-2022; d=mailchannels.net; t=1657916266; a=rsa-sha256; cv=none; b=conZWtvaLb8leNctbhzTBy0itpgi7a6EYRIKnVwu/9dHrxztgr/VQBYXC23NjByQnCW5sN P8O8l1GNfXQMva2UMg8GEygQrnGFZyESOrpsYhfRxxf2prRVEKqmUZbH6wWKbRPoBR7eV4 6t2nyXQIA80MpV9U908Tvfk5ASqGJVNTJNiKcy3KoD4LtLU69bXOEcbJZFtIR78m2mq7xW dy38LpRKBTCboWtOZY4DERcyhznAEd+PUs23u8zBsr/DmLaGuDZu1879KiWaVD6l13xvh1 QQB/fsbB/hxg3tPjXSHIOm8q6xVLBs86I/dTw9vL/Uzm5l4HWEMUU9KEHNT7rw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=mailchannels.net; s=arc-2022; t=1657916266; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SYK18b1hhU2thRBwWHUzN7ytYM5/Q6Nhxq6SaNm2vDk=; b=6HuJTdzgidePNIVRPceo8UgrrITGJWX78jQDmh3jzc4UQEb3SoyHLUAOoAm+KaBdTB14RP gN0lwkID6KE/w5onp+gU4VyYnD9reVvR2DCRqaStuC4usW5j9TfqK66i+8JeAhhx8+PYOf KSE1F4RVj8Xgjs8s2mpKBtCr0HeUtX0+Na4lXID760Pr8iqCLForlySaA/bMRxwmx9zoYv QOHN6rUUhlGdw68sTDSWUwOAkygJFZSGjnhjSR5zdPfCtlUlLvFn/hWCSD79WDxTI/8HbR 5aPDQYS1d+kL00yjQ9JM1uMARPC+68soetXMjnpuBcWTqsjTSuDcr00EkYX93g== ARC-Authentication-Results: i=1; rspamd-674ffb986c-j8hc2; auth=pass smtp.auth=dreamhost smtp.mailfrom=tuliom@ascii.art.br X-Sender-Id: dreamhost|x-authsender|tuliom@ascii.art.br X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|tuliom@ascii.art.br X-MailChannels-Auth-Id: dreamhost X-Interest-Tasty: 3d09516725622e95_1657916266538_587779153 X-MC-Loop-Signature: 1657916266538:4032144885 X-MC-Ingress-Time: 1657916266538 Received: from pdx1-sub0-mail-a246.dreamhost.com (pop.dreamhost.com [64.90.62.162]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384) by 100.124.238.78 (trex/6.7.1); Fri, 15 Jul 2022 20:17:46 +0000 Received: from ascii.art.br (unknown [138.121.65.190]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: tuliom@ascii.art.br) by pdx1-sub0-mail-a246.dreamhost.com (Postfix) with ESMTPSA id 4Ll2j53fNKz3g; Fri, 15 Jul 2022 13:17:45 -0700 (PDT) From: Tulio Magno Quites Machado Filho To: Segher Boessenkool Cc: Nicholas Piggin , linuxppc-dev@lists.ozlabs.org, Florian Weimer , gcc@gcc.gnu.org, libc-alpha@sourceware.org, Paul E Murphy Subject: Re: [PATCH v2] powerpc: add documentation for HWCAPs In-Reply-To: <20220715195951.GA25951@gate.crashing.org> References: <20220715012636.165948-1-npiggin@gmail.com> <877d4euskv.fsf@linux.ibm.com> <20220715195951.GA25951@gate.crashing.org> User-Agent: Notmuch/0.36 (http://notmuchmail.org) Emacs/27.2 (x86_64-redhat-linux-gnu) Date: Fri, 15 Jul 2022 17:17:42 -0300 Message-ID: <874jziuo49.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-0.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, RCVD_IN_SBL_CSS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Jul 2022 20:17:51 -0000 Segher Boessenkool writes: > That is a usability problem. Can it be fixed, or will that create its > own compatibility problems? In practice I mean. If it is, the C > libraries could fix it up, for new programs, and then after a while the > kernel can do the sane thing? > > How big is the problem, anyway? Is it only 2.05, or also 2.04, 2.03? PPC_FEATURE_ARCH_2_05 is the first bit referring to an ISA level. Before that, AT_HWCAP used to have bits for specific processors, e.g. PPC_FEATURE_CELL and PPC_FEATURE_POWER4. Notice that glibc creates its own hwcap-based information that is used by __builtin_cpu_supports(). In this case bits PPC_FEATURE_ARCH_2_05, PPC_FEATURE_POWER5_PLUS, PPC_FEATURE_POWER5 and PPC_FEATURE_POWER4 are enabled whenever if the processor is compatible with the features provided by any of the previous processors [1]. AT_HWCAP and AT_HWCAP2 are kept intact, though. [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/powerpc/hwcapinfo.c;h=afde05f86382413ce1f0c38e33c9bdd38d6b7e9d;hb=HEAD#l45 -- Tulio Magno