From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from xry111.site (xry111.site [89.208.246.23]) by sourceware.org (Postfix) with ESMTPS id 184083858CD1 for ; Sat, 25 Nov 2023 10:43:02 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 184083858CD1 Authentication-Results: sourceware.org; dmarc=pass (p=reject dis=none) header.from=xry111.site Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=xry111.site ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 184083858CD1 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=89.208.246.23 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1700908983; cv=none; b=G9qxETeusCvbdsxKEFEtGKDFYG/0MtV8JPLyHbRURC5onyLOTzfFPf4EG82KD6JAK9oODsFUqXc1mKD6w3T+BdjH8mQU/5Jz7+0knUzXvNrZypD+a+ipKv5QCdj4yJRswfVE7QFkgZpDXliOt/0RxLXNMBd7sQz5vEloSupifhE= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1700908983; c=relaxed/simple; bh=bu01mnY9r5aFKjQEtEMmymAHlJ0Y0k+OtelWqAoTbwo=; h=DKIM-Signature:Message-ID:Subject:From:To:Date:MIME-Version; b=Zqkjbn1HymAuzzvuGmwHiYQ0OY2mQCUiu+aZVcjDw5Yx/JKYOn5iTVeT5wflAxpWI3qEDHsGQINfasJdnz8fmSkzU+IJbCySLrHqaQufUhGM6a1hX9C7T3tKsu9XYTqV5YhJyHgai9FxWS1UisQrYVWOjm/k7VQZ8+I+Yjr947g= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=xry111.site; s=default; t=1700908980; bh=bu01mnY9r5aFKjQEtEMmymAHlJ0Y0k+OtelWqAoTbwo=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=bcvguva04Q+cv/HtC8qTpEcu70FWka/NyJ3eMThYTH0j2yO1hNR9HF94tfMjQVqcu pZMoan4y3U4t0QCQsckmJ4WAJ4fCB8s4c3DhnGXWPYzD+xLtXB5zORs7qwSv8A2+eF nkqHjVkhB3bbUgX8p2Q3gu6RxU81qt7VAGTLzL9M= Received: from [127.0.0.1] (unknown [IPv6:2001:470:683e::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature ECDSA (P-384) server-digest SHA384) (Client did not present a certificate) (Authenticated sender: xry111@xry111.site) by xry111.site (Postfix) with ESMTPSA id BB6BF66B39; Sat, 25 Nov 2023 05:42:58 -0500 (EST) Message-ID: <60b5367881c834d1b0f7377a4f352c7c512e2d37.camel@xry111.site> Subject: Re: [PATCH] rs6000: Canonicalize copysign (x, -1) back to -abs (x) in the backend [PR112606] From: Xi Ruoyao To: Jakub Jelinek , Segher Boessenkool , David Edelsohn Cc: gcc-patches@gcc.gnu.org, Tamar Christina , Andrew Pinski Date: Sat, 25 Nov 2023 18:42:56 +0800 In-Reply-To: References: Autocrypt: addr=xry111@xry111.site; prefer-encrypt=mutual; keydata=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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.1 MIME-Version: 1.0 X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,LIKELY_SPAM_FROM,SPF_HELO_PASS,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Sat, 2023-11-25 at 11:17 +0100, Jakub Jelinek wrote: > The middle-end has been changed quite recently to canonicalize > -abs (x) to copysign (x, -1) rather than the other way around. > While I agree with that at GIMPLE level, since it matches the GIMPLE > goal of as few operations as possible for a canonical form (-abs (x) > is 2 GIMPLE statements, copysign (x, -1) is just one), I must say > I don't really like that being done on RTL as well (or at least > not canonicalizing (COPYSIGN x, negative) back to (NEG (ABS x))), > because on most targets most of floating point constants need to be loade= d > from memory, there are a few exceptions but -1 is often not one of them. On LoongArch fneg+fabs is even slower than loading a -1 from mem then do copysign for some micro-architectural reason I don't know. (FWIW on LoongArch with LSX, the fastest way may be directly setting the sign bit with LSX vbitseti instruction - it will also set the sign bits for "junk" elements in the high bits of the vector register but there is no harm.) Can we make a target hook to control this? --=20 Xi Ruoyao School of Aerospace Science and Technology, Xidian University