From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id B7D383858297 for ; Tue, 8 Nov 2022 18:11:44 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org B7D383858297 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667931104; h=from:from:reply-to: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; bh=f0nzDI8FKKGO+uoiCmS8HbnQyaXabUrVMKfM3uqFhe8=; b=Q1T+zAUEBNfl2G3rk4uhISmHmLWWzEWZ2LAuQOVY7tNZSWCzmRpJ3w/ISZPjAg+RT54F1t kFTtA3/bv59+uaNX5167gAG/944ud3hCLUwUOcOgYRvcCgf7cEOL5on0oCSYfkpO81M9vI yN2fY+KZlVk0CYbTz/IYqj68cXjkvks= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-524-zS79lS6eM5egqn_0mlwiDA-1; Tue, 08 Nov 2022 13:11:41 -0500 X-MC-Unique: zS79lS6eM5egqn_0mlwiDA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 13D7B101A52A; Tue, 8 Nov 2022 18:11:41 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.194.183]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C6CB34B3FC8; Tue, 8 Nov 2022 18:11:40 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.17.1/8.17.1) with ESMTPS id 2A8IBbhh2246225 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 8 Nov 2022 19:11:38 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 2A8IBaE92246224; Tue, 8 Nov 2022 19:11:36 +0100 Date: Tue, 8 Nov 2022 19:11:36 +0100 From: Jakub Jelinek To: Andrew Waterman Cc: Aldy Hernandez , GCC patches , Andrew MacLeod Subject: Re: [PATCH] [PR24021] Implement PLUS_EXPR range-op entry for floats. Message-ID: Reply-To: Jakub Jelinek References: <20221013123649.474497-1-aldyh@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham 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 Tue, Nov 08, 2022 at 09:44:40AM -0800, Andrew Waterman wrote: > On Tue, Nov 8, 2022 at 3:20 AM Jakub Jelinek via Gcc-patches > wrote: > > > > On Mon, Nov 07, 2022 at 04:41:23PM +0100, Aldy Hernandez wrote: > > > As suggested upthread, I have also adjusted update_nan_sign() to drop > > > the NAN sign to VARYING if both operands are NAN. As an optimization > > > I keep the sign if both operands are NAN and have the same sign. > > > > For NaNs this still relies on something IEEE754 doesn't guarantee, > > as I cited, after a binary operation the sign bit of the NaN is > > unspecified, whether there is one NaN operand or two. > > It might be that all CPUs handle it the way you've implemented > > (that for one NaN operand the sign of NaN result will be the same > > as that NaN operand and for two it will be the sign of one of the two > > NaNs operands, never something else), but I think we'd need to check > > more than one implementation for that (I've only tried x86_64 and thus > > SSE behavior in it), so one would need to test i387 long double behavior > > too, ARM/AArch64, PowerPC, s390{,x}, RISCV, ... > > The guarantee given by IEEE754 is only for those copy, negate, abs, copySign > > operations, so copying values around, NEG_EXPR, ABS_EXPR, __builtin_fabs*, > > __builtin_copysign*. > > FWIW, RISC-V canonicalizes NaNs by clearing the sign bit; the signs of > the input NaNs do not factor in. Just for binary operations and some unary, or also the ones that IEEE754 spells out (moves, negations, absolute value and copysign)? Jakub