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 BF0933858D32 for ; Fri, 4 Nov 2022 19:53:32 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org BF0933858D32 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=1667591612; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=ci/7Dj1Lz8aRjbCupfcDQPNnvJWFT0PfWtmz4GPvjlk=; b=V1Dg8p6DXGKFVbBXBosRh0ML9TI2tOK3ltKyjy9P+A6ZjMtq/xUbknkf/VJj6M6XAoJwIw xf+I0zl+21nMBtOaxCM7EIho0TFvre0tPGoCGaby0BSET6RLSA4o1ebPKRyaQsvGCxi7VX kewuigCJ20To0i+2EBb4+ectzj3PyB8= 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-386-jvGbgBUuO_2_iWSlEbPJmw-1; Fri, 04 Nov 2022 15:53:29 -0400 X-MC-Unique: jvGbgBUuO_2_iWSlEbPJmw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0E538811E67 for ; Fri, 4 Nov 2022 19:53:29 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.193.252]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BDB7FC1908B; Fri, 4 Nov 2022 19:53:28 +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 2A4JrQhM2686743 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 4 Nov 2022 20:53:26 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 2A4JrPmt2686742; Fri, 4 Nov 2022 20:53:25 +0100 Date: Fri, 4 Nov 2022 20:53:24 +0100 From: Jakub Jelinek To: Aldy Hernandez , GCC patches 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 10.11.54.8 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=-4.0 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 Fri, Nov 04, 2022 at 08:14:23PM +0100, Jakub Jelinek via Gcc-patches wrote: > One thing that is clear is that real_isdenormal is never true for these > (but then a question is if flush_denormals_to_zero actually works). So, after some more investigation, I think that is actually the case, real_isdenormal is only meaningful (will ever return true) right after round_for_format. The uses inside of real.cc are fine, real_to_target first calls round_for_format and then calls fmt->encode in which the real_isdenormal calls are done. And, round_for_format is what transforms the normalized way of expressing the number into the denormal form: /* Check the range of the exponent. If we're out of range, either underflow or overflow. */ if (REAL_EXP (r) > emax2) goto overflow; else if (REAL_EXP (r) <= emin2m1) { int diff; if (!fmt->has_denorm) { /* Don't underflow completely until we've had a chance to round. */ if (REAL_EXP (r) < emin2m1) goto underflow; } else { diff = emin2m1 - REAL_EXP (r) + 1; if (diff > p2) goto underflow; /* De-normalize the significand. */ r->sig[0] |= sticky_rshift_significand (r, r, diff); SET_REAL_EXP (r, REAL_EXP (r) + diff); } } But, real_to_target is one of the 4 callers of static round_for_format, another one is real_convert, but that one undoes that immediately: round_for_format (fmt, r); /* Make resulting NaN value to be qNaN. The caller has the responsibility to avoid the operation if flag_signaling_nans is on. */ if (r->cl == rvc_nan) r->signalling = 0; /* round_for_format de-normalizes denormals. Undo just that part. */ if (r->cl == rvc_normal) normalize (r); and the last two are inside of encoding the IBM double double composite. So, I think everywhere in the frange you'll see normalized REAL_VALUE_TYPE and so real_isdenormal will always be false there. You need to check for REAL_EXP (r) < fmt->emin or so (and ideally only on REAL_VALUE_TYPE already real_converted to the right mode (your frange_arithmetics does that already, which is good, but say conversions and other unary ops might need it too). If I in the hack from last mail replace - fprintf (stderr, "%d %d %s %s\n", i, real_isdenormal (&result), buf, buf2); + fprintf (stderr, "%d %d %s %s\n", i, REAL_EXP (&result) < REAL_MODE_FORMAT (mode)->emin, buf, buf2); then it is 1 until: 102 1 0x0.8p-971 0x0.80000000000008p-971 103 1 0x0.8p-970 0x0.80000000000008p-970 104 1 0x0.8p-969 0x0.80000000000008p-969 105 0 0x0.8p-968 0x0.80000000000008p-968 106 0 0x0.8p-967 0x0.80000000000008p-967 107 0 0x0.8p-966 0x0.80000000000008p-966 Now, the __LDBL_MIN__ powerpc64 gcc announces is 2.00416836000897277799610805135016205e-292L which is equivalent to: 0x1p-969 and that is equivalent to 0x0.8p-968, so I think that is exactly what we want. Jakub