From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:32870) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f8YQY-0007sw-4h for qemu-devel@nongnu.org; Tue, 17 Apr 2018 17:46:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f8YQX-0007Ul-6Y for qemu-devel@nongnu.org; Tue, 17 Apr 2018 17:46:14 -0400 Received: from mail-ot0-x230.google.com ([2607:f8b0:4003:c0f::230]:43967) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1f8YQW-0007RX-Uq for qemu-devel@nongnu.org; Tue, 17 Apr 2018 17:46:13 -0400 Received: by mail-ot0-x230.google.com with SMTP id d9-v6so23071638oth.10 for ; Tue, 17 Apr 2018 14:46:12 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180417212710.GA10948@flamenco> References: <20180416135442.30606-1-alex.bennee@linaro.org> <20180417190439.GA28717@flamenco> <20180417212710.GA10948@flamenco> From: Peter Maydell Date: Tue, 17 Apr 2018 22:45:51 +0100 Message-ID: Content-Type: text/plain; charset="UTF-8" Subject: Re: [Qemu-devel] [PATCH] fpu/softfloat: check for Inf / x or 0 / x before /0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Emilio G. Cota" Cc: =?UTF-8?B?QWxleCBCZW5uw6ll?= , QEMU Developers , Aurelien Jarno , Bastian Koppelmann On 17 April 2018 at 22:27, Emilio G. Cota wrote: > BTW I just checked with -t host on an IBM Power8, and we get > the same 1049 flag errors we get with -t soft plus two additional ones: > > +A 0xffb00000, expected: 0x7fa00000, returned: 0x7fa00000, \ > expected exceptions: i, returned: none > +error: flags mismatch for input @ ibm/Basic-Types-Inputs.fptest:382: > +b32A =0 S -> S i That's Abs of an SNaN; the test expects Invalid, which is wrong, because IEEE754 says absolute-value is a "quiet-computational operation" that never signals an exception. What's odd is that we don't report that error for the softfloat implementation! I also don't understand why the expected value isn't just the input value with the sign bit flipped. > (...) > +cff 0xffb00000, expected: 0x7ff8000000000000, returned: 0x7ff4000000000000, \ > expected exceptions: i, returned: none > +error: flags mismatch for input @ ibm/Basic-Types-Inputs.fptest:26170: > +b32b64cff =0 S -> Q i SNaN conversion from 32 bit to 64 bit. Here I agree with the test -- we should quieten the NaN and raise Invalid -- which implies that the hardware is wrong ?!? thanks -- PMM