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[91.12.97.136]) by smtp.gmail.com with ESMTPSA id h9sm13353156wmb.35.2021.06.07.02.06.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Jun 2021 02:06:37 -0700 (PDT) Subject: Re: [PATCH v2 24/26] s390x/tcg: Implement VECTOR FP (MAXIMUM|MINIMUM) To: Richard Henderson , qemu-devel@nongnu.org References: <20210517142739.38597-1-david@redhat.com> <20210517142739.38597-25-david@redhat.com> From: David Hildenbrand Organization: Red Hat Message-ID: <52f61460-ab82-af00-04a7-11aefd6c3f65@redhat.com> Date: Mon, 7 Jun 2021 11:06:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.2, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Thomas Huth , Cornelia Huck , Halil Pasic , Christian Borntraeger , qemu-s390x@nongnu.org, =?UTF-8?Q?Alex_Benn=c3=a9e?= , Aurelien Jarno Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 03.06.21 20:13, Richard Henderson wrote: > On 5/17/21 7:27 AM, David Hildenbrand wrote: >> + if (unlikely(nan_a || nan_b)) { > > Perhaps better as (dcmask_a | dcmask_b) & DCMASK_NAN ? > >> + if (sig_a || sig_b) { > > Similarly. > Will do, thanks. >> + } else if (unlikely(inf_a && inf_b)) { >> + switch (type) { >> + case S390_MINMAX_TYPE_JAVA: >> + return neg_a && !neg_b ? S390_MINMAX_RES_A : S390_MINMAX_RES_B; >> + case S390_MINMAX_TYPE_C_MACRO: >> + case S390_MINMAX_TYPE_CPP: >> + return neg_b ? S390_MINMAX_RES_B : S390_MINMAX_RES_A; >> + case S390_MINMAX_TYPE_F: >> + return !neg_a && neg_b ? S390_MINMAX_RES_B : S390_MINMAX_RES_A; >> + default: >> + g_assert_not_reached(); >> + } > > I don't understand why inf_a && inf_b gets a special case. Inf is > well-ordered. If the arguments are equal you can't tell the difference between > them, so it doesn't matter whether A or B is returned. > > I would pass this case along to S390_MINMAX_RES_MINMAX. Thinking about it, that makes sense. I have no clue why the PoP has these special cases expressed in the tables, at least it managed to confuse me. > >> + } else if (unlikely(zero_a && zero_b)) { >> + switch (type) { >> + case S390_MINMAX_TYPE_JAVA: >> + return neg_a && !neg_b ? S390_MINMAX_RES_A : S390_MINMAX_RES_B; > > If neg_a && neg_b, both A and B are -0, and you can't distinguish them. So > this would seem to simplify to Another case of "let's make the tables inconsistent to confuse David". > > neg_a ? S390_MINMAX_RES_A : S390_MINMAX_RES_B > >> + case S390_MINMAX_TYPE_C_MACRO: >> + return S390_MINMAX_RES_B; >> + case S390_MINMAX_TYPE_F: >> + return !neg_a && neg_b ? S390_MINMAX_RES_B : S390_MINMAX_RES_A; > > Similarly if !neg_a && !neg_b, both A and B are +0. > > Otherwise this looks good. Agreed, thanks! -- Thanks, David / dhildenb