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[189.204.200.163]) by smtp.gmail.com with ESMTPSA id n15sm2216453qti.51.2021.05.13.05.38.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 May 2021 05:38:57 -0700 (PDT) Subject: Re: [PATCH 33/72] softfloat: Use uadd64_carry, usub64_borrow in softfloat-macros.h To: =?UTF-8?Q?Alex_Benn=c3=a9e?= References: <20210508014802.892561-1-richard.henderson@linaro.org> <20210508014802.892561-34-richard.henderson@linaro.org> <87r1ibdk9q.fsf@linaro.org> From: Richard Henderson Message-ID: Date: Thu, 13 May 2021 07:38:55 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <87r1ibdk9q.fsf@linaro.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::82c; envelope-from=richard.henderson@linaro.org; helo=mail-qt1-x82c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, 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_NONE=-0.0001, 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: qemu-devel@nongnu.org, david@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/13/21 5:00 AM, Alex Bennée wrote: > > Richard Henderson writes: > >> Use compiler support for carry arithmetic. > > Didn't we have a series that attempted to take advantage of compiler > support for Int128? Is the compiler end up smart enough to use 128 bit > wide ops if it can? That was one of the iterations of this patch set, yes. In the end it turned out to be easier to be able to address frac_hi and frac_lo directly. It's likely that this choice would have been different if we didn't have to deal with 32-bit hosts and could rely on the compiler having the 128-bit type. r~