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Mon, 24 Feb 2025 07:27:15 -0800 (PST) Received: from eleanor-wkdl ([140.116.96.203]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7346d9b1af1sm1359758b3a.71.2025.02.24.07.27.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2025 07:27:14 -0800 (PST) Date: Mon, 24 Feb 2025 23:27:01 +0800 From: Yu-Chun Lin To: Uros Bizjak Cc: Kuan-Wei Chiu , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, jk@ozlabs.org, joel@jms.id.au, eajames@linux.ibm.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, dmitry.torokhov@gmail.com, mchehab@kernel.org, awalls@md.metrocast.net, hverkuil@xs4all.nl, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, louis.peens@corigine.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, parthiban.veerasooran@microchip.com, arend.vanspriel@broadcom.com, johannes@sipsolutions.net, gregkh@linuxfoundation.org, jirislaby@kernel.org, yury.norov@gmail.com, akpm@linux-foundation.org, hpa@zytor.com, alistair@popple.id.au, linux@rasmusvillemoes.dk, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-fsi@lists.ozlabs.org, dri-devel@lists.freedesktop.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, oss-drivers@corigine.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, brcm80211@lists.linux.dev, brcm80211-dev-list.pdl@broadcom.com, linux-serial@vger.kernel.org, bpf@vger.kernel.org, jserv@ccns.ncku.edu.tw Subject: Re: [PATCH 00/17] Introduce and use generic parity32/64 helper Message-ID: References: <20250223164217.2139331-1-visitorckw@gmail.com> <602e03fd-ce4b-feef-5053-e95834ab35d7@gmail.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <602e03fd-ce4b-feef-5053-e95834ab35d7@gmail.com> On Sun, Feb 23, 2025 at 09:25:42PM +0100, Uros Bizjak wrote: > > Please note that GCC (and clang) provide __builtin_parity{,l,ll}() family of > builtin functions. Recently, I have tried to use this builtin in a couple of > places [1], [2], but I had to retract the patches, because __builtin > functions aren't strictly required to be inlined and can generate a library > call [3]. > > As explained in [2], the compilers are able to emit optimized > target-dependent code (also automatically using popcnt insn when avaialble), > so ideally the generic parity64() and parity32() would be implemented using > __builtin_parity(), where the generic library would provide a fallback > __paritydi2() and __paritysi2() functions, otherwise provided by the > compiler support library. > > For x86, we would like to exercise the hardware parity calculation or > optimized code sequences involving HW parity calculation, as shown in [1] > and [2]. > > [1] https://lore.kernel.org/lkml/20250129205746.10963-1-ubizjak@gmail.com/ > > [2] https://lore.kernel.org/lkml/20250129154920.6773-2-ubizjak@gmail.com/ > > [3] https://lore.kernel.org/linux-mm/CAKbZUD0N7bkuw_Le3Pr9o1V2BjjcY_YiLm8a8DPceubTdZ00GQ@mail.gmail.com/ Hi Uros, Thanks for your information. We originally planned to implement hardware optimizations after this patch series. However, for V2, We will incorporate __builtin_parity(), while keeping our current implementation as the fallback function. Best regards, Yu-Chun Lin