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([140.113.216.168]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-223501fa8f1sm49231965ad.90.2025.03.01.06.25.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 01 Mar 2025 06:25:35 -0800 (PST) From: Kuan-Wei Chiu To: 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 Cc: 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, david.laight.linux@gmail.com, andrew.cooper3@citrix.com, Kuan-Wei Chiu , Yu-Chun Lin Subject: [PATCH v2 02/18] bitops: Optimize parity8() using __builtin_parity() Date: Sat, 1 Mar 2025 22:23:53 +0800 Message-Id: <20250301142409.2513835-3-visitorckw@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250301142409.2513835-1-visitorckw@gmail.com> References: <20250301142409.2513835-1-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Refactor parity8() to use __builtin_parity() when no architecture-specific implementation is available. If the input is a compile-time constant, expand it using the _parity_const() macro to enable constant folding, allowing the compiler to optimize it at compile time. Additionally, mark parity8() with __attribute_const__ to indicate its pure nature, ensuring better optimization opportunities. This change improves efficiency by leveraging compiler intrinsics while maintaining a fallback mechanism for architectures without specific implementations. Co-developed-by: Yu-Chun Lin Signed-off-by: Yu-Chun Lin Signed-off-by: Kuan-Wei Chiu --- include/linux/bitops.h | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/include/linux/bitops.h b/include/linux/bitops.h index c1cb53cf2f0f..4c307d9c1545 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -229,6 +229,27 @@ static inline int get_count_order_long(unsigned long l) return (int)fls_long(--l); } +#define _parity_const(val) \ +({ \ + u64 __v = (val); \ + int __ret; \ + __v ^= __v >> 32; \ + __v ^= __v >> 16; \ + __v ^= __v >> 8; \ + __v ^= __v >> 4; \ + __v ^= __v >> 2; \ + __v ^= __v >> 1; \ + __ret = __v & 1; \ + __ret; \ +}) + +#ifndef _parity8 +static inline __attribute_const__ int _parity8(u8 val) +{ + return __builtin_parity(val); +} +#endif + /** * parity8 - get the parity of an u8 value * @value: the value to be examined @@ -250,14 +271,9 @@ static inline int get_count_order_long(unsigned long l) * if (parity8(val) == 0) * val ^= BIT(7); */ -static inline int parity8(u8 val) +static inline __attribute_const__ int parity8(u8 val) { - /* - * One explanation of this algorithm: - * https://funloop.org/codex/problem/parity/README.html - */ - val ^= val >> 4; - return (0x6996 >> (val & 0xf)) & 1; + return __builtin_constant_p(val) ? _parity_const(val) : _parity8(val); } /**