From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E247F35972 for ; Thu, 15 Jan 2026 02:03:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768442601; cv=none; b=s248Abq++UYJYV/Oo5jh3QSe5zzHS0RBY7IOcxNkKnvOvR/trLNYJ/5gIKyRJ/cX6V3zDjKYXf0M6ZtDdnpzT8P1QHg6PBxG35/xAxiLvlSxx5fA8DWPhvHRV+HL/CHACeBepPIwNbtxcsdtvN09fPU2ZNUiS3mSejXTIue01Is= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768442601; c=relaxed/simple; bh=O7klGUKze+JmEoVWfPW64zehXyQ9vx/NEeQSIvzysoo=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=mwPQXunnOMMb6G3mA09/hrY8n46ZHuUgeqKmSWXFIa04j1dvLUUGM8q29FGQuWBC7r63sJ72Jit0VKBuCQgg84Y4ahr6p32kzTIBgFivFiChdewXUyMRGcvPMGx5JRXPLpcXgKecroKYNw2qnFowgkvnPc6lhNVD8vr4kEKRunw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jSCSXaUW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jSCSXaUW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E69DFC4CEF7; Thu, 15 Jan 2026 02:03:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768442600; bh=O7klGUKze+JmEoVWfPW64zehXyQ9vx/NEeQSIvzysoo=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=jSCSXaUWHa4wn6LLzvefUJ/dDd3nhwq7Dm1CTj97CClkvihy4hZ6tg/zFiCeGg5Se Qqlaq1MHlOyAWgvS3Kh4vnJcJ14JKHInzdpdQ6MWXstaTTbUQM3Yk7RnWL3vLYHXil kGDXatKy4yxMzCkw0/TkbDocXEI0qC3CA7nFYjW2NNUD/mjQJACekmv2di7Hz//apK 8A+o+POj1XQoOaqKmECpdydI0wZ0oPZwf6KFLLaQSeR3mWSddgGhyHiCzXwixnE5uG 4WXj+ZN5o/NDHIoCZrPu2L/79b4j10kwWjBsTg1+031Reb7bUpbgfGpsQjQVYOj0BF /71iiDlpFOIBQ== Date: Wed, 14 Jan 2026 19:03:17 -0700 (MST) From: Paul Walmsley To: Feng Jiang cc: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, samuel.holland@sifive.com, charlie@rivosinc.com, conor.dooley@microchip.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: lib: optimize strlen loop efficiency In-Reply-To: <20251218032614.57356-1-jiangfeng@kylinos.cn> Message-ID: References: <20251218032614.57356-1-jiangfeng@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Thu, 18 Dec 2025, Feng Jiang wrote: > Optimize the generic strlen implementation by using a pre-decrement > pointer. This reduces the loop body from 4 instructions to 3 and > eliminates the unconditional jump ('j'). > > Old loop (4 instructions, 2 branches): > 1: lbu t0, 0(t1); beqz t0, 2f; addi t1, t1, 1; j 1b > > New loop (3 instructions, 1 branch): > 1: addi t1, t1, 1; lbu t0, 0(t1); bnez t0, 1b > > This change improves execution efficiency and reduces branch pressure > for systems without the Zbb extension. Looks reasonable; do you have any benchmarks on hardware that you can share? Any reason why this patch stands alone and isn't rolled up as part of your "optimize string function" series? - Paul