linux-kernel - Re: [PATCH] fat: Refactor fat_tolower with branchless implementation

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Message-ID: <20250318040323.GW2023217@ZenIV>
Date: Tue, 18 Mar 2025 04:03:23 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: I Hsin Cheng <richard120310@...il.com>
Cc: hirofumi@...l.parknet.co.jp, linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev,
	jserv@...s.ncku.edu.tw
Subject: Re: [PATCH] fat: Refactor fat_tolower with branchless implementation

On Tue, Mar 18, 2025 at 11:43:09AM +0800, I Hsin Cheng wrote:
> Elimate the need of if-else branch within fat_tolower, replace it with a
> branchless bitwise operation. This can reduce the number of branch ~130
> regarding to the test script[1].

... and for values outside of 32..126 it would give wrong results.