linux-kernel - Re: [PATCH v3 0/4] do_div() with constant divisor simplification

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Message-ID: <r8r3nno4-45r3-09rr-797q-3o79s35n91ro@syhkavp.arg>
Date: Thu, 5 Sep 2024 21:47:29 -0400 (EDT)
From: Nicolas Pitre <nico@...xnic.net>
To: Arnd Bergmann <arnd@...db.de>
cc: Russell King <linux@...linux.org.uk>, linux-arch@...r.kernel.org, 
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/4] do_div() with constant divisor simplification

Ping.


On Sun, 7 Jul 2024, Nicolas Pitre wrote:

> While working on mul_u64_u64_div_u64() improvements I realized that there
> is a better way to perform a 64x64->128 bits multiplication with overflow
> handling. This is not as lean as v1 of the series but still much better
> than the existing code IMHO.
> 
> Change from v2:
> 
> - Fix last minute edit screw-up (missing one function return type).
> 
> Link to v2: https://lore.kernel.org/lkml/20240707171919.1951895-1-nico@fluxnic.net/
> 
> Changes from v1:
> 
> - Formalize condition for when overflow handling can be skipped.
> - Make this condition apply only if it can be determined at compile time
>   (beware of the compiler not always inling code).
> - Keep the ARM assembly but apply the above changes to it as well.
> - Force __always_inline when optimizing for performance.
> - Augment test_div64.c with important edge cases.
> 
> Link to v1: https://lore.kernel.org/lkml/20240705022334.1378363-1-nico@fluxnic.net/
> 
> The diffstat is:
> 
>  arch/arm/include/asm/div64.h |  13 +++-
>  include/asm-generic/div64.h  | 121 ++++++++++++-----------------------
>  lib/math/test_div64.c        |  85 +++++++++++++++++++++++-
>  3 files changed, 134 insertions(+), 85 deletions(-)
> 
>