linux-kernel - Re: [PATCH 4/8] lib: introduce BITS

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Date:   Mon, 1 Feb 2021 15:42:26 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
        linux-sh@...r.kernel.org, linux-arch@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, Arnd Bergmann <arnd@...db.de>,
        Dennis Zhou <dennis@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        David Sterba <dsterba@...e.com>,
        Stefano Brivio <sbrivio@...hat.com>,
        "Ma, Jianpeng" <jianpeng.ma@...el.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 4/8] lib: introduce BITS_{FIRST,LAST} macro

On Sat, Jan 30, 2021 at 11:17:15AM -0800, Yury Norov wrote:
> BITMAP_{LAST,FIRST}_WORD_MASK() in linux/bitmap.h duplicates the
> functionality of GENMASK(). The scope of there macros is wider than just
> bitmap. This patch defines 4 new macros: BITS_FIRST(), BITS_LAST(),
> BITS_FIRST_MASK() and BITS_LAST_MASK() in linux/bits.h on top of GENMASK()
> and replaces BITMAP_{LAST,FIRST}_WORD_MASK() to avoid duplication and
> increases scope of the macros.

...

>  include/linux/bitmap.h            | 27 ++++++++++++---------------
>  include/linux/bits.h              |  6 ++++++
>  include/linux/cpumask.h           |  8 ++++----
>  include/linux/netdev_features.h   |  2 +-
>  include/linux/nodemask.h          |  2 +-
>  lib/bitmap.c                      | 26 +++++++++++++-------------
>  lib/find_bit.c                    |  4 ++--
>  lib/genalloc.c                    |  8 ++++----

Answering to your reply. I meant to split the below to a separate patch.

>  tools/include/linux/bitmap.h      | 20 ++++++--------------
>  tools/include/linux/bits.h        |  6 ++++++
>  tools/lib/bitmap.c                |  6 +++---
>  tools/lib/find_bit.c              |  2 +-
>  tools/testing/radix-tree/bitmap.c |  4 ++--

...

> +#define BITS_FIRST(nr)		GENMASK((nr), 0)
> +#define BITS_LAST(nr)		GENMASK(BITS_PER_LONG - 1, (nr))
> +
> +#define BITS_FIRST_MASK(nr)	BITS_FIRST((nr) % BITS_PER_LONG)
> +#define BITS_LAST_MASK(nr)	BITS_LAST((nr) % BITS_PER_LONG)

Any pointers to the difference in generated code for popular architectures
(x86. x86_64, arm, aarch64, ppc, ppc64)?

-- 
With Best Regards,
Andy Shevchenko