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SubjectRe: [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


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