Re: [PATCH 04/14] lib: introduce BITS_{FIRST,LAST} macro

[Rasmus Villemoes]

On 18/02/2021 05.05, 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 increase the scope of the macros.
> 

Please include some info on changes in generated code, if any. When the
parameter to the macro is a constant I'm sure it all folds to a
compile-time constant either way, but when it's not, I'm not sure gcc
can do the same optimizations when the expressions become more complicated.

Rasmus