From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Yury Norov <yury.norov@gmail.com>
Cc: Alexander Potapenko <glider@google.com>,
catalin.marinas@arm.com, will@kernel.org, pcc@google.com,
andreyknvl@gmail.com, linux@rasmusvillemoes.dk,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, eugenis@google.com,
syednwaris@gmail.com, william.gray@linaro.org,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v4 1/5] lib/bitmap: add bitmap_{set,get}_value()
Date: Fri, 4 Aug 2023 23:05:19 +0300 [thread overview]
Message-ID: <ZM1Z/6l6yCaOEjjF@smile.fi.intel.com> (raw)
In-Reply-To: <ZM1XlUbAJ7Qpd6OO@yury-ThinkPad>
On Fri, Aug 04, 2023 at 12:55:01PM -0700, Yury Norov wrote:
> On Fri, Aug 04, 2023 at 06:07:00PM +0200, Alexander Potapenko wrote:
> > > > ~BITMAP_FIRST_WORD_MASK(start));
> > >
> > > As I said, ~BITMAP_FIRST_WORD_MASK() is the same as BITMAP_LAST_WORD_MASK()
> > > and vise-versa.
> >
> > Surprisingly, ~BITMAP_FIRST_WORD_MASK() generates better code than
> > BITMAP_LAST_WORD_MASK().
>
> Wow... If that's consistent across different compilers/arches, we'd
> just drop the latter. Thanks for pointing that. I'll check.
It might be...
...
> > map[index] &= (fit ? (~(GENMASK(nbits - 1, 0) << offset)) :
> > ~BITMAP_FIRST_WORD_MASK(start));
...that both parts of ternary are using negation. So compiler may use negation
only once. (Haven't looked at the assembly.)
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2023-08-04 20:05 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-20 17:39 [PATCH v4 0/5] Implement MTE tag compression for swapped pages Alexander Potapenko
2023-07-20 17:39 ` [PATCH v4 1/5] lib/bitmap: add bitmap_{set,get}_value() Alexander Potapenko
2023-07-23 1:57 ` Yury Norov
2023-07-23 15:38 ` Yury Norov
2023-09-22 7:48 ` Alexander Potapenko
2023-07-24 8:36 ` Andy Shevchenko
2023-07-25 5:04 ` Yury Norov
2023-07-25 9:00 ` Andy Shevchenko
2023-07-26 8:08 ` Alexander Potapenko
2023-07-27 0:14 ` Yury Norov
2023-08-04 16:07 ` Alexander Potapenko
2023-08-04 19:55 ` Yury Norov
2023-08-04 20:05 ` Andy Shevchenko [this message]
2023-09-22 7:49 ` Alexander Potapenko
2023-09-22 7:47 ` Alexander Potapenko
2023-07-20 17:39 ` [PATCH v4 2/5] lib/test_bitmap: add tests for bitmap_{set,get}_value() Alexander Potapenko
2023-07-23 2:29 ` Yury Norov
2023-09-22 7:57 ` Alexander Potapenko
2023-09-22 13:28 ` Yury Norov
2023-09-27 12:33 ` Alexander Potapenko
2023-07-20 17:39 ` [PATCH v4 3/5] arm64: mte: implement CONFIG_ARM64_MTE_COMP Alexander Potapenko
2023-07-21 11:22 ` Andy Shevchenko
2023-09-22 8:03 ` Alexander Potapenko
2023-08-18 17:57 ` Catalin Marinas
2023-09-22 8:04 ` Alexander Potapenko
2023-07-20 17:39 ` [PATCH v4 4/5] arm64: mte: add a test for MTE tags compression Alexander Potapenko
2023-07-21 11:25 ` Andy Shevchenko
2023-09-22 8:05 ` Alexander Potapenko
2023-07-20 17:39 ` [PATCH v4 5/5] arm64: mte: add compression support to mteswap.c Alexander Potapenko
2023-08-18 18:18 ` Catalin Marinas
2023-09-20 13:26 ` Alexander Potapenko
2023-09-20 16:18 ` Alexander Potapenko
2023-09-20 14:22 ` Alexander Potapenko
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