From: cp0613@linux.alibaba.com
To: yury.norov@gmail.com
Cc: alex@ghiti.fr, aou@eecs.berkeley.edu, arnd@arndb.de,
cp0613@linux.alibaba.com, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
linux@rasmusvillemoes.dk, palmer@dabbelt.com,
paul.walmsley@sifive.com
Subject: Re: [PATCH 2/2] bitops: rotate: Add riscv implementation using Zbb extension
Date: Sat, 28 Jun 2025 19:13:57 +0800 [thread overview]
Message-ID: <20250628111357.1627-1-cp0613@linux.alibaba.com> (raw)
In-Reply-To: <aFWKX4rpuNCDBP67@yury>
On Fri, 20 Jun 2025 12:20:47 -0400, yury.norov@gmail.com wrote:
> Can you add a comment about what is happening here? Are you sure it's
> optimized out in case of the 'legacy' alternative?
Thank you for your review. Yes, I referred to the existing variable__fls()
implementation, which should be fine.
> Here you wire ror/rol() to the variable_ror/rol() unconditionally, and
> that breaks compile-time rotation if the parameter is known at compile
> time.
>
> I believe, generic implementation will allow compiler to handle this
> case better. Can you do a similar thing to what fls() does in the same
> file?
I did consider it, but I did not find any toolchain that provides an
implementation similar to __builtin_ror or __builtin_rol. If there is one,
please help point it out.
In addition, I did not consider it carefully before. If the rotate function
is to be genericized, all archneed to include <asm-generic/bitops/rotate.h>.
I missed this step.
next prev parent reply other threads:[~2025-06-28 11:14 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-20 11:16 [PATCH 0/2] Implementing bitops rotate using riscv " cp0613
2025-06-20 11:16 ` [PATCH 1/2] bitops: generic rotate cp0613
2025-06-20 15:47 ` kernel test robot
2025-06-23 11:59 ` kernel test robot
2025-06-20 11:16 ` [PATCH 2/2] bitops: rotate: Add riscv implementation using Zbb extension cp0613
2025-06-20 16:20 ` Yury Norov
2025-06-25 16:02 ` David Laight
2025-06-28 12:08 ` cp0613
2025-06-29 10:38 ` David Laight
2025-06-30 12:14 ` cp0613
2025-06-30 17:35 ` David Laight
2025-07-01 13:01 ` cp0613
2025-06-28 11:13 ` cp0613 [this message]
2025-06-29 1:48 ` Yury Norov
2025-06-30 12:04 ` cp0613
2025-06-30 16:53 ` Yury Norov
2025-07-01 12:47 ` cp0613
2025-07-01 18:32 ` Yury Norov
2025-07-02 10:11 ` David Laight
2025-07-03 16:58 ` Yury Norov
2025-07-02 12:30 ` cp0613
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