From: Guenter Roeck <linux@roeck-us.net>
To: Charlie Jenkins <charlie@rivosinc.com>
Cc: "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
Helge Deller <deller@gmx.de>, Arnd Bergmann <arnd@arndb.de>,
Andrew Morton <akpm@linux-foundation.org>,
linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org
Subject: Re: [PATCH 4/4] parisc: checksum: Optimize from32to16
Date: Thu, 22 Feb 2024 08:04:49 -0800 [thread overview]
Message-ID: <e00be589-4e9e-48ec-8a25-ad7460f304fa@roeck-us.net> (raw)
In-Reply-To: <20240221-parisc_use_generic_checksum-v1-4-ad34d895fd1b@rivosinc.com>
On Wed, Feb 21, 2024 at 06:37:14PM -0800, Charlie Jenkins wrote:
> Replace the shifting and masking of x with a rotation. This generates
> better assembly.
>
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
> ---
> arch/parisc/lib/checksum.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/arch/parisc/lib/checksum.c b/arch/parisc/lib/checksum.c
> index eaa660491e24..1ae8cc730d13 100644
> --- a/arch/parisc/lib/checksum.c
> +++ b/arch/parisc/lib/checksum.c
> @@ -27,11 +27,8 @@
>
> static inline unsigned short from32to16(unsigned int x)
> {
> - /* 32 bits --> 16 bits + carry */
> - x = (x & 0xffff) + (x >> 16);
> - /* 16 bits + carry --> 16 bits including carry */
> - x = (x & 0xffff) + (x >> 16);
> - return (unsigned short)x;
> + x += ror32(x, 16);
> + return (unsigned short)(x >> 16);
> }
>
> unsigned int do_csum(const unsigned char *buff, int len)
>
> --
> 2.34.1
>
prev parent reply other threads:[~2024-02-22 16:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-22 2:37 [PATCH 0/4] parisc: checksum: Use generic implementations and optimize checksum Charlie Jenkins
2024-02-22 2:37 ` [PATCH 1/4] asm-generic headers: Allow csum_partial arch override Charlie Jenkins
2024-02-22 16:04 ` Guenter Roeck
2024-02-22 2:37 ` [PATCH 2/4] parisc: checksum: Use generic implementations Charlie Jenkins
2024-02-22 16:04 ` Guenter Roeck
2024-02-22 2:37 ` [PATCH 3/4] parisc: checksum: Remove folding from csum_partial Charlie Jenkins
2024-02-22 16:04 ` Guenter Roeck
2024-02-22 2:37 ` [PATCH 4/4] parisc: checksum: Optimize from32to16 Charlie Jenkins
2024-02-22 16:04 ` Guenter Roeck [this message]
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