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Message-Id: <20240221-parisc_use_generic_checksum-v1-4-ad34d895fd1b@rivosinc.com>
Date: Wed, 21 Feb 2024 18:37:14 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
Helge Deller <deller@....de>, Arnd Bergmann <arnd@...db.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Guenter Roeck <linux@...ck-us.net>
Cc: linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 4/4] parisc: checksum: Optimize from32to16
Replace the shifting and masking of x with a rotation. This generates
better assembly.
Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
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
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