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authorCharlie Jenkins <charlie@rivosinc.com>2024-01-08 15:57:02 -0800
committerPalmer Dabbelt <palmer@rivosinc.com>2024-01-17 17:52:29 -0800
commit1e7196fa5b0312a6a3e49e7c1300e145afcba96b (patch)
tree999227adddf6063d7dbdf1661cb2a734780f128d /include/asm-generic
parentb85ea95d086471afb4ad062012a4d73cd328fa86 (diff)
asm-generic: Improve csum_fold
This csum_fold implementation introduced into arch/arc by Vineet Gupta is better than the default implementation on at least arc, x86, and riscv. Using GCC trunk and compiling non-inlined version, this implementation has 41.6667%, 25% fewer instructions on riscv64, x86-64 respectively with -O3 optimization. Most implmentations override this default in asm, but this should be more performant than all of those other implementations except for arm which has barrel shifting and sparc32 which has a carry flag. Signed-off-by: Charlie Jenkins <charlie@rivosinc.com> Reviewed-by: David Laight <david.laight@aculab.com> Link: https://lore.kernel.org/r/20240108-optimize_checksum-v15-1-1c50de5f2167@rivosinc.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/checksum.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/asm-generic/checksum.h b/include/asm-generic/checksum.h
index 43e18db89c14..ad928cce268b 100644
--- a/include/asm-generic/checksum.h
+++ b/include/asm-generic/checksum.h
@@ -2,6 +2,8 @@
#ifndef __ASM_GENERIC_CHECKSUM_H
#define __ASM_GENERIC_CHECKSUM_H
+#include <linux/bitops.h>
+
/*
* computes the checksum of a memory block at buff, length len,
* and adds in "sum" (32-bit)
@@ -31,9 +33,7 @@ extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
static inline __sum16 csum_fold(__wsum csum)
{
u32 sum = (__force u32)csum;
- sum = (sum & 0xffff) + (sum >> 16);
- sum = (sum & 0xffff) + (sum >> 16);
- return (__force __sum16)~sum;
+ return (__force __sum16)((~sum - ror32(sum, 16)) >> 16);
}
#endif