diff options
| author | Charlie Jenkins | 2024-01-08 15:57:02 -0800 |
|---|---|---|
| committer | Palmer Dabbelt | 2024-01-17 17:52:29 -0800 |
| commit | 1e7196fa5b0312a6a3e49e7c1300e145afcba96b (patch) | |
| tree | 999227adddf6063d7dbdf1661cb2a734780f128d /include | |
| parent | b85ea95d086471afb4ad062012a4d73cd328fa86 (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')
| -rw-r--r-- | include/asm-generic/checksum.h | 6 |
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 |