1 // SPDX-License-Identifier: GPL-2.0
3  * arch/x86_64/lib/csum-partial.c
6  * in an architecture-specific manner due to speed.
12 #include <asm/word-at-a-time.h>
42  * it's best to have buff aligned on a 64-bit boundary
44 __wsum csum_partial(const void *buff, int len, __wsum sum)  in csum_partial()  argument
48 	/* Do two 40-byte chunks in parallel to get better ILP */  in csum_partial()
49 	if (likely(len >= 80)) {  in csum_partial()
55 			len -= 80;  in csum_partial()
56 		} while (len >= 80);  in csum_partial()
64 	 * len == 40 is the hot case due to IPv6 headers, so return  in csum_partial()
65 	 * early for that exact case without checking the tail bytes.  in csum_partial()
67 	if (len >= 40) {  in csum_partial()
69 		len -= 40;  in csum_partial()
70 		if (!len)  in csum_partial()
75 	if (len & 32) {  in csum_partial()
85 	if (len & 16) {  in csum_partial()
93 	if (len & 8) {  in csum_partial()
100 	if (len & 7) {  in csum_partial()
101 		unsigned int shift = (-len << 3) & 63;  in csum_partial()
116  * this routine is used for miscellaneous IP-like checksums, mainly
119 __sum16 ip_compute_csum(const void *buff, int len)  in ip_compute_csum()  argument
121 	return csum_fold(csum_partial(buff, len, 0));  in ip_compute_csum()