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AArch64 is capable of 128-bit memory accesses without alignment restrictions, which makes it both possible and highly practical to slurp up a typical 20-byte IP header in just 2 loads. Implement our own version of ip_fast_checksum() to take advantage of that, resulting in considerably fewer instructions and memory accesses than the generic version. We can also get more optimal code generation for csum_fold() by defining it a slightly different way round from the generic version, so throw that into the mix too. Suggested-by: Luke Starrett <luke.starrett@broadcom.com> Acked-by: Luke Starrett <luke.starrett@broadcom.com> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
52 lines
1.3 KiB
C
52 lines
1.3 KiB
C
/*
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* Copyright (C) 2016 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __ASM_CHECKSUM_H
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#define __ASM_CHECKSUM_H
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#include <linux/types.h>
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static inline __sum16 csum_fold(__wsum csum)
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{
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u32 sum = (__force u32)csum;
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sum += (sum >> 16) | (sum << 16);
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return ~(__force __sum16)(sum >> 16);
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}
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#define csum_fold csum_fold
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static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
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{
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__uint128_t tmp;
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u64 sum;
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tmp = *(const __uint128_t *)iph;
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iph += 16;
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ihl -= 4;
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tmp += ((tmp >> 64) | (tmp << 64));
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sum = tmp >> 64;
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do {
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sum += *(const u32 *)iph;
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iph += 4;
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} while (--ihl);
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sum += ((sum >> 32) | (sum << 32));
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return csum_fold(sum >> 32);
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}
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#define ip_fast_csum ip_fast_csum
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#include <asm-generic/checksum.h>
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#endif /* __ASM_CHECKSUM_H */
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