projects / ipfire-2.x.git / blame
| Commit | Line | Data |
|---|---|---|
| 82094b55 AF |
1 | From: Gerald Schaefer <geraldsc@de.ibm.com> |
| 2 | Subject: [PATCH] convert/optimize csum_fold() to C | |
| 3 | References: bnc#532063,LTC#55526 | |
| 4 | ||
| 5 | From: Heiko Carstens <heiko.carstens@de.ibm.com> | |
| 6 | ||
| 7 | In the meantime gcc generates better code than the old inline | |
| 8 | assemblies do. Original inline assembly results in: | |
| 9 | ||
| 10 | lr %r1,%r2 | |
| 11 | sr %r3,%r3 | |
| 12 | lr %r2,%r1 | |
| 13 | srdl %r2,16 | |
| 14 | alr %r2,%r3 | |
| 15 | alr %r1,%r2 | |
| 16 | srl %r1,16 | |
| 17 | xilf %r1,65535 | |
| 18 | llghr %r2,%r1 | |
| 19 | br %r14 | |
| 20 | ||
| 21 | Out of the C code gcc generates this: | |
| 22 | ||
| 23 | rll %r1,%r2,16 | |
| 24 | ar %r1,%r2 | |
| 25 | srl %r1,16 | |
| 26 | xilf %r1,65535 | |
| 27 | llghr %r2,%r1 | |
| 28 | br %r14 | |
| 29 | ||
| 30 | In addition we don't have any static register allocations anymore and | |
| 31 | gcc is free to shuffle instructions around for better pipeline usage. | |
| 32 | ||
| 33 | Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> | |
| 34 | Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> | |
| 35 | ||
| 36 | Acked-by: John Jolly <jjolly@suse.de> | |
| 37 | --- | |
| 38 | ||
| 39 | arch/s390/include/asm/checksum.h | 25 ++++--------------------- | |
| 40 | 1 file changed, 4 insertions(+), 21 deletions(-) | |
| 41 | ||
| 42 | diff -urpN linux-2.6/arch/s390/include/asm/checksum.h linux-2.6-patched/arch/s390/include/asm/checksum.h | |
| 43 | --- linux-2.6/arch/s390/include/asm/checksum.h 2009-06-10 05:05:27.000000000 +0200 | |
| 44 | +++ linux-2.6-patched/arch/s390/include/asm/checksum.h 2009-06-30 09:21:36.000000000 +0200 | |
| 45 | @@ -78,28 +78,11 @@ csum_partial_copy_nocheck (const void *s | |
| 46 | */ | |
| 47 | static inline __sum16 csum_fold(__wsum sum) | |
| 48 | { | |
| 49 | -#ifndef __s390x__ | |
| 50 | - register_pair rp; | |
| 51 | + u32 csum = (__force u32) sum; | |
| 52 | ||
| 53 | - asm volatile( | |
| 54 | - " slr %N1,%N1\n" /* %0 = H L */ | |
| 55 | - " lr %1,%0\n" /* %0 = H L, %1 = H L 0 0 */ | |
| 56 | - " srdl %1,16\n" /* %0 = H L, %1 = 0 H L 0 */ | |
| 57 | - " alr %1,%N1\n" /* %0 = H L, %1 = L H L 0 */ | |
| 58 | - " alr %0,%1\n" /* %0 = H+L+C L+H */ | |
| 59 | - " srl %0,16\n" /* %0 = H+L+C */ | |
| 60 | - : "+&d" (sum), "=d" (rp) : : "cc"); | |
| 61 | -#else /* __s390x__ */ | |
| 62 | - asm volatile( | |
| 63 | - " sr 3,3\n" /* %0 = H*65536 + L */ | |
| 64 | - " lr 2,%0\n" /* %0 = H L, 2/3 = H L / 0 0 */ | |
| 65 | - " srdl 2,16\n" /* %0 = H L, 2/3 = 0 H / L 0 */ | |
| 66 | - " alr 2,3\n" /* %0 = H L, 2/3 = L H / L 0 */ | |
| 67 | - " alr %0,2\n" /* %0 = H+L+C L+H */ | |
| 68 | - " srl %0,16\n" /* %0 = H+L+C */ | |
| 69 | - : "+&d" (sum) : : "cc", "2", "3"); | |
| 70 | -#endif /* __s390x__ */ | |
| 71 | - return (__force __sum16) ~sum; | |
| 72 | + csum += (csum >> 16) + (csum << 16); | |
| 73 | + csum >>= 16; | |
| 74 | + return (__force __sum16) ~csum; | |
| 75 | } | |
| 76 | ||
| 77 | /* |