Messages in this thread Patch in this message | | | Date | Fri, 14 Aug 2009 13:25:31 +0200 | From | Martin Schwidefsky <> | Subject | [patch 14/34] convert/optimize csum_fold() to C |
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
In the meantime gcc generates better code than the old inline assemblies do. Original inline assembly results in:
lr %r1,%r2 sr %r3,%r3 lr %r2,%r1 srdl %r2,16 alr %r2,%r3 alr %r1,%r2 srl %r1,16 xilf %r1,65535 llghr %r2,%r1 br %r14
Out of the C code gcc generates this:
rll %r1,%r2,16 ar %r1,%r2 srl %r1,16 xilf %r1,65535 llghr %r2,%r1 br %r14
In addition we don't have any static register allocations anymore and gcc is free to shuffle instructions around for better pipeline usage.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> ---
arch/s390/include/asm/checksum.h | 25 ++++--------------------- 1 file changed, 4 insertions(+), 21 deletions(-)
Index: quilt-2.6/arch/s390/include/asm/checksum.h =================================================================== --- quilt-2.6.orig/arch/s390/include/asm/checksum.h +++ quilt-2.6/arch/s390/include/asm/checksum.h @@ -78,28 +78,11 @@ csum_partial_copy_nocheck (const void *s */ static inline __sum16 csum_fold(__wsum sum) { -#ifndef __s390x__ - register_pair rp; + u32 csum = (__force u32) sum; - asm volatile( - " slr %N1,%N1\n" /* %0 = H L */ - " lr %1,%0\n" /* %0 = H L, %1 = H L 0 0 */ - " srdl %1,16\n" /* %0 = H L, %1 = 0 H L 0 */ - " alr %1,%N1\n" /* %0 = H L, %1 = L H L 0 */ - " alr %0,%1\n" /* %0 = H+L+C L+H */ - " srl %0,16\n" /* %0 = H+L+C */ - : "+&d" (sum), "=d" (rp) : : "cc"); -#else /* __s390x__ */ - asm volatile( - " sr 3,3\n" /* %0 = H*65536 + L */ - " lr 2,%0\n" /* %0 = H L, 2/3 = H L / 0 0 */ - " srdl 2,16\n" /* %0 = H L, 2/3 = 0 H / L 0 */ - " alr 2,3\n" /* %0 = H L, 2/3 = L H / L 0 */ - " alr %0,2\n" /* %0 = H+L+C L+H */ - " srl %0,16\n" /* %0 = H+L+C */ - : "+&d" (sum) : : "cc", "2", "3"); -#endif /* __s390x__ */ - return (__force __sum16) ~sum; + csum += (csum >> 16) + (csum << 16); + csum >>= 16; + return (__force __sum16) ~csum; } /* -- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
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