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authorHeiko Carstens <heiko.carstens@de.ibm.com>2009-09-11 10:28:32 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2009-09-11 10:29:43 +0200
commit04efc3be767cfed0d348fd598eba8fe5f5bf5fe6 (patch)
tree53a6509f836e2f85c34e5a3af66fa9fbff910f77 /arch/s390/include
parent05e7ff7da78bad3edc1290ed86b4a37da72ced62 (diff)
downloadop-kernel-dev-04efc3be767cfed0d348fd598eba8fe5f5bf5fe6.zip
op-kernel-dev-04efc3be767cfed0d348fd598eba8fe5f5bf5fe6.tar.gz
[S390] convert/optimize csum_fold() to C
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>
Diffstat (limited to 'arch/s390/include')
-rw-r--r--arch/s390/include/asm/checksum.h25
1 files changed, 4 insertions, 21 deletions
diff --git a/arch/s390/include/asm/checksum.h b/arch/s390/include/asm/checksum.h
index d5a8e7c..6c00f68 100644
--- a/arch/s390/include/asm/checksum.h
+++ b/arch/s390/include/asm/checksum.h
@@ -78,28 +78,11 @@ csum_partial_copy_nocheck (const void *src, void *dst, int len, __wsum sum)
*/
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;
}
/*
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