From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
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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