Le 23/10/2015 05:33, Scott Wood a écrit :
On Tue, 2015-09-22 at 16:34 +0200, Christophe Leroy wrote:
Simplify csum_add(a, b) in case a or b is constant 0
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
arch/powerpc/include/asm/checksum.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/powerpc/include/asm/checksum.h
b/arch/powerpc/include/asm/checksum.h
index 56deea8..f8a9704 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -119,7 +119,13 @@ static inline __wsum csum_add(__wsum csum, __wsum
addend)
{
#ifdef __powerpc64__
u64 res = (__force u64)csum;
+#endif
+ if (__builtin_constant_p(csum) && csum == 0)
+ return addend;
+ if (__builtin_constant_p(addend) && addend == 0)
+ return csum;
+#ifdef __powerpc64__
res += (__force u64)addend;
return (__force __wsum)((u32)res + (res >> 32));
#else
How often does this happen?
In the following patch (9/9), csum_add() is used to implement
csum_partial() for small blocks.
In several places in the networking code, csum_partial() is called with
0 as initial sum.
Christophe