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?
-Scott
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