Messages in this thread | | | From | Christophe Leroy <> | Subject | Re: [PATCH 8/9] powerpc: simplify csum_add(a, b) in case a or b is constant 0 | Date | Mon, 29 Feb 2016 08:26:42 +0100 |
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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.leroy@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
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