| Message ID | 5549ecca2c921f34d076c47b5e2a91a3e78b20a7.1442876807.git.christophe.leroy@c-s.fr |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
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? -Scott -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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
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
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(+)