| From | David Laight <> | Subject | RE: [PATCH 3.12 065/122] lib/checksum.c: fix carry in csum_tcpudp_nofold | Date | Tue, 17 Feb 2015 12:04:22 +0000 |
| |
> +static inline u32 from64to32(u64 x) > +{ > + /* add up 32-bit and 32-bit for 32+c bit */ > + x = (x & 0xffffffff) + (x >> 32); > + /* add up carry.. */ > + x = (x & 0xffffffff) + (x >> 32); > + return (u32)x; > +}
As a matter of interest, does the compiler optimise away the second (x & 0xffffffff) ? The code could just be: x = (x & 0xffffffff) + (x >> 32); return x + (x >> 32);
David
|