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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CAE4D1E@AcuExch.aculab.com> Date: Tue, 17 Feb 2015 12:04:22 +0000 From: David Laight <David.Laight@...LAB.COM> To: 'Jiri Slaby' <jslaby@...e.cz>, "stable@...r.kernel.org" <stable@...r.kernel.org> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, karl beldan <karl.beldan@...il.com>, Karl Beldan <karl.beldan@...ierawaves.com>, Al Viro <viro@...IV.linux.org.uk>, Eric Dumazet <eric.dumazet@...il.com>, "Arnd Bergmann" <arnd@...db.de>, Mike Frysinger <vapier@...too.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net> Subject: RE: [PATCH 3.12 065/122] lib/checksum.c: fix carry in csum_tcpudp_nofold > +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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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