On Mon, Feb 01, 2016 at 04:36:38PM -0800, Eric Dumazet wrote: > On Tue, 2016-02-02 at 00:08 +0100, Rasmus Villemoes wrote: > > > Thanks. (Is there a good way to tell gcc that avg*avg is actually a > > 32x32->64 multiplication?) > > If avg is 32bit, compiler does that for you. > > u32 avg = ... > > u64 result = (u64)avg * avg;
It does not in fact do that :/ See commit:
9e3d6223d209 ("math64, timers: Fix 32bit mul_u64_u32_shr() and friends")
