On 22 August 2013 10:09, Paolo Bonzini <pbonz...@redhat.com> wrote: > Il 22/08/2013 10:20, Alexey Kardashevskiy ha scritto: >> +static inline Int128 int128_exts64(int64_t a) >> +{ >> + return (Int128) { .lo = a, .hi = (a >> 63) ? -1 : 0 }; >> +} > > The "? -1 : 0" is not necessary, but the compiler will remove it at -O1 > or more (interestingly, or -O0 it will remove the shift and leave the > conditional!).
We can avoid relying on implementation defined behaviour here by using .hi = (a < 0) ? -1 : 0; (I know we allow ourselves to assume right-shift of signed ints is arithmetic shift, but I think it's nicer to avoid it unless it really makes the code better.) -- PMM