Re: [Qemu-devel] [PATCH v2 1/3] int128: add int128_exts64()

[Paolo Bonzini <pbonzini@redhat.com>]

Il 22/08/2013 10:20, Alexey Kardashevskiy ha scritto:
> This adds macro to extend signed 64bit value to signed 128bit value.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>  include/qemu/int128.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/qemu/int128.h b/include/qemu/int128.h
> index 9ed47aa..987a1a9 100644
> --- a/include/qemu/int128.h
> +++ b/include/qemu/int128.h
> @@ -38,6 +38,11 @@ static inline Int128 int128_2_64(void)
>      return (Int128) { 0, 1 };
>  }
>  
> +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!).

>  static inline Int128 int128_and(Int128 a, Int128 b)
>  {
>      return (Int128) { a.lo & b.lo, a.hi & b.hi };
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo