Re: [PATCH 02/19] host-utils: move abs64() to host-utils

[David Gibson]

On Tue, Aug 24, 2021 at 11:27:13AM -0300, Luis Pires wrote:
> Move abs64 to host-utils so it can be reused elsewhere.
> Also made it inline.
> 
> Signed-off-by: Luis Pires <luis.pires@eldorado.org.br>
> ---
>  hw/i386/kvm/i8254.c       | 5 -----
>  include/qemu/host-utils.h | 8 ++++++++
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/i386/kvm/i8254.c b/hw/i386/kvm/i8254.c
> index fa68669e8a..761034743b 100644
> --- a/hw/i386/kvm/i8254.c
> +++ b/hw/i386/kvm/i8254.c
> @@ -59,11 +59,6 @@ struct KVMPITClass {
>      DeviceRealize parent_realize;
>  };
>  
> -static int64_t abs64(int64_t v)
> -{
> -    return v < 0 ? -v : v;

Hrm..  I'm a bit concerned about mkaing this a more widespread
function, because it has a nasty edge case... which is basically
unavoidable in an abs64() implementation.  Specifically:

abs64(0x800_0000_0000_00000) == 0x800_0000_0000_0000 < 0

At least in the most likely 2's complement implementation.

> -}
> -
>  static void kvm_pit_update_clock_offset(KVMPITState *s)
>  {
>      int64_t offset, clock_offset;
> diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
> index 711b221704..5fec44a9c4 100644
> --- a/include/qemu/host-utils.h
> +++ b/include/qemu/host-utils.h
> @@ -357,6 +357,14 @@ static inline uint64_t revbit64(uint64_t x)
>  #endif
>  }
>  
> +/**
> + * Return the absolute value of a 64-bit integer
> + */
> +static inline int64_t abs64(int64_t v)
> +{
> +    return v < 0 ? -v : v;
> +}
> +
>  /**
>   * sadd32_overflow - addition with overflow indication
>   * @x, @y: addends

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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