Re: [qemu-s390x] [Qemu-devel] [PATCH v1 14/15] s390x/tcg: Handle all rounding modes overwritten by BFP instructions

[Richard Henderson]

On 2/12/19 3:03 AM, David Hildenbrand wrote:
> PoP describes "Round to nearest with ties away from 0" as
>   "The candidate nearest to the input value is selected. In case of a tie,
>    the candidate selected is the one that is larger in magnitude."
> 
> While float_round_ties_away is according to the introducing commit
> f9288a76f181 ("softfloat: Add support for ties-away rounding")
>   "roundTiesToAway: the floating-point number nearest to the infinitely
>    precise result shall be delivered; if the two nearest floating-point
>    numbers bracketing an unrepresentable infinitely precise result are
>    equally near, the one with larger magnitude shall be delivered."
> 
> So this could be it if we're lucky ;)

Yep, that's right.

> 
> Handle "round to prepare for shorter precision" just as when setting it
> via SET FLOATING POINT and friends.
> 
> As all instructions properly check for valid rounding modes in translate.c
> we can add an assert. Fix one missing empty line.
> 
> Cc: Peter Maydell <address@hidden>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---

Reviewed-by: Richard Henderson <address@hidden>


r~