Re: [Qemu-devel] [PATCH v2 06/24] softfloat: Only raise Invalid when conversions to int are out of range

[Richard Henderson <rth@twiddle.net>]

On 01/06/2014 05:11 AM, Peter Maydell wrote:
> We implement a number of float-to-integer conversions using conversion
> to an integer type with a wider range and then a check against the
> narrower range we are actually converting to. If we find the result to
> be out of range we correctly raise the Invalid exception, but we must
> also suppress other exceptions which might have been raised by the
> conversion function we called.
> 
> This won't throw away exceptions we should have preserved, because for
> the 'core' exception flags the IEEE spec mandates that the only valid
> combinations of exception that can be raised by a single operation are
> Inexact + Overflow and Inexact + Underflow. For the non-IEEE softfloat
> flag for input denormals, we can guarantee that that flag won't have
> been set for out of range float-to-int conversions because a squashed
> denormal by definition goes to plus or minus zero, which is always in
> range after conversion to integer zero.
> 
> This bug has been fixed for some of the float-to-int conversion routines
> by previous patches; fix it for the remaining functions as well, so
> that they all restore the pre-conversion status flags prior to raising
> Invalid.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
>  fpu/softfloat.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)

Reviewed-by: Richard Henderson <rth@twiddle.net>


r~