Re: [Qemu-devel] [PATCH v5 20/28] fpu/softfloat: Use float*_silence_nan in propagateFloat*NaN

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> We have already checked the arguments for SNaN;
> we don't need to do it again.
>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  fpu/softfloat-specialize.h | 44 +++++++++++++++++++++++++++++---------
>  1 file changed, 34 insertions(+), 10 deletions(-)
>
> diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
> index 995a0132c6..4fa068a5dc 100644
> --- a/fpu/softfloat-specialize.h
> +++ b/fpu/softfloat-specialize.h
> @@ -498,7 +498,7 @@ static float32 commonNaNToFloat32(commonNaNT a, float_status *status)
>  | The routine is passed various bits of information about the
>  | two NaNs and should return 0 to select NaN a and 1 for NaN b.
>  | Note that signalling NaNs are always squashed to quiet NaNs
> -| by the caller, by calling floatXX_maybe_silence_nan() before
> +| by the caller, by calling floatXX_silence_nan() before
>  | returning them.
>  |
>  | aIsLargerSignificand is only valid if both a and b are NaNs
> @@ -536,7 +536,7 @@ static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
>  {
>      /* According to MIPS specifications, if one of the two operands is
>       * a sNaN, a new qNaN has to be generated. This is done in
> -     * floatXX_maybe_silence_nan(). For qNaN inputs the specifications
> +     * floatXX_silence_nan(). For qNaN inputs the specifications
>       * says: "When possible, this QNaN result is one of the operand QNaN
>       * values." In practice it seems that most implementations choose
>       * the first operand if both operands are qNaN. In short this gives
> @@ -788,9 +788,15 @@ static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
>
>      if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
>                  aIsLargerSignificand)) {
> -        return float32_maybe_silence_nan(b, status);
> +        if (bIsSignalingNaN) {
> +            return float32_silence_nan(b, status);
> +        }
> +        return b;
>      } else {
> -        return float32_maybe_silence_nan(a, status);
> +        if (aIsSignalingNaN) {
> +            return float32_silence_nan(a, status);
> +        }
> +        return a;
>      }
>  }
>
> @@ -950,9 +956,15 @@ static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
>
>      if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
>                  aIsLargerSignificand)) {
> -        return float64_maybe_silence_nan(b, status);
> +        if (bIsSignalingNaN) {
> +            return float64_silence_nan(b, status);
> +        }
> +        return b;
>      } else {
> -        return float64_maybe_silence_nan(a, status);
> +        if (aIsSignalingNaN) {
> +            return float64_silence_nan(a, status);
> +        }
> +        return a;
>      }
>  }
>
> @@ -1121,9 +1133,15 @@ floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b, float_status *status)
>
>      if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
>                  aIsLargerSignificand)) {
> -        return floatx80_maybe_silence_nan(b, status);
> +        if (bIsSignalingNaN) {
> +            return floatx80_silence_nan(b, status);
> +        }
> +        return b;
>      } else {
> -        return floatx80_maybe_silence_nan(a, status);
> +        if (aIsSignalingNaN) {
> +            return floatx80_silence_nan(a, status);
> +        }
> +        return a;
>      }
>  }
>
> @@ -1270,8 +1288,14 @@ static float128 propagateFloat128NaN(float128 a, float128 b,
>
>      if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
>                  aIsLargerSignificand)) {
> -        return float128_maybe_silence_nan(b, status);
> +        if (bIsSignalingNaN) {
> +            return float128_silence_nan(b, status);
> +        }
> +        return b;
>      } else {
> -        return float128_maybe_silence_nan(a, status);
> +        if (aIsSignalingNaN) {
> +            return float128_silence_nan(a, status);
> +        }
> +        return a;
>      }
>  }


--
Alex Bennée