Re: [Qemu-devel] [PATCH 07/20] softfloat: fix float*_scalnb() corner cases

[Peter Maydell]

On 18 April 2011 21:59, Aurelien Jarno <address@hidden> wrote:

> @@ -6349,6 +6352,12 @@ float32 float32_scalbn( float32 a, int n STATUS_PARAM )
>     else if ( aSig == 0 )
>         return a;
>
> +    if (n > 0x80) {
> +        n = 0x80;
> +    } else if (n < -0x80) {
> +        n = -0x80;
> +    }
> +
>     aExp += n - 1;
>     aSig <<= 7;
>     return normalizeRoundAndPackFloat32( aSign, aExp, aSig STATUS_VAR );

I don't think your if() condition is right here. Consider the
float32 00800000 (1.0 * 2 ^ -126 ; the smallest possible normalised
number); you can multiply this by, say, 2^253, without overflowing
to infinity. However your if() here means we'll incorrectly
compute the result of multiplying by 2^128 instead. s/0x80/0x200/
should work.

The others look OK to me. I would personally prefer to retain the int16
etc rather than moving to int16_t, but I don't quite feel strongly enough
to argue about it.

-- PMM