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Date: Tue, 19 Apr 2011 18:06:57 +0100
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From: Peter Maydell <peter.maydell@linaro.org>
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Subject: Re: [Qemu-devel] [PATCH 11/20] target-i386: fix helper_flbd_ST0()
	wrt softfloat
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To: Aurelien Jarno <aurelien@aurel32.net>
Cc: qemu-devel@nongnu.org

On 18 April 2011 22:00, Aurelien Jarno <aurelien@aurel32.net> wrote:
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
> =C2=A0target-i386/op_helper.c | =C2=A0 =C2=A07 ++++---
> =C2=A01 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/target-i386/op_helper.c b/target-i386/op_helper.c
> index f614893..7dddd37 100644
> --- a/target-i386/op_helper.c
> +++ b/target-i386/op_helper.c
> @@ -3920,9 +3920,10 @@ void helper_fbld_ST0(target_ulong ptr)
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 v =3D ldub(ptr + i);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 val =3D (val * 100) + ((v >> 4) * 10) + (v & =
0xf);
> =C2=A0 =C2=A0 }
> - =C2=A0 =C2=A0tmp =3D val;
> - =C2=A0 =C2=A0if (ldub(ptr + 9) & 0x80)
> - =C2=A0 =C2=A0 =C2=A0 =C2=A0tmp =3D -tmp;
> + =C2=A0 =C2=A0if (ldub(ptr + 9) & 0x80) {
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0val =3D -val;
> + =C2=A0 =C2=A0}
> + =C2=A0 =C2=A0tmp =3D int64_to_floatx(val, &env->fp_status);
> =C2=A0 =C2=A0 fpush();
> =C2=A0 =C2=A0 ST0 =3D tmp;
> =C2=A0}

This doesn't do the right thing for -0 (should generate -0,
not +0). I think:

 tmp =3D int64_to_floatx(val, &env->fp_status);
 if (ldub(ptr + 9) & 0x80) {
     floatx_chs(tmp);
 }

ought to do the right thing and work for both softfloat and
sf-native, but I haven't tested it.

-- PMM