Re: [PATCH v3 10/16] MIPS: math-emu: MINA.<D|S>: Fix some cases of infinity and zero inputs

From: James Hogan
Date: Fri Jul 21 2017 - 12:01:53 EST


On Fri, Jul 21, 2017 at 04:09:08PM +0200, Aleksandar Markovic wrote:
> From: Aleksandar Markovic <aleksandar.markovic@xxxxxxxxxx>
>
> Fix following special cases for MINA>.<D|S>:
>
> - if one of the inputs is zero, and the other is subnormal, normal,
> or infinity, the value of the former should be returned (that is,
> a zero).
> - if one of the inputs is infinity, and the other input is normal,
> or subnormal, the value of the latter should be returned.
>
> The previous implementation's logic for such cases was incorrect - it
> appears as if it implements MAXA, and not MINA instruction.
>
> The relevant example:
>
> MINA.S fd,fs,ft:
> If fs contains 100.0, and ft contains 0.0, fd is going to contain
> 0.0 (without this patch, it used to contain 100.0).

Another ouch!

>

Fixes/stable

> Signed-off-by: Miodrag Dinic <miodrag.dinic@xxxxxxxxxx>
> Signed-off-by: Goran Ferenc <goran.ferenc@xxxxxxxxxx>
> Signed-off-by: Aleksandar Markovic <aleksandar.markovic@xxxxxxxxxx>

Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx>

Cheers
James

> ---
> arch/mips/math-emu/dp_fmin.c | 4 ++--
> arch/mips/math-emu/sp_fmin.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/mips/math-emu/dp_fmin.c b/arch/mips/math-emu/dp_fmin.c
> index d4cd243..1e9ee3d 100644
> --- a/arch/mips/math-emu/dp_fmin.c
> +++ b/arch/mips/math-emu/dp_fmin.c
> @@ -191,14 +191,14 @@ union ieee754dp ieee754dp_fmina(union ieee754dp x, union ieee754dp y)
> case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
> case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
> case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
> - return x;
> + return y;
>
> case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
> case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
> - return y;
> + return x;
>
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
> return ieee754dp_zero(xs | ys);
> diff --git a/arch/mips/math-emu/sp_fmin.c b/arch/mips/math-emu/sp_fmin.c
> index 5f1d650..685ce75 100644
> --- a/arch/mips/math-emu/sp_fmin.c
> +++ b/arch/mips/math-emu/sp_fmin.c
> @@ -192,14 +192,14 @@ union ieee754sp ieee754sp_fmina(union ieee754sp x, union ieee754sp y)
> case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
> case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
> case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
> - return x;
> + return y;
>
> case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
> case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
> - return y;
> + return x;
>
> case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
> return ieee754sp_zero(xs | ys);
> --
> 2.7.4
>

Attachment: signature.asc
Description: Digital signature