linux-kernel - Re: [PATCH v3 05/16] MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix quiet NaN propagation

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Date:   Fri, 21 Jul 2017 15:45:04 +0100
From:   James Hogan <james.hogan@...tec.com>
To:     Aleksandar Markovic <aleksandar.markovic@...rk.com>
CC:     <linux-mips@...ux-mips.org>,
        Aleksandar Markovic <aleksandar.markovic@...tec.com>,
        Miodrag Dinic <miodrag.dinic@...tec.com>,
        Goran Ferenc <goran.ferenc@...tec.com>,
        Douglas Leung <douglas.leung@...tec.com>,
        <linux-kernel@...r.kernel.org>,
        Paul Burton <paul.burton@...tec.com>,
        Petar Jovanovic <petar.jovanovic@...tec.com>,
        Raghu Gandham <raghu.gandham@...tec.com>,
        Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH v3 05/16] MIPS: math-emu: <MAX|MAXA|MIN|MINA>.<D|S>: Fix
 quiet NaN propagation

On Fri, Jul 21, 2017 at 04:09:03PM +0200, Aleksandar Markovic wrote:
> From: Aleksandar Markovic <aleksandar.markovic@...tec.com>
> 
> Fix the value returned by <MAX|MAXA|MIN|MINA>.<D|S>, if both inputs
> are quiet NaNs. The specifications of <MAX|MAXA|MIN|MINA>.<D|S> state
> that the returned value in such cases should be the quiet NaN
> contained in register fs.
> 
> The relevant example:
> 
> MAX.S fd,fs,ft:
>   If fs contains qNaN1, and ft contains qNaN2, fd is going to contain
>   qNaN1 (without this patch, it used to contain qNaN2).
> 

Consider adding:

Fixes: a79f5f9ba508 ("MIPS: math-emu: Add support for the MIPS R6 MAX{, A} FPU instruction")
Fixes: 4e9561b20e2f ("MIPS: math-emu: Add support for the MIPS R6 MIN{, A} FPU instruction")

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

Consider adding:

Cc: <stable@...r.kernel.org> # 4.3+

> ---
>  arch/mips/math-emu/dp_fmax.c | 8 ++++++--
>  arch/mips/math-emu/dp_fmin.c | 8 ++++++--
>  arch/mips/math-emu/sp_fmax.c | 8 ++++++--
>  arch/mips/math-emu/sp_fmin.c | 8 ++++++--
>  4 files changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/mips/math-emu/dp_fmax.c b/arch/mips/math-emu/dp_fmax.c
> index fd71b8d..567fc33 100644
> --- a/arch/mips/math-emu/dp_fmax.c
> +++ b/arch/mips/math-emu/dp_fmax.c
> @@ -47,6 +47,9 @@ union ieee754dp ieee754dp_fmax(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754dp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;

couldn't the above...

> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -54,7 +57,6 @@ union ieee754dp ieee754dp_fmax(union ieee754dp x, union ieee754dp y)

... go somewhere around here and fall through to the existing return x
case?

and same below of course.

Otherwise:
Reviewed-by: James Hogan <james.hogan@...tec.com>

Cheers
James



>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> @@ -147,6 +149,9 @@ union ieee754dp ieee754dp_fmaxa(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754dp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -154,7 +159,6 @@ union ieee754dp ieee754dp_fmaxa(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> diff --git a/arch/mips/math-emu/dp_fmin.c b/arch/mips/math-emu/dp_fmin.c
> index c1072b0..77f7ca9 100644
> --- a/arch/mips/math-emu/dp_fmin.c
> +++ b/arch/mips/math-emu/dp_fmin.c
> @@ -47,6 +47,9 @@ union ieee754dp ieee754dp_fmin(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754dp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -54,7 +57,6 @@ union ieee754dp ieee754dp_fmin(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> @@ -147,6 +149,9 @@ union ieee754dp ieee754dp_fmina(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754dp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -154,7 +159,6 @@ union ieee754dp ieee754dp_fmina(union ieee754dp x, union ieee754dp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> diff --git a/arch/mips/math-emu/sp_fmax.c b/arch/mips/math-emu/sp_fmax.c
> index 4d00084..d46e8e4 100644
> --- a/arch/mips/math-emu/sp_fmax.c
> +++ b/arch/mips/math-emu/sp_fmax.c
> @@ -47,6 +47,9 @@ union ieee754sp ieee754sp_fmax(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754sp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -54,7 +57,6 @@ union ieee754sp ieee754sp_fmax(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> @@ -147,6 +149,9 @@ union ieee754sp ieee754sp_fmaxa(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754sp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -154,7 +159,6 @@ union ieee754sp ieee754sp_fmaxa(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> diff --git a/arch/mips/math-emu/sp_fmin.c b/arch/mips/math-emu/sp_fmin.c
> index 4eb1bb9..b528c4b 100644
> --- a/arch/mips/math-emu/sp_fmin.c
> +++ b/arch/mips/math-emu/sp_fmin.c
> @@ -47,6 +47,9 @@ union ieee754sp ieee754sp_fmin(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754sp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -54,7 +57,6 @@ union ieee754sp ieee754sp_fmin(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> @@ -147,6 +149,9 @@ union ieee754sp ieee754sp_fmina(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
>  		return ieee754sp_nanxcpt(x);
>  
> +	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
> +		return x;
> +
>  	/* numbers are preferred to NaNs */
>  	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
> @@ -154,7 +159,6 @@ union ieee754sp ieee754sp_fmina(union ieee754sp x, union ieee754sp y)
>  	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
>  		return x;
>  
> -	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
>  	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
> -- 
> 2.7.4
> 

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