Re: [PATCH v3 07/16] MIPS: math-emu: <MAX|MIN>.<D|S>: Fix cases of both inputs negative

[James Hogan <james.hogan@imgtec.com>]

[-- Attachment #1: Type: text/plain, Size: 6327 bytes --]

On Fri, Jul 21, 2017 at 04:09:05PM +0200, Aleksandar Markovic wrote:
> From: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
> 
> Fix the value returned by <MAX|MIN>.<D|S>, if both inputs are negative
> normal fp numbers. The previous logic did not take into account that
> if both inputs have the same sign, there should be separate treatment
> of the cases when both inputs are negative and when both inputs are
> positive.
> 
> The relevant example:
> 
> MAX.S fd,fs,ft:
>   If fs contains -5, and ft contains -7, fd is going to contain -5
>   (without this patch, it used to contain -7).

ouch!

> 

same fixes/stable comment as for previous min/max patches

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

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

Cheers
James

> ---
>  arch/mips/math-emu/dp_fmax.c | 33 +++++++++++++++++++++++++--------
>  arch/mips/math-emu/dp_fmin.c | 33 +++++++++++++++++++++++++--------
>  arch/mips/math-emu/sp_fmax.c | 33 +++++++++++++++++++++++++--------
>  arch/mips/math-emu/sp_fmin.c | 32 +++++++++++++++++++++++++-------
>  4 files changed, 100 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/mips/math-emu/dp_fmax.c b/arch/mips/math-emu/dp_fmax.c
> index 9517572..a0175cc 100644
> --- a/arch/mips/math-emu/dp_fmax.c
> +++ b/arch/mips/math-emu/dp_fmax.c
> @@ -106,16 +106,33 @@ union ieee754dp ieee754dp_fmax(union ieee754dp x, union ieee754dp y)
>  	else if (xs < ys)
>  		return x;
>  
> -	/* Compare exponent */
> -	if (xe > ye)
> -		return x;
> -	else if (xe < ye)
> -		return y;
> +	/* Signs of inputs are the same, let's compare exponents */
> +	if (xs == 0) {
> +		/* Inputs are both positive */
> +		if (xe > ye)
> +			return x;
> +		else if (xe < ye)
> +			return y;
> +	} else {
> +		/* Inputs are both negative */
> +		if (xe > ye)
> +			return y;
> +		else if (xe < ye)
> +			return x;
> +	}
>  
> -	/* Compare mantissa */
> -	if (xm <= ym)
> +	/* Signs and exponents of inputs are the same, let's compare mantissas */
> +	if (xs == 0) {
> +		/* Inputs are both positive, with equal exponents */
> +		if (xm <= ym)
> +			return y;
> +		return x;
> +	} else {
> +		/* Inputs are both negative, with equal exponents */
> +		if (xm <= ym)
> +			return x;
>  		return y;
> -	return x;
> +	}
>  }
>  
>  union ieee754dp ieee754dp_fmaxa(union ieee754dp x, union ieee754dp y)
> diff --git a/arch/mips/math-emu/dp_fmin.c b/arch/mips/math-emu/dp_fmin.c
> index 7069320..074a858 100644
> --- a/arch/mips/math-emu/dp_fmin.c
> +++ b/arch/mips/math-emu/dp_fmin.c
> @@ -106,16 +106,33 @@ union ieee754dp ieee754dp_fmin(union ieee754dp x, union ieee754dp y)
>  	else if (xs < ys)
>  		return y;
>  
> -	/* Compare exponent */
> -	if (xe > ye)
> -		return y;
> -	else if (xe < ye)
> -		return x;
> +	/* Signs of inputs are the same, let's compare exponents */
> +	if (xs == 0) {
> +		/* Inputs are both positive */
> +		if (xe > ye)
> +			return y;
> +		else if (xe < ye)
> +			return x;
> +	} else {
> +		/* Inputs are both negative */
> +		if (xe > ye)
> +			return x;
> +		else if (xe < ye)
> +			return y;
> +	}
>  
> -	/* Compare mantissa */
> -	if (xm <= ym)
> +	/* Signs and exponents of inputs are the same, let's compare mantissas */
> +	if (xs == 0) {
> +		/* Inputs are both positive, with equal exponents */
> +		if (xm <= ym)
> +			return x;
> +		return y;
> +	} else {
> +		/* Inputs are both negative, with equal exponents */
> +		if (xm <= ym)
> +			return y;
>  		return x;
> -	return y;
> +	}
>  }
>  
>  union ieee754dp ieee754dp_fmina(union ieee754dp x, union ieee754dp y)
> diff --git a/arch/mips/math-emu/sp_fmax.c b/arch/mips/math-emu/sp_fmax.c
> index d72111a..15825db 100644
> --- a/arch/mips/math-emu/sp_fmax.c
> +++ b/arch/mips/math-emu/sp_fmax.c
> @@ -106,16 +106,33 @@ union ieee754sp ieee754sp_fmax(union ieee754sp x, union ieee754sp y)
>  	else if (xs < ys)
>  		return x;
>  
> -	/* Compare exponent */
> -	if (xe > ye)
> -		return x;
> -	else if (xe < ye)
> -		return y;
> +	/* Signs of inputs are the same, let's compare exponents */
> +	if (xs == 0) {
> +		/* Inputs are both positive */
> +		if (xe > ye)
> +			return x;
> +		else if (xe < ye)
> +			return y;
> +	} else {
> +		/* Inputs are both negative */
> +		if (xe > ye)
> +			return y;
> +		else if (xe < ye)
> +			return x;
> +	}
>  
> -	/* Compare mantissa */
> -	if (xm <= ym)
> +	/* Signs and exponents of inputs are the same, let's compare mantissas */
> +	if (xs == 0) {
> +		/* Inputs are both positive, with equal exponents */
> +		if (xm <= ym)
> +			return y;
> +		return x;
> +	} else {
> +		/* Inputs are both negative, with equal exponents */
> +		if (xm <= ym)
> +			return x;
>  		return y;
> -	return x;
> +	}
>  }
>  
>  union ieee754sp ieee754sp_fmaxa(union ieee754sp x, union ieee754sp y)
> diff --git a/arch/mips/math-emu/sp_fmin.c b/arch/mips/math-emu/sp_fmin.c
> index 61ff9c6..f1418f7 100644
> --- a/arch/mips/math-emu/sp_fmin.c
> +++ b/arch/mips/math-emu/sp_fmin.c
> @@ -106,16 +106,34 @@ union ieee754sp ieee754sp_fmin(union ieee754sp x, union ieee754sp y)
>  	else if (xs < ys)
>  		return y;
>  
> -	/* Compare exponent */
> -	if (xe > ye)
> +	/* Signs of inputs are the same, let's compare exponents */
> +	if (xs == 0) {
> +		/* Inputs are both positive */
> +		if (xe > ye)
> +			return y;
> +		else if (xe < ye)
> +			return x;
> +	} else {
> +		/* Inputs are both negative */
> +		if (xe > ye)
> +			return x;
> +		else if (xe < ye)
> +			return y;
> +	}
> +
> +	/* Signs and exponents of inputs are the same, let's compare mantissas */
> +	if (xs == 0) {
> +		/* Inputs are both positive, with equal exponents */
> +		if (xm <= ym)
> +			return x;
>  		return y;
> -	else if (xe < ye)
> +	} else {
> +		/* Inputs are both negative, with equal exponents */
> +		if (xm <= ym)
> +			return y;
>  		return x;
> +	}
>  
> -	/* Compare mantissa */
> -	if (xm <= ym)
> -		return x;
> -	return y;
>  }
>  
>  union ieee754sp ieee754sp_fmina(union ieee754sp x, union ieee754sp y)
> -- 
> 2.7.4
> 

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]