Re: [PATCH] Remove __isinf uses that rely on signed return value

[Szabolcs Nagy <szabolcs dot nagy at arm dot com>]

On 02/06/15 18:15, Wilco Dijkstra wrote:
> The printf code contains a few uses of __isinf where the sign is used - replace these with separate
> isinf and signbit. Also change __isnan into isnan.
> 

i suspect it slightly changes semantics on x86 (for the better).

i386 __isnanl does not seem to handle invalid ld80 representations.

if exponent != 0 and significand>>63 == 0 then it's a "pseudo normal"
or "pseudo infinite" value that the fpu would categorize as nan, but
not __isnanl.

(passing around long doubles with invalid representation is ub,
but probably __isnanl should be consistent with fcom instruction
to be safe when it is used on random bytes).

> OK for commit?
> 
> Wilco
> 
> 2015-06-02  Wilco Dijkstra  <wdijkstr@arm.com>
> 
> 	* stdio-common/printf_fp.c (___printf_fp):
> 	Use signbit to get the sign. Use isinf/isnan macros.
> 	* stdio-common/printf_fphex.c (__printf_fphex): Likewise.
> 	* stdio-common/printf_size.c (__printf_size): Likewise.
> 
> ---
>  stdio-common/printf_fp.c    | 17 +++++++----------
>  stdio-common/printf_fphex.c | 14 +++++---------
>  stdio-common/printf_size.c  | 23 +++++++++++------------
>  3 files changed, 23 insertions(+), 31 deletions(-)
> 
> diff --git a/stdio-common/printf_fp.c b/stdio-common/printf_fp.c
> index 575842b..11f3145 100644
> --- a/stdio-common/printf_fp.c
> +++ b/stdio-common/printf_fp.c
> @@ -332,8 +332,7 @@ ___printf_fp (FILE *fp,
>        fpnum.ldbl = *(const long double *) args[0];
>  
>        /* Check for special values: not a number or infinity.  */
> -      int res;
> -      if (__isnanl (fpnum.ldbl))
> +      if (isnan (fpnum.ldbl))
>  	{
>  	  is_neg = signbit (fpnum.ldbl);
>  	  if (isupper (info->spec))
> @@ -347,9 +346,9 @@ ___printf_fp (FILE *fp,
>  		wspecial = L"nan";
>  	      }
>  	}
> -      else if ((res = __isinfl (fpnum.ldbl)))
> +      else if (isinf (fpnum.ldbl))
>  	{
> -	  is_neg = res < 0;
> +	  is_neg = signbit (fpnum.ldbl);
>  	  if (isupper (info->spec))
>  	    {
>  	      special = "INF";
> @@ -377,11 +376,9 @@ ___printf_fp (FILE *fp,
>        fpnum.dbl = *(const double *) args[0];
>  
>        /* Check for special values: not a number or infinity.  */
> -      int res;
> -      if (__isnan (fpnum.dbl))
> +      if (isnan (fpnum.dbl))
>  	{
> -	  union ieee754_double u = { .d = fpnum.dbl };
> -	  is_neg = u.ieee.negative != 0;
> +	  is_neg = signbit (fpnum.dbl);
>  	  if (isupper (info->spec))
>  	    {
>  	      special = "NAN";
> @@ -393,9 +390,9 @@ ___printf_fp (FILE *fp,
>  	      wspecial = L"nan";
>  	    }
>  	}
> -      else if ((res = __isinf (fpnum.dbl)))
> +      else if (isinf (fpnum.dbl))
>  	{
> -	  is_neg = res < 0;
> +	  is_neg = signbit (fpnum.dbl);
>  	  if (isupper (info->spec))
>  	    {
>  	      special = "INF";
> diff --git a/stdio-common/printf_fphex.c b/stdio-common/printf_fphex.c
> index ba0639f..0627bea 100644
> --- a/stdio-common/printf_fphex.c
> +++ b/stdio-common/printf_fphex.c
> @@ -165,7 +165,7 @@ __printf_fphex (FILE *fp,
>        fpnum.ldbl = *(const long double *) args[0];
>  
>        /* Check for special values: not a number or infinity.  */
> -      if (__isnanl (fpnum.ldbl))
> +      if (isnan (fpnum.ldbl))
>  	{
>  	  if (isupper (info->spec))
>  	    {
> @@ -180,7 +180,7 @@ __printf_fphex (FILE *fp,
>  	}
>        else
>  	{
> -	  if (__isinfl (fpnum.ldbl))
> +	  if (isinf (fpnum.ldbl))
>  	    {
>  	      if (isupper (info->spec))
>  		{
> @@ -202,9 +202,8 @@ __printf_fphex (FILE *fp,
>        fpnum.dbl.d = *(const double *) args[0];
>  
>        /* Check for special values: not a number or infinity.  */
> -      if (__isnan (fpnum.dbl.d))
> +      if (isnan (fpnum.dbl.d))
>  	{
> -	  negative = fpnum.dbl.ieee.negative != 0;
>  	  if (isupper (info->spec))
>  	    {
>  	      special = "NAN";
> @@ -218,8 +217,7 @@ __printf_fphex (FILE *fp,
>  	}
>        else
>  	{
> -	  int res = __isinf (fpnum.dbl.d);
> -	  if (res)
> +	  if (isinf (fpnum.dbl.d))
>  	    {
>  	      if (isupper (info->spec))
>  		{
> @@ -231,11 +229,9 @@ __printf_fphex (FILE *fp,
>  		  special = "inf";
>  		  wspecial = L"inf";
>  		}
> -	      negative = res < 0;
>  	    }
> -	  else
> -	    negative = signbit (fpnum.dbl.d);
>  	}
> +      negative = signbit (fpnum.dbl.d);
>      }
>  
>    if (special)
> diff --git a/stdio-common/printf_size.c b/stdio-common/printf_size.c
> index 6ee753f..216f170 100644
> --- a/stdio-common/printf_size.c
> +++ b/stdio-common/printf_size.c
> @@ -108,7 +108,7 @@ __printf_size (FILE *fp, const struct printf_info *info,
>    fpnum;
>    const void *ptr = &fpnum;
>  
> -  int fpnum_sign = 0;
> +  int is_neg = 0;
>  
>    /* "NaN" or "Inf" for the special cases.  */
>    const char *special = NULL;
> @@ -117,7 +117,6 @@ __printf_size (FILE *fp, const struct printf_info *info,
>    struct printf_info fp_info;
>    int done = 0;
>    int wide = info->wide;
> -  int res;
>  
>    /* Fetch the argument value.	*/
>  #ifndef __NO_LONG_DOUBLE_MATH
> @@ -126,15 +125,15 @@ __printf_size (FILE *fp, const struct printf_info *info,
>        fpnum.ldbl = *(const long double *) args[0];
>  
>        /* Check for special values: not a number or infinity.  */
> -      if (__isnanl (fpnum.ldbl))
> +      if (isnan (fpnum.ldbl))
>  	{
>  	  special = "nan";
>  	  wspecial = L"nan";
> -	  // fpnum_sign = 0;	Already zero
> +	  // is_neg = 0;	Already zero
>  	}
> -      else if ((res = __isinfl (fpnum.ldbl)))
> +      else if (isinf (fpnum.ldbl))
>  	{
> -	  fpnum_sign = res;
> +	  is_neg = signbit (fpnum.ldbl);
>  	  special = "inf";
>  	  wspecial = L"inf";
>  	}
> @@ -151,15 +150,15 @@ __printf_size (FILE *fp, const struct printf_info *info,
>        fpnum.dbl.d = *(const double *) args[0];
>  
>        /* Check for special values: not a number or infinity.  */
> -      if (__isnan (fpnum.dbl.d))
> +      if (isnan (fpnum.dbl.d))
>  	{
>  	  special = "nan";
>  	  wspecial = L"nan";
> -	  // fpnum_sign = 0;	Already zero
> +	  // is_neg = 0;	Already zero
>  	}
> -      else if ((res = __isinf (fpnum.dbl.d)))
> +      else if (isinf (fpnum.dbl.d))
>  	{
> -	  fpnum_sign = res;
> +	  is_neg = signbit (fpnum.dbl.d);
>  	  special = "inf";
>  	  wspecial = L"inf";
>  	}
> @@ -175,14 +174,14 @@ __printf_size (FILE *fp, const struct printf_info *info,
>      {
>        int width = info->prec > info->width ? info->prec : info->width;
>  
> -      if (fpnum_sign < 0 || info->showsign || info->space)
> +      if (is_neg || info->showsign || info->space)
>  	--width;
>        width -= 3;
>  
>        if (!info->left && width > 0)
>  	PADN (' ', width);
>  
> -      if (fpnum_sign < 0)
> +      if (is_neg)
>  	outchar ('-');
>        else if (info->showsign)
>  	outchar ('+');
>