glibc/sysdeps/ieee754/ldbl-128/s_nexttowardf.c
Gabriel F. T. Gomes d967237443 ldbl-128ibm-compat: Provide nexttoward functions
The functions in the nexttoward family are special, in the sense that
they always have a long double argument, regardless of their suffix
(i.e.: nexttowardf and nexttoward have a long double argument, besides
the float and double arguments).

On top of that, they are also special because nexttoward functions are
not part of the _FloatN API, hence __nexttowardf128 do not exist.

This patch adds 4 new function implementations for the new long double
format:

  __nexttoward_to_ieee128
  __nexttowardf_to_ieee128
  __nexttowardieee128 (as an alias to __nextafterieee128)

Likewise, rename "long double" "_Float128" in shared ldbl-128
files to ensure correct type is used irrespective of ABI
switches.

Thank you to those who helped out with this patch:

Co-Authored-By: Tulio Magno Quites Machado Filho  <tuliom@linux.ibm.com>
2020-02-28 08:20:02 -06:00

78 lines
2.0 KiB
C

/* s_nexttowardf.c -- float version of s_nextafter.c.
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com
* and Jakub Jelinek, jj@ultra.linux.cz.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: $";
#endif
#include <errno.h>
#include <math.h>
#include <math-barriers.h>
#include <math_private.h>
float __nexttowardf(float x, _Float128 y)
{
int32_t hx,ix;
int64_t hy,iy;
uint64_t ly;
GET_FLOAT_WORD(hx,x);
GET_LDOUBLE_WORDS64(hy,ly,y);
ix = hx&0x7fffffff; /* |x| */
iy = hy&0x7fffffffffffffffLL; /* |y| */
if((ix>0x7f800000) || /* x is nan */
((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))
/* y is nan */
return x+y;
if((_Float128) x==y) return y; /* x=y, return y */
if(ix==0) { /* x == 0 */
float u;
SET_FLOAT_WORD(x,(uint32_t)((hy>>32)&0x80000000)|1);/* return +-minsub*/
u = math_opt_barrier (x);
u = u * u;
math_force_eval (u); /* raise underflow flag */
return x;
}
if(hx>=0) { /* x > 0 */
if(x > y) { /* x -= ulp */
hx -= 1;
} else { /* x < y, x += ulp */
hx += 1;
}
} else { /* x < 0 */
if(x < y) { /* x < y, x -= ulp */
hx -= 1;
} else { /* x > y, x += ulp */
hx += 1;
}
}
hy = hx&0x7f800000;
if(hy>=0x7f800000) {
float u = x+x; /* overflow */
math_force_eval (u);
__set_errno (ERANGE);
}
if(hy<0x00800000) {
float u = x*x; /* underflow */
math_force_eval (u); /* raise underflow flag */
__set_errno (ERANGE);
}
SET_FLOAT_WORD(x,hx);
return x;
}
weak_alias (__nexttowardf, nexttowardf)