glibc/sysdeps/ieee754/flt-32/s_nearbyintf.c
Stefan Liebler ae3577f607 Use GCC builtins for nearbyint functions if desired.
This patch is using the corresponding GCC builtin for nearbyintf, nearbyint,
nearbintl and nearbyintf128 if the USE_FUNCTION_BUILTIN macros are defined to one
in math-use-builtins.h.

This is the case for s390 if build with at least --march=z196 --mzarch.
Otherwise the generic implementation is used.  The code of the generic
implementation is not changed.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2019-12-11 15:12:15 +01:00

68 lines
1.7 KiB
C

/* s_rintf.c -- float version of s_rint.c.
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/* Adapted for use as nearbyint by Ulrich Drepper <drepper@cygnus.com>. */
/*
* ====================================================
* 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.
* ====================================================
*/
#include <fenv.h>
#include <math.h>
#include <math-barriers.h>
#include <math_private.h>
#include <fenv_private.h>
#include <libm-alias-float.h>
#include <math-use-builtins.h>
float
__nearbyintf(float x)
{
#if USE_NEARBYINTF_BUILTIN
return __builtin_nearbyintf (x);
#else
/* Use generic implementation. */
static const float
TWO23[2] = {
8.3886080000e+06, /* 0x4b000000 */
-8.3886080000e+06, /* 0xcb000000 */
};
fenv_t env;
int32_t i0,j0,sx;
float w,t;
GET_FLOAT_WORD(i0,x);
sx = (i0>>31)&1;
j0 = ((i0>>23)&0xff)-0x7f;
if(j0<23) {
if(j0<0) {
libc_feholdexceptf (&env);
w = TWO23[sx] + math_opt_barrier (x);
t = w-TWO23[sx];
math_force_eval (t);
libc_fesetenvf (&env);
GET_FLOAT_WORD(i0,t);
SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
return t;
}
} else {
if(__builtin_expect(j0==0x80, 0)) return x+x; /* inf or NaN */
else return x; /* x is integral */
}
libc_feholdexceptf (&env);
w = TWO23[sx] + math_opt_barrier (x);
t = w-TWO23[sx];
math_force_eval (t);
libc_fesetenvf (&env);
return t;
#endif /* ! USE_NEARBYINT_BUILTIN */
}
libm_alias_float (__nearbyint, nearbyint)