sysdeps/s390/fpu/s_lrint.c

   1 /* lrint() - S390 version.
   2    Copyright (C) 2019-2021 Free Software Foundation, Inc.
   3
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public License as
   8    published by the Free Software Foundation; either version 2.1 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #ifdef HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT
  21 # include <math.h>
  22 # include <libm-alias-double.h>
  23
  24 /* The sizeof (long int) differs between s390x (8byte) and s390 (4byte).
  25    Thus we need different instructions as the target size is encoded there.
  26    Note: On s390 this instruction is only used if build with -mzarch.  */
  27 # ifdef __s390x__
  28 #  define INSN "cgdbra"
  29 # else
  30 #  define INSN "cfdbra"
  31 # endif
  32
  33 long int
  34 __lrint (double x)
  35 {
  36   long int y;
  37   /* The z196 zarch "convert to fixed" (cgdbra) instruction is rounding
  38      according to current rounding mode (M3-field: 0).
  39      First convert x with suppressed inexact exception and check if the
  40      resulting value is beyond the target limits (indicated by cc=3;
  41      Note: a nan is also indicated by cc=3).
  42      If the resulting value is within the target limits, redo
  43      without suppressing the inexact exception.  */
  44   __asm__ (INSN " %0,0,%1,4 \n\t"
  45            "jo 1f \n\t"
  46            INSN " %0,0,%1,0 \n\t"
  47            "1:"
  48            : "=&d" (y) : "f" (x) : "cc");
  49   return y;
  50 }
  51 libm_alias_double (__lrint, lrint)
  52
  53 #else
  54 # include <sysdeps/ieee754/dbl-64/s_lrint.c>
  55 #endif