sysdeps/alpha/fpu/s_floorf.c

   1 /* Copyright (C) 1998-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Richard Henderson.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library.  If not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <math.h>
  20
  21
  22 /* Use the -inf rounding mode conversion instructions to implement
  23    floor.  We note when the exponent is large enough that the value
  24    must be integral, as this avoids unpleasant integer overflows.  */
  25
  26 float
  27 __floorf (float x)
  28 {
  29   if (isless (fabsf (x), 16777216.0f))  /* 1 << FLT_MANT_DIG */
  30     {
  31       /* Note that Alpha S_Floating is stored in registers in a
  32          restricted T_Floating format, so we don't even need to
  33          convert back to S_Floating in the end.  The initial
  34          conversion to T_Floating is needed to handle denormals.  */
  35
  36       float tmp1, tmp2, new_x;
  37
  38       __asm ("cvtst/s %3,%2\n\t"
  39 #ifdef _IEEE_FP_INEXACT
  40              "cvttq/svim %2,%1\n\t"
  41 #else
  42              "cvttq/svm %2,%1\n\t"
  43 #endif
  44              "cvtqt/m %1,%0\n\t"
  45              : "=f"(new_x), "=&f"(tmp1), "=&f"(tmp2)
  46              : "f"(x));
  47
  48       /* floor(-0) == -0, and in general we'll always have the same
  49          sign as our input.  */
  50       x = copysignf(new_x, x);
  51     }
  52   return x;
  53 }
  54
  55 weak_alias (__floorf, floorf)