sysdeps/alpha/fpu/s_floorf.c

   1 /* Copyright (C) 1998, 1999, 2000 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <math.h>
  21
  22
  23 /* Use the -inf rounding mode conversion instructions to implement
  24    floor.  We note when the exponent is large enough that the value
  25    must be integral, as this avoids unpleasant integer overflows.  */
  26
  27 float
  28 __floorf (float x)
  29 {
  30   if (isless (fabsf (x), 16777216.0f))  /* 1 << FLT_MANT_DIG */
  31     {
  32       /* Note that Alpha S_Floating is stored in registers in a
  33          restricted T_Floating format, so we don't even need to
  34          convert back to S_Floating in the end.  The initial
  35          conversion to T_Floating is needed to handle denormals.  */
  36
  37       float tmp1, tmp2, new_x;
  38
  39       __asm ("cvtst/s %3,%2\n\t"
  40 #ifdef _IEEE_FP_INEXACT
  41              "cvttq/svim %2,%1\n\t"
  42 #else
  43              "cvttq/svm %2,%1\n\t"
  44 #endif
  45              "cvtqt/m %1,%0\n\t"
  46              : "=f"(new_x), "=&f"(tmp1), "=&f"(tmp2)
  47              : "f"(x));
  48
  49       /* floor(-0) == -0, and in general we'll always have the same
  50          sign as our input.  */
  51       x = copysignf(new_x, x);
  52     }
  53   return x;
  54 }
  55
  56 weak_alias (__floorf, floorf)