sysdeps/alpha/fpu/s_floorf.c

   1 /* Copyright (C) 1998, 1999 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 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   /* Check not zero since floor(-0) == -0.  */
  31   if (x != 0 && fabsf (x) < 16777216.0f)  /* 1 << FLT_MANT_DIG */
  32     {
  33       /* Note that Alpha S_Floating is stored in registers in a
  34          restricted T_Floating format, so we don't even need to
  35          convert back to S_Floating in the end.  The initial
  36          conversion to T_Floating is needed to handle denormals.  */
  37
  38       float tmp1, tmp2;
  39
  40       __asm ("cvtst/s %3,%2\n\t"
  41 #ifdef _IEEE_FP_INEXACT
  42              "cvttq/svim %2,%1\n\t"
  43 #else
  44              "cvttq/svm %2,%1\n\t"
  45 #endif
  46              "cvtqt/m %1,%0\n\t"
  47              : "=f"(x), "=&f"(tmp1), "=&f"(tmp2)
  48              : "f"(x));
  49     }
  50   return x;
  51 }
  52
  53 weak_alias (__floorf, floorf)