sysdeps/powerpc/q_lltoq.c

   1 /* 64-bit fixed point signed integer to 128-bit floating point.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 <quad_float.h>
  21
  22 /* long double _q_ulltoq(long long a);
  23    Convert 'a' to long double.
  24    */
  25
  26 void
  27 __q_lltoq(unsigned int result[4], long long a)
  28 {
  29   unsigned rx;
  30   int cs, css;
  31
  32   /* Calculate absolute value of 'a'.  */
  33   unsigned long long ua = (a  ^  a >> 63) - (a >> 63);
  34
  35   /* Normalize.  */
  36   cs = cntlzd(a);
  37   ua <<= cs+1;
  38
  39   /* Calculate the exponent, in 4 easy instructions.  */
  40   css = 63-cs;
  41   rx = 16383+css << 16  &  ~css;
  42
  43   /* Copy the sign bit from 'a'.  */
  44   asm ("rlwimi %0,%1,0,0,0": "=r"(rx) : "r"(a >> 32), "0"(rx));
  45
  46   /* Put it all together.  */
  47   result[3] = 0;
  48   asm ("rlwimi %0,%1,16,16,31": "=r"(result[0]) : "r"(ua >> 32), "0"(rx));
  49   ua <<= 16;
  50   result[2] = ua;
  51   result[1] = ua >> 32;
  52 }