sys/external/bsd/compiler_rt/dist/lib/builtins/ppc/gcc_qdiv.c

   1 /* This file is distributed under the University of Illinois Open Source
   2  * License. See LICENSE.TXT for details.
   3  */
   4
   5 /* long double __gcc_qdiv(long double x, long double y);
   6  * This file implements the PowerPC 128-bit double-double division operation.
   7  * This implementation is shamelessly cribbed from Apple's DDRT, circa 1993(!)
   8  */
   9
  10 #include "DD.h"
  11
  12 long double __gcc_qdiv(long double a, long double b)
  13 {
  14         static const uint32_t infinityHi = UINT32_C(0x7ff00000);
  15         DD dst = { .ld = a }, src = { .ld = b };
  16
  17         register double x = dst.s.hi, x1 = dst.s.lo,
  18                                         y = src.s.hi, y1 = src.s.lo;
  19
  20     double yHi, yLo, qHi, qLo;
  21     double yq, tmp, q;
  22
  23     q = x / y;
  24
  25         /* Detect special cases */
  26         if (q == 0.0) {
  27                 dst.s.hi = q;
  28                 dst.s.lo = 0.0;
  29                 return dst.ld;
  30         }
  31
  32         const doublebits qBits = { .d = q };
  33         if (((uint32_t)(qBits.x >> 32) & infinityHi) == infinityHi) {
  34                 dst.s.hi = q;
  35                 dst.s.lo = 0.0;
  36                 return dst.ld;
  37         }
  38
  39     yHi = high26bits(y);
  40     qHi = high26bits(q);
  41
  42     yq = y * q;
  43     yLo = y - yHi;
  44     qLo = q - qHi;
  45
  46     tmp = LOWORDER(yq, yHi, yLo, qHi, qLo);
  47     tmp = (x - yq) - tmp;
  48     tmp = ((tmp + x1) - y1 * q) / y;
  49     x = q + tmp;
  50
  51     dst.s.lo = (q - x) + tmp;
  52     dst.s.hi = x;
  53
  54     return dst.ld;
  55 }