Python/pymath.c

   1 #include "Python.h"
   2
   3 #ifdef X87_DOUBLE_ROUNDING
   4 /* On x86 platforms using an x87 FPU, this function is called from the
   5    Py_FORCE_DOUBLE macro (defined in pymath.h) to force a floating-point
   6    number out of an 80-bit x87 FPU register and into a 64-bit memory location,
   7    thus rounding from extended precision to double precision. */
   8 double _Py_force_double(double x)
   9 {
  10         volatile double y;
  11         y = x;
  12         return y;
  13 }
  14 #endif
  15
  16 #ifdef HAVE_GCC_ASM_FOR_X87
  17
  18 /* inline assembly for getting and setting the 387 FPU control word on
  19    gcc/x86 */
  20
  21 unsigned short _Py_get_387controlword(void) {
  22     unsigned short cw;
  23     __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
  24     return cw;
  25 }
  26
  27 void _Py_set_387controlword(unsigned short cw) {
  28     __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
  29 }
  30
  31 #endif
  32
  33
  34 #ifndef HAVE_HYPOT
  35 double hypot(double x, double y)
  36 {
  37         double yx;
  38
  39         x = fabs(x);
  40         y = fabs(y);
  41         if (x < y) {
  42                 double temp = x;
  43                 x = y;
  44                 y = temp;
  45         }
  46         if (x == 0.)
  47                 return 0.;
  48         else {
  49                 yx = y/x;
  50                 return x*sqrt(1.+yx*yx);
  51         }
  52 }
  53 #endif /* HAVE_HYPOT */
  54
  55 #ifndef HAVE_COPYSIGN
  56 double
  57 copysign(double x, double y)
  58 {
  59         /* use atan2 to distinguish -0. from 0. */
  60         if (y > 0. || (y == 0. && atan2(y, -1.) > 0.)) {
  61                 return fabs(x);
  62         } else {
  63                 return -fabs(x);
  64         }
  65 }
  66 #endif /* HAVE_COPYSIGN */
  67
  68 #ifndef HAVE_ROUND
  69 double
  70 round(double x)
  71 {
  72     double absx, y;
  73     absx = fabs(x);
  74     y = floor(absx);
  75     if (absx - y >= 0.5)
  76         y += 1.0;
  77     return copysign(y, x);
  78 }
  79 #endif /* HAVE_ROUND */