nsz Git - musl/blob - src/math/scalbn.c

   1 #include "libm.h"
   2
   3 double scalbn(double x, int n)
   4 {
   5         /* make sure result is stored as double on overflow or underflow */
   6         volatile double z;
   7         double scale;
   8
   9         if (n > 1023) {
  10                 x *= 0x1p1023;
  11                 n -= 1023;
  12                 if (n > 1023) {
  13                         x *= 0x1p1023;
  14                         n -= 1023;
  15                         if (n > 1023) {
  16                                 z = x * 0x1p1023;
  17                                 return z;
  18                         }
  19                 }
  20         } else if (n < -1022) {
  21                 x *= 0x1p-1022;
  22                 n += 1022;
  23                 if (n < -1022) {
  24                         x *= 0x1p-1022;
  25                         n += 1022;
  26                         if (n < -1022) {
  27                                 z = x * 0x1p-1022;
  28                                 return z;
  29                         }
  30                 }
  31         }
  32         INSERT_WORDS(scale, (uint32_t)(0x3ff+n)<<20, 0);
  33         z = x * scale;
  34         return z;
  35 }