1 #include "libm.h" 2 trunc(double x)3 double trunc(double x) 4 { 5 union {double f; uint64_t i;} u = {x}; 6 int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12; 7 uint64_t m; 8 9 if (e >= 52 + 12) 10 return x; 11 if (e < 12) 12 e = 1; 13 m = -1ULL >> e; 14 if ((u.i & m) == 0) 15 return x; 16 FORCE_EVAL(x + 0x1p120f); 17 u.i &= ~m; 18 return u.f; 19 } 20