diff options
Diffstat (limited to 'src/math/trunc.c')
| -rw-r--r-- | src/math/trunc.c | 70 |
1 files changed, 13 insertions, 57 deletions
diff --git a/src/math/trunc.c b/src/math/trunc.c index 44b04ecc..d13711b5 100644 --- a/src/math/trunc.c +++ b/src/math/trunc.c @@ -1,63 +1,19 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/s_trunc.c */ -/* - * ==================================================== - * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. - * - * Developed at SunPro, a Sun Microsystems, Inc. business. - * Permission to use, copy, modify, and distribute this - * software is freely granted, provided that this notice - * is preserved. - * ==================================================== - */ -/* - * trunc(x) - * Return x rounded toward 0 to integral value - * Method: - * Bit twiddling. - * Exception: - * Inexact flag raised if x not equal to trunc(x). - */ - #include "libm.h" -static const double huge = 1.0e300; - double trunc(double x) { - int32_t i0,i1,j0; - uint32_t i; + union {double f; uint64_t i;} u = {x}; + int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12; + uint64_t m; - EXTRACT_WORDS(i0, i1, x); - j0 = ((i0>>20)&0x7ff) - 0x3ff; - if (j0 < 20) { - if (j0 < 0) { /* |x|<1, return 0*sign(x) */ - /* raise inexact if x != 0 */ - if (huge+x > 0.0) { - i0 &= 0x80000000U; - i1 = 0; - } - } else { - i = 0x000fffff>>j0; - if (((i0&i)|i1) == 0) - return x; /* x is integral */ - /* raise inexact */ - if (huge+x > 0.0) { - i0 &= ~i; - i1 = 0; - } - } - } else if (j0 > 51) { - if (j0 == 0x400) - return x + x; /* inf or NaN */ - return x; /* x is integral */ - } else { - i = (uint32_t)0xffffffff>>(j0-20); - if ((i1&i) == 0) - return x; /* x is integral */ - /* raise inexact */ - if (huge+x > 0.0) - i1 &= ~i; - } - INSERT_WORDS(x, i0, i1); - return x; + if (e >= 52 + 12) + return x; + if (e < 12) + e = 1; + m = -1ULL >> e; + if ((u.i & m) == 0) + return x; + FORCE_EVAL(x + 0x1p120f); + u.i &= ~m; + return u.f; } |