1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 *
11 * From: @(#)s_floor.c 5.1 93/09/24
12 */
13
14 /*
15 * truncl(x)
16 * Return x rounded toward 0 to integral value
17 * Method:
18 * Bit twiddling.
19 * Exception:
20 * Inexact flag raised if x not equal to truncl(x).
21 */
22
23 #include <sys/types.h>
24 #include <machine/ieee.h>
25
26 #include <float.h>
27 #include <math.h>
28 #include <stdint.h>
29
30 #include "math_private.h"
31
32 #ifdef LDBL_IMPLICIT_NBIT
33 #define MANH_SIZE (EXT_FRACHBITS + EXT_FRACHMBITS + 1)
34 #else
35 #define MANH_SIZE (EXT_FRACHBITS + EXT_FRACHMBITS)
36 #endif
37
38 static const long double huge = 1.0e300;
39 static const float zero[] = { 0.0, -0.0 };
40
41 long double
truncl(long double x)42 truncl(long double x)
43 {
44 int e;
45 int64_t ix0, ix1;
46
47 GET_LDOUBLE_WORDS64(ix0,ix1,x);
48 e = ((ix0>>48)&0x7fff) - LDBL_MAX_EXP + 1;
49
50 if (e < MANH_SIZE - 1) {
51 if (e < 0) { /* raise inexact if x != 0 */
52 if (huge + x > 0.0)
53 return (zero[((ix0>>48)&0x8000)!=0]);
54 } else {
55 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
56 if (((ix0 & m) | ix1) == 0)
57 return (x); /* x is integral */
58 if (huge + x > 0.0) { /* raise inexact flag */
59 ix0 &= ~m;
60 ix1 = 0;
61 }
62 }
63 } else if (e < LDBL_MANT_DIG - 1) {
64 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
65 if ((ix1 & m) == 0)
66 return (x); /* x is integral */
67 if (huge + x > 0.0) /* raise inexact flag */
68 ix1 &= ~m;
69 }
70 SET_LDOUBLE_WORDS64(x,ix0,ix1);
71 return (x);
72 }
73