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 #ifndef lint 15 static char rcsid[] = "$FreeBSD$"; 16 #endif 17 18 /* 19 * floorl(x) 20 * Return x rounded toward -inf to integral value 21 * Method: 22 * Bit twiddling. 23 * Exception: 24 * Inexact flag raised if x not equal to floorl(x). 25 */ 26 27 #include <float.h> 28 #include <math.h> 29 #include <stdint.h> 30 31 #include "fpmath.h" 32 33 #ifdef LDBL_IMPLICIT_NBIT 34 #define MANH_SIZE (LDBL_MANH_SIZE + 1) 35 #define INC_MANH(u, c) do { \ 36 uint64_t o = u.bits.manh; \ 37 u.bits.manh += (c); \ 38 if (u.bits.manh < o) \ 39 u.bits.exp++; \ 40 } while (0) 41 #else 42 #define MANH_SIZE LDBL_MANH_SIZE 43 #define INC_MANH(u, c) do { \ 44 uint64_t o = u.bits.manh; \ 45 u.bits.manh += (c); \ 46 if (u.bits.manh < o) { \ 47 u.bits.exp++; \ 48 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \ 49 } \ 50 } while (0) 51 #endif 52 53 static const long double huge = 1.0e300; 54 55 long double 56 floorl(long double x) 57 { 58 union IEEEl2bits u = { .e = x }; 59 int e = u.bits.exp - LDBL_MAX_EXP + 1; 60 61 if (e < MANH_SIZE - 1) { 62 if (e < 0) { /* raise inexact if x != 0 */ 63 if (huge + x > 0.0) 64 if (u.bits.exp > 0 || 65 (u.bits.manh | u.bits.manl) != 0) 66 u.e = u.bits.sign ? -1.0 : 0.0; 67 } else { 68 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1); 69 if (((u.bits.manh & m) | u.bits.manl) == 0) 70 return (x); /* x is integral */ 71 if (u.bits.sign) { 72 #ifdef LDBL_IMPLICIT_NBIT 73 if (e == 0) 74 u.bits.exp++; 75 else 76 #endif 77 INC_MANH(u, 1llu << (MANH_SIZE - e - 1)); 78 } 79 if (huge + x > 0.0) { /* raise inexact flag */ 80 u.bits.manh &= ~m; 81 u.bits.manl = 0; 82 } 83 } 84 } else if (e < LDBL_MANT_DIG - 1) { 85 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1); 86 if ((u.bits.manl & m) == 0) 87 return (x); /* x is integral */ 88 if (u.bits.sign) { 89 if (e == MANH_SIZE - 1) 90 INC_MANH(u, 1); 91 else { 92 uint64_t o = u.bits.manl; 93 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1); 94 if (u.bits.manl < o) /* got a carry */ 95 INC_MANH(u, 1); 96 } 97 } 98 if (huge + x > 0.0) /* raise inexact flag */ 99 u.bits.manl &= ~m; 100 } 101 return (u.e); 102 } 103