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