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