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 12 #include <sys/cdefs.h> 13 /* 14 * floorl(x) 15 * Return x rounded toward -inf to integral value 16 * Method: 17 * Bit twiddling. 18 * Exception: 19 * Inexact flag raised if x not equal to floorl(x). 20 */ 21 22 #include <float.h> 23 #include <math.h> 24 #include <stdint.h> 25 26 #include "fpmath.h" 27 28 #ifdef LDBL_IMPLICIT_NBIT 29 #define MANH_SIZE (LDBL_MANH_SIZE + 1) 30 #define INC_MANH(u, c) do { \ 31 uint64_t o = u.bits.manh; \ 32 u.bits.manh += (c); \ 33 if (u.bits.manh < o) \ 34 u.bits.exp++; \ 35 } while (0) 36 #else 37 #define MANH_SIZE LDBL_MANH_SIZE 38 #define INC_MANH(u, c) do { \ 39 uint64_t o = u.bits.manh; \ 40 u.bits.manh += (c); \ 41 if (u.bits.manh < o) { \ 42 u.bits.exp++; \ 43 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \ 44 } \ 45 } while (0) 46 #endif 47 48 static const long double huge = 1.0e300; 49 50 long double 51 floorl(long double x) 52 { 53 union IEEEl2bits u = { .e = x }; 54 int e = u.bits.exp - LDBL_MAX_EXP + 1; 55 56 if (e < MANH_SIZE - 1) { 57 if (e < 0) { /* raise inexact if x != 0 */ 58 if (huge + x > 0.0) 59 if (u.bits.exp > 0 || 60 (u.bits.manh | u.bits.manl) != 0) 61 u.e = u.bits.sign ? -1.0 : 0.0; 62 } else { 63 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1); 64 if (((u.bits.manh & m) | u.bits.manl) == 0) 65 return (x); /* x is integral */ 66 if (u.bits.sign) { 67 #ifdef LDBL_IMPLICIT_NBIT 68 if (e == 0) 69 u.bits.exp++; 70 else 71 #endif 72 INC_MANH(u, 1llu << (MANH_SIZE - e - 1)); 73 } 74 if (huge + x > 0.0) { /* raise inexact flag */ 75 u.bits.manh &= ~m; 76 u.bits.manl = 0; 77 } 78 } 79 } else if (e < LDBL_MANT_DIG - 1) { 80 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1); 81 if ((u.bits.manl & m) == 0) 82 return (x); /* x is integral */ 83 if (u.bits.sign) { 84 if (e == MANH_SIZE - 1) 85 INC_MANH(u, 1); 86 else { 87 uint64_t o = u.bits.manl; 88 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1); 89 if (u.bits.manl < o) /* got a carry */ 90 INC_MANH(u, 1); 91 } 92 } 93 if (huge + x > 0.0) /* raise inexact flag */ 94 u.bits.manl &= ~m; 95 } 96 return (u.e); 97 } 98