1 /* Implementations for copysign, ilogb, and nextafter for float16 based on 2 * corresponding float32 implementations in 3 * bionic/libm/upstream-freebsd/lib/msun/src 4 */ 5 6 /* 7 * ==================================================== 8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 9 * 10 * Developed at SunPro, a Sun Microsystems, Inc. business. 11 * Permission to use, copy, modify, and distribute this 12 * software is freely granted, provided that this notice 13 * is preserved. 14 * ==================================================== 15 */ 16 17 #include "rs_core.rsh" 18 #include "rs_f16_util.h" 19 20 // Based on bionic/libm/upstream-freebsd/lib/msun/src/s_copysignf.c 21 extern half __attribute__((overloadable)) copysign(half x, half y) { 22 short hx, hy; 23 GET_HALF_WORD(hx, x); 24 GET_HALF_WORD(hy, y); 25 26 SET_HALF_WORD(x, (hx & 0x7fff) | (hy & 0x8000)); 27 return x; 28 } 29 30 // Based on bionic/libm/upstream-freebsd/lib/msun/src/s_frexpf.c 31 extern half __attribute__((overloadable)) frexp(half x, int *eptr) { 32 short hx, ix; 33 static const half two12 = 4096; 34 35 GET_HALF_WORD(hx, x); 36 ix = hx & 0x7fff; 37 38 *eptr = 0; 39 if (ix >= 0x7c00 || ix == 0) return x; // NaN, infinity or zero 40 if (ix <= 0x0400) { 41 // x is subnormal. Scale it by 2^12 (and adjust eptr accordingly) so 42 // that even the smallest subnormal value becomes normal. 43 x *= two12; 44 GET_HALF_WORD(hx, x); 45 ix = hx & 0x7fff; 46 *eptr = -12; 47 } 48 49 // Adjust eptr by (non-biased exponent of hx + 1). Set the non-biased 50 // exponent to be equal to -1 so that abs(hx) is between 0.5 and 1. 51 *eptr += (ix >> 10) - 14; 52 hx = (hx & 0x83ff) | 0x3800; 53 SET_HALF_WORD(x, hx); 54 return x; 55 } 56 57 // Based on bionic/libm/upstream-freebsd/lib/msun/src/s_ilogbf.c 58 extern int __attribute__((overloadable)) ilogb(half x) { 59 const int RS_INT_MAX = 0x7fffffff; 60 const int RS_INT_MIN = 0x80000000; 61 62 short hx, ix; 63 GET_HALF_WORD(hx, x); 64 hx &= 0x7fff; 65 66 if (hx < 0x0400) { // subnormal 67 if (hx == 0) 68 return RS_INT_MIN; // for zero 69 for (hx <<= 5, ix = -14; hx > 0; hx <<= 1) 70 ix -= 1; 71 return ix; 72 } 73 else if (hx < 0x7c00) { 74 return (hx >> 10) - 15; 75 } 76 else { // hx >= 0x7c00 77 return RS_INT_MAX; // for NaN and infinity 78 } 79 } 80 81 // Based on bionic/libm/upstream-freebsd/lib/msun/src/s_modff.c 82 extern half __attribute__((overloadable)) modf(half x, half *iptr) { 83 short i0, j0; 84 unsigned short i; 85 GET_HALF_WORD(i0, x); 86 j0 = ((i0 >> 10) & 0x1f) - 15; // exponent of x 87 if (j0 < 10) { 88 if (j0 < 0) { // No integral part 89 SET_HALF_WORD(*iptr, i0 & 0x8000); // *iptr = +/- 0 90 return x; 91 } 92 else { 93 i = 0x03ff >> j0; // mask to check fractional parts of x 94 if ((i0 & i) == 0) { // no bits set in fractional part 95 *iptr = x; 96 SET_HALF_WORD(x, i0 & 0x8000); 97 return x; 98 } 99 else { 100 SET_HALF_WORD(*iptr, i0 & ~i); // zero out fractional parts 101 return x - *iptr; 102 } 103 } 104 } 105 else { // No fractional part 106 unsigned short ix; 107 *iptr = x; 108 if (x != x) 109 return x; 110 GET_HALF_WORD(ix, x); 111 SET_HALF_WORD(x, ix & 0x8000); // x = +/- 0 112 return x; 113 } 114 } 115 116 // Based on bionic/libm/upstream-freebsd/lib/msun/src/s_nextafterf.c 117 extern half __attribute__((overloadable)) nextafter(half x, half y) { 118 short hx, hy, ix, iy; 119 120 GET_HALF_WORD(hx, x); 121 GET_HALF_WORD(hy, y); 122 ix = hx & 0x7fff; // |x| 123 iy = hy & 0x7fff; // |y| 124 125 if ((ix > 0x7c00) || // x is nan 126 (iy > 0x7c00)) // y is nan 127 return x + y; // return nan 128 129 if (x == y) return y; // x == y. return y 130 if (ix == 0) { 131 SET_HALF_WORD(x, (hy & 0x8000) | 1); 132 return x; 133 } 134 135 if (hx >= 0) { // x >= 0 136 if (hx > hy) 137 hx -= 1; // x > y, x -= 1 ulp 138 else 139 hx += 1; // x < y, x += 1 ulp 140 } 141 else { // x < 0 142 if (hy>= 0 || hx > hy) 143 hx -= 1; // x < y, x -= 1 ulp 144 else 145 hx += 1; 146 } 147 148 SET_HALF_WORD(x, hx); 149 return x; 150 } 151
