1 // SPDX-License-Identifier: GPL-2.0-only 2 /* IEEE754 floating point arithmetic 3 * double precision: common utilities 4 */ 5 /* 6 * MIPS floating point support 7 * Copyright (C) 1994-2000 Algorithmics Ltd. 8 */ 9 10 #include "ieee754dp.h" 11 12 union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y) 13 { 14 int s; 15 16 COMPXDP; 17 COMPYDP; 18 19 EXPLODEXDP; 20 EXPLODEYDP; 21 22 ieee754_clearcx(); 23 24 FLUSHXDP; 25 FLUSHYDP; 26 27 switch (CLPAIR(xc, yc)) { 28 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN): 29 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN): 30 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN): 31 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN): 32 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN): 33 return ieee754dp_nanxcpt(y); 34 35 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN): 36 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN): 37 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO): 38 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM): 39 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM): 40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF): 41 return ieee754dp_nanxcpt(x); 42 43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN): 44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN): 45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN): 46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN): 47 return y; 48 49 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN): 50 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO): 51 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM): 52 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM): 53 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF): 54 return x; 55 56 57 /* 58 * Infinity handling 59 */ 60 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF): 61 if (xs == ys) 62 return x; 63 ieee754_setcx(IEEE754_INVALID_OPERATION); 64 return ieee754dp_indef(); 65 66 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF): 67 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF): 68 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF): 69 return y; 70 71 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO): 72 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM): 73 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM): 74 return x; 75 76 /* 77 * Zero handling 78 */ 79 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO): 80 if (xs == ys) 81 return x; 82 else 83 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD); 84 85 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO): 86 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): 87 return x; 88 89 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM): 90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM): 91 return y; 92 93 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): 94 DPDNORMX; 95 fallthrough; 96 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): 97 DPDNORMY; 98 break; 99 100 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): 101 DPDNORMX; 102 break; 103 104 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): 105 break; 106 } 107 assert(xm & DP_HIDDEN_BIT); 108 assert(ym & DP_HIDDEN_BIT); 109 110 /* 111 * Provide guard,round and stick bit space. 112 */ 113 xm <<= 3; 114 ym <<= 3; 115 116 if (xe > ye) { 117 /* 118 * Have to shift y fraction right to align. 119 */ 120 s = xe - ye; 121 ym = XDPSRS(ym, s); 122 ye += s; 123 } else if (ye > xe) { 124 /* 125 * Have to shift x fraction right to align. 126 */ 127 s = ye - xe; 128 xm = XDPSRS(xm, s); 129 xe += s; 130 } 131 assert(xe == ye); 132 assert(xe <= DP_EMAX); 133 134 if (xs == ys) { 135 /* 136 * Generate 28 bit result of adding two 27 bit numbers 137 * leaving result in xm, xs and xe. 138 */ 139 xm = xm + ym; 140 141 if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */ 142 xm = XDPSRS1(xm); 143 xe++; 144 } 145 } else { 146 if (xm >= ym) { 147 xm = xm - ym; 148 } else { 149 xm = ym - xm; 150 xs = ys; 151 } 152 if (xm == 0) 153 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD); 154 155 /* 156 * Normalize to rounding precision. 157 */ 158 while ((xm >> (DP_FBITS + 3)) == 0) { 159 xm <<= 1; 160 xe--; 161 } 162 } 163 164 return ieee754dp_format(xs, xe, xm); 165 } 166