1 // SPDX-License-Identifier: GPL-2.0-only 1 // SPDX-License-Identifier: GPL-2.0-only
2 /* IEEE754 floating point arithmetic 2 /* IEEE754 floating point arithmetic
3 * single precision 3 * single precision
4 */ 4 */
5 /* 5 /*
6 * MIPS floating point support 6 * MIPS floating point support
7 * Copyright (C) 1994-2000 Algorithmics Ltd. 7 * Copyright (C) 1994-2000 Algorithmics Ltd.
8 */ 8 */
9 9
10 #include "ieee754sp.h" 10 #include "ieee754sp.h"
11 11
12 union ieee754sp ieee754sp_sub(union ieee754sp 12 union ieee754sp ieee754sp_sub(union ieee754sp x, union ieee754sp y)
13 { 13 {
14 int s; 14 int s;
15 15
16 COMPXSP; 16 COMPXSP;
17 COMPYSP; 17 COMPYSP;
18 18
19 EXPLODEXSP; 19 EXPLODEXSP;
20 EXPLODEYSP; 20 EXPLODEYSP;
21 21
22 ieee754_clearcx(); 22 ieee754_clearcx();
23 23
24 FLUSHXSP; 24 FLUSHXSP;
25 FLUSHYSP; 25 FLUSHYSP;
26 26
27 switch (CLPAIR(xc, yc)) { 27 switch (CLPAIR(xc, yc)) {
28 case CLPAIR(IEEE754_CLASS_QNAN, IEEE75 28 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
29 case CLPAIR(IEEE754_CLASS_ZERO, IEEE75 29 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
30 case CLPAIR(IEEE754_CLASS_NORM, IEEE75 30 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
31 case CLPAIR(IEEE754_CLASS_DNORM, IEEE7 31 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
32 case CLPAIR(IEEE754_CLASS_INF, IEEE754 32 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
33 return ieee754sp_nanxcpt(y); 33 return ieee754sp_nanxcpt(y);
34 34
35 case CLPAIR(IEEE754_CLASS_SNAN, IEEE75 35 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
36 case CLPAIR(IEEE754_CLASS_SNAN, IEEE75 36 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
37 case CLPAIR(IEEE754_CLASS_SNAN, IEEE75 37 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
38 case CLPAIR(IEEE754_CLASS_SNAN, IEEE75 38 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
39 case CLPAIR(IEEE754_CLASS_SNAN, IEEE75 39 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE75 40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
41 return ieee754sp_nanxcpt(x); 41 return ieee754sp_nanxcpt(x);
42 42
43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE75 43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
44 case CLPAIR(IEEE754_CLASS_NORM, IEEE75 44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE7 45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
46 case CLPAIR(IEEE754_CLASS_INF, IEEE754 46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
47 return y; 47 return y;
48 48
49 case CLPAIR(IEEE754_CLASS_QNAN, IEEE75 49 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
50 case CLPAIR(IEEE754_CLASS_QNAN, IEEE75 50 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
51 case CLPAIR(IEEE754_CLASS_QNAN, IEEE75 51 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
52 case CLPAIR(IEEE754_CLASS_QNAN, IEEE75 52 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
53 case CLPAIR(IEEE754_CLASS_QNAN, IEEE75 53 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
54 return x; 54 return x;
55 55
56 56
57 /* 57 /*
58 * Infinity handling 58 * Infinity handling
59 */ 59 */
60 case CLPAIR(IEEE754_CLASS_INF, IEEE754 60 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
61 if (xs != ys) 61 if (xs != ys)
62 return x; 62 return x;
63 ieee754_setcx(IEEE754_INVALID_ 63 ieee754_setcx(IEEE754_INVALID_OPERATION);
64 return ieee754sp_indef(); 64 return ieee754sp_indef();
65 65
66 case CLPAIR(IEEE754_CLASS_ZERO, IEEE75 66 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
67 case CLPAIR(IEEE754_CLASS_DNORM, IEEE7 67 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
68 case CLPAIR(IEEE754_CLASS_NORM, IEEE75 68 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
69 return ieee754sp_inf(ys ^ 1); 69 return ieee754sp_inf(ys ^ 1);
70 70
71 case CLPAIR(IEEE754_CLASS_INF, IEEE754 71 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
72 case CLPAIR(IEEE754_CLASS_INF, IEEE754 72 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
73 case CLPAIR(IEEE754_CLASS_INF, IEEE754 73 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
74 return x; 74 return x;
75 75
76 /* 76 /*
77 * Zero handling 77 * Zero handling
78 */ 78 */
79 case CLPAIR(IEEE754_CLASS_ZERO, IEEE75 79 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
80 if (xs != ys) 80 if (xs != ys)
81 return x; 81 return x;
82 else 82 else
83 return ieee754sp_zero( 83 return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
84 84
85 case CLPAIR(IEEE754_CLASS_NORM, IEEE75 85 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
86 case CLPAIR(IEEE754_CLASS_DNORM, IEEE7 86 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
87 return x; 87 return x;
88 88
89 case CLPAIR(IEEE754_CLASS_ZERO, IEEE75 89 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE75 90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
91 /* quick fix up */ 91 /* quick fix up */
92 SPSIGN(y) ^= 1; 92 SPSIGN(y) ^= 1;
93 return y; 93 return y;
94 94
95 case CLPAIR(IEEE754_CLASS_DNORM, IEEE7 95 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
96 SPDNORMX; 96 SPDNORMX;
97 fallthrough; 97 fallthrough;
98 case CLPAIR(IEEE754_CLASS_NORM, IEEE75 98 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
99 SPDNORMY; 99 SPDNORMY;
100 break; 100 break;
101 101
102 case CLPAIR(IEEE754_CLASS_DNORM, IEEE7 102 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
103 SPDNORMX; 103 SPDNORMX;
104 break; 104 break;
105 105
106 case CLPAIR(IEEE754_CLASS_NORM, IEEE75 106 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
107 break; 107 break;
108 } 108 }
109 /* flip sign of y and handle as add */ 109 /* flip sign of y and handle as add */
110 ys ^= 1; 110 ys ^= 1;
111 111
112 assert(xm & SP_HIDDEN_BIT); 112 assert(xm & SP_HIDDEN_BIT);
113 assert(ym & SP_HIDDEN_BIT); 113 assert(ym & SP_HIDDEN_BIT);
114 114
115 115
116 /* provide guard,round and stick bit s 116 /* provide guard,round and stick bit space */
117 xm <<= 3; 117 xm <<= 3;
118 ym <<= 3; 118 ym <<= 3;
119 119
120 if (xe > ye) { 120 if (xe > ye) {
121 /* 121 /*
122 * have to shift y fraction ri 122 * have to shift y fraction right to align
123 */ 123 */
124 s = xe - ye; 124 s = xe - ye;
125 ym = XSPSRS(ym, s); 125 ym = XSPSRS(ym, s);
126 ye += s; 126 ye += s;
127 } else if (ye > xe) { 127 } else if (ye > xe) {
128 /* 128 /*
129 * have to shift x fraction ri 129 * have to shift x fraction right to align
130 */ 130 */
131 s = ye - xe; 131 s = ye - xe;
132 xm = XSPSRS(xm, s); 132 xm = XSPSRS(xm, s);
133 xe += s; 133 xe += s;
134 } 134 }
135 assert(xe == ye); 135 assert(xe == ye);
136 assert(xe <= SP_EMAX); 136 assert(xe <= SP_EMAX);
137 137
138 if (xs == ys) { 138 if (xs == ys) {
139 /* generate 28 bit result of a 139 /* generate 28 bit result of adding two 27 bit numbers
140 */ 140 */
141 xm = xm + ym; 141 xm = xm + ym;
142 142
143 if (xm >> (SP_FBITS + 1 + 3)) 143 if (xm >> (SP_FBITS + 1 + 3)) { /* carry out */
144 SPXSRSX1(); /* shi 144 SPXSRSX1(); /* shift preserving sticky */
145 } 145 }
146 } else { 146 } else {
147 if (xm >= ym) { 147 if (xm >= ym) {
148 xm = xm - ym; 148 xm = xm - ym;
149 } else { 149 } else {
150 xm = ym - xm; 150 xm = ym - xm;
151 xs = ys; 151 xs = ys;
152 } 152 }
153 if (xm == 0) { 153 if (xm == 0) {
154 if (ieee754_csr.rm == 154 if (ieee754_csr.rm == FPU_CSR_RD)
155 return ieee754 155 return ieee754sp_zero(1); /* round negative inf. => sign = -1 */
156 else 156 else
157 return ieee754 157 return ieee754sp_zero(0); /* other round modes => sign = 1 */
158 } 158 }
159 /* normalize to rounding preci 159 /* normalize to rounding precision
160 */ 160 */
161 while ((xm >> (SP_FBITS + 3)) 161 while ((xm >> (SP_FBITS + 3)) == 0) {
162 xm <<= 1; 162 xm <<= 1;
163 xe--; 163 xe--;
164 } 164 }
165 } 165 }
166 166
167 return ieee754sp_format(xs, xe, xm); 167 return ieee754sp_format(xs, xe, xm);
168 } 168 }
169 169
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.