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 int ieee754dp_tint(union ieee754dp x)
13 {
14 u64 residue;
15 int round;
16 int sticky;
17 int odd;
18
19 COMPXDP;
20
21 ieee754_clearcx();
22
23 EXPLODEXDP;
24 FLUSHXDP;
25
26 switch (xc) {
27 case IEEE754_CLASS_SNAN:
28 case IEEE754_CLASS_QNAN:
29 ieee754_setcx(IEEE754_INVALID_OPERATION);
30 return ieee754si_indef();
31
32 case IEEE754_CLASS_INF:
33 ieee754_setcx(IEEE754_INVALID_OPERATION);
34 return ieee754si_overflow(xs);
35
36 case IEEE754_CLASS_ZERO:
37 return 0;
38
39 case IEEE754_CLASS_DNORM:
40 case IEEE754_CLASS_NORM:
41 break;
42 }
43 if (xe > 31) {
44 /* Set invalid. We will only use overflow for floating
45 point overflow */
46 ieee754_setcx(IEEE754_INVALID_OPERATION);
47 return ieee754si_overflow(xs);
48 }
49 /* oh gawd */
50 if (xe > DP_FBITS) {
51 xm <<= xe - DP_FBITS;
52 } else if (xe < DP_FBITS) {
53 if (xe < -1) {
54 residue = xm;
55 round = 0;
56 sticky = residue != 0;
57 xm = 0;
58 } else {
59 residue = xm << (64 - DP_FBITS + xe);
60 round = (residue >> 63) != 0;
61 sticky = (residue << 1) != 0;
62 xm >>= DP_FBITS - xe;
63 }
64 /* Note: At this point upper 32 bits of xm are guaranteed
65 to be zero */
66 odd = (xm & 0x1) != 0x0;
67 switch (ieee754_csr.rm) {
68 case FPU_CSR_RN:
69 if (round && (sticky || odd))
70 xm++;
71 break;
72 case FPU_CSR_RZ:
73 break;
74 case FPU_CSR_RU: /* toward +Infinity */
75 if ((round || sticky) && !xs)
76 xm++;
77 break;
78 case FPU_CSR_RD: /* toward -Infinity */
79 if ((round || sticky) && xs)
80 xm++;
81 break;
82 }
83 /* look for valid corner case 0x80000000 */
84 if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
85 /* This can happen after rounding */
86 ieee754_setcx(IEEE754_INVALID_OPERATION);
87 return ieee754si_overflow(xs);
88 }
89 if (round || sticky)
90 ieee754_setcx(IEEE754_INEXACT);
91 }
92 if (xs)
93 return -xm;
94 else
95 return xm;
96 }
97
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