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 * Copyright (C) 2017 Imagination Technologies, Ltd.
9 * Author: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
10 */
11
12 #include "ieee754dp.h"
13
14 union ieee754dp ieee754dp_rint(union ieee754dp x)
15 {
16 union ieee754dp ret;
17 u64 residue;
18 int sticky;
19 int round;
20 int odd;
21
22 COMPXDP;
23
24 ieee754_clearcx();
25
26 EXPLODEXDP;
27 FLUSHXDP;
28
29 if (xc == IEEE754_CLASS_SNAN)
30 return ieee754dp_nanxcpt(x);
31
32 if ((xc == IEEE754_CLASS_QNAN) ||
33 (xc == IEEE754_CLASS_INF) ||
34 (xc == IEEE754_CLASS_ZERO))
35 return x;
36
37 if (xe >= DP_FBITS)
38 return x;
39
40 if (xe < -1) {
41 residue = xm;
42 round = 0;
43 sticky = residue != 0;
44 xm = 0;
45 } else {
46 residue = xm << (64 - DP_FBITS + xe);
47 round = (residue >> 63) != 0;
48 sticky = (residue << 1) != 0;
49 xm >>= DP_FBITS - xe;
50 }
51
52 odd = (xm & 0x1) != 0x0;
53
54 switch (ieee754_csr.rm) {
55 case FPU_CSR_RN: /* toward nearest */
56 if (round && (sticky || odd))
57 xm++;
58 break;
59 case FPU_CSR_RZ: /* toward zero */
60 break;
61 case FPU_CSR_RU: /* toward +infinity */
62 if ((round || sticky) && !xs)
63 xm++;
64 break;
65 case FPU_CSR_RD: /* toward -infinity */
66 if ((round || sticky) && xs)
67 xm++;
68 break;
69 }
70
71 if (round || sticky)
72 ieee754_setcx(IEEE754_INEXACT);
73
74 ret = ieee754dp_flong(xm);
75 DPSIGN(ret) = xs;
76
77 return ret;
78 }
79
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