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 
ieee754dp_rint(union ieee754dp x)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