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
12s64 ieee754dp_tlong(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 ieee754di_indef();
31
32	case IEEE754_CLASS_INF:
33		ieee754_setcx(IEEE754_INVALID_OPERATION);
34		return ieee754di_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 >= 63) {
44		/* look for valid corner case */
45		if (xe == 63 && xs && xm == DP_HIDDEN_BIT)
46			return -0x8000000000000000LL;
47		/* Set invalid. We will only use overflow for floating
48		   point overflow */
49		ieee754_setcx(IEEE754_INVALID_OPERATION);
50		return ieee754di_overflow(xs);
51	}
52	/* oh gawd */
53	if (xe > DP_FBITS) {
54		xm <<= xe - DP_FBITS;
55	} else if (xe < DP_FBITS) {
56		if (xe < -1) {
57			residue = xm;
58			round = 0;
59			sticky = residue != 0;
60			xm = 0;
61		} else {
62			/* Shifting a u64 64 times does not work,
63			* so we do it in two steps. Be aware that xe
64			* may be -1 */
65			residue = xm << (xe + 1);
66			residue <<= 63 - DP_FBITS;
67			round = (residue >> 63) != 0;
68			sticky = (residue << 1) != 0;
69			xm >>= DP_FBITS - xe;
70		}
71		odd = (xm & 0x1) != 0x0;
72		switch (ieee754_csr.rm) {
73		case FPU_CSR_RN:
74			if (round && (sticky || odd))
75				xm++;
76			break;
77		case FPU_CSR_RZ:
78			break;
79		case FPU_CSR_RU:	/* toward +Infinity */
80			if ((round || sticky) && !xs)
81				xm++;
82			break;
83		case FPU_CSR_RD:	/* toward -Infinity */
84			if ((round || sticky) && xs)
85				xm++;
86			break;
87		}
88		if ((xm >> 63) != 0) {
89			/* This can happen after rounding */
90			ieee754_setcx(IEEE754_INVALID_OPERATION);
91			return ieee754di_overflow(xs);
92		}
93		if (round || sticky)
94			ieee754_setcx(IEEE754_INEXACT);
95	}
96	if (xs)
97		return -xm;
98	else
99		return xm;
100}
101