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 
ieee754dp_tint(union ieee754dp x)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