xref: /OK3568_Linux_fs/kernel/arch/mips/math-emu/sp_tint.c (revision 4882a59341e53eb6f0b4789bf948001014eff981) 
1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-only
2*4882a593Smuzhiyun /* IEEE754 floating point arithmetic
3*4882a593Smuzhiyun  * single precision
4*4882a593Smuzhiyun  */
5*4882a593Smuzhiyun /*
6*4882a593Smuzhiyun  * MIPS floating point support
7*4882a593Smuzhiyun  * Copyright (C) 1994-2000 Algorithmics Ltd.
8*4882a593Smuzhiyun  */
9*4882a593Smuzhiyun 
10*4882a593Smuzhiyun #include "ieee754sp.h"
11*4882a593Smuzhiyun 
ieee754sp_tint(union ieee754sp x)12*4882a593Smuzhiyun int ieee754sp_tint(union ieee754sp x)
13*4882a593Smuzhiyun {
14*4882a593Smuzhiyun 	u32 residue;
15*4882a593Smuzhiyun 	int round;
16*4882a593Smuzhiyun 	int sticky;
17*4882a593Smuzhiyun 	int odd;
18*4882a593Smuzhiyun 
19*4882a593Smuzhiyun 	COMPXSP;
20*4882a593Smuzhiyun 
21*4882a593Smuzhiyun 	ieee754_clearcx();
22*4882a593Smuzhiyun 
23*4882a593Smuzhiyun 	EXPLODEXSP;
24*4882a593Smuzhiyun 	FLUSHXSP;
25*4882a593Smuzhiyun 
26*4882a593Smuzhiyun 	switch (xc) {
27*4882a593Smuzhiyun 	case IEEE754_CLASS_SNAN:
28*4882a593Smuzhiyun 	case IEEE754_CLASS_QNAN:
29*4882a593Smuzhiyun 		ieee754_setcx(IEEE754_INVALID_OPERATION);
30*4882a593Smuzhiyun 		return ieee754si_indef();
31*4882a593Smuzhiyun 
32*4882a593Smuzhiyun 	case IEEE754_CLASS_INF:
33*4882a593Smuzhiyun 		ieee754_setcx(IEEE754_INVALID_OPERATION);
34*4882a593Smuzhiyun 		return ieee754si_overflow(xs);
35*4882a593Smuzhiyun 
36*4882a593Smuzhiyun 	case IEEE754_CLASS_ZERO:
37*4882a593Smuzhiyun 		return 0;
38*4882a593Smuzhiyun 
39*4882a593Smuzhiyun 	case IEEE754_CLASS_DNORM:
40*4882a593Smuzhiyun 	case IEEE754_CLASS_NORM:
41*4882a593Smuzhiyun 		break;
42*4882a593Smuzhiyun 	}
43*4882a593Smuzhiyun 	if (xe >= 31) {
44*4882a593Smuzhiyun 		/* look for valid corner case */
45*4882a593Smuzhiyun 		if (xe == 31 && xs && xm == SP_HIDDEN_BIT)
46*4882a593Smuzhiyun 			return -0x80000000;
47*4882a593Smuzhiyun 		/* Set invalid. We will only use overflow for floating
48*4882a593Smuzhiyun 		   point overflow */
49*4882a593Smuzhiyun 		ieee754_setcx(IEEE754_INVALID_OPERATION);
50*4882a593Smuzhiyun 		return ieee754si_overflow(xs);
51*4882a593Smuzhiyun 	}
52*4882a593Smuzhiyun 	/* oh gawd */
53*4882a593Smuzhiyun 	if (xe > SP_FBITS) {
54*4882a593Smuzhiyun 		xm <<= xe - SP_FBITS;
55*4882a593Smuzhiyun 	} else {
56*4882a593Smuzhiyun 		if (xe < -1) {
57*4882a593Smuzhiyun 			residue = xm;
58*4882a593Smuzhiyun 			round = 0;
59*4882a593Smuzhiyun 			sticky = residue != 0;
60*4882a593Smuzhiyun 			xm = 0;
61*4882a593Smuzhiyun 		} else {
62*4882a593Smuzhiyun 			/* Shifting a u32 32 times does not work,
63*4882a593Smuzhiyun 			* so we do it in two steps. Be aware that xe
64*4882a593Smuzhiyun 			* may be -1 */
65*4882a593Smuzhiyun 			residue = xm << (xe + 1);
66*4882a593Smuzhiyun 			residue <<= 31 - SP_FBITS;
67*4882a593Smuzhiyun 			round = (residue >> 31) != 0;
68*4882a593Smuzhiyun 			sticky = (residue << 1) != 0;
69*4882a593Smuzhiyun 			xm >>= SP_FBITS - xe;
70*4882a593Smuzhiyun 		}
71*4882a593Smuzhiyun 		odd = (xm & 0x1) != 0x0;
72*4882a593Smuzhiyun 		switch (ieee754_csr.rm) {
73*4882a593Smuzhiyun 		case FPU_CSR_RN:
74*4882a593Smuzhiyun 			if (round && (sticky || odd))
75*4882a593Smuzhiyun 				xm++;
76*4882a593Smuzhiyun 			break;
77*4882a593Smuzhiyun 		case FPU_CSR_RZ:
78*4882a593Smuzhiyun 			break;
79*4882a593Smuzhiyun 		case FPU_CSR_RU:	/* toward +Infinity */
80*4882a593Smuzhiyun 			if ((round || sticky) && !xs)
81*4882a593Smuzhiyun 				xm++;
82*4882a593Smuzhiyun 			break;
83*4882a593Smuzhiyun 		case FPU_CSR_RD:	/* toward -Infinity */
84*4882a593Smuzhiyun 			if ((round || sticky) && xs)
85*4882a593Smuzhiyun 				xm++;
86*4882a593Smuzhiyun 			break;
87*4882a593Smuzhiyun 		}
88*4882a593Smuzhiyun 		if ((xm >> 31) != 0) {
89*4882a593Smuzhiyun 			/* This can happen after rounding */
90*4882a593Smuzhiyun 			ieee754_setcx(IEEE754_INVALID_OPERATION);
91*4882a593Smuzhiyun 			return ieee754si_overflow(xs);
92*4882a593Smuzhiyun 		}
93*4882a593Smuzhiyun 		if (round || sticky)
94*4882a593Smuzhiyun 			ieee754_setcx(IEEE754_INEXACT);
95*4882a593Smuzhiyun 	}
96*4882a593Smuzhiyun 	if (xs)
97*4882a593Smuzhiyun 		return -xm;
98*4882a593Smuzhiyun 	else
99*4882a593Smuzhiyun 		return xm;
100*4882a593Smuzhiyun }
101