dp_div.c

  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
 12union ieee754dp ieee754dp_div(union ieee754dp x, union ieee754dp y)
 13{
 14	u64 rm;
 15	int re;
 16	u64 bm;
 17
 18	COMPXDP;
 19	COMPYDP;
 20
 21	EXPLODEXDP;
 22	EXPLODEYDP;
 23
 24	ieee754_clearcx();
 25
 26	FLUSHXDP;
 27	FLUSHYDP;
 28
 29	switch (CLPAIR(xc, yc)) {
 30	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
 31	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
 32	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
 33	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
 34	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
 35		return ieee754dp_nanxcpt(y);
 36
 37	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
 38	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
 39	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
 40	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
 41	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
 42	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
 43		return ieee754dp_nanxcpt(x);
 44
 45	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
 46	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
 47	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
 48	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
 49		return y;
 50
 51	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
 52	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
 53	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
 54	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
 55	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
 56		return x;
 57
 58
 59	/*
 60	 * Infinity handling
 61	 */
 62	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
 63		ieee754_setcx(IEEE754_INVALID_OPERATION);
 64		return ieee754dp_indef();
 65
 66	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
 67	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
 68	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
 69		return ieee754dp_zero(xs ^ ys);
 70
 71	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
 72	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
 73	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
 74		return ieee754dp_inf(xs ^ ys);
 75
 76	/*
 77	 * Zero handling
 78	 */
 79	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
 80		ieee754_setcx(IEEE754_INVALID_OPERATION);
 81		return ieee754dp_indef();
 82
 83	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
 84	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
 85		ieee754_setcx(IEEE754_ZERO_DIVIDE);
 86		return ieee754dp_inf(xs ^ ys);
 87
 88	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
 89	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
 90		return ieee754dp_zero(xs == ys ? 0 : 1);
 91
 92	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
 93		DPDNORMX;
 94		fallthrough;
 95	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
 96		DPDNORMY;
 97		break;
 98
 99	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
100		DPDNORMX;
101		break;
102
103	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
104		break;
105	}
106	assert(xm & DP_HIDDEN_BIT);
107	assert(ym & DP_HIDDEN_BIT);
108
109	/* provide rounding space */
110	xm <<= 3;
111	ym <<= 3;
112
113	/* now the dirty work */
114
115	rm = 0;
116	re = xe - ye;
117
118	for (bm = DP_MBIT(DP_FBITS + 2); bm; bm >>= 1) {
119		if (xm >= ym) {
120			xm -= ym;
121			rm |= bm;
122			if (xm == 0)
123				break;
124		}
125		xm <<= 1;
126	}
127
128	rm <<= 1;
129	if (xm)
130		rm |= 1;	/* have remainder, set sticky */
131
132	assert(rm);
133
134	/*
135	 * Normalise rm to rounding precision ?
136	 */
137	while ((rm >> (DP_FBITS + 3)) == 0) {
138		rm <<= 1;
139		re--;
140	}
141
142	return ieee754dp_format(xs == ys ? 0 : 1, re, rm);
143}