cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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sp_div.c (3499B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* IEEE754 floating point arithmetic
      3 * single precision
      4 */
      5/*
      6 * MIPS floating point support
      7 * Copyright (C) 1994-2000 Algorithmics Ltd.
      8 */
      9
     10#include "ieee754sp.h"
     11
     12union ieee754sp ieee754sp_div(union ieee754sp x, union ieee754sp y)
     13{
     14	unsigned int rm;
     15	int re;
     16	unsigned int bm;
     17
     18	COMPXSP;
     19	COMPYSP;
     20
     21	EXPLODEXSP;
     22	EXPLODEYSP;
     23
     24	ieee754_clearcx();
     25
     26	FLUSHXSP;
     27	FLUSHYSP;
     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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_inf(xs ^ ys);
     87
     88	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
     89	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
     90		return ieee754sp_zero(xs == ys ? 0 : 1);
     91
     92	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
     93		SPDNORMX;
     94		fallthrough;
     95	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
     96		SPDNORMY;
     97		break;
     98
     99	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
    100		SPDNORMX;
    101		break;
    102
    103	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
    104		break;
    105	}
    106	assert(xm & SP_HIDDEN_BIT);
    107	assert(ym & SP_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 = SP_MBIT(SP_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	/* normalise rm to rounding precision ?
    135	 */
    136	while ((rm >> (SP_FBITS + 3)) == 0) {
    137		rm <<= 1;
    138		re--;
    139	}
    140
    141	return ieee754sp_format(xs == ys ? 0 : 1, re, rm);
    142}