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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dp_mul.c (3846B)

      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_mul(union ieee754dp x, union ieee754dp y)
     13{
     14	int re;
     15	int rs;
     16	u64 rm;
     17	unsigned int lxm;
     18	unsigned int hxm;
     19	unsigned int lym;
     20	unsigned int hym;
     21	u64 lrm;
     22	u64 hrm;
     23	u64 t;
     24	u64 at;
     25
     26	COMPXDP;
     27	COMPYDP;
     28
     29	EXPLODEXDP;
     30	EXPLODEYDP;
     31
     32	ieee754_clearcx();
     33
     34	FLUSHXDP;
     35	FLUSHYDP;
     36
     37	switch (CLPAIR(xc, yc)) {
     38	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
     39	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
     40	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
     41	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
     42	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
     43		return ieee754dp_nanxcpt(y);
     44
     45	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
     46	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
     47	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
     48	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
     49	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
     50	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
     51		return ieee754dp_nanxcpt(x);
     52
     53	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
     54	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
     55	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
     56	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
     57		return y;
     58
     59	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
     60	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
     61	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
     62	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
     63	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
     64		return x;
     65
     66
     67	/*
     68	 * Infinity handling
     69	 */
     70	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
     71	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
     72		ieee754_setcx(IEEE754_INVALID_OPERATION);
     73		return ieee754dp_indef();
     74
     75	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
     76	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
     77	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
     78	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
     79	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
     80		return ieee754dp_inf(xs ^ ys);
     81
     82	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
     83	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
     84	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
     85	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
     86	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
     87		return ieee754dp_zero(xs ^ ys);
     88
     89
     90	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
     91		DPDNORMX;
     92		fallthrough;
     93	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
     94		DPDNORMY;
     95		break;
     96
     97	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
     98		DPDNORMX;
     99		break;
    100
    101	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
    102		break;
    103	}
    104	/* rm = xm * ym, re = xe+ye basically */
    105	assert(xm & DP_HIDDEN_BIT);
    106	assert(ym & DP_HIDDEN_BIT);
    107
    108	re = xe + ye;
    109	rs = xs ^ ys;
    110
    111	/* shunt to top of word */
    112	xm <<= 64 - (DP_FBITS + 1);
    113	ym <<= 64 - (DP_FBITS + 1);
    114
    115	/*
    116	 * Multiply 64 bits xm, ym to give high 64 bits rm with stickness.
    117	 */
    118
    119	lxm = xm;
    120	hxm = xm >> 32;
    121	lym = ym;
    122	hym = ym >> 32;
    123
    124	lrm = DPXMULT(lxm, lym);
    125	hrm = DPXMULT(hxm, hym);
    126
    127	t = DPXMULT(lxm, hym);
    128
    129	at = lrm + (t << 32);
    130	hrm += at < lrm;
    131	lrm = at;
    132
    133	hrm = hrm + (t >> 32);
    134
    135	t = DPXMULT(hxm, lym);
    136
    137	at = lrm + (t << 32);
    138	hrm += at < lrm;
    139	lrm = at;
    140
    141	hrm = hrm + (t >> 32);
    142
    143	rm = hrm | (lrm != 0);
    144
    145	/*
    146	 * Sticky shift down to normal rounding precision.
    147	 */
    148	if ((s64) rm < 0) {
    149		rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
    150		     ((rm << (DP_FBITS + 1 + 3)) != 0);
    151		re++;
    152	} else {
    153		rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
    154		     ((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
    155	}
    156	assert(rm & (DP_HIDDEN_BIT << 3));
    157
    158	return ieee754dp_format(rs, re, rm);
    159}