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_tint.c (1980B)

      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
     12int 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}