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_tint.c (2018B)

      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
     12int ieee754sp_tint(union ieee754sp x)
     13{
     14	u32 residue;
     15	int round;
     16	int sticky;
     17	int odd;
     18
     19	COMPXSP;
     20
     21	ieee754_clearcx();
     22
     23	EXPLODEXSP;
     24	FLUSHXSP;
     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		/* look for valid corner case */
     45		if (xe == 31 && xs && xm == SP_HIDDEN_BIT)
     46			return -0x80000000;
     47		/* Set invalid. We will only use overflow for floating
     48		   point overflow */
     49		ieee754_setcx(IEEE754_INVALID_OPERATION);
     50		return ieee754si_overflow(xs);
     51	}
     52	/* oh gawd */
     53	if (xe > SP_FBITS) {
     54		xm <<= xe - SP_FBITS;
     55	} else {
     56		if (xe < -1) {
     57			residue = xm;
     58			round = 0;
     59			sticky = residue != 0;
     60			xm = 0;
     61		} else {
     62			/* Shifting a u32 32 times does not work,
     63			* so we do it in two steps. Be aware that xe
     64			* may be -1 */
     65			residue = xm << (xe + 1);
     66			residue <<= 31 - SP_FBITS;
     67			round = (residue >> 31) != 0;
     68			sticky = (residue << 1) != 0;
     69			xm >>= SP_FBITS - xe;
     70		}
     71		odd = (xm & 0x1) != 0x0;
     72		switch (ieee754_csr.rm) {
     73		case FPU_CSR_RN:
     74			if (round && (sticky || odd))
     75				xm++;
     76			break;
     77		case FPU_CSR_RZ:
     78			break;
     79		case FPU_CSR_RU:	/* toward +Infinity */
     80			if ((round || sticky) && !xs)
     81				xm++;
     82			break;
     83		case FPU_CSR_RD:	/* toward -Infinity */
     84			if ((round || sticky) && xs)
     85				xm++;
     86			break;
     87		}
     88		if ((xm >> 31) != 0) {
     89			/* This can happen after rounding */
     90			ieee754_setcx(IEEE754_INVALID_OPERATION);
     91			return ieee754si_overflow(xs);
     92		}
     93		if (round || sticky)
     94			ieee754_setcx(IEEE754_INEXACT);
     95	}
     96	if (xs)
     97		return -xm;
     98	else
     99		return xm;
    100}