113 строки
2.6 KiB
C
113 строки
2.6 KiB
C
/* IEEE754 floating point arithmetic
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* double precision: common utilities
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*/
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/*
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* MIPS floating point support
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* Copyright (C) 1994-2000 Algorithmics Ltd.
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*
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* This program is free software; you can distribute it and/or modify it
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* under the terms of the GNU General Public License (Version 2) as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "ieee754dp.h"
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s64 ieee754dp_tlong(union ieee754dp x)
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{
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u64 residue;
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int round;
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int sticky;
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int odd;
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COMPXDP;
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ieee754_clearcx();
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EXPLODEXDP;
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FLUSHXDP;
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switch (xc) {
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case IEEE754_CLASS_SNAN:
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case IEEE754_CLASS_QNAN:
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754di_indef();
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case IEEE754_CLASS_INF:
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754di_overflow(xs);
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case IEEE754_CLASS_ZERO:
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return 0;
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case IEEE754_CLASS_DNORM:
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case IEEE754_CLASS_NORM:
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break;
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}
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if (xe >= 63) {
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/* look for valid corner case */
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if (xe == 63 && xs && xm == DP_HIDDEN_BIT)
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return -0x8000000000000000LL;
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/* Set invalid. We will only use overflow for floating
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point overflow */
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754di_overflow(xs);
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}
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/* oh gawd */
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if (xe > DP_FBITS) {
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xm <<= xe - DP_FBITS;
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} else if (xe < DP_FBITS) {
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if (xe < -1) {
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residue = xm;
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round = 0;
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sticky = residue != 0;
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xm = 0;
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} else {
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/* Shifting a u64 64 times does not work,
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* so we do it in two steps. Be aware that xe
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* may be -1 */
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residue = xm << (xe + 1);
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residue <<= 63 - DP_FBITS;
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round = (residue >> 63) != 0;
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sticky = (residue << 1) != 0;
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xm >>= DP_FBITS - xe;
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}
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odd = (xm & 0x1) != 0x0;
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switch (ieee754_csr.rm) {
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case FPU_CSR_RN:
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if (round && (sticky || odd))
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xm++;
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break;
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case FPU_CSR_RZ:
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break;
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case FPU_CSR_RU: /* toward +Infinity */
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if ((round || sticky) && !xs)
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xm++;
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break;
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case FPU_CSR_RD: /* toward -Infinity */
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if ((round || sticky) && xs)
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xm++;
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break;
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}
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if ((xm >> 63) != 0) {
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/* This can happen after rounding */
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754di_overflow(xs);
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}
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if (round || sticky)
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ieee754_setcx(IEEE754_INEXACT);
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}
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if (xs)
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return -xm;
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else
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return xm;
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}
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