/* IEEE754 floating point arithmetic * single precision */ /* * MIPS floating point support * Copyright (C) 1994-2000 Algorithmics Ltd. All rights reserved. * http://www.algor.co.uk * * ######################################################################## * * This program is free software; you can distribute it and/or modify it * under the terms of the GNU General Public License (Version 2) as * published by the Free Software Foundation. * * This program is distributed in the hope it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. * * ######################################################################## */ #include "ieee754sp.h" ieee754sp ieee754sp_sub(ieee754sp x, ieee754sp y) { COMPXSP; COMPYSP; EXPLODEXSP; EXPLODEYSP; CLEARCX; FLUSHXSP; FLUSHYSP; switch (CLPAIR(xc, yc)) { case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN): case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN): case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN): case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN): case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN): case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN): case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO): case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM): case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM): case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF): SETCX(IEEE754_INVALID_OPERATION); return ieee754sp_nanxcpt(ieee754sp_indef(), "sub", x, y); case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN): case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN): case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN): return y; case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN): case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO): case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM): case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM): case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF): return x; /* Inifity handeling */ case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF): if (xs != ys) return x; SETCX(IEEE754_INVALID_OPERATION); return ieee754sp_xcpt(ieee754sp_indef(), "sub", x, y); case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF): case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF): return ieee754sp_inf(ys ^ 1); case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO): case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM): case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM): return x; /* Zero handeling */ case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO): if (xs != ys) return x; else return ieee754sp_zero(ieee754_csr.rm == IEEE754_RD); case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO): case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): return x; case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM): case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM): /* quick fix up */ DPSIGN(y) ^= 1; return y; case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): SPDNORMX; case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): SPDNORMY; break; case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): SPDNORMX; break; case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): break; } /* flip sign of y and handle as add */ ys ^= 1; assert(xm & SP_HIDDEN_BIT); assert(ym & SP_HIDDEN_BIT); /* provide guard,round and stick bit space */ xm <<= 3; ym <<= 3; if (xe > ye) { /* have to shift y fraction right to align */ int s = xe - ye; SPXSRSYn(s); } else if (ye > xe) { /* have to shift x fraction right to align */ int s = ye - xe; SPXSRSXn(s); } assert(xe == ye); assert(xe <= SP_EMAX); if (xs == ys) { /* generate 28 bit result of adding two 27 bit numbers */ xm = xm + ym; xe = xe; xs = xs; if (xm >> (SP_MBITS + 1 + 3)) { /* carry out */ SPXSRSX1(); /* shift preserving sticky */ } } else { if (xm >= ym) { xm = xm - ym; xe = xe; xs = xs; } else { xm = ym - xm; xe = xe; xs = ys; } if (xm == 0) { if (ieee754_csr.rm == IEEE754_RD) return ieee754sp_zero(1); /* round negative inf. => sign = -1 */ else return ieee754sp_zero(0); /* other round modes => sign = 1 */ } /* normalize to rounding precision */ while ((xm >> (SP_MBITS + 3)) == 0) { xm <<= 1; xe--; } } SPNORMRET2(xs, xe, xm, "sub", x, y); }