/* 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" int ieee754sp_class(ieee754sp x) { COMPXSP; EXPLODEXSP; return xc; } int ieee754sp_isnan(ieee754sp x) { return ieee754sp_class(x) >= IEEE754_CLASS_SNAN; } int ieee754sp_issnan(ieee754sp x) { assert(ieee754sp_isnan(x)); return (SPMANT(x) & SP_MBIT(SP_MBITS-1)); } ieee754sp ieee754sp_xcpt(ieee754sp r, const char *op, ...) { struct ieee754xctx ax; if (!TSTX()) return r; ax.op = op; ax.rt = IEEE754_RT_SP; ax.rv.sp = r; va_start(ax.ap, op); ieee754_xcpt(&ax); return ax.rv.sp; } ieee754sp ieee754sp_nanxcpt(ieee754sp r, const char *op, ...) { struct ieee754xctx ax; assert(ieee754sp_isnan(r)); if (!ieee754sp_issnan(r)) /* QNAN does not cause invalid op !! */ return r; if (!SETANDTESTCX(IEEE754_INVALID_OPERATION)) { /* not enabled convert to a quiet NaN */ SPMANT(r) &= (~SP_MBIT(SP_MBITS-1)); if (ieee754sp_isnan(r)) return r; else return ieee754sp_indef(); } ax.op = op; ax.rt = 0; ax.rv.sp = r; va_start(ax.ap, op); ieee754_xcpt(&ax); return ax.rv.sp; } ieee754sp ieee754sp_bestnan(ieee754sp x, ieee754sp y) { assert(ieee754sp_isnan(x)); assert(ieee754sp_isnan(y)); if (SPMANT(x) > SPMANT(y)) return x; else return y; } static unsigned get_rounding(int sn, unsigned xm) { /* inexact must round of 3 bits */ if (xm & (SP_MBIT(3) - 1)) { switch (ieee754_csr.rm) { case IEEE754_RZ: break; case IEEE754_RN: xm += 0x3 + ((xm >> 3) & 1); /* xm += (xm&0x8)?0x4:0x3 */ break; case IEEE754_RU: /* toward +Infinity */ if (!sn) /* ?? */ xm += 0x8; break; case IEEE754_RD: /* toward -Infinity */ if (sn) /* ?? */ xm += 0x8; break; } } return xm; } /* generate a normal/denormal number with over,under handeling * sn is sign * xe is an unbiased exponent * xm is 3bit extended precision value. */ ieee754sp ieee754sp_format(int sn, int xe, unsigned xm) { assert(xm); /* we dont gen exact zeros (probably should) */ assert((xm >> (SP_MBITS + 1 + 3)) == 0); /* no execess */ assert(xm & (SP_HIDDEN_BIT << 3)); if (xe < SP_EMIN) { /* strip lower bits */ int es = SP_EMIN - xe; if (ieee754_csr.nod) { SETCX(IEEE754_UNDERFLOW); SETCX(IEEE754_INEXACT); switch(ieee754_csr.rm) { case IEEE754_RN: return ieee754sp_zero(sn); case IEEE754_RZ: return ieee754sp_zero(sn); case IEEE754_RU: /* toward +Infinity */ if(sn == 0) return ieee754sp_min(0); else return ieee754sp_zero(1); case IEEE754_RD: /* toward -Infinity */ if(sn == 0) return ieee754sp_zero(0); else return ieee754sp_min(1); } } if (xe == SP_EMIN - 1 && get_rounding(sn, xm) >> (SP_MBITS + 1 + 3)) { /* Not tiny after rounding */ SETCX(IEEE754_INEXACT); xm = get_rounding(sn, xm); xm >>= 1; /* Clear grs bits */ xm &= ~(SP_MBIT(3) - 1); xe++; } else { /* sticky right shift es bits */ SPXSRSXn(es); assert((xm & (SP_HIDDEN_BIT << 3)) == 0); assert(xe == SP_EMIN); } } if (xm & (SP_MBIT(3) - 1)) { SETCX(IEEE754_INEXACT); if ((xm & (SP_HIDDEN_BIT << 3)) == 0) { SETCX(IEEE754_UNDERFLOW); } /* inexact must round of 3 bits */ xm = get_rounding(sn, xm); /* adjust exponent for rounding add overflowing */ if (xm >> (SP_MBITS + 1 + 3)) { /* add causes mantissa overflow */ xm >>= 1; xe++; } } /* strip grs bits */ xm >>= 3; assert((xm >> (SP_MBITS + 1)) == 0); /* no execess */ assert(xe >= SP_EMIN); if (xe > SP_EMAX) { SETCX(IEEE754_OVERFLOW); SETCX(IEEE754_INEXACT); /* -O can be table indexed by (rm,sn) */ switch (ieee754_csr.rm) { case IEEE754_RN: return ieee754sp_inf(sn); case IEEE754_RZ: return ieee754sp_max(sn); case IEEE754_RU: /* toward +Infinity */ if (sn == 0) return ieee754sp_inf(0); else return ieee754sp_max(1); case IEEE754_RD: /* toward -Infinity */ if (sn == 0) return ieee754sp_max(0); else return ieee754sp_inf(1); } } /* gen norm/denorm/zero */ if ((xm & SP_HIDDEN_BIT) == 0) { /* we underflow (tiny/zero) */ assert(xe == SP_EMIN); if (ieee754_csr.mx & IEEE754_UNDERFLOW) SETCX(IEEE754_UNDERFLOW); return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm); } else { assert((xm >> (SP_MBITS + 1)) == 0); /* no execess */ assert(xm & SP_HIDDEN_BIT); return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT); } }