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Diffstat (limited to 'arch/mips/math-emu/sp_sub.c')
| -rw-r--r-- | arch/mips/math-emu/sp_sub.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/arch/mips/math-emu/sp_sub.c b/arch/mips/math-emu/sp_sub.c new file mode 100644 index 0000000..dbb802c --- /dev/null +++ b/arch/mips/math-emu/sp_sub.c @@ -0,0 +1,184 @@ +/* IEEE754 floating point arithmetic + * single precision + */ +/* + * MIPS floating point support + * Copyright (C) 1994-2000 Algorithmics Ltd. + * 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; + + + /* Infinity handling + */ + + 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 handling + */ + + 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); +} |