diff options
Diffstat (limited to 'arch/mips/math-emu/sp_sub.c')
| -rw-r--r-- | arch/mips/math-emu/sp_sub.c | 168 |
1 files changed, 168 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 000000000..16c8e9ae6 --- /dev/null +++ b/arch/mips/math-emu/sp_sub.c @@ -0,0 +1,168 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* IEEE754 floating point arithmetic + * single precision + */ +/* + * MIPS floating point support + * Copyright (C) 1994-2000 Algorithmics Ltd. + */ + +#include "ieee754sp.h" + +union ieee754sp ieee754sp_sub(union ieee754sp x, union ieee754sp y) +{ + int s; + + COMPXSP; + COMPYSP; + + EXPLODEXSP; + EXPLODEYSP; + + ieee754_clearcx(); + + FLUSHXSP; + FLUSHYSP; + + switch (CLPAIR(xc, yc)) { + case CLPAIR(IEEE754_CLASS_QNAN, 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): + return ieee754sp_nanxcpt(y); + + case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN): + case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN): + 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): + return ieee754sp_nanxcpt(x); + + 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; + ieee754_setcx(IEEE754_INVALID_OPERATION); + return ieee754sp_indef(); + + 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 == FPU_CSR_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 */ + SPSIGN(y) ^= 1; + return y; + + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): + SPDNORMX; + fallthrough; + 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 + */ + s = xe - ye; + ym = XSPSRS(ym, s); + ye += s; + } else if (ye > xe) { + /* + * have to shift x fraction right to align + */ + s = ye - xe; + xm = XSPSRS(xm, s); + xe += s; + } + assert(xe == ye); + assert(xe <= SP_EMAX); + + if (xs == ys) { + /* generate 28 bit result of adding two 27 bit numbers + */ + xm = xm + ym; + + if (xm >> (SP_FBITS + 1 + 3)) { /* carry out */ + SPXSRSX1(); /* shift preserving sticky */ + } + } else { + if (xm >= ym) { + xm = xm - ym; + } else { + xm = ym - xm; + xs = ys; + } + if (xm == 0) { + if (ieee754_csr.rm == FPU_CSR_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_FBITS + 3)) == 0) { + xm <<= 1; + xe--; + } + } + + return ieee754sp_format(xs, xe, xm); +} |