diff options
Diffstat (limited to 'arch/mips/math-emu/dp_sub.c')
| -rw-r--r-- | arch/mips/math-emu/dp_sub.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/arch/mips/math-emu/dp_sub.c b/arch/mips/math-emu/dp_sub.c new file mode 100644 index 0000000000..08474ad2a6 --- /dev/null +++ b/arch/mips/math-emu/dp_sub.c @@ -0,0 +1,172 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* IEEE754 floating point arithmetic + * double precision: common utilities + */ +/* + * MIPS floating point support + * Copyright (C) 1994-2000 Algorithmics Ltd. + */ + +#include "ieee754dp.h" + +union ieee754dp ieee754dp_sub(union ieee754dp x, union ieee754dp y) +{ + int s; + + COMPXDP; + COMPYDP; + + EXPLODEXDP; + EXPLODEYDP; + + ieee754_clearcx(); + + FLUSHXDP; + FLUSHYDP; + + 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 ieee754dp_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 ieee754dp_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 ieee754dp_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 ieee754dp_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 ieee754dp_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 */ + DPSIGN(y) ^= 1; + return y; + + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): + DPDNORMX; + fallthrough; + case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): + /* normalize ym,ye */ + DPDNORMY; + break; + + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): + /* normalize xm,xe */ + DPDNORMX; + break; + + case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): + break; + } + /* flip sign of y and handle as add */ + ys ^= 1; + + assert(xm & DP_HIDDEN_BIT); + assert(ym & DP_HIDDEN_BIT); + + + /* provide guard,round and stick bit dpace */ + xm <<= 3; + ym <<= 3; + + if (xe > ye) { + /* + * Have to shift y fraction right to align + */ + s = xe - ye; + ym = XDPSRS(ym, s); + ye += s; + } else if (ye > xe) { + /* + * Have to shift x fraction right to align + */ + s = ye - xe; + xm = XDPSRS(xm, s); + xe += s; + } + assert(xe == ye); + assert(xe <= DP_EMAX); + + if (xs == ys) { + /* generate 28 bit result of adding two 27 bit numbers + */ + xm = xm + ym; + + if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */ + xm = XDPSRS1(xm); /* shift preserving sticky */ + xe++; + } + } else { + if (xm >= ym) { + xm = xm - ym; + } else { + xm = ym - xm; + xs = ys; + } + if (xm == 0) { + if (ieee754_csr.rm == FPU_CSR_RD) + return ieee754dp_zero(1); /* round negative inf. => sign = -1 */ + else + return ieee754dp_zero(0); /* other round modes => sign = 1 */ + } + + /* normalize to rounding precision + */ + while ((xm >> (DP_FBITS + 3)) == 0) { + xm <<= 1; + xe--; + } + } + + return ieee754dp_format(xs, xe, xm); +} |