diff options
Diffstat (limited to 'arch/mips/math-emu/dp_msubf.c')
| -rw-r--r-- | arch/mips/math-emu/dp_msubf.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/arch/mips/math-emu/dp_msubf.c b/arch/mips/math-emu/dp_msubf.c new file mode 100644 index 000000000000..12241262f856 --- /dev/null +++ b/arch/mips/math-emu/dp_msubf.c @@ -0,0 +1,269 @@ +/* + * IEEE754 floating point arithmetic + * double precision: MSUB.f (Fused Multiply Subtract) + * MSUBF.fmt: FPR[fd] = FPR[fd] - (FPR[fs] x FPR[ft]) + * + * MIPS floating point support + * Copyright (C) 2015 Imagination Technologies, Ltd. + * Author: Markos Chandras <markos.chandras@imgtec.com> + * + * This program is free software; you can distribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; version 2 of the License. + */ + +#include "ieee754dp.h" + +union ieee754dp ieee754dp_msubf(union ieee754dp z, union ieee754dp x, + union ieee754dp y) +{ + int re; + int rs; + u64 rm; + unsigned lxm; + unsigned hxm; + unsigned lym; + unsigned hym; + u64 lrm; + u64 hrm; + u64 t; + u64 at; + int s; + + COMPXDP; + COMPYDP; + + u64 zm; int ze; int zs __maybe_unused; int zc; + + EXPLODEXDP; + EXPLODEYDP; + EXPLODEDP(z, zc, zs, ze, zm) + + FLUSHXDP; + FLUSHYDP; + FLUSHDP(z, zc, zs, ze, zm); + + ieee754_clearcx(); + + switch (zc) { + case IEEE754_CLASS_SNAN: + ieee754_setcx(IEEE754_INVALID_OPERATION); + return ieee754dp_nanxcpt(z); + case IEEE754_CLASS_DNORM: + DPDNORMx(zm, ze); + /* QNAN is handled separately below */ + } + + 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_ZERO): + case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF): + if (zc == IEEE754_CLASS_QNAN) + return z; + ieee754_setcx(IEEE754_INVALID_OPERATION); + return ieee754dp_indef(); + + case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF): + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF): + case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM): + case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM): + case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF): + if (zc == IEEE754_CLASS_QNAN) + return z; + return ieee754dp_inf(xs ^ ys); + + case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO): + case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM): + case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM): + case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO): + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): + if (zc == IEEE754_CLASS_INF) + return ieee754dp_inf(zs); + /* Multiplication is 0 so just return z */ + return z; + + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): + DPDNORMX; + + case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): + if (zc == IEEE754_CLASS_QNAN) + return z; + else if (zc == IEEE754_CLASS_INF) + return ieee754dp_inf(zs); + DPDNORMY; + break; + + case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): + if (zc == IEEE754_CLASS_QNAN) + return z; + else if (zc == IEEE754_CLASS_INF) + return ieee754dp_inf(zs); + DPDNORMX; + break; + + case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): + if (zc == IEEE754_CLASS_QNAN) + return z; + else if (zc == IEEE754_CLASS_INF) + return ieee754dp_inf(zs); + /* fall through to real computations */ + } + + /* Finally get to do some computation */ + + /* + * Do the multiplication bit first + * + * rm = xm * ym, re = xe + ye basically + * + * At this point xm and ym should have been normalized. + */ + assert(xm & DP_HIDDEN_BIT); + assert(ym & DP_HIDDEN_BIT); + + re = xe + ye; + rs = xs ^ ys; + + /* shunt to top of word */ + xm <<= 64 - (DP_FBITS + 1); + ym <<= 64 - (DP_FBITS + 1); + + /* + * Multiply 32 bits xm, ym to give high 32 bits rm with stickness. + */ + + /* 32 * 32 => 64 */ +#define DPXMULT(x, y) ((u64)(x) * (u64)y) + + lxm = xm; + hxm = xm >> 32; + lym = ym; + hym = ym >> 32; + + lrm = DPXMULT(lxm, lym); + hrm = DPXMULT(hxm, hym); + + t = DPXMULT(lxm, hym); + + at = lrm + (t << 32); + hrm += at < lrm; + lrm = at; + + hrm = hrm + (t >> 32); + + t = DPXMULT(hxm, lym); + + at = lrm + (t << 32); + hrm += at < lrm; + lrm = at; + + hrm = hrm + (t >> 32); + + rm = hrm | (lrm != 0); + + /* + * Sticky shift down to normal rounding precision. + */ + if ((s64) rm < 0) { + rm = (rm >> (64 - (DP_FBITS + 1 + 3))) | + ((rm << (DP_FBITS + 1 + 3)) != 0); + re++; + } else { + rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) | + ((rm << (DP_FBITS + 1 + 3 + 1)) != 0); + } + assert(rm & (DP_HIDDEN_BIT << 3)); + + /* And now the subtraction */ + + /* flip sign of r and handle as add */ + rs ^= 1; + + assert(zm & DP_HIDDEN_BIT); + + /* + * Provide guard,round and stick bit space. + */ + zm <<= 3; + + if (ze > re) { + /* + * Have to shift y fraction right to align. + */ + s = ze - re; + rm = XDPSRS(rm, s); + re += s; + } else if (re > ze) { + /* + * Have to shift x fraction right to align. + */ + s = re - ze; + zm = XDPSRS(zm, s); + ze += s; + } + assert(ze == re); + assert(ze <= DP_EMAX); + + if (zs == rs) { + /* + * Generate 28 bit result of adding two 27 bit numbers + * leaving result in xm, xs and xe. + */ + zm = zm + rm; + + if (zm >> (DP_FBITS + 1 + 3)) { /* carry out */ + zm = XDPSRS1(zm); + ze++; + } + } else { + if (zm >= rm) { + zm = zm - rm; + } else { + zm = rm - zm; + zs = rs; + } + if (zm == 0) + return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD); + + /* + * Normalize to rounding precision. + */ + while ((zm >> (DP_FBITS + 3)) == 0) { + zm <<= 1; + ze--; + } + } + + return ieee754dp_format(zs, ze, zm); +} |