266 lines
6.4 KiB
C
266 lines
6.4 KiB
C
/*
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* IEEE754 floating point arithmetic
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* single precision: MADDF.f (Fused Multiply Add)
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* MADDF.fmt: FPR[fd] = FPR[fd] + (FPR[fs] x FPR[ft])
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*
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* MIPS floating point support
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* Copyright (C) 2015 Imagination Technologies, Ltd.
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* Author: Markos Chandras <markos.chandras@imgtec.com>
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*
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* This program is free software; you can distribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; version 2 of the License.
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*/
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#include "ieee754sp.h"
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static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
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union ieee754sp y, enum maddf_flags flags)
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{
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int re;
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int rs;
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unsigned int rm;
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u64 rm64;
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u64 zm64;
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int s;
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COMPXSP;
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COMPYSP;
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COMPZSP;
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EXPLODEXSP;
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EXPLODEYSP;
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EXPLODEZSP;
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FLUSHXSP;
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FLUSHYSP;
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FLUSHZSP;
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ieee754_clearcx();
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/*
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* Handle the cases when at least one of x, y or z is a NaN.
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* Order of precedence is sNaN, qNaN and z, x, y.
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*/
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if (zc == IEEE754_CLASS_SNAN)
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return ieee754sp_nanxcpt(z);
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if (xc == IEEE754_CLASS_SNAN)
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return ieee754sp_nanxcpt(x);
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if (yc == IEEE754_CLASS_SNAN)
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return ieee754sp_nanxcpt(y);
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if (zc == IEEE754_CLASS_QNAN)
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return z;
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if (xc == IEEE754_CLASS_QNAN)
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return x;
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if (yc == IEEE754_CLASS_QNAN)
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return y;
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if (zc == IEEE754_CLASS_DNORM)
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SPDNORMZ;
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/* ZERO z cases are handled separately below */
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switch (CLPAIR(xc, yc)) {
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/*
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* Infinity handling
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*/
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754sp_indef();
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
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if ((zc == IEEE754_CLASS_INF) &&
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((!(flags & MADDF_NEGATE_PRODUCT) && (zs != (xs ^ ys))) ||
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((flags & MADDF_NEGATE_PRODUCT) && (zs == (xs ^ ys))))) {
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/*
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* Cases of addition of infinities with opposite signs
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* or subtraction of infinities with same signs.
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*/
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ieee754_setcx(IEEE754_INVALID_OPERATION);
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return ieee754sp_indef();
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}
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/*
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* z is here either not an infinity, or an infinity having the
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* same sign as product (x*y) (in case of MADDF.D instruction)
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* or product -(x*y) (in MSUBF.D case). The result must be an
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* infinity, and its sign is determined only by the value of
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* (flags & MADDF_NEGATE_PRODUCT) and the signs of x and y.
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*/
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if (flags & MADDF_NEGATE_PRODUCT)
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return ieee754sp_inf(1 ^ (xs ^ ys));
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else
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return ieee754sp_inf(xs ^ ys);
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
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if (zc == IEEE754_CLASS_INF)
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return ieee754sp_inf(zs);
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if (zc == IEEE754_CLASS_ZERO) {
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/* Handle cases +0 + (-0) and similar ones. */
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if ((!(flags & MADDF_NEGATE_PRODUCT)
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&& (zs == (xs ^ ys))) ||
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((flags & MADDF_NEGATE_PRODUCT)
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&& (zs != (xs ^ ys))))
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/*
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* Cases of addition of zeros of equal signs
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* or subtraction of zeroes of opposite signs.
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* The sign of the resulting zero is in any
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* such case determined only by the sign of z.
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*/
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return z;
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return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
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}
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/* x*y is here 0, and z is not 0, so just return z */
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return z;
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
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SPDNORMX;
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/* fall through */
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
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if (zc == IEEE754_CLASS_INF)
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return ieee754sp_inf(zs);
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SPDNORMY;
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break;
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
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if (zc == IEEE754_CLASS_INF)
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return ieee754sp_inf(zs);
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SPDNORMX;
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break;
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
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if (zc == IEEE754_CLASS_INF)
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return ieee754sp_inf(zs);
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/* continue to real computations */
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}
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/* Finally get to do some computation */
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/*
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* Do the multiplication bit first
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*
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* rm = xm * ym, re = xe + ye basically
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*
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* At this point xm and ym should have been normalized.
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*/
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/* rm = xm * ym, re = xe+ye basically */
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assert(xm & SP_HIDDEN_BIT);
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assert(ym & SP_HIDDEN_BIT);
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re = xe + ye;
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rs = xs ^ ys;
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if (flags & MADDF_NEGATE_PRODUCT)
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rs ^= 1;
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/* Multiple 24 bit xm and ym to give 48 bit results */
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rm64 = (uint64_t)xm * ym;
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/* Shunt to top of word */
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rm64 = rm64 << 16;
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/* Put explicit bit at bit 62 if necessary */
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if ((int64_t) rm64 < 0) {
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rm64 = rm64 >> 1;
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re++;
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}
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assert(rm64 & (1 << 62));
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if (zc == IEEE754_CLASS_ZERO) {
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/*
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* Move explicit bit from bit 62 to bit 26 since the
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* ieee754sp_format code expects the mantissa to be
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* 27 bits wide (24 + 3 rounding bits).
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*/
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rm = XSPSRS64(rm64, (62 - 26));
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return ieee754sp_format(rs, re, rm);
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}
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/* Move explicit bit from bit 23 to bit 62 */
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zm64 = (uint64_t)zm << (62 - 23);
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assert(zm64 & (1 << 62));
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/* Make the exponents the same */
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if (ze > re) {
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/*
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* Have to shift r fraction right to align.
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*/
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s = ze - re;
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rm64 = XSPSRS64(rm64, s);
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re += s;
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} else if (re > ze) {
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/*
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* Have to shift z fraction right to align.
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*/
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s = re - ze;
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zm64 = XSPSRS64(zm64, s);
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ze += s;
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}
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assert(ze == re);
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assert(ze <= SP_EMAX);
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/* Do the addition */
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if (zs == rs) {
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/*
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* Generate 64 bit result by adding two 63 bit numbers
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* leaving result in zm64, zs and ze.
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*/
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zm64 = zm64 + rm64;
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if ((int64_t)zm64 < 0) { /* carry out */
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zm64 = XSPSRS1(zm64);
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ze++;
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}
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} else {
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if (zm64 >= rm64) {
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zm64 = zm64 - rm64;
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} else {
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zm64 = rm64 - zm64;
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zs = rs;
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}
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if (zm64 == 0)
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return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
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/*
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* Put explicit bit at bit 62 if necessary.
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*/
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while ((zm64 >> 62) == 0) {
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zm64 <<= 1;
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ze--;
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}
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}
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/*
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* Move explicit bit from bit 62 to bit 26 since the
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* ieee754sp_format code expects the mantissa to be
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* 27 bits wide (24 + 3 rounding bits).
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*/
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zm = XSPSRS64(zm64, (62 - 26));
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return ieee754sp_format(zs, ze, zm);
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}
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union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
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union ieee754sp y)
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{
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return _sp_maddf(z, x, y, 0);
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}
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union ieee754sp ieee754sp_msubf(union ieee754sp z, union ieee754sp x,
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union ieee754sp y)
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{
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return _sp_maddf(z, x, y, MADDF_NEGATE_PRODUCT);
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}
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