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- /* $NetBSD: fpu_subr.c,v 1.4 2005/12/11 12:18:42 christos Exp $ */
- /*
- * SPDX-License-Identifier: BSD-3-Clause
- *
- * Copyright (c) 1992, 1993
- * The Regents of the University of California. All rights reserved.
- *
- * This software was developed by the Computer Systems Engineering group
- * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
- * contributed to Berkeley.
- *
- * All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- * This product includes software developed by the University of
- * California, Lawrence Berkeley Laboratory.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. Neither the name of the University nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
- /*
- * FPU subroutines.
- */
- #include <sys/types.h>
- #include <sys/systm.h>
- #include <machine/fpu.h>
- #include <powerpc/fpu/fpu_arith.h>
- #include <powerpc/fpu/fpu_emu.h>
- /*
- * Shift the given number right rsh bits. Any bits that `fall off' will get
- * shoved into the sticky field; we return the resulting sticky. Note that
- * shifting NaNs is legal (this will never shift all bits out); a NaN's
- * sticky field is ignored anyway.
- */
- int
- fpu_shr(struct fpn *fp, int rsh)
- {
- u_int m0, m1, m2, m3, s;
- int lsh;
- #ifdef DIAGNOSTIC
- if (rsh <= 0 || (fp->fp_class != FPC_NUM && !ISNAN(fp)))
- panic("fpu_rightshift 1");
- #endif
- m0 = fp->fp_mant[0];
- m1 = fp->fp_mant[1];
- m2 = fp->fp_mant[2];
- m3 = fp->fp_mant[3];
- /* If shifting all the bits out, take a shortcut. */
- if (rsh >= FP_NMANT) {
- #ifdef DIAGNOSTIC
- if ((m0 | m1 | m2 | m3) == 0)
- panic("fpu_rightshift 2");
- #endif
- fp->fp_mant[0] = 0;
- fp->fp_mant[1] = 0;
- fp->fp_mant[2] = 0;
- fp->fp_mant[3] = 0;
- #ifdef notdef
- if ((m0 | m1 | m2 | m3) == 0)
- fp->fp_class = FPC_ZERO;
- else
- #endif
- fp->fp_sticky = 1;
- return (1);
- }
- /* Squish out full words. */
- s = fp->fp_sticky;
- if (rsh >= 32 * 3) {
- s |= m3 | m2 | m1;
- m3 = m0, m2 = 0, m1 = 0, m0 = 0;
- } else if (rsh >= 32 * 2) {
- s |= m3 | m2;
- m3 = m1, m2 = m0, m1 = 0, m0 = 0;
- } else if (rsh >= 32) {
- s |= m3;
- m3 = m2, m2 = m1, m1 = m0, m0 = 0;
- }
- /* Handle any remaining partial word. */
- if ((rsh &= 31) != 0) {
- lsh = 32 - rsh;
- s |= m3 << lsh;
- m3 = (m3 >> rsh) | (m2 << lsh);
- m2 = (m2 >> rsh) | (m1 << lsh);
- m1 = (m1 >> rsh) | (m0 << lsh);
- m0 >>= rsh;
- }
- fp->fp_mant[0] = m0;
- fp->fp_mant[1] = m1;
- fp->fp_mant[2] = m2;
- fp->fp_mant[3] = m3;
- fp->fp_sticky = s;
- return (s);
- }
- /*
- * Force a number to be normal, i.e., make its fraction have all zero
- * bits before FP_1, then FP_1, then all 1 bits. This is used for denorms
- * and (sometimes) for intermediate results.
- *
- * Internally, this may use a `supernormal' -- a number whose fp_mant
- * is greater than or equal to 2.0 -- so as a side effect you can hand it
- * a supernormal and it will fix it (provided fp->fp_mant[3] == 0).
- */
- void
- fpu_norm(struct fpn *fp)
- {
- u_int m0, m1, m2, m3, top, sup, nrm;
- int lsh, rsh, exp;
- exp = fp->fp_exp;
- m0 = fp->fp_mant[0];
- m1 = fp->fp_mant[1];
- m2 = fp->fp_mant[2];
- m3 = fp->fp_mant[3];
- /* Handle severe subnormals with 32-bit moves. */
- if (m0 == 0) {
- if (m1)
- m0 = m1, m1 = m2, m2 = m3, m3 = 0, exp -= 32;
- else if (m2)
- m0 = m2, m1 = m3, m2 = 0, m3 = 0, exp -= 2 * 32;
- else if (m3)
- m0 = m3, m1 = 0, m2 = 0, m3 = 0, exp -= 3 * 32;
- else {
- fp->fp_class = FPC_ZERO;
- return;
- }
- }
- /* Now fix any supernormal or remaining subnormal. */
- nrm = FP_1;
- sup = nrm << 1;
- if (m0 >= sup) {
- /*
- * We have a supernormal number. We need to shift it right.
- * We may assume m3==0.
- */
- for (rsh = 1, top = m0 >> 1; top >= sup; rsh++) /* XXX slow */
- top >>= 1;
- exp += rsh;
- lsh = 32 - rsh;
- m3 = m2 << lsh;
- m2 = (m2 >> rsh) | (m1 << lsh);
- m1 = (m1 >> rsh) | (m0 << lsh);
- m0 = top;
- } else if (m0 < nrm) {
- /*
- * We have a regular denorm (a subnormal number), and need
- * to shift it left.
- */
- for (lsh = 1, top = m0 << 1; top < nrm; lsh++) /* XXX slow */
- top <<= 1;
- exp -= lsh;
- rsh = 32 - lsh;
- m0 = top | (m1 >> rsh);
- m1 = (m1 << lsh) | (m2 >> rsh);
- m2 = (m2 << lsh) | (m3 >> rsh);
- m3 <<= lsh;
- }
- fp->fp_exp = exp;
- fp->fp_mant[0] = m0;
- fp->fp_mant[1] = m1;
- fp->fp_mant[2] = m2;
- fp->fp_mant[3] = m3;
- }
- /*
- * Concoct a `fresh' Quiet NaN per Appendix N.
- * As a side effect, we set NV (invalid) for the current exceptions.
- */
- struct fpn *
- fpu_newnan(struct fpemu *fe)
- {
- struct fpn *fp;
- fe->fe_cx |= FPSCR_VXSNAN;
- fp = &fe->fe_f3;
- fp->fp_class = FPC_QNAN;
- fp->fp_sign = 0;
- fp->fp_mant[0] = FP_1 - 1;
- fp->fp_mant[1] = fp->fp_mant[2] = fp->fp_mant[3] = ~0;
- DUMPFPN(FPE_REG, fp);
- return (fp);
- }
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