/* $NetBSD: fpu_subr.c,v 1.6 2005/12/11 12:19:05 christos Exp $ */ /* * 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_subr.c 8.1 (Berkeley) 6/11/93 */ /* * FPU subroutines. */ #include __KERNEL_RCSID(0, "$NetBSD: fpu_subr.c,v 1.6 2005/12/11 12:19:05 christos Exp $"); #include #ifdef DIAGNOSTIC #include #endif #include #include #include #include #include /* * 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(register struct fpn *fp, register int rsh) { register u_int m0, m1, m2, m3, s; register 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(register struct fpn *fp) { register u_int m0, m1, m2, m3, top, sup, nrm; register 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(register struct fpemu *fe) { register struct fpn *fp; fe->fe_cx = FSR_NV; 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; return (fp); }