51369649b0
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165 lines
5.1 KiB
C
165 lines
5.1 KiB
C
/* $NetBSD: fpu_compare.c,v 1.4 2005/12/11 12:18:42 christos Exp $ */
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/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This software was developed by the Computer Systems Engineering group
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* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
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* contributed to Berkeley.
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*
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* All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Lawrence Berkeley Laboratory.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93
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*/
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/*
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* FCMPU and FCMPO instructions.
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*
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* These rely on the fact that our internal wide format is achieved by
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* adding zero bits to the end of narrower mantissas.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/systm.h>
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#include <machine/fpu.h>
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#include <machine/reg.h>
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#include <powerpc/fpu/fpu_arith.h>
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#include <powerpc/fpu/fpu_emu.h>
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/*
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* Perform a compare instruction (with or without unordered exception).
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* This updates the fcc field in the fsr.
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*
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* If either operand is NaN, the result is unordered. For ordered, this
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* causes an NV exception. Everything else is ordered:
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* |Inf| > |numbers| > |0|.
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* We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
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* so we get this directly. Note, however, that two zeros compare equal
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* regardless of sign, while everything else depends on sign.
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*
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* Incidentally, two Infs of the same sign compare equal (per the 80387
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* manual---it would be nice if the SPARC documentation were more
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* complete).
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*/
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void
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fpu_compare(struct fpemu *fe, int ordered)
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{
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struct fpn *a, *b, *r;
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int cc;
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a = &fe->fe_f1;
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b = &fe->fe_f2;
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r = &fe->fe_f3;
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if (ISNAN(a) || ISNAN(b)) {
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/*
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* In any case, we already got an exception for signalling
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* NaNs; here we may replace that one with an identical
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* exception, but so what?.
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*/
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cc = FPSCR_FU;
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if (ISSNAN(a) || ISSNAN(b))
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cc |= FPSCR_VXSNAN;
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if (ordered) {
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if (fe->fe_fpscr & FPSCR_VE || ISQNAN(a) || ISQNAN(b))
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cc |= FPSCR_VXVC;
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}
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goto done;
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}
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/*
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* Must handle both-zero early to avoid sign goofs. Otherwise,
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* at most one is 0, and if the signs differ we are done.
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*/
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if (ISZERO(a) && ISZERO(b)) {
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cc = FPSCR_FE;
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goto done;
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}
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if (a->fp_sign) { /* a < 0 (or -0) */
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if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */
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cc = FPSCR_FL;
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goto done;
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}
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} else { /* a > 0 (or +0) */
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if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */
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cc = FPSCR_FG;
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goto done;
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}
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}
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/*
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* Now the signs are the same (but may both be negative). All
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* we have left are these cases:
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*
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* |a| < |b| [classes or values differ]
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* |a| > |b| [classes or values differ]
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* |a| == |b| [classes and values identical]
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*
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* We define `diff' here to expand these as:
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*
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* |a| < |b|, a,b >= 0: a < b => FSR_CC_LT
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* |a| < |b|, a,b < 0: a > b => FSR_CC_GT
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* |a| > |b|, a,b >= 0: a > b => FSR_CC_GT
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* |a| > |b|, a,b < 0: a < b => FSR_CC_LT
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*/
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#define opposite_cc(cc) ((cc) == FPSCR_FL ? FPSCR_FG : FPSCR_FL)
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#define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude))
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if (a->fp_class < b->fp_class) { /* |a| < |b| */
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cc = diff(FPSCR_FL);
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goto done;
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}
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if (a->fp_class > b->fp_class) { /* |a| > |b| */
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cc = diff(FPSCR_FG);
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goto done;
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}
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/* now none can be 0: only Inf and numbers remain */
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if (ISINF(a)) { /* |Inf| = |Inf| */
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cc = FPSCR_FE;
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goto done;
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}
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fpu_sub(fe);
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if (ISZERO(r))
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cc = FPSCR_FE;
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else if (r->fp_sign)
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cc = FPSCR_FL;
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else
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cc = FPSCR_FG;
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done:
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fe->fe_cx = cc;
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}
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