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- /* $NetBSD: fpu_compare.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.
- */
- /*
- * FCMPU and FCMPO instructions.
- *
- * These rely on the fact that our internal wide format is achieved by
- * adding zero bits to the end of narrower mantissas.
- */
- #include <sys/types.h>
- #include <sys/systm.h>
- #include <machine/fpu.h>
- #include <powerpc/fpu/fpu_arith.h>
- #include <powerpc/fpu/fpu_emu.h>
- /*
- * Perform a compare instruction (with or without unordered exception).
- * This updates the fcc field in the fsr.
- *
- * If either operand is NaN, the result is unordered. For ordered, this
- * causes an NV exception. Everything else is ordered:
- * |Inf| > |numbers| > |0|.
- * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
- * so we get this directly. Note, however, that two zeros compare equal
- * regardless of sign, while everything else depends on sign.
- *
- * Incidentally, two Infs of the same sign compare equal (per the 80387
- * manual---it would be nice if the SPARC documentation were more
- * complete).
- */
- void
- fpu_compare(struct fpemu *fe, int ordered)
- {
- struct fpn *a, *b, *r;
- int cc;
- a = &fe->fe_f1;
- b = &fe->fe_f2;
- r = &fe->fe_f3;
- if (ISNAN(a) || ISNAN(b)) {
- /*
- * In any case, we already got an exception for signalling
- * NaNs; here we may replace that one with an identical
- * exception, but so what?.
- */
- cc = FPSCR_FU;
- if (ISSNAN(a) || ISSNAN(b))
- cc |= FPSCR_VXSNAN;
- if (ordered) {
- if (fe->fe_fpscr & FPSCR_VE || ISQNAN(a) || ISQNAN(b))
- cc |= FPSCR_VXVC;
- }
- goto done;
- }
- /*
- * Must handle both-zero early to avoid sign goofs. Otherwise,
- * at most one is 0, and if the signs differ we are done.
- */
- if (ISZERO(a) && ISZERO(b)) {
- cc = FPSCR_FE;
- goto done;
- }
- if (a->fp_sign) { /* a < 0 (or -0) */
- if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */
- cc = FPSCR_FL;
- goto done;
- }
- } else { /* a > 0 (or +0) */
- if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */
- cc = FPSCR_FG;
- goto done;
- }
- }
- /*
- * Now the signs are the same (but may both be negative). All
- * we have left are these cases:
- *
- * |a| < |b| [classes or values differ]
- * |a| > |b| [classes or values differ]
- * |a| == |b| [classes and values identical]
- *
- * We define `diff' here to expand these as:
- *
- * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT
- * |a| < |b|, a,b < 0: a > b => FSR_CC_GT
- * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT
- * |a| > |b|, a,b < 0: a < b => FSR_CC_LT
- */
- #define opposite_cc(cc) ((cc) == FPSCR_FL ? FPSCR_FG : FPSCR_FL)
- #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude))
- if (a->fp_class < b->fp_class) { /* |a| < |b| */
- cc = diff(FPSCR_FL);
- goto done;
- }
- if (a->fp_class > b->fp_class) { /* |a| > |b| */
- cc = diff(FPSCR_FG);
- goto done;
- }
- /* now none can be 0: only Inf and numbers remain */
- if (ISINF(a)) { /* |Inf| = |Inf| */
- cc = FPSCR_FE;
- goto done;
- }
- fpu_sub(fe);
- if (ISZERO(r))
- cc = FPSCR_FE;
- else if (r->fp_sign)
- cc = FPSCR_FL;
- else
- cc = FPSCR_FG;
- done:
- fe->fe_cx = cc;
- }
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