1 /* $NetBSD: fpu_compare.c,v 1.4 2005/12/11 12:18:42 christos Exp $ */
4 * Copyright (c) 1992, 1993
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8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
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40 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93
44 * FCMPU and FCMPO instructions.
46 * These rely on the fact that our internal wide format is achieved by
47 * adding zero bits to the end of narrower mantissas.
50 #include <sys/cdefs.h>
51 __FBSDID("$FreeBSD$");
53 #include <sys/types.h>
54 #include <sys/systm.h>
56 #include <machine/fpu.h>
57 #include <machine/reg.h>
59 #include <powerpc/fpu/fpu_arith.h>
60 #include <powerpc/fpu/fpu_emu.h>
63 * Perform a compare instruction (with or without unordered exception).
64 * This updates the fcc field in the fsr.
66 * If either operand is NaN, the result is unordered. For ordered, this
67 * causes an NV exception. Everything else is ordered:
68 * |Inf| > |numbers| > |0|.
69 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
70 * so we get this directly. Note, however, that two zeros compare equal
71 * regardless of sign, while everything else depends on sign.
73 * Incidentally, two Infs of the same sign compare equal (per the 80387
74 * manual---it would be nice if the SPARC documentation were more
78 fpu_compare(struct fpemu *fe, int ordered)
80 struct fpn *a, *b, *r;
87 if (ISNAN(a) || ISNAN(b)) {
89 * In any case, we already got an exception for signalling
90 * NaNs; here we may replace that one with an identical
91 * exception, but so what?.
94 if (ISSNAN(a) || ISSNAN(b))
97 if (fe->fe_fpscr & FPSCR_VE || ISQNAN(a) || ISQNAN(b))
104 * Must handle both-zero early to avoid sign goofs. Otherwise,
105 * at most one is 0, and if the signs differ we are done.
107 if (ISZERO(a) && ISZERO(b)) {
111 if (a->fp_sign) { /* a < 0 (or -0) */
112 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */
116 } else { /* a > 0 (or +0) */
117 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */
124 * Now the signs are the same (but may both be negative). All
125 * we have left are these cases:
127 * |a| < |b| [classes or values differ]
128 * |a| > |b| [classes or values differ]
129 * |a| == |b| [classes and values identical]
131 * We define `diff' here to expand these as:
133 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT
134 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT
135 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT
136 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT
138 #define opposite_cc(cc) ((cc) == FPSCR_FL ? FPSCR_FG : FPSCR_FL)
139 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude))
140 if (a->fp_class < b->fp_class) { /* |a| < |b| */
144 if (a->fp_class > b->fp_class) { /* |a| > |b| */
148 /* now none can be 0: only Inf and numbers remain */
149 if (ISINF(a)) { /* |Inf| = |Inf| */