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38 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93
39 * $NetBSD: fpu_compare.c,v 1.3 2001/08/26 05:46:31 eeh Exp $
42 #include <sys/cdefs.h>
43 __FBSDID("$FreeBSD$");
46 * CMP and CMPE instructions.
48 * These rely on the fact that our internal wide format is achieved by
49 * adding zero bits to the end of narrower mantissas.
52 #include <sys/types.h>
54 #include <machine/frame.h>
55 #include <machine/fp.h>
56 #include <machine/fsr.h>
58 #include "fpu_arith.h"
60 #include "fpu_extern.h"
62 static u_long fcc_nmask[] = {
69 /* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */
70 static int fcc_shift[] = {
78 * Perform a compare instruction (with or without unordered exception).
79 * This updates the fcc field in the fsr.
81 * If either operand is NaN, the result is unordered. For cmpe, this
82 * causes an NV exception. Everything else is ordered:
83 * |Inf| > |numbers| > |0|.
84 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
85 * so we get this directly. Note, however, that two zeros compare equal
86 * regardless of sign, while everything else depends on sign.
88 * Incidentally, two Infs of the same sign compare equal (per the 80387
89 * manual---it would be nice if the SPARC documentation were more
93 __fpu_compare(struct fpemu *fe, int cmpe, int fcc)
102 if (ISNAN(a) || ISNAN(b)) {
104 * In any case, we already got an exception for signalling
105 * NaNs; here we may replace that one with an identical
106 * exception, but so what?.
115 * Must handle both-zero early to avoid sign goofs. Otherwise,
116 * at most one is 0, and if the signs differ we are done.
118 if (ISZERO(a) && ISZERO(b)) {
122 if (a->fp_sign) { /* a < 0 (or -0) */
123 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */
127 } else { /* a > 0 (or +0) */
128 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */
135 * Now the signs are the same (but may both be negative). All
136 * we have left are these cases:
138 * |a| < |b| [classes or values differ]
139 * |a| > |b| [classes or values differ]
140 * |a| == |b| [classes and values identical]
142 * We define `diff' here to expand these as:
144 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT
145 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT
146 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT
147 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT
149 #define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT)
150 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude))
151 if (a->fp_class < b->fp_class) { /* |a| < |b| */
152 cc = diff(FSR_CC_LT);
155 if (a->fp_class > b->fp_class) { /* |a| > |b| */
156 cc = diff(FSR_CC_GT);
159 /* now none can be 0: only Inf and numbers remain */
160 if (ISINF(a)) { /* |Inf| = |Inf| */
165 * Only numbers remain. To compare two numbers in magnitude, we
166 * simply subtract them.
169 if (a->fp_class == FPC_ZERO)
172 cc = diff(FSR_CC_GT);
175 fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) |
176 ((u_long)cc << fcc_shift[fcc]);