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40 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93
41 * $NetBSD: fpu_compare.c,v 1.3 2001/08/26 05:46:31 eeh Exp $
44 #include <sys/cdefs.h>
45 __FBSDID("$FreeBSD$");
48 * CMP and CMPE instructions.
50 * These rely on the fact that our internal wide format is achieved by
51 * adding zero bits to the end of narrower mantissas.
54 #include <sys/types.h>
56 #include <machine/frame.h>
57 #include <machine/fp.h>
58 #include <machine/fsr.h>
60 #include "fpu_arith.h"
62 #include "fpu_extern.h"
64 static u_long fcc_nmask[] = {
71 /* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */
72 static int fcc_shift[] = {
80 * Perform a compare instruction (with or without unordered exception).
81 * This updates the fcc field in the fsr.
83 * If either operand is NaN, the result is unordered. For cmpe, this
84 * causes an NV exception. Everything else is ordered:
85 * |Inf| > |numbers| > |0|.
86 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
87 * so we get this directly. Note, however, that two zeros compare equal
88 * regardless of sign, while everything else depends on sign.
90 * Incidentally, two Infs of the same sign compare equal (per the 80387
91 * manual---it would be nice if the SPARC documentation were more
95 __fpu_compare(struct fpemu *fe, int cmpe, int fcc)
104 if (ISNAN(a) || ISNAN(b)) {
106 * In any case, we already got an exception for signalling
107 * NaNs; here we may replace that one with an identical
108 * exception, but so what?.
117 * Must handle both-zero early to avoid sign goofs. Otherwise,
118 * at most one is 0, and if the signs differ we are done.
120 if (ISZERO(a) && ISZERO(b)) {
124 if (a->fp_sign) { /* a < 0 (or -0) */
125 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */
129 } else { /* a > 0 (or +0) */
130 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */
137 * Now the signs are the same (but may both be negative). All
138 * we have left are these cases:
140 * |a| < |b| [classes or values differ]
141 * |a| > |b| [classes or values differ]
142 * |a| == |b| [classes and values identical]
144 * We define `diff' here to expand these as:
146 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT
147 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT
148 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT
149 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT
151 #define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT)
152 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude))
153 if (a->fp_class < b->fp_class) { /* |a| < |b| */
154 cc = diff(FSR_CC_LT);
157 if (a->fp_class > b->fp_class) { /* |a| > |b| */
158 cc = diff(FSR_CC_GT);
161 /* now none can be 0: only Inf and numbers remain */
162 if (ISINF(a)) { /* |Inf| = |Inf| */
167 * Only numbers remain. To compare two numbers in magnitude, we
168 * simply subtract them.
171 if (a->fp_class == FPC_ZERO)
174 cc = diff(FSR_CC_GT);
177 fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) |
178 ((u_long)cc << fcc_shift[fcc]);