2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
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12 * modification, are permitted provided that the following conditions
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35 * @(#)fpu_emu.h 8.1 (Berkeley) 6/11/93
36 * $NetBSD: fpu_emu.h,v 1.4 2000/08/03 18:32:07 eeh Exp $
41 * Floating point emulator (tailored for SPARC, but structurally
42 * machine-independent).
44 * Floating point numbers are carried around internally in an `expanded'
45 * or `unpacked' form consisting of:
48 * - mantissa (`1.' + 112-bit fraction + guard + round)
50 * Any implied `1' bit is inserted, giving a 113-bit mantissa that is
51 * always nonzero. Additional low-order `guard' and `round' bits are
52 * scrunched in, making the entire mantissa 115 bits long. This is divided
53 * into four 32-bit words, with `spare' bits left over in the upper part
54 * of the top word (the high bits of fp_mant[0]). An internal `exploded'
55 * number is thus kept within the half-open interval [1.0,2.0) (but see
56 * the `number classes' below). This holds even for denormalized numbers:
57 * when we explode an external denorm, we normalize it, introducing low-order
58 * zero bits, so that the rest of the code always sees normalized values.
60 * Note that a number of our algorithms use the `spare' bits at the top.
61 * The most demanding algorithm---the one for sqrt---depends on two such
62 * bits, so that it can represent values up to (but not including) 8.0,
63 * and then it needs a carry on top of that, so that we need three `spares'.
65 * The sticky-word is 32 bits so that we can use `OR' operators to goosh
66 * whole words from the mantissa into it.
68 * All operations are done in this internal extended precision. According
69 * to Hennesey & Patterson, Appendix A, rounding can be repeated---that is,
70 * it is OK to do a+b in extended precision and then round the result to
71 * single precision---provided single, double, and extended precisions are
72 * `far enough apart' (they always are), but we will try to avoid any such
73 * extra work where possible.
76 #ifndef _SPARC64_FPU_FPU_EMU_H_
77 #define _SPARC64_FPU_FPU_EMU_H_
82 int fp_class; /* see below */
83 int fp_sign; /* 0 => positive, 1 => negative */
84 int fp_exp; /* exponent (unbiased) */
85 int fp_sticky; /* nonzero bits lost at right end */
86 u_int fp_mant[4]; /* 115-bit mantissa */
89 #define FP_NMANT 115 /* total bits in mantissa (incl g,r) */
90 #define FP_NG 2 /* number of low-order guard bits */
91 #define FP_LG ((FP_NMANT - 1) & 31) /* log2(1.0) for fp_mant[0] */
92 #define FP_LG2 ((FP_NMANT - 1) & 63) /* log2(1.0) for fp_mant[0] and fp_mant[1] */
93 #define FP_QUIETBIT (1 << (FP_LG - 1)) /* Quiet bit in NaNs (0.5) */
94 #define FP_1 (1 << FP_LG) /* 1.0 in fp_mant[0] */
95 #define FP_2 (1 << (FP_LG + 1)) /* 2.0 in fp_mant[0] */
98 * Number classes. Since zero, Inf, and NaN cannot be represented using
99 * the above layout, we distinguish these from other numbers via a class.
100 * In addition, to make computation easier and to follow Appendix N of
101 * the SPARC Version 8 standard, we give each kind of NaN a separate class.
103 #define FPC_SNAN -2 /* signalling NaN (sign irrelevant) */
104 #define FPC_QNAN -1 /* quiet NaN (sign irrelevant) */
105 #define FPC_ZERO 0 /* zero (sign matters) */
106 #define FPC_NUM 1 /* number (sign matters) */
107 #define FPC_INF 2 /* infinity (sign matters) */
109 #define ISNAN(fp) ((fp)->fp_class < 0)
110 #define ISZERO(fp) ((fp)->fp_class == 0)
111 #define ISINF(fp) ((fp)->fp_class == FPC_INF)
114 * ORDER(x,y) `sorts' a pair of `fpn *'s so that the right operand (y) points
115 * to the `more significant' operand for our purposes. Appendix N says that
116 * the result of a computation involving two numbers are:
118 * If both are SNaN: operand 2, converted to Quiet
119 * If only one is SNaN: the SNaN operand, converted to Quiet
120 * If both are QNaN: operand 2
121 * If only one is QNaN: the QNaN operand
123 * In addition, in operations with an Inf operand, the result is usually
124 * Inf. The class numbers are carefully arranged so that if
125 * (unsigned)class(op1) > (unsigned)class(op2)
126 * then op1 is the one we want; otherwise op2 is the one we want.
128 #define ORDER(x, y) { \
129 if ((u_int)(x)->fp_class > (u_int)(y)->fp_class) \
132 #define SWAP(x, y) { \
133 register struct fpn *swap; \
134 swap = (x), (x) = (y), (y) = swap; \
138 * Floating point operand types. FTYPE_LNG is syntethic (it does not occur in
141 #define FTYPE_INT INSFP_i
142 #define FTYPE_SNG INSFP_s
143 #define FTYPE_DBL INSFP_d
144 #define FTYPE_EXT INSFP_q
151 u_long fe_fsr; /* fsr copy (modified during op) */
152 int fe_cx; /* exceptions */
153 int pad; /* align access to following fields */
154 struct fpn fe_f1; /* operand 1 */
155 struct fpn fe_f2; /* operand 2, if required */
156 struct fpn fe_f3; /* available storage for result */
160 * Arithmetic functions.
161 * Each of these may modify its inputs (f1,f2) and/or the temporary.
162 * Each returns a pointer to the result and/or sets exceptions.
164 #define __fpu_sub(fe) (ISNAN(&(fe)->fe_f2) ? 0 : ((fe)->fe_f2.fp_sign ^= 1), \
170 extern int __fpe_debug;
171 void __fpu_dumpfpn(struct fpn *);
172 #define DPRINTF(x, y) if (__fpe_debug & (x)) printf y
173 #define DUMPFPN(x, f) if (__fpe_debug & (x)) __fpu_dumpfpn((f))
175 #define DPRINTF(x, y)
176 #define DUMPFPN(x, f)
179 #endif /* !_SPARC64_FPU_FPU_EXTERN_H_ */