1 /* $OpenBSD: sfrem.c,v 1.5 2002/05/07 22:19:30 mickey Exp $ */
2 /*
3 (c) Copyright 1986 HEWLETT-PACKARD COMPANY
4 To anyone who acknowledges that this file is provided "AS IS"
5 without any express or implied warranty:
6 permission to use, copy, modify, and distribute this file
7 for any purpose is hereby granted without fee, provided that
8 the above copyright notice and this notice appears in all
9 copies, and that the name of Hewlett-Packard Company not be
10 used in advertising or publicity pertaining to distribution
11 of the software without specific, written prior permission.
12 Hewlett-Packard Company makes no representations about the
13 suitability of this software for any purpose.
14 */
15 /* @(#)sfrem.c: Revision: 1.7.88.1 Date: 93/12/07 15:07:10 */
16
17 #include "float.h"
18 #include "sgl_float.h"
19
20 /*
21 * Single Precision Floating-point Remainder
22 */
23 int
sgl_frem(srcptr1,srcptr2,dstptr,status)24 sgl_frem(srcptr1,srcptr2,dstptr,status)
25 sgl_floating_point *srcptr1, *srcptr2, *dstptr;
26 unsigned int *status;
27 {
28 register unsigned int opnd1, opnd2, result;
29 register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
30 register int roundup = FALSE;
31
32 opnd1 = *srcptr1;
33 opnd2 = *srcptr2;
34 /*
35 * check first operand for NaN's or infinity
36 */
37 if ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
38 if (Sgl_iszero_mantissa(opnd1)) {
39 if (Sgl_isnotnan(opnd2)) {
40 /* invalid since first operand is infinity */
41 if (Is_invalidtrap_enabled())
42 return(INVALIDEXCEPTION);
43 Set_invalidflag();
44 Sgl_makequietnan(result);
45 *dstptr = result;
46 return(NOEXCEPTION);
47 }
48 }
49 else {
50 /*
51 * is NaN; signaling or quiet?
52 */
53 if (Sgl_isone_signaling(opnd1)) {
54 /* trap if INVALIDTRAP enabled */
55 if (Is_invalidtrap_enabled())
56 return(INVALIDEXCEPTION);
57 /* make NaN quiet */
58 Set_invalidflag();
59 Sgl_set_quiet(opnd1);
60 }
61 /*
62 * is second operand a signaling NaN?
63 */
64 else if (Sgl_is_signalingnan(opnd2)) {
65 /* trap if INVALIDTRAP enabled */
66 if (Is_invalidtrap_enabled())
67 return(INVALIDEXCEPTION);
68 /* make NaN quiet */
69 Set_invalidflag();
70 Sgl_set_quiet(opnd2);
71 *dstptr = opnd2;
72 return(NOEXCEPTION);
73 }
74 /*
75 * return quiet NaN
76 */
77 *dstptr = opnd1;
78 return(NOEXCEPTION);
79 }
80 }
81 /*
82 * check second operand for NaN's or infinity
83 */
84 if ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
85 if (Sgl_iszero_mantissa(opnd2)) {
86 /*
87 * return first operand
88 */
89 *dstptr = opnd1;
90 return(NOEXCEPTION);
91 }
92 /*
93 * is NaN; signaling or quiet?
94 */
95 if (Sgl_isone_signaling(opnd2)) {
96 /* trap if INVALIDTRAP enabled */
97 if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
98 /* make NaN quiet */
99 Set_invalidflag();
100 Sgl_set_quiet(opnd2);
101 }
102 /*
103 * return quiet NaN
104 */
105 *dstptr = opnd2;
106 return(NOEXCEPTION);
107 }
108 /*
109 * check second operand for zero
110 */
111 if (Sgl_iszero_exponentmantissa(opnd2)) {
112 /* invalid since second operand is zero */
113 if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
114 Set_invalidflag();
115 Sgl_makequietnan(result);
116 *dstptr = result;
117 return(NOEXCEPTION);
118 }
119
120 /*
121 * get sign of result
122 */
123 result = opnd1;
124
125 /*
126 * check for denormalized operands
127 */
128 if (opnd1_exponent == 0) {
129 /* check for zero */
130 if (Sgl_iszero_mantissa(opnd1)) {
131 *dstptr = opnd1;
132 return(NOEXCEPTION);
133 }
134 /* normalize, then continue */
135 opnd1_exponent = 1;
136 Sgl_normalize(opnd1,opnd1_exponent);
137 }
138 else {
139 Sgl_clear_signexponent_set_hidden(opnd1);
140 }
141 if (opnd2_exponent == 0) {
142 /* normalize, then continue */
143 opnd2_exponent = 1;
144 Sgl_normalize(opnd2,opnd2_exponent);
145 }
146 else {
147 Sgl_clear_signexponent_set_hidden(opnd2);
148 }
149
150 /* find result exponent and divide step loop count */
151 dest_exponent = opnd2_exponent - 1;
152 stepcount = opnd1_exponent - opnd2_exponent;
153
154 /*
155 * check for opnd1/opnd2 < 1
156 */
157 if (stepcount < 0) {
158 /*
159 * check for opnd1/opnd2 > 1/2
160 *
161 * In this case n will round to 1, so
162 * r = opnd1 - opnd2
163 */
164 if (stepcount == -1 && Sgl_isgreaterthan(opnd1,opnd2)) {
165 Sgl_all(result) = ~Sgl_all(result); /* set sign */
166 /* align opnd2 with opnd1 */
167 Sgl_leftshiftby1(opnd2);
168 Sgl_subtract(opnd2,opnd1,opnd2);
169 /* now normalize */
170 while (Sgl_iszero_hidden(opnd2)) {
171 Sgl_leftshiftby1(opnd2);
172 dest_exponent--;
173 }
174 Sgl_set_exponentmantissa(result,opnd2);
175 goto testforunderflow;
176 }
177 /*
178 * opnd1/opnd2 <= 1/2
179 *
180 * In this case n will round to zero, so
181 * r = opnd1
182 */
183 Sgl_set_exponentmantissa(result,opnd1);
184 dest_exponent = opnd1_exponent;
185 goto testforunderflow;
186 }
187
188 /*
189 * Generate result
190 *
191 * Do iterative subtract until remainder is less than operand 2.
192 */
193 while (stepcount-- > 0 && Sgl_all(opnd1)) {
194 if (Sgl_isnotlessthan(opnd1,opnd2))
195 Sgl_subtract(opnd1,opnd2,opnd1);
196 Sgl_leftshiftby1(opnd1);
197 }
198 /*
199 * Do last subtract, then determine which way to round if remainder
200 * is exactly 1/2 of opnd2
201 */
202 if (Sgl_isnotlessthan(opnd1,opnd2)) {
203 Sgl_subtract(opnd1,opnd2,opnd1);
204 roundup = TRUE;
205 }
206 if (stepcount > 0 || Sgl_iszero(opnd1)) {
207 /* division is exact, remainder is zero */
208 Sgl_setzero_exponentmantissa(result);
209 *dstptr = result;
210 return(NOEXCEPTION);
211 }
212
213 /*
214 * Check for cases where opnd1/opnd2 < n
215 *
216 * In this case the result's sign will be opposite that of
217 * opnd1. The mantissa also needs some correction.
218 */
219 Sgl_leftshiftby1(opnd1);
220 if (Sgl_isgreaterthan(opnd1,opnd2)) {
221 Sgl_invert_sign(result);
222 Sgl_subtract((opnd2<<1),opnd1,opnd1);
223 }
224 /* check for remainder being exactly 1/2 of opnd2 */
225 else if (Sgl_isequal(opnd1,opnd2) && roundup) {
226 Sgl_invert_sign(result);
227 }
228
229 /* normalize result's mantissa */
230 while (Sgl_iszero_hidden(opnd1)) {
231 dest_exponent--;
232 Sgl_leftshiftby1(opnd1);
233 }
234 Sgl_set_exponentmantissa(result,opnd1);
235
236 /*
237 * Test for underflow
238 */
239 testforunderflow:
240 if (dest_exponent <= 0) {
241 /* trap if UNDERFLOWTRAP enabled */
242 if (Is_underflowtrap_enabled()) {
243 /*
244 * Adjust bias of result
245 */
246 Sgl_setwrapped_exponent(result,dest_exponent,unfl);
247 *dstptr = result;
248 /* frem is always exact */
249 return(UNDERFLOWEXCEPTION);
250 }
251 /*
252 * denormalize result or set to signed zero
253 */
254 if (dest_exponent >= (1 - SGL_P)) {
255 Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
256 } else {
257 Sgl_setzero_exponentmantissa(result);
258 }
259 }
260 else Sgl_set_exponent(result,dest_exponent);
261 *dstptr = result;
262 return(NOEXCEPTION);
263 }
264