xref: /illumos-gate/usr/src/lib/libm/common/m9x/fminf.c (revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
24  */
25 /*
26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
27  * Use is subject to license terms.
28  */
29 
30 #if defined(ELFOBJ)
31 #pragma weak fminf = __fminf
32 #endif
33 
34 #include "libm.h"	/* for islessequal macro */
35 
36 float
37 __fminf(float x, float y) {
38 	/*
39 	 * On SPARC v8plus/v9, this could be implemented as follows
40 	 * (assuming %f0 = x, %f1 = y, return value left in %f0):
41 	 *
42 	 * fcmps	%fcc0,%f1,%f1
43 	 * fmovsu	%fcc0,%f0,%f1
44 	 * fcmps	%fcc0,%f0,%f1
45 	 * fmovsug	%fcc0,%f1,%f0
46 	 * st		%f0,[x]
47 	 * st		%f1,[y]
48 	 * ld		[x],%l0
49 	 * ld		[y],%l1
50 	 * or		%l0,%l1,%l2
51 	 * sethi	%hi(0x80000000),%l3
52 	 * and		%l3,%l2,%l2
53 	 * or		%l0,%l2,%l0
54 	 * st		%l0,[x]
55 	 * ld		[x],%f0
56 	 *
57 	 * If VIS instructions are available, use this code instead:
58 	 *
59 	 * fcmps	%fcc0,%f1,%f1
60 	 * fmovsu	%fcc0,%f0,%f1
61 	 * fcmps	%fcc0,%f0,%f1
62 	 * fmovsug	%fcc0,%f1,%f0
63 	 * fors		%f0,%f1,%f2
64 	 * fzeros	%f3
65 	 * fnegs	%f3,%f3
66 	 * fands	%f3,%f2,%f2
67 	 * fors		%f0,%f2,%f0
68 	 *
69 	 * If VIS 3.0 instructions are available, use this:
70 	 *
71 	 * flcmps	%fcc0,%f0,%f1
72 	 * fmovsge	%fcc0,%f1,%f0	! move if %fcc0 is 0 or 2
73 	 */
74 
75 	union {
76 		unsigned i;
77 		float f;
78 	} xx, yy;
79 	unsigned s;
80 
81 	/* if y is nan, replace it by x */
82 	if (y != y)
83 		y = x;
84 
85 	/* if x is nan, replace it by y */
86 	if (x != x)
87 		x = y;
88 
89 	/* At this point, x and y are either both numeric, or both NaN */
90 	if (!isnan(x) && !islessequal(x, y))
91 		x = y;
92 
93 	/*
94 	 * set the sign of the result if either x or y has its sign set
95 	 */
96 	xx.f = x;
97 	yy.f = y;
98 	s = (xx.i | yy.i) & 0x80000000;
99 	xx.i |= s;
100 
101 	return (xx.f);
102 }
103