1 /*
2 * University of Illinois/NCSA Open Source License
3 *
4 * Copyright (c) 2003-2012 University of Illinois at Urbana-Champaign.
5 * All rights reserved.
6 *
7 * Developed by:
8 *
9 * LLVM Team
10 *
11 * University of Illinois at Urbana-Champaign
12 *
13 * http://llvm.org
14 *
15 * Permission is hereby granted, free of charge, to any person obtaining a copy
16 * of this software and associated documentation files (the "Software"), to deal
17 * with the Software without restriction, including without limitation the
18 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
19 * sell copies of the Software, and to permit persons to whom the Software is
20 * furnished to do so, subject to the following conditions:
21 *
22 * * Redistributions of source code must retain the above copyright notice,
23 * this list of conditions and the following disclaimers.
24 *
25 * * Redistributions in binary form must reproduce the above copyright
26 * notice, this list of conditions and the following disclaimers in the
27 * documentation and/or other materials provided with the distribution.
28 *
29 * * Neither the names of the LLVM Team, University of Illinois at
30 * Urbana-Champaign, nor the names of its contributors may be used to
31 * endorse or promote products derived from this Software without specific
32 * prior written permission.
33 *
34 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
35 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
36 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
37 * CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
38 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
39 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH
40 * THE SOFTWARE.
41 */
42
43 /*
44 * C compiler runtime logic for popcount() related builtins taken from LLVM. See
45 * also the Hacker's Delight 2nd Edition.
46 */
47
48 int
__popcountdi2(unsigned long long val)49 __popcountdi2(unsigned long long val)
50 {
51 unsigned long long x2 = (unsigned long long)val;
52 x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL);
53 /* Every 2 bits holds the sum of every pair of bits (32) */
54 x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL);
55 /*
56 * Every 4 bits holds the sum of every 4-set of bits (3 significant
57 * bits) (16)
58 */
59 x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL;
60 /*
61 * Every 8 bits holds the sum of every 8-set of bits (4 significant
62 * bits) (8).
63 */
64 unsigned x = (unsigned)(x2 + (x2 >> 32));
65 /*
66 * The lower 32 bits hold four 16 bit sums (5 significant bits). The
67 * upper 32 bits are garbage.
68 */
69 x = x + (x >> 16);
70 /*
71 * The lower 16 bits hold two 32 bit sums (6 significant bits). The
72 * upper 16 bits are garbage. Extract the 7 significant bits.
73 */
74 return ((x + (x >> 8)) & 0x0000007F);
75 }
76
77 int
__popcountsi2(unsigned val)78 __popcountsi2(unsigned val)
79 {
80 unsigned x = (unsigned)val;
81 x = x - ((x >> 1) & 0x55555555);
82 /* Every 2 bits holds the sum of every pair of bits */
83 x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
84 /*
85 * Every 4 bits holds the sum of every 4-set of bits (3 significant
86 * bits).
87 */
88 x = (x + (x >> 4)) & 0x0F0F0F0F;
89 /*
90 * Every 8 bits holds the sum of every 8-set of bits (4 significant
91 * bits).
92 */
93 x = (x + (x >> 16));
94 /*
95 * The lower 16 bits hold two 8 bit sums (5 significant bits). The
96 * upper 16 bits are garbage. Extract the 6 significant bits.
97 */
98 return ((x + (x >> 8)) & 0x0000003F); /* (6 significant bits) */
99 }
100