1 /* ===-- popcountti2.c - Implement __popcountti2 ----------------------------===
2 *
3 * The LLVM Compiler Infrastructure
4 *
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. See LICENSE.TXT for details.
7 *
8 * ===----------------------------------------------------------------------===
9 *
10 * This file implements __popcountti2 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14
15 #include "int_lib.h"
16
17 #if __x86_64
18
19 /* Returns: count of 1 bits */
20
21 si_int
__popcountti2(ti_int a)22 __popcountti2(ti_int a)
23 {
24 tu_int x3 = (tu_int)a;
25 x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) |
26 0x5555555555555555uLL));
27 /* Every 2 bits holds the sum of every pair of bits (64) */
28 x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL))
29 + (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL));
30 /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) */
31 x3 = (x3 + (x3 >> 4))
32 & (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL);
33 /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) */
34 du_int x2 = (du_int)(x3 + (x3 >> 64));
35 /* Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) */
36 su_int x = (su_int)(x2 + (x2 >> 32));
37 /* Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) */
38 x = x + (x >> 16);
39 /* Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) */
40 /* Upper 16 bits are garbage */
41 return (x + (x >> 8)) & 0xFF; /* (8 significant bits) */
42 }
43
44 #endif
45