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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 #ifdef CRT_HAS_128BIT
18 
19 /* Returns: count of 1 bits */
20 
21 COMPILER_RT_ABI 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 /* CRT_HAS_128BIT */
45