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 |
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 | |