1214152Sed/* ===-- popcountdi2.c - Implement __popcountdi2 ----------------------------===
2214152Sed *
3214152Sed *                     The LLVM Compiler Infrastructure
4214152Sed *
5222656Sed * This file is dual licensed under the MIT and the University of Illinois Open
6222656Sed * Source Licenses. See LICENSE.TXT for details.
7214152Sed *
8214152Sed * ===----------------------------------------------------------------------===
9214152Sed *
10214152Sed * This file implements __popcountdi2 for the compiler_rt library.
11214152Sed *
12214152Sed * ===----------------------------------------------------------------------===
13214152Sed */
14214152Sed
15214152Sed#include "int_lib.h"
16214152Sed
17214152Sed/* Returns: count of 1 bits */
18214152Sed
19222656SedCOMPILER_RT_ABI si_int
20214152Sed__popcountdi2(di_int a)
21214152Sed{
22214152Sed    du_int x2 = (du_int)a;
23214152Sed    x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL);
24214152Sed    /* Every 2 bits holds the sum of every pair of bits (32) */
25214152Sed    x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL);
26214152Sed    /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) */
27214152Sed    x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL;
28214152Sed    /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) */
29214152Sed    su_int x = (su_int)(x2 + (x2 >> 32));
30214152Sed    /* The lower 32 bits hold four 16 bit sums (5 significant bits). */
31214152Sed    /*   Upper 32 bits are garbage */
32214152Sed    x = x + (x >> 16);
33214152Sed    /* The lower 16 bits hold two 32 bit sums (6 significant bits). */
34214152Sed    /*   Upper 16 bits are garbage */
35214152Sed    return (x + (x >> 8)) & 0x0000007F;  /* (7 significant bits) */
36214152Sed}
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