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/* ===-- popcountti2.c - Implement __popcountti2 ----------------------------===
*
* The LLVM Compiler Infrastructure
*
* This file is distributed under the University of Illinois Open Source
* License. See LICENSE.TXT for details.
*
* ===----------------------------------------------------------------------===
*
* This file implements __popcountti2 for the compiler_rt library.
*
* ===----------------------------------------------------------------------===
*/
#if __x86_64
#include "int_lib.h"
/* Returns: count of 1 bits */
si_int
__popcountti2(ti_int a)
{
tu_int x3 = (tu_int)a;
x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) |
0x5555555555555555uLL));
/* Every 2 bits holds the sum of every pair of bits (64) */
x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL))
+ (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL));
/* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) */
x3 = (x3 + (x3 >> 4))
& (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL);
/* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) */
du_int x2 = (du_int)(x3 + (x3 >> 64));
/* Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) */
su_int x = (su_int)(x2 + (x2 >> 32));
/* Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) */
x = x + (x >> 16);
/* Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) */
/* Upper 16 bits are garbage */
return (x + (x >> 8)) & 0xFF; /* (8 significant bits) */
}
#endif
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