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//===-- popcountdi2.c - Implement __popcountdi2 ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements __popcountdi2 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//
#include "int_lib.h"
// Returns: count of 1 bits
si_int
__popcountdi2(di_int a)
{
du_int x2 = (du_int)a;
x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL);
// Every 2 bits holds the sum of every pair of bits (32)
x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL);
// Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16)
x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL;
// Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8)
su_int x = (su_int)(x2 + (x2 >> 32));
// The lower 32 bits hold four 16 bit sums (5 significant bits).
// Upper 32 bits are garbage
x = x + (x >> 16);
// The lower 16 bits hold two 32 bit sums (6 significant bits).
// Upper 16 bits are garbage
return (x + (x >> 8)) & 0x0000007F; // (7 significant bits)
}
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