/* ===-- popcountdi2.c - Implement __popcountdi2 ----------------------------=== * * The LLVM Compiler Infrastructure * * This file is dual licensed under the MIT and the University of Illinois Open * Source Licenses. See LICENSE.TXT for details. * * ===----------------------------------------------------------------------=== * * This file implements __popcountdi2 for the compiler_rt library. * * ===----------------------------------------------------------------------=== */ #include "int_lib.h" /* Returns: count of 1 bits */ COMPILER_RT_ABI 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) */ }