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} 37