1*162fc183SLionel Debieve /* ===-- popcountdi2.c - Implement __popcountdi2 ----------------------------=== 2*162fc183SLionel Debieve * 3*162fc183SLionel Debieve * The LLVM Compiler Infrastructure 4*162fc183SLionel Debieve * 5*162fc183SLionel Debieve * This file is dual licensed under the MIT and the University of Illinois Open 6*162fc183SLionel Debieve * Source Licenses. See LICENSE.TXT for details. 7*162fc183SLionel Debieve * 8*162fc183SLionel Debieve * ===----------------------------------------------------------------------=== 9*162fc183SLionel Debieve * 10*162fc183SLionel Debieve * This file implements __popcountdi2 for the compiler_rt library. 11*162fc183SLionel Debieve * 12*162fc183SLionel Debieve * ===----------------------------------------------------------------------=== 13*162fc183SLionel Debieve */ 14*162fc183SLionel Debieve 15*162fc183SLionel Debieve #include "int_lib.h" 16*162fc183SLionel Debieve 17*162fc183SLionel Debieve /* Returns: count of 1 bits */ 18*162fc183SLionel Debieve 19*162fc183SLionel Debieve COMPILER_RT_ABI si_int 20*162fc183SLionel Debieve __popcountdi2(di_int a) 21*162fc183SLionel Debieve { 22*162fc183SLionel Debieve du_int x2 = (du_int)a; 23*162fc183SLionel Debieve x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL); 24*162fc183SLionel Debieve /* Every 2 bits holds the sum of every pair of bits (32) */ 25*162fc183SLionel Debieve x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL); 26*162fc183SLionel Debieve /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) */ 27*162fc183SLionel Debieve x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL; 28*162fc183SLionel Debieve /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) */ 29*162fc183SLionel Debieve su_int x = (su_int)(x2 + (x2 >> 32)); 30*162fc183SLionel Debieve /* The lower 32 bits hold four 16 bit sums (5 significant bits). */ 31*162fc183SLionel Debieve /* Upper 32 bits are garbage */ 32*162fc183SLionel Debieve x = x + (x >> 16); 33*162fc183SLionel Debieve /* The lower 16 bits hold two 32 bit sums (6 significant bits). */ 34*162fc183SLionel Debieve /* Upper 16 bits are garbage */ 35*162fc183SLionel Debieve return (x + (x >> 8)) & 0x0000007F; /* (7 significant bits) */ 36*162fc183SLionel Debieve } 37