1*156cd587Sjoerg /* ===-- popcountdi2.c - Implement __popcountdi2 ----------------------------=== 2*156cd587Sjoerg * 3*156cd587Sjoerg * The LLVM Compiler Infrastructure 4*156cd587Sjoerg * 5*156cd587Sjoerg * This file is dual licensed under the MIT and the University of Illinois Open 6*156cd587Sjoerg * Source Licenses. See LICENSE.TXT for details. 7*156cd587Sjoerg * 8*156cd587Sjoerg * ===----------------------------------------------------------------------=== 9*156cd587Sjoerg * 10*156cd587Sjoerg * This file implements __popcountdi2 for the compiler_rt library. 11*156cd587Sjoerg * 12*156cd587Sjoerg * ===----------------------------------------------------------------------=== 13*156cd587Sjoerg */ 14*156cd587Sjoerg 15*156cd587Sjoerg #include "int_lib.h" 16*156cd587Sjoerg 17*156cd587Sjoerg /* Returns: count of 1 bits */ 18*156cd587Sjoerg 19*156cd587Sjoerg COMPILER_RT_ABI si_int __popcountdi2(di_int a)20*156cd587Sjoerg__popcountdi2(di_int a) 21*156cd587Sjoerg { 22*156cd587Sjoerg du_int x2 = (du_int)a; 23*156cd587Sjoerg x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL); 24*156cd587Sjoerg /* Every 2 bits holds the sum of every pair of bits (32) */ 25*156cd587Sjoerg x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL); 26*156cd587Sjoerg /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) */ 27*156cd587Sjoerg x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL; 28*156cd587Sjoerg /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) */ 29*156cd587Sjoerg su_int x = (su_int)(x2 + (x2 >> 32)); 30*156cd587Sjoerg /* The lower 32 bits hold four 16 bit sums (5 significant bits). */ 31*156cd587Sjoerg /* Upper 32 bits are garbage */ 32*156cd587Sjoerg x = x + (x >> 16); 33*156cd587Sjoerg /* The lower 16 bits hold two 32 bit sums (6 significant bits). */ 34*156cd587Sjoerg /* Upper 16 bits are garbage */ 35*156cd587Sjoerg return (x + (x >> 8)) & 0x0000007F; /* (7 significant bits) */ 36*156cd587Sjoerg } 37