138451Smsmith/* ===-- popcountdi2.c - Implement __popcountdi2 ----------------------------=== 238451Smsmith * 338451Smsmith * The LLVM Compiler Infrastructure 438451Smsmith * 538451Smsmith * This file is dual licensed under the MIT and the University of Illinois Open 638451Smsmith * Source Licenses. See LICENSE.TXT for details. 738451Smsmith * 838451Smsmith * ===----------------------------------------------------------------------=== 938451Smsmith * 1084221Sdillon * This file implements __popcountdi2 for the compiler_rt library. 1184221Sdillon * 1284221Sdillon * ===----------------------------------------------------------------------=== 1338451Smsmith */ 1438451Smsmith 1538451Smsmith#include "int_lib.h" 1638451Smsmith 1738451Smsmith/* Returns: count of 1 bits */ 1838451Smsmith 1938451SmsmithCOMPILER_RT_ABI si_int 2038451Smsmith__popcountdi2(di_int a) 2138451Smsmith{ 2238451Smsmith du_int x2 = (du_int)a; 2338451Smsmith x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL); 2438451Smsmith /* Every 2 bits holds the sum of every pair of bits (32) */ 2538451Smsmith x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL); 2638451Smsmith /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) */ 2738451Smsmith x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL; 2838451Smsmith /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) */ 2938451Smsmith su_int x = (su_int)(x2 + (x2 >> 32)); 3038451Smsmith /* The lower 32 bits hold four 16 bit sums (5 significant bits). */ 3138451Smsmith /* Upper 32 bits are garbage */ 3238451Smsmith x = x + (x >> 16); 3338451Smsmith /* The lower 16 bits hold two 32 bit sums (6 significant bits). */ 3438451Smsmith /* Upper 16 bits are garbage */ 35301056Sian return (x + (x >> 8)) & 0x0000007F; /* (7 significant bits) */ 3638451Smsmith} 3738451Smsmith