1*8a6a9560SDaniel Boulby //===-- popcountdi2.c - Implement __popcountdi2 ---------------------------===// 2*8a6a9560SDaniel Boulby // 3*8a6a9560SDaniel Boulby // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*8a6a9560SDaniel Boulby // See https://llvm.org/LICENSE.txt for license information. 5*8a6a9560SDaniel Boulby // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*8a6a9560SDaniel Boulby // 7*8a6a9560SDaniel Boulby //===----------------------------------------------------------------------===// 8*8a6a9560SDaniel Boulby // 9*8a6a9560SDaniel Boulby // This file implements __popcountdi2 for the compiler_rt library. 10*8a6a9560SDaniel Boulby // 11*8a6a9560SDaniel Boulby //===----------------------------------------------------------------------===// 12162fc183SLionel Debieve 13162fc183SLionel Debieve #include "int_lib.h" 14162fc183SLionel Debieve 15*8a6a9560SDaniel Boulby // Returns: count of 1 bits 16162fc183SLionel Debieve 17*8a6a9560SDaniel Boulby COMPILER_RT_ABI int __popcountdi2(di_int a) { 18162fc183SLionel Debieve du_int x2 = (du_int)a; 19162fc183SLionel Debieve x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL); 20*8a6a9560SDaniel Boulby // Every 2 bits holds the sum of every pair of bits (32) 21162fc183SLionel Debieve x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL); 22*8a6a9560SDaniel Boulby // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) 23162fc183SLionel Debieve x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL; 24*8a6a9560SDaniel Boulby // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) 25162fc183SLionel Debieve su_int x = (su_int)(x2 + (x2 >> 32)); 26*8a6a9560SDaniel Boulby // The lower 32 bits hold four 16 bit sums (5 significant bits). 27*8a6a9560SDaniel Boulby // Upper 32 bits are garbage 28162fc183SLionel Debieve x = x + (x >> 16); 29*8a6a9560SDaniel Boulby // The lower 16 bits hold two 32 bit sums (6 significant bits). 30*8a6a9560SDaniel Boulby // Upper 16 bits are garbage 31*8a6a9560SDaniel Boulby return (x + (x >> 8)) & 0x0000007F; // (7 significant bits) 32162fc183SLionel Debieve } 33