1*0b57cec5SDimitry Andric //===-- popcountdi2.c - Implement __popcountdi2 ---------------------------===// 2*0b57cec5SDimitry Andric // 3*0b57cec5SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*0b57cec5SDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 5*0b57cec5SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*0b57cec5SDimitry Andric // 7*0b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 8*0b57cec5SDimitry Andric // 9*0b57cec5SDimitry Andric // This file implements __popcountdi2 for the compiler_rt library. 10*0b57cec5SDimitry Andric // 11*0b57cec5SDimitry Andric //===----------------------------------------------------------------------===// 12*0b57cec5SDimitry Andric 13*0b57cec5SDimitry Andric #include "int_lib.h" 14*0b57cec5SDimitry Andric 15*0b57cec5SDimitry Andric // Returns: count of 1 bits 16*0b57cec5SDimitry Andric 17*0b57cec5SDimitry Andric COMPILER_RT_ABI si_int __popcountdi2(di_int a) { 18*0b57cec5SDimitry Andric du_int x2 = (du_int)a; 19*0b57cec5SDimitry Andric x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL); 20*0b57cec5SDimitry Andric // Every 2 bits holds the sum of every pair of bits (32) 21*0b57cec5SDimitry Andric x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL); 22*0b57cec5SDimitry Andric // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16) 23*0b57cec5SDimitry Andric x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL; 24*0b57cec5SDimitry Andric // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8) 25*0b57cec5SDimitry Andric su_int x = (su_int)(x2 + (x2 >> 32)); 26*0b57cec5SDimitry Andric // The lower 32 bits hold four 16 bit sums (5 significant bits). 27*0b57cec5SDimitry Andric // Upper 32 bits are garbage 28*0b57cec5SDimitry Andric x = x + (x >> 16); 29*0b57cec5SDimitry Andric // The lower 16 bits hold two 32 bit sums (6 significant bits). 30*0b57cec5SDimitry Andric // Upper 16 bits are garbage 31*0b57cec5SDimitry Andric return (x + (x >> 8)) & 0x0000007F; // (7 significant bits) 32*0b57cec5SDimitry Andric } 33