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1//===-- popcountdi2.c - Implement __popcountdi2 ---------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements __popcountdi2 for the compiler_rt library.10//11//===----------------------------------------------------------------------===//12 13#include "int_lib.h"14 15// Returns: count of 1 bits16 17COMPILER_RT_ABI int __popcountdi2(di_int a) {18 du_int x2 = (du_int)a;19 x2 = x2 - ((x2 >> 1) & 0x5555555555555555uLL);20 // Every 2 bits holds the sum of every pair of bits (32)21 x2 = ((x2 >> 2) & 0x3333333333333333uLL) + (x2 & 0x3333333333333333uLL);22 // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16)23 x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0FuLL;24 // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8)25 su_int x = (su_int)(x2 + (x2 >> 32));26 // The lower 32 bits hold four 16 bit sums (5 significant bits).27 // Upper 32 bits are garbage28 x = x + (x >> 16);29 // The lower 16 bits hold two 32 bit sums (6 significant bits).30 // Upper 16 bits are garbage31 return (x + (x >> 8)) & 0x0000007F; // (7 significant bits)32}33