1 //===-- popcountti2.c - Implement __popcountti2 2 //----------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements __popcountti2 for the compiler_rt library. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "int_lib.h" 15 16 #ifdef CRT_HAS_128BIT 17 18 // Returns: count of 1 bits 19 20 COMPILER_RT_ABI int __popcountti2(ti_int a) { 21 tu_int x3 = (tu_int)a; 22 x3 = x3 - ((x3 >> 1) & 23 (((tu_int)0x5555555555555555uLL << 64) | 0x5555555555555555uLL)); 24 // Every 2 bits holds the sum of every pair of bits (64) 25 x3 = ((x3 >> 2) & 26 (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)) + 27 (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)); 28 // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) 29 x3 = (x3 + (x3 >> 4)) & 30 (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL); 31 // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) 32 du_int x2 = (du_int)(x3 + (x3 >> 64)); 33 // Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) 34 su_int x = (su_int)(x2 + (x2 >> 32)); 35 // Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) 36 x = x + (x >> 16); 37 // Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) 38 // 39 // Upper 16 bits are garbage 40 return (x + (x >> 8)) & 0xFF; // (8 significant bits) 41 } 42 43 #endif // CRT_HAS_128BIT 44