1 /* ===-- popcountti2.c - Implement __popcountti2 ----------------------------=== 2 * 3 * The LLVM Compiler Infrastructure 4 * 5 * This file is dual licensed under the MIT and the University of Illinois Open 6 * Source Licenses. See LICENSE.TXT for details. 7 * 8 * ===----------------------------------------------------------------------=== 9 * 10 * This file implements __popcountti2 for the compiler_rt library. 11 * 12 * ===----------------------------------------------------------------------=== 13 */ 14 15 #include "int_lib.h" 16 17 #if __x86_64 18 19 /* Returns: count of 1 bits */ 20 21 si_int 22 __popcountti2(ti_int a) 23 { 24 tu_int x3 = (tu_int)a; 25 x3 = x3 - ((x3 >> 1) & (((tu_int)0x5555555555555555uLL << 64) | 26 0x5555555555555555uLL)); 27 /* Every 2 bits holds the sum of every pair of bits (64) */ 28 x3 = ((x3 >> 2) & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)) 29 + (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)); 30 /* Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) */ 31 x3 = (x3 + (x3 >> 4)) 32 & (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL); 33 /* Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) */ 34 du_int x2 = (du_int)(x3 + (x3 >> 64)); 35 /* Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) */ 36 su_int x = (su_int)(x2 + (x2 >> 32)); 37 /* Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) */ 38 x = x + (x >> 16); 39 /* Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) */ 40 /* Upper 16 bits are garbage */ 41 return (x + (x >> 8)) & 0xFF; /* (8 significant bits) */ 42 } 43 44 #endif 45
