| //===-- popcountti2.c - Implement __popcountti2 |
| //----------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements __popcountti2 for the compiler_rt library. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "int_lib.h" |
| |
| #ifdef CRT_HAS_128BIT |
| |
| // Returns: count of 1 bits |
| |
| COMPILER_RT_ABI int __popcountti2(ti_int a) { |
| tu_int x3 = (tu_int)a; |
| x3 = x3 - ((x3 >> 1) & |
| (((tu_int)0x5555555555555555uLL << 64) | 0x5555555555555555uLL)); |
| // Every 2 bits holds the sum of every pair of bits (64) |
| x3 = ((x3 >> 2) & |
| (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)) + |
| (x3 & (((tu_int)0x3333333333333333uLL << 64) | 0x3333333333333333uLL)); |
| // Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (32) |
| x3 = (x3 + (x3 >> 4)) & |
| (((tu_int)0x0F0F0F0F0F0F0F0FuLL << 64) | 0x0F0F0F0F0F0F0F0FuLL); |
| // Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (16) |
| du_int x2 = (du_int)(x3 + (x3 >> 64)); |
| // Every 8 bits holds the sum of every 8-set of bits (5 significant bits) (8) |
| su_int x = (su_int)(x2 + (x2 >> 32)); |
| // Every 8 bits holds the sum of every 8-set of bits (6 significant bits) (4) |
| x = x + (x >> 16); |
| // Every 8 bits holds the sum of every 8-set of bits (7 significant bits) (2) |
| // |
| // Upper 16 bits are garbage |
| return (x + (x >> 8)) & 0xFF; // (8 significant bits) |
| } |
| |
| #endif // CRT_HAS_128BIT |
