2 * Copyright 2014 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #ifndef FOLLY_DETAIL_BITSDETAIL_H_
18 #define FOLLY_DETAIL_BITSDETAIL_H_
23 // If we're targeting an architecture with popcnt support, use
24 // __builtin_popcount directly, as it's presumably inlined.
25 // If not, use runtime detection using __attribute__((__ifunc__))
28 inline int popcount(unsigned int x) {
31 inline int popcountll(unsigned long long x) {
34 #elif defined(__POPCNT__)
36 inline int popcount(unsigned int x) {
37 return __builtin_popcount(x);
39 inline int popcountll(unsigned long long x) {
40 return __builtin_popcountll(x);
43 #else /* !__POPCNT__ */
45 int popcount(unsigned int x);
46 int popcountll(unsigned long long x);
48 #endif /* !__POPCNT__ */
53 #endif /* FOLLY_DETAIL_BITSDETAIL_H_ */