2 * Copyright 2012 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 #include "folly/Bits.h"
19 #include "folly/CpuId.h"
21 // None of this is necessary if we're compiling for a target that supports
27 int popcount_inst(unsigned int x) {
28 asm ("popcntl %0, %0" : "=r" (x) : "0" (x));
32 int popcount_builtin(unsigned int x) {
33 return __builtin_popcount(x);
36 int popcountll_inst(unsigned long long x) {
37 asm ("popcntq %0, %0" : "=r" (x) : "0" (x));
41 int popcountll_builtin(unsigned long long x) {
42 return __builtin_popcountll(x);
45 typedef decltype(popcount_builtin) Type_popcount;
46 typedef decltype(popcountll_builtin) Type_popcountll;
50 // This function is called on startup to resolve folly::detail::popcount
51 extern "C" Type_popcount* folly_popcount_ifunc() {
52 return folly::CpuId().popcnt() ? popcount_inst : popcount_builtin;
55 // This function is called on startup to resolve folly::detail::popcountll
56 extern "C" Type_popcountll* folly_popcountll_ifunc() {
57 return folly::CpuId().popcnt() ? popcountll_inst : popcountll_builtin;
63 // Call folly_popcount_ifunc on startup to resolve to either popcount_inst
64 // or popcount_builtin
65 int popcount(unsigned int x)
66 __attribute__((ifunc("folly_popcount_ifunc")));
68 // Call folly_popcount_ifunc on startup to resolve to either popcountll_inst
69 // or popcountll_builtin
70 int popcountll(unsigned long long x)
71 __attribute__((ifunc("folly_popcountll_ifunc")));
76 #endif /* !__POPCNT__ */