2 * Copyright 2016 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.
19 #include <glog/logging.h>
20 #include <immintrin.h>
22 #include <folly/CpuId.h>
23 #include <folly/portability/Builtins.h>
25 namespace folly { namespace compression { namespace instructions {
27 // NOTE: It's recommended to compile EF coding with -msse4.2, starting
28 // with Nehalem, Intel CPUs support POPCNT instruction and gcc will emit
29 // it for __builtin_popcountll intrinsic.
30 // But we provide an alternative way for the client code: it can switch to
31 // the appropriate version of EliasFanoReader<> in realtime (client should
32 // implement this switching logic itself) by specifying instruction set to
36 static bool supported(const folly::CpuId& /* cpuId */ = {}) { return true; }
37 static inline uint64_t popcount(uint64_t value) {
38 return __builtin_popcountll(value);
40 static inline int ctz(uint64_t value) {
42 return __builtin_ctzll(value);
44 static inline int clz(uint64_t value) {
46 return __builtin_clzll(value);
48 static inline uint64_t blsr(uint64_t value) {
49 return value & (value - 1);
53 struct Nehalem : public Default {
54 static bool supported(const folly::CpuId& cpuId = {}) {
55 return cpuId.popcnt();
57 static inline uint64_t popcount(uint64_t value)
58 FOLLY_TARGET_ATTRIBUTE("popcnt") {
59 // POPCNT is supported starting with Intel Nehalem, AMD K10.
60 #if defined(__GNUC__) && !__GNUC_PREREQ(4, 9)
61 // GCC 4.8 doesn't support the intrinsics.
63 asm ("popcntq %1, %0" : "=r" (result) : "r" (value));
66 return _mm_popcnt_u64(value);
71 struct Haswell : public Nehalem {
72 static bool supported(const folly::CpuId& cpuId = {}) {
73 return Nehalem::supported(cpuId) && cpuId.bmi1();
75 static inline uint64_t blsr(uint64_t value) FOLLY_TARGET_ATTRIBUTE("bmi") {
76 // BMI1 is supported starting with Intel Haswell, AMD Piledriver.
77 // BLSR combines two instuctions into one and reduces register pressure.
78 #if defined(__GNUC__) && !__GNUC_PREREQ(4, 9)
79 // GCC 4.8 doesn't support the intrinsics.
81 asm ("blsrq %1, %0" : "=r" (result) : "r" (value));
84 return _blsr_u64(value);