mirror of
https://github.com/capstone-engine/llvm-capstone.git
synced 2025-01-19 22:53:52 +00:00
improve performance of string::find
string::find used to call the generic algorithm ::find. The patch special case string::find such that it ultimately gets converted to calls to memchr and memcmp. The patch improves the performance of the string::find routine by about 20x. Without the patch, the performance on an x86_64-linux 3400 MHz machine is: Benchmark Time CPU Iterations ----------------------------------------------------------------- BM_StringFindNoMatch/10 4 ns 4 ns 166421326 BM_StringFindNoMatch/64 37 ns 37 ns 18754392 BM_StringFindNoMatch/512 268 ns 268 ns 2586060 BM_StringFindNoMatch/4k 2143 ns 2144 ns 328342 BM_StringFindNoMatch/32k 16910 ns 16917 ns 40623 BM_StringFindNoMatch/128k 67577 ns 67602 ns 10138 BM_StringFindAllMatch/1 3 ns 3 ns 265163471 BM_StringFindAllMatch/8 6 ns 6 ns 112582467 BM_StringFindAllMatch/64 36 ns 36 ns 19566457 BM_StringFindAllMatch/512 209 ns 209 ns 3318893 BM_StringFindAllMatch/4k 1618 ns 1618 ns 432963 BM_StringFindAllMatch/32k 12909 ns 12914 ns 54317 BM_StringFindAllMatch/128k 48342 ns 48361 ns 13922 BM_StringFindMatch1/1 33777 ns 33790 ns 20698 BM_StringFindMatch1/8 33940 ns 33953 ns 20619 BM_StringFindMatch1/64 34038 ns 34051 ns 20571 BM_StringFindMatch1/512 34217 ns 34230 ns 20480 BM_StringFindMatch1/4k 35510 ns 35524 ns 19752 BM_StringFindMatch1/32k 46438 ns 46456 ns 15030 BM_StringFindMatch2/1 33839 ns 33852 ns 20648 BM_StringFindMatch2/8 33950 ns 33963 ns 20594 BM_StringFindMatch2/64 33846 ns 33859 ns 20668 BM_StringFindMatch2/512 34023 ns 34036 ns 20279 BM_StringFindMatch2/4k 35422 ns 35436 ns 19716 BM_StringFindMatch2/32k 46570 ns 46588 ns 15027 With the patch applied Benchmark Time CPU Iterations ----------------------------------------------------------------- BM_StringFindNoMatch/10 5 ns 5 ns 133724346 BM_StringFindNoMatch/64 6 ns 6 ns 119312184 BM_StringFindNoMatch/512 13 ns 13 ns 51539628 BM_StringFindNoMatch/4k 77 ns 77 ns 8935934 BM_StringFindNoMatch/32k 551 ns 551 ns 1222808 BM_StringFindNoMatch/128k 2684 ns 2685 ns 259957 BM_StringFindAllMatch/1 7 ns 7 ns 98017959 BM_StringFindAllMatch/8 7 ns 7 ns 91466911 BM_StringFindAllMatch/64 8 ns 8 ns 85707392 BM_StringFindAllMatch/512 20 ns 20 ns 34490895 BM_StringFindAllMatch/4k 93 ns 93 ns 7360375 BM_StringFindAllMatch/32k 827 ns 828 ns 829944 BM_StringFindAllMatch/128k 3593 ns 3594 ns 195815 BM_StringFindMatch1/1 1332 ns 1332 ns 516354 BM_StringFindMatch1/8 1336 ns 1336 ns 495876 BM_StringFindMatch1/64 1338 ns 1339 ns 516656 BM_StringFindMatch1/512 1357 ns 1357 ns 510717 BM_StringFindMatch1/4k 1485 ns 1486 ns 461228 BM_StringFindMatch1/32k 2235 ns 2236 ns 318253 BM_StringFindMatch2/1 1335 ns 1335 ns 517105 BM_StringFindMatch2/8 1336 ns 1337 ns 518004 BM_StringFindMatch2/64 1344 ns 1345 ns 511751 BM_StringFindMatch2/512 1361 ns 1361 ns 508150 BM_StringFindMatch2/4k 1611 ns 1611 ns 463388 BM_StringFindMatch2/32k 2187 ns 2187 ns 317532 Patch written by Aditya Kumar and Sebastian Pop. Differential Revision: https://reviews.llvm.org/D27068 llvm-svn: 290761
This commit is contained in:
Sebastian Pop
parent
a570a2303c
commit
9070500633
49
libcxx/benchmarks/string.bench.cpp
Normal file
49
libcxx/benchmarks/string.bench.cpp
Normal file
@ -0,0 +1,49 @@
|
||||
#include <unordered_set>
|
||||
#include <vector>
|
||||
#include <cstdint>
|
||||
|
||||
#include "benchmark/benchmark_api.h"
|
||||
#include "GenerateInput.hpp"
|
||||
|
||||
constexpr std::size_t MAX_STRING_LEN = 8 << 14;
|
||||
|
||||
// Benchmark when there is no match.
|
||||
static void BM_StringFindNoMatch(benchmark::State &state) {
|
||||
std::string s1(state.range(0), '-');
|
||||
std::string s2(8, '*');
|
||||
while (state.KeepRunning())
|
||||
benchmark::DoNotOptimize(s1.find(s2));
|
||||
}
|
||||
BENCHMARK(BM_StringFindNoMatch)->Range(10, MAX_STRING_LEN);
|
||||
|
||||
// Benchmark when the string matches first time.
|
||||
static void BM_StringFindAllMatch(benchmark::State &state) {
|
||||
std::string s1(MAX_STRING_LEN, '-');
|
||||
std::string s2(state.range(0), '-');
|
||||
while (state.KeepRunning())
|
||||
benchmark::DoNotOptimize(s1.find(s2));
|
||||
}
|
||||
BENCHMARK(BM_StringFindAllMatch)->Range(1, MAX_STRING_LEN);
|
||||
|
||||
// Benchmark when the string matches somewhere in the end.
|
||||
static void BM_StringFindMatch1(benchmark::State &state) {
|
||||
std::string s1(MAX_STRING_LEN / 2, '*');
|
||||
s1 += std::string(state.range(0), '-');
|
||||
std::string s2(state.range(0), '-');
|
||||
while (state.KeepRunning())
|
||||
benchmark::DoNotOptimize(s1.find(s2));
|
||||
}
|
||||
BENCHMARK(BM_StringFindMatch1)->Range(1, MAX_STRING_LEN / 4);
|
||||
|
||||
// Benchmark when the string matches somewhere from middle to the end.
|
||||
static void BM_StringFindMatch2(benchmark::State &state) {
|
||||
std::string s1(MAX_STRING_LEN / 2, '*');
|
||||
s1 += std::string(state.range(0), '-');
|
||||
s1 += std::string(state.range(0), '*');
|
||||
std::string s2(state.range(0), '-');
|
||||
while (state.KeepRunning())
|
||||
benchmark::DoNotOptimize(s1.find(s2));
|
||||
}
|
||||
BENCHMARK(BM_StringFindMatch2)->Range(1, MAX_STRING_LEN / 4);
|
||||
|
||||
BENCHMARK_MAIN()
|
||||
@ -538,19 +538,59 @@ __str_find(const _CharT *__p, _SizeT __sz,
|
||||
return static_cast<_SizeT>(__r - __p);
|
||||
}
|
||||
|
||||
template <class _CharT, class _Traits>
|
||||
inline _LIBCPP_CONSTEXPR_AFTER_CXX11 const _CharT *
|
||||
__search_substring(const _CharT *__first1, const _CharT *__last1,
|
||||
const _CharT *__first2, const _CharT *__last2) {
|
||||
// Take advantage of knowing source and pattern lengths.
|
||||
// Stop short when source is smaller than pattern.
|
||||
const ptrdiff_t __len2 = __last2 - __first2;
|
||||
if (__len2 == 0)
|
||||
return __first1;
|
||||
|
||||
ptrdiff_t __len1 = __last1 - __first1;
|
||||
if (__len1 < __len2)
|
||||
return __last1;
|
||||
|
||||
// First element of __first2 is loop invariant.
|
||||
_CharT __f2 = *__first2;
|
||||
while (true) {
|
||||
__len1 = __last1 - __first1;
|
||||
// Check whether __first1 still has at least __len2 bytes.
|
||||
if (__len1 < __len2)
|
||||
return __last1;
|
||||
|
||||
// Find __f2 the first byte matching in __first1.
|
||||
__first1 = _Traits::find(__first1, __len1 - __len2 + 1, __f2);
|
||||
if (__first1 == 0)
|
||||
return __last1;
|
||||
|
||||
// It is faster to compare from the first byte of __first1 even if we
|
||||
// already know that it matches the first byte of __first2: this is because
|
||||
// __first2 is most likely aligned, as it is user's "pattern" string, and
|
||||
// __first1 + 1 is most likely not aligned, as the match is in the middle of
|
||||
// the string.
|
||||
if (_Traits::compare(__first1, __first2, __len2) == 0)
|
||||
return __first1;
|
||||
|
||||
++__first1;
|
||||
}
|
||||
}
|
||||
|
||||
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
|
||||
inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
|
||||
__str_find(const _CharT *__p, _SizeT __sz,
|
||||
const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
|
||||
{
|
||||
if (__pos > __sz || __sz - __pos < __n)
|
||||
if (__pos > __sz)
|
||||
return __npos;
|
||||
if (__n == 0)
|
||||
|
||||
if (__n == 0) // There is nothing to search, just return __pos.
|
||||
return __pos;
|
||||
const _CharT* __r =
|
||||
_VSTD::__search(__p + __pos, __p + __sz,
|
||||
__s, __s + __n, _Traits::eq,
|
||||
random_access_iterator_tag(), random_access_iterator_tag()).first;
|
||||
|
||||
const _CharT *__r = __search_substring<_CharT, _Traits>(
|
||||
__p + __pos, __p + __sz, __s, __s + __n);
|
||||
|
||||
if (__r == __p + __sz)
|
||||
return __npos;
|
||||
return static_cast<_SizeT>(__r - __p);
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user