hiraditya updated this revision to Diff 80090.
hiraditya added a comment.
Addressed Tim's comments.
https://reviews.llvm.org/D27068
Files:
libcxx/benchmarks/string.bench.cpp
libcxx/include/__string
Index: libcxx/include/__string
===================================================================
--- libcxx/include/__string
+++ libcxx/include/__string
@@ -538,25 +538,60 @@
return static_cast<_SizeT>(__r - __p);
}
+template <class _CharT, class _Traits>
+_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.
+ 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;
+ if (__len1 < __len2)
+ return __last1;
+
+ __first1 = _Traits::find(__first1, __len1 - __len2 + 1, __f2);
+ if (__first1 == 0)
+ return __last1;
+
+ // Comparing __first2 as well because the first pointer will be aligned
+ // and we dont know if __first1+1 is going to be aligned.
+ 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);
}
-
// __str_rfind
template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
Index: libcxx/benchmarks/string.bench.cpp
===================================================================
--- /dev/null
+++ libcxx/benchmarks/string.bench.cpp
@@ -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()
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
