Author: ericwf
Date: Sun Oct 30 18:53:50 2016
New Revision: 285530
URL: http://llvm.org/viewvc/llvm-project?rev=285530&view=rev
Log:
Improve performance of constructing filesystem::path from strings.
This patch fixes a performance bug when constructing or appending to a path
from a string or c-string. Previously we called 'push_back' to append every
single character. This caused multiple re-allocation and copies when at most
one reallocation is necessary. The new behavior is to simply call
`string::append` so it can correctly handle reallocation.
For large strings this change is a ~4x improvement. This also makes our path
faster to construct than libstdc++'s.
Modified:
libcxx/trunk/benchmarks/filesystem.bench.cpp
libcxx/trunk/include/experimental/filesystem
libcxx/trunk/src/experimental/filesystem/path.cpp
Modified: libcxx/trunk/benchmarks/filesystem.bench.cpp
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/benchmarks/filesystem.bench.cpp?rev=285530&r1=285529&r2=285530&view=diff
==============================================================================
--- libcxx/trunk/benchmarks/filesystem.bench.cpp (original)
+++ libcxx/trunk/benchmarks/filesystem.bench.cpp Sun Oct 30 18:53:50 2016
@@ -21,11 +21,27 @@ void BM_PathConstructString(benchmark::S
benchmark::DoNotOptimize(P.native().data());
}
}
-BENCHMARK_CAPTURE(BM_PathConstructString, iterate_elements,
+BENCHMARK_CAPTURE(BM_PathConstructString, large_string,
getRandomStringInputs)->Arg(TestNumInputs);
template <class GenInputs>
+void BM_PathConstructCStr(benchmark::State &st, GenInputs gen) {
+ using namespace fs;
+ const auto in = gen(st.range(0));
+ path PP;
+ for (auto& Part : in)
+ PP /= Part;
+ benchmark::DoNotOptimize(PP.native().data());
+ while (st.KeepRunning()) {
+ const path P(PP.native().c_str());
+ benchmark::DoNotOptimize(P.native().data());
+ }
+}
+BENCHMARK_CAPTURE(BM_PathConstructCStr, large_string,
+ getRandomStringInputs)->Arg(TestNumInputs);
+
+template <class GenInputs>
void BM_PathIterateMultipleTimes(benchmark::State &st, GenInputs gen) {
using namespace fs;
const auto in = gen(st.range(0));
@@ -85,6 +101,4 @@ void BM_PathIterateOnceBackwards(benchma
BENCHMARK_CAPTURE(BM_PathIterateOnceBackwards, iterate_elements,
getRandomStringInputs)->Arg(TestNumInputs);
-
-
BENCHMARK_MAIN()
Modified: libcxx/trunk/include/experimental/filesystem
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/experimental/filesystem?rev=285530&r1=285529&r2=285530&view=diff
==============================================================================
--- libcxx/trunk/include/experimental/filesystem (original)
+++ libcxx/trunk/include/experimental/filesystem Sun Oct 30 18:53:50 2016
@@ -623,10 +623,10 @@ struct _PathCVT {
template <>
struct _PathCVT<char> {
+
template <class _Iter>
static void __append_range(string& __dest, _Iter __b, _Iter __e) {
- for (; __b != __e; ++__b)
- __dest.push_back(*__b);
+ __dest.append(__b, __e);
}
template <class _Iter>
@@ -640,7 +640,8 @@ struct _PathCVT<char> {
static void __append_source(string& __dest, _Source const& __s)
{
using _Traits = __is_pathable<_Source>;
- __append_range(__dest, _Traits::__range_begin(__s),
_Traits::__range_end(__s));
+ __append_range(__dest, _Traits::__range_begin(__s),
+ _Traits::__range_end(__s));
}
};
Modified: libcxx/trunk/src/experimental/filesystem/path.cpp
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/experimental/filesystem/path.cpp?rev=285530&r1=285529&r2=285530&view=diff
==============================================================================
--- libcxx/trunk/src/experimental/filesystem/path.cpp (original)
+++ libcxx/trunk/src/experimental/filesystem/path.cpp Sun Oct 30 18:53:50 2016
@@ -42,8 +42,7 @@ private:
public:
PathParser(string_view_t P, string_view_t E, unsigned char S)
: Path(P), RawEntry(E), State(static_cast<ParserState>(S)) {
- assert(S != 0);
- assert(S != PS_BeforeBegin);
+ // S cannot be '0' or PS_BeforeBegin.
}
static PathParser CreateBegin(string_view_t P) noexcept {
@@ -94,7 +93,6 @@ public:
case PS_InFilenames: {
PosPtr SepEnd = consumeSeparator(Start, End);
- assert(SepEnd);
if (SepEnd != End) {
PosPtr TkEnd = consumeName(SepEnd, End);
if (TkEnd)
@@ -131,7 +129,6 @@ public:
SepEnd + 1, RStart + 1);
} else {
PosPtr TkStart = consumeName(RStart, REnd);
- assert(TkStart);
if (TkStart == REnd + 2 && consumeSeparator(TkStart, REnd) == REnd)
return makeState(PS_InRootName, Path.data(), RStart + 1);
else
@@ -192,14 +189,10 @@ public:
private:
void makeState(ParserState NewState, PosPtr Start, PosPtr End) noexcept {
- assert(NewState != PS_BeforeBegin && NewState != PS_AtEnd);
State = NewState;
- assert(Start < End);
- assert(Start >= &Path.front() && End <= &Path.back() + 1);
RawEntry = string_view_t(Start, End - Start);
}
void makeState(ParserState NewState) noexcept {
- assert(NewState == PS_BeforeBegin || NewState == PS_AtEnd);
State = NewState;
RawEntry = {};
}
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
