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De-pessimize QBenchmarkValgrindUtils::extractResult()

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As if QIODevice::readLine() and QIODevice::Text open-mode aren't slow
enough, the old code took the line QByteArray, converted it to a
QString so it could apply a trivial regex to it: '^summary: (\d+)'.

We can, of course, use QByteArray::startsWith("summary: ") followed by
std::from_chars(), these days, to get the same effect, without having
to JIT-compile an RX and convert every line into UTF-16 first.

Change-Id: I20d80ffb469329d3c3efd08c71fcf5abf9f486d3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
This commit is contained in:
Marc Mutz 2022-05-02 23:18:52 +02:00
parent 8ece12e466
commit 664b84c137
1 changed files with 12 additions and 8 deletions
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20
src/testlib/qbenchmarkvalgrind.cpp
View File

@ -48,6 +48,7 @@
#include <QtCore/qset.h>
#include <QtTest/private/callgrind_p.h>
#include <charconv>
#include <optional>
QT_BEGIN_NAMESPACE
@ -92,15 +93,18 @@ qint64 QBenchmarkValgrindUtils::extractResult(const QString &fileName)
Q_UNUSED(openOk);
std::optional<qint64> val = std::nullopt;
QRegularExpression rxValue(u"^summary: (\\d+)"_s);
while (!file.atEnd()) {
const QString line(QLatin1StringView(file.readLine()));
QRegularExpressionMatch match = rxValue.match(line);
if (match.hasMatch()) {
bool ok;
val = match.captured(1).toLongLong(&ok);
Q_ASSERT(ok);
break;
const QByteArray line = file.readLine();
constexpr QByteArrayView tag = "summary: ";
if (line.startsWith(tag)) {
const auto maybeNumber = line.data() + tag.size();
const auto end = line.data() + line.size();
qint64 v;
const auto r = std::from_chars(maybeNumber, end, v);
if (r.ec == std::errc{}) {
val = v;
break;
}
}
}
if (Q_UNLIKELY(!val))