diff options
| -rw-r--r-- | src/corelib/tools/qstring.cpp | 78 | ||||
| -rw-r--r-- | tests/benchmarks/qstring/main.cpp | 123 | ||||
| -rw-r--r-- | tests/benchmarks/qstring/qstring.pro | 4 |
3 files changed, 199 insertions, 6 deletions
diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp index c3649e3..29509c5 100644 --- a/src/corelib/tools/qstring.cpp +++ b/src/corelib/tools/qstring.cpp @@ -195,6 +195,68 @@ static int ucstrnicmp(const ushort *a, const ushort *b, int l) return ucstricmp(a, a + l, b, b + l); } +static bool qMemEquals(const quint16 *a, const quint16 *b, int length) +{ + // Benchmarking indicates that doing memcmp is much slower than + // executing the comparison ourselves. + // To make it even faster, we do a 32-bit comparison, comparing + // twice the amount of data as a normal word-by-word comparison. + // + // Benchmarking results on a 2.33 GHz Core2 Duo, with a 64-QChar + // block of data, with 4194304 iterations (per iteration): + // operation usec cpu ticks + // memcmp 330 710 + // 16-bit 79 167-171 + // 32-bit aligned 49 105-109 + // + // Testing also indicates that unaligned 32-bit loads are as + // performant as 32-bit aligned. + if (a == b || !length) + return true; + + register union { + const quint16 *w; + const quint32 *d; + quintptr value; + } sa, sb; + sa.w = a; + sb.w = b; + + // check alignment + if ((sa.value & 2) == (sb.value & 2)) { + // both addresses have the same alignment + if (sa.value & 2) { + // both addresses are not aligned to 4-bytes boundaries + // compare the first character + if (*sa.w != *sb.w) + return false; + --length; + ++sa.w; + ++sb.w; + + // now both addresses are 4-bytes aligned + } + + // both addresses are 4-bytes aligned + // do a fast 32-bit comparison + register const quint32 *e = sa.d + (length >> 1); + for ( ; sa.d != e; ++sa.d, ++sb.d) { + if (*sa.d != *sb.d) + return false; + } + + // do we have a tail? + return (length & 1) ? *sa.w == *sb.w : true; + } else { + // one of the addresses isn't 4-byte aligned but the other is + register const quint16 *e = sa.w + length; + for ( ; sa.w != e; ++sa.w, ++sb.w) { + if (*sa.w != *sb.w) + return false; + } + } + return true; +} /*! \internal @@ -1908,8 +1970,10 @@ QString &QString::replace(QChar c, const QLatin1String &after, Qt::CaseSensitivi */ bool QString::operator==(const QString &other) const { - return (size() == other.size()) && - (memcmp((char*)unicode(),(char*)other.unicode(), size()*sizeof(QChar))==0); + if (d->size != other.d->size) + return false; + + return qMemEquals(d->data, other.d->data, d->size); } /*! @@ -3136,7 +3200,7 @@ bool QString::startsWith(const QString& s, Qt::CaseSensitivity cs) const if (s.d->size > d->size) return false; if (cs == Qt::CaseSensitive) { - return memcmp((char*)d->data, (char*)s.d->data, s.d->size*sizeof(QChar)) == 0; + return qMemEquals(d->data, s.d->data, s.d->size); } else { uint last = 0; uint olast = 0; @@ -3207,7 +3271,7 @@ bool QString::endsWith(const QString& s, Qt::CaseSensitivity cs) const if (pos < 0) return false; if (cs == Qt::CaseSensitive) { - return memcmp((char*)&d->data[pos], (char*)s.d->data, s.d->size*sizeof(QChar)) == 0; + return qMemEquals(d->data + pos, s.d->data, s.d->size); } else { uint last = 0; uint olast = 0; @@ -7692,7 +7756,8 @@ QString QStringRef::toString() const { */ bool operator==(const QStringRef &s1,const QStringRef &s2) { return (s1.size() == s2.size() && - (memcmp((char*)s1.unicode(), (char*)s2.unicode(), s1.size()*sizeof(QChar))==0)); } + qMemEquals((const ushort *)s1.unicode(), (const ushort *)s2.unicode(), s1.size())); +} /*! \relates QStringRef @@ -7701,7 +7766,8 @@ bool operator==(const QStringRef &s1,const QStringRef &s2) */ bool operator==(const QString &s1,const QStringRef &s2) { return (s1.size() == s2.size() && - (memcmp((char*)s1.unicode(), (char*)s2.unicode(), s1.size()*sizeof(QChar))==0)); } + qMemEquals((const ushort *)s1.unicode(), (const ushort *)s2.unicode(), s1.size())); +} /*! \relates QStringRef diff --git a/tests/benchmarks/qstring/main.cpp b/tests/benchmarks/qstring/main.cpp new file mode 100644 index 0000000..cbbf0a1 --- /dev/null +++ b/tests/benchmarks/qstring/main.cpp @@ -0,0 +1,123 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Qt Software Information (qt-info@nokia.com) +** +** This file is part of the test suite of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at qt-sales@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ +#include <QStringList> +#include <qtest.h> + +class tst_QString: public QObject +{ + Q_OBJECT +private slots: + void equals() const; + void equals_data() const; +}; + +void tst_QString::equals() const +{ + QFETCH(QString, a); + QFETCH(QString, b); + + QBENCHMARK { + a == b; + } +} + +void tst_QString::equals_data() const +{ + static const struct { + ushort data[80]; + int dummy; // just to ensure 4-byte alignment + } data = { + { + 64, 64, 64, 64, 64, 64, 64, 64, + 64, 64, 64, 64, 64, 64, 64, 64, // 16 + 64, 64, 64, 64, 64, 64, 64, 64, + 64, 64, 64, 64, 64, 64, 64, 64, // 32 + 64, 64, 64, 64, 64, 64, 64, 64, + 64, 64, 64, 64, 64, 64, 64, 64, // 48 + 64, 64, 64, 64, 64, 64, 64, 64, + 64, 64, 64, 64, 64, 64, 64, 64, // 64 + 64, 64, 64, 64, 96, 96, 96, 96, + 64, 64, 96, 96, 96, 96, 96, 96 // 80 + }, 0 + }; + const QChar *ptr = reinterpret_cast<const QChar *>(data.data); + + QTest::addColumn<QString>("a"); + QTest::addColumn<QString>("b"); + QString base = QString::fromRawData(ptr, 64); + + QTest::newRow("different-length") << base << QString::fromRawData(ptr, 4); + QTest::newRow("same-string") << base << base; + QTest::newRow("same-data") << base << QString::fromRawData(ptr, 64); + + // try to avoid crossing a cache line (that is, at ptr[64]) + QTest::newRow("aligned-aligned-4n") + << QString::fromRawData(ptr, 60) << QString::fromRawData(ptr + 2, 60); + QTest::newRow("aligned-unaligned-4n") + << QString::fromRawData(ptr, 60) << QString::fromRawData(ptr + 1, 60); + QTest::newRow("unaligned-unaligned-4n") + << QString::fromRawData(ptr + 1, 60) << QString::fromRawData(ptr + 3, 60); + + QTest::newRow("aligned-aligned-4n+1") + << QString::fromRawData(ptr, 61) << QString::fromRawData(ptr + 2, 61); + QTest::newRow("aligned-unaligned-4n+1") + << QString::fromRawData(ptr, 61) << QString::fromRawData(ptr + 1, 61); + QTest::newRow("unaligned-unaligned-4n+1") + << QString::fromRawData(ptr + 1, 61) << QString::fromRawData(ptr + 3, 61); + + QTest::newRow("aligned-aligned-4n-1") + << QString::fromRawData(ptr, 59) << QString::fromRawData(ptr + 2, 59); + QTest::newRow("aligned-unaligned-4n-1") + << QString::fromRawData(ptr, 59) << QString::fromRawData(ptr + 1, 59); + QTest::newRow("unaligned-unaligned-4n-1") + << QString::fromRawData(ptr + 1, 59) << QString::fromRawData(ptr + 3, 59); + + QTest::newRow("aligned-aligned-2n") + << QString::fromRawData(ptr, 58) << QString::fromRawData(ptr + 2, 58); + QTest::newRow("aligned-unaligned-2n") + << QString::fromRawData(ptr, 58) << QString::fromRawData(ptr + 1, 58); + QTest::newRow("unaligned-unaligned-2n") + << QString::fromRawData(ptr + 1, 58) << QString::fromRawData(ptr + 3, 58); +} + +QTEST_MAIN(tst_QString) + +#include "main.moc" diff --git a/tests/benchmarks/qstring/qstring.pro b/tests/benchmarks/qstring/qstring.pro new file mode 100644 index 0000000..74423e7 --- /dev/null +++ b/tests/benchmarks/qstring/qstring.pro @@ -0,0 +1,4 @@ +load(qttest_p4) +TARGET = tst_qstring +QT -= gui +SOURCES += main.cpp |