V4: fix range splitting when split is between intervals.

Also added some "white-box" unit tests and sprinkled in a bit of
documentation. The case that went wrong is covered by the test
rangeSplitting_1: before the fix, the new interval would have
two ranges: [66-64],[70-71]. The first range is invalid and should not
be there at all.

Change-Id: If0742f4e6a96d98ea5d696f95126886ba66f92bb
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

src/qml/compiler/qv4jsir_p.h

@@ -248,7 +248,7 @@ struct MemberExpressionResolver
     unsigned int isQObjectResolver; // neede for IR dump helpers
 };
 
-struct Expr {
+struct Q_AUTOTEST_EXPORT Expr {
     Type type;
 
     Expr(): type(UnknownType) {}
@@ -380,7 +380,7 @@ struct Name: Expr {
     virtual void dump(QTextStream &out) const;
 };
 
-struct Temp: Expr {
+struct Q_AUTOTEST_EXPORT Temp: Expr {
     enum Kind {
         Formal = 0,
         ScopedFormal,

src/qml/compiler/qv4regalloc.cpp

@@ -913,8 +913,9 @@ private:
                 }
             }
             if (!moveFrom) {
+#if defined(QT_NO_DEBUG)
                 Q_UNUSED(lifeTimeHole);
-#if !defined(QT_NO_DEBUG)
+#else
                 Q_ASSERT(!_info->isPhiTarget(it->temp()) || it->isSplitFromInterval() || lifeTimeHole);
                 if (_info->def(it->temp()) != successorStart && !it->isSplitFromInterval()) {
                     const int successorEnd = successor->statements.last()->id;
@@ -1492,6 +1493,7 @@ int RegisterAllocator::nextUse(const Temp &t, int startPosition) const
 
 static inline void insertSorted(QVector<LifeTimeInterval> &intervals, const LifeTimeInterval &newInterval)
 {
+    newInterval.validate();
     for (int i = 0, ei = intervals.size(); i != ei; ++i) {
         if (LifeTimeInterval::lessThan(newInterval, intervals.at(i))) {
             intervals.insert(i, newInterval);

src/qml/compiler/qv4ssa.cpp

@@ -3634,12 +3634,20 @@ LifeTimeInterval LifeTimeInterval::split(int atPosition, int newStart)
     LifeTimeInterval newInterval = *this;
     newInterval.setSplitFromInterval(true);
 
+    // search where to split the interval
     for (int i = 0, ei = _ranges.size(); i < ei; ++i) {
-        if (_ranges[i].covers(atPosition)) {
-            while (_ranges.size() > i + 1)
-                _ranges.removeLast();
-            while (newInterval._ranges.size() > ei - i)
-                newInterval._ranges.removeFirst();
+        if (_ranges[i].start <= atPosition) {
+            if (_ranges[i].end >= atPosition) {
+                // split happens in the middle of a range. Keep this range in both the old and the
+                // new interval, and correct the end/start later
+                _ranges.resize(i + 1);
+                newInterval._ranges.remove(0, i);
+                break;
+            }
+        } else {
+            // split happens between two ranges.
+            _ranges.resize(i);
+            newInterval._ranges.remove(0, i);
             break;
         }
     }
@@ -3648,14 +3656,37 @@ LifeTimeInterval LifeTimeInterval::split(int atPosition, int newStart)
         newInterval._ranges.removeFirst();
 
     if (newStart == Invalid) {
-        newInterval._ranges.clear();
-        newInterval._end = Invalid;
+        // the temp stays inactive for the rest of its lifetime
+        newInterval = LifeTimeInterval();
     } else {
+        // find the first range where the temp will get active again:
+        while (!newInterval._ranges.isEmpty()) {
+            const Range &range = newInterval._ranges.first();
+            if (range.start > newStart) {
+                // The split position is before the start of the range. Either we managed to skip
+                // over the correct range, or we got an invalid split request. Either way, this
+                // Should Never Happen <TM>.
+                Q_ASSERT(range.start > newStart);
+                return LifeTimeInterval();
+            } else if (range.start <= newStart && range.end >= newStart) {
+                // yay, we found the range that should be the new first range in the new interval!
+                break;
+            } else {
+                // the temp stays inactive for this interval, so remove it.
+                newInterval._ranges.removeFirst();
+            }
+        }
+        Q_ASSERT(!newInterval._ranges.isEmpty());
         newInterval._ranges.first().start = newStart;
         _end = newStart;
     }
 
-    _ranges.last().end = atPosition;
+    // if we're in the middle of a range, set the end to the split position
+    if (_ranges.last().end > atPosition)
+        _ranges.last().end = atPosition;
+
+    validate();
+    newInterval.validate();
 
     return newInterval;
 }

src/qml/compiler/qv4ssa_p.h

@@ -51,7 +51,7 @@ class QQmlEnginePrivate;
 namespace QQmlJS {
 namespace V4IR {
 
-class LifeTimeInterval {
+class Q_AUTOTEST_EXPORT LifeTimeInterval {
 public:
     struct Range {
         int start;
@@ -121,6 +121,20 @@ public:
     void dump(QTextStream &out) const;
     static bool lessThan(const LifeTimeInterval &r1, const LifeTimeInterval &r2);
     static bool lessThanForTemp(const LifeTimeInterval &r1, const LifeTimeInterval &r2);
+
+    void validate() const {
+#if !defined(QT_NO_DEBUG)
+        // Validate the new range
+        if (_end != Invalid) {
+            Q_ASSERT(!_ranges.isEmpty());
+            foreach (const Range &range, _ranges) {
+                Q_ASSERT(range.start >= 0);
+                Q_ASSERT(range.end >= 0);
+                Q_ASSERT(range.start <= range.end);
+            }
+        }
+#endif
+    }
 };
 
 class Optimizer

tests/auto/qml/qml.pro

@@ -58,7 +58,8 @@ PRIVATETESTS += \
     qqmltimer \
     qqmlinstantiator \
     qv4debugger \
-    qqmlenginecleanup
+    qqmlenginecleanup \
+    v4misc
 
 qtHaveModule(widgets) {
     PUBLICTESTS += \

tests/auto/qml/v4misc/tst_v4misc.cpp

@@ -0,0 +1,157 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** 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, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, 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.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <qtest.h>
+
+#include <private/qv4ssa_p.h>
+
+class tst_v4misc: public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void initTestCase();
+
+    void rangeSplitting_1();
+    void rangeSplitting_2();
+    void rangeSplitting_3();
+};
+
+QT_BEGIN_NAMESPACE
+// Avoid QHash randomization so that the temp numbering is stable.
+extern Q_CORE_EXPORT QBasicAtomicInt qt_qhash_seed; // from qhash.cpp
+QT_END_NAMESPACE
+
+using namespace QT_PREPEND_NAMESPACE(QQmlJS::V4IR);
+
+void tst_v4misc::initTestCase()
+{
+    qt_qhash_seed.store(0);
+    QCOMPARE(qt_qhash_seed.load(), 0);
+}
+
+// split between two ranges
+void tst_v4misc::rangeSplitting_1()
+{
+    LifeTimeInterval interval;
+    interval.addRange(59, 59);
+    interval.addRange(61, 62);
+    interval.addRange(64, 64);
+    interval.addRange(69, 71);
+    interval.validate();
+    QCOMPARE(interval.end(), 71);
+
+    LifeTimeInterval newInterval = interval.split(66, 70);
+    interval.validate();
+    newInterval.validate();
+    QVERIFY(newInterval.isSplitFromInterval());
+
+    QCOMPARE(interval.ranges().size(), 3);
+    QCOMPARE(interval.ranges()[0].start, 59);
+    QCOMPARE(interval.ranges()[0].end, 59);
+    QCOMPARE(interval.ranges()[1].start, 61);
+    QCOMPARE(interval.ranges()[1].end, 62);
+    QCOMPARE(interval.ranges()[2].start, 64);
+    QCOMPARE(interval.ranges()[2].end, 64);
+    QCOMPARE(interval.end(), 70);
+
+    QCOMPARE(newInterval.ranges().size(), 1);
+    QCOMPARE(newInterval.ranges()[0].start, 70);
+    QCOMPARE(newInterval.ranges()[0].end, 71);
+    QCOMPARE(newInterval.end(), 71);
+}
+
+// split in the middle of a range
+void tst_v4misc::rangeSplitting_2()
+{
+    LifeTimeInterval interval;
+    interval.addRange(59, 59);
+    interval.addRange(61, 64);
+    interval.addRange(69, 71);
+    interval.validate();
+    QCOMPARE(interval.end(), 71);
+
+    LifeTimeInterval newInterval = interval.split(62, 64);
+    interval.validate();
+    newInterval.validate();
+    QVERIFY(newInterval.isSplitFromInterval());
+
+    QCOMPARE(interval.ranges().size(), 2);
+    QCOMPARE(interval.ranges()[0].start, 59);
+    QCOMPARE(interval.ranges()[0].end, 59);
+    QCOMPARE(interval.ranges()[1].start, 61);
+    QCOMPARE(interval.ranges()[1].end, 62);
+    QCOMPARE(interval.end(), 64);
+
+    QCOMPARE(newInterval.ranges().size(), 2);
+    QCOMPARE(newInterval.ranges()[0].start, 64);
+    QCOMPARE(newInterval.ranges()[0].end, 64);
+    QCOMPARE(newInterval.ranges()[1].start, 69);
+    QCOMPARE(newInterval.ranges()[1].end, 71);
+    QCOMPARE(newInterval.end(), 71);
+}
+
+// split in the middle of a range, and let it never go back to active again
+void tst_v4misc::rangeSplitting_3()
+{
+    LifeTimeInterval interval;
+    interval.addRange(59, 59);
+    interval.addRange(61, 64);
+    interval.addRange(69, 71);
+    interval.validate();
+    QCOMPARE(interval.end(), 71);
+
+    LifeTimeInterval newInterval = interval.split(64, LifeTimeInterval::Invalid);
+    interval.validate();
+    newInterval.validate();
+    QVERIFY(!newInterval.isValid());
+
+    QCOMPARE(interval.ranges().size(), 2);
+    QCOMPARE(interval.ranges()[0].start, 59);
+    QCOMPARE(interval.ranges()[0].end, 59);
+    QCOMPARE(interval.ranges()[1].start, 61);
+    QCOMPARE(interval.ranges()[1].end, 64);
+    QCOMPARE(interval.end(), 71);
+}
+
+QTEST_MAIN(tst_v4misc)
+
+#include "tst_v4misc.moc"

tests/auto/qml/v4misc/v4misc.pro

@@ -0,0 +1,9 @@
+CONFIG += testcase
+TARGET = tst_v4misc
+macx:CONFIG -= app_bundle
+
+SOURCES += tst_v4misc.cpp
+
+CONFIG += parallel_test
+QT += core-private qml-private testlib
+DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0