Temporarily collect a map of all functions in the engine

At the moment we collect a lot of compilation units (one per binding
expression!), which for long running QML accumulates and creates a horrible
performance when trying to retrieve back traces. There is work in progress
to reduces the number of units down to one per QML file, and then the
fixed sorted QVector might proof to be a more efficient data structure
for the lookups.

But until that code lands, this patch proposes to use a QMap instead for the
time being, that tracks all functions. This brings down the qtquickcontrols
auto-test run from 2.5 minutes to just under a minute on my machine.

Change-Id: I45bf609055877081daa984de90f291a030f2f24f
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index b272e69fb0..ca0ea916a3 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -795,6 +795,9 @@ namespace {
 
 Function *ExecutionEngine::functionForProgramCounter(quintptr pc) const
 {
+    // ### Use this code path instead of the "else" when the number of compilation units went down to
+    // one per (qml) file.
+#if 0
     for (QSet<QV4::CompiledData::CompilationUnit*>::ConstIterator unitIt = compilationUnits.constBegin(), unitEnd = compilationUnits.constEnd();
          unitIt != unitEnd; ++unitIt) {
         const QVector<Function*> &functions = (*unitIt)->runtimeFunctionsSortedByAddress;
@@ -805,6 +808,17 @@ Function *ExecutionEngine::functionForProgramCounter(quintptr pc) const
             return *it;
     }
     return 0;
+#else
+    QMap<quintptr, Function*>::ConstIterator it = allFunctions.lowerBound(pc);
+    if (it != allFunctions.begin() && allFunctions.count() > 0)
+        --it;
+    if (it == allFunctions.end())
+        return 0;
+
+    if (pc < it.key() || pc >= it.key() + (*it)->codeSize)
+        return 0;
+    return *it;
+#endif
 }
 
 QmlExtensions *ExecutionEngine::qmlExtensions()