diff --git a/src/models/costdelegate.cpp b/src/models/costdelegate.cpp
index 69af56f5..96f6e082 100644
--- a/src/models/costdelegate.cpp
+++ b/src/models/costdelegate.cpp
@@ -44,13 +44,13 @@ CostDelegate::~CostDelegate() = default;
 void CostDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
 {
     // TODO: handle negative values
-    const auto cost = index.data(m_sortRole).toULongLong();
+    const auto cost = index.data(m_sortRole).toLongLong();
     if (cost == 0) {
         QStyledItemDelegate::paint(painter, option, index);
         return;
     }
 
-    const auto totalCost = index.data(m_totalCostRole).toULongLong();
+    const auto totalCost = index.data(m_totalCostRole).toLongLong();
     const auto fraction = std::abs(float(cost) / totalCost);
 
     auto rect = option.rect;
diff --git a/src/models/data.h b/src/models/data.h
index 4dc63523..7487e6c2 100644
--- a/src/models/data.h
+++ b/src/models/data.h
@@ -278,12 +278,12 @@ class Costs
         m_totalCosts = rhs.m_totalCosts;
     }
 
-    QString formatCost(int type, quint64 cost) const
+    QString formatCost(int type, qint64 cost) const
     {
         return formatCost(m_units[type], cost);
     }
 
-    static QString formatCost(Unit unit, quint64 cost)
+    static QString formatCost(Unit unit, qint64 cost)
     {
         switch (unit) {
         case Unit::Time:
@@ -408,7 +408,7 @@ struct BottomUpResults
 
     // callback return type is ignored, all frames will be iterated over
     template<typename FrameCallback>
-    const BottomUp* addEvent(int type, quint64 cost, const QVector<qint32>& frames, FrameCallback frameCallback)
+    const BottomUp* addEvent(int type, qint64 cost, const QVector<qint32>& frames, FrameCallback frameCallback)
     {
         costs.addTotalCost(type, cost);
         auto parent = &root;
diff --git a/src/models/topproxy.cpp b/src/models/topproxy.cpp
index 107b5e8e..52291fd5 100644
--- a/src/models/topproxy.cpp
+++ b/src/models/topproxy.cpp
@@ -66,7 +66,7 @@ bool TopProxy::filterAcceptsRow(int source_row, const QModelIndex& source_parent
     if (source_parent.isValid()) {
         return false;
     }
-    if (!sourceModel()->index(source_row, m_costColumn, source_parent).data(sortRole()).value<quint64>()) {
+    if (!sourceModel()->index(source_row, m_costColumn, source_parent).data(sortRole()).value<qint64>()) {
         return false;
     }
     return true;
diff --git a/src/parsers/perf/perfparser.cpp b/src/parsers/perf/perfparser.cpp
index 1f154f9d..cff64793 100644
--- a/src/parsers/perf/perfparser.cpp
+++ b/src/parsers/perf/perfparser.cpp
@@ -1543,7 +1543,7 @@ void PerfParser::startParseFile(const QString& path, const QString& diffFile)
                     this->m_callerCalleeResults = {};
 
                     const auto diffResults =
-                        Data::BottomUpResults::mergeBottomUpResults(m_bottomUpResults, otherResults);
+                        Data::BottomUpResults::diffBottomUpResults(m_bottomUpResults, otherResults);
                     m_bottomUpResults = diffResults;
                     const auto topDown = Data::TopDownResults::fromBottomUp(diffResults);
                     Data::CallerCalleeResults callerCalleeResults;
@@ -1558,7 +1558,7 @@ void PerfParser::startParseFile(const QString& path, const QString& diffFile)
                                 this->m_callerCalleeResults = {};
 
                                 const auto diffResults =
-                                    Data::BottomUpResults::mergeBottomUpResults(results, otherResults);
+                                    Data::BottomUpResults::diffBottomUpResults(results, otherResults);
                                 const auto topDown = Data::TopDownResults::fromBottomUp(diffResults);
                                 Data::CallerCalleeResults callerCalleeResults;
                                 Data::callerCalleesFromBottomUpData(diffResults, &callerCalleeResults);
diff --git a/src/util.cpp b/src/util.cpp
index 489f2783..fd132a28 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -136,13 +136,13 @@ QString Util::formatSymbol(const Data::Symbol& symbol, bool replaceEmptyString)
     return formatString(symbolString, replaceEmptyString);
 }
 
-QString Util::formatCost(quint64 cost)
+QString Util::formatCost(qint64 cost)
 {
     // resulting format: 1.234E56
     return QString::number(static_cast<double>(cost), 'G', 4);
 }
 
-QString Util::formatCostRelative(quint64 selfCost, quint64 totalCost, bool addPercentSign)
+QString Util::formatCostRelative(qint64 selfCost, qint64 totalCost, bool addPercentSign)
 {
     if (!totalCost) {
         return QString();
diff --git a/src/util.h b/src/util.h
index 3f50e58a..d6400d4c 100644
--- a/src/util.h
+++ b/src/util.h
@@ -67,8 +67,8 @@ struct HashCombine
 
 QString formatString(const QString& input, bool replaceEmptyString = true);
 QString formatSymbol(const Data::Symbol& symbol, bool replaceEmptyString = true);
-QString formatCost(quint64 cost);
-QString formatCostRelative(quint64 selfCost, quint64 totalCost, bool addPercentSign = false);
+QString formatCost(qint64 cost);
+QString formatCostRelative(qint64 selfCost, qint64 totalCost, bool addPercentSign = false);
 QString formatTimeString(quint64 nanoseconds, bool shortForm = false);
 QString formatFrequency(quint64 occurrences, quint64 nanoseconds);
 QString formatTooltip(int id, const Data::Symbol& symbol, const Data::Costs& costs);