Fix line number mapping to work with non increasing line numbers

The old map assumed that line numbers are always increasing, something
that isn't always true. So move to a format where we map blocks of
bytecode to a line number instead.

Change-Id: I1cd9dd1329d415122cd3d560294ef53007f879f8
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

1 files changed, 9 insertions, 8 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index ce21e0f7e5..618565a806 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -796,15 +796,16 @@ QString CppStackFrame::function() const
 
 int CppStackFrame::lineNumber() const
 {
+    auto findLine = [](const CompiledData::CodeOffsetToLine &entry, uint offset) {
+        return entry.codeOffset < offset;
+    };
+
     const QV4::CompiledData::Function *cf = v4Function->compiledFunction;
-    uint offset = static_cast<uint>(instructionPointer - v4Function->codeData - 1); // -1 because the instructionPointer points to the next instruction
-    const quint32_le *lineNumbers = cf->lineNumberTable();
-    int nLineNumbers = cf->nLineNumbers;
-    for (int i = 0; i < nLineNumbers; ++i) {
-        if (offset <= lineNumbers[i])
-            return cf->location.line + i;
-    }
-    return cf->location.line + nLineNumbers;
+    uint offset = static_cast<uint>(instructionPointer - v4Function->codeData);
+    const CompiledData::CodeOffsetToLine *lineNumbers = cf->lineNumberTable();
+    uint nLineNumbers = cf->nLineNumbers;
+    const CompiledData::CodeOffsetToLine *line = std::lower_bound(lineNumbers, lineNumbers + nLineNumbers, offset, findLine) - 1;
+    return line->line;
 }
 
 ReturnedValue CppStackFrame::thisObject() const {