[ignition, debugger] correctly set position for return with elided bytecode.

src/interpreter/source-position-table.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERPRETER_SOURCE_POSITION_TABLE_H_
 #define V8_INTERPRETER_SOURCE_POSITION_TABLE_H_
 
 #include "src/assert-scope.h"
 #include "src/checks.h"
 #include "src/handles.h"
@@ skipping 24 matching lines @@
 };
 
 class SourcePositionTableBuilder : public PositionsRecorder {
  public:
   explicit SourcePositionTableBuilder(Isolate* isolate, Zone* zone)
       : isolate_(isolate),
         bytes_(zone),
 #ifdef ENABLE_SLOW_DCHECKS
         raw_entries_(zone),
 #endif
-        previous_() {
+        candidate_(kUninitializedCandidateOffset, 0, false) {
   }
 
-  void AddStatementPosition(size_t bytecode_offset, int source_position);
+  enum OnDuplicateCodeOffset {

[vogelheim, 2016/03/14 10:41:15]

style nitpick: c++ style wants an enum declaration before the constructors.

Ref: https://google.github.io/styleguide/cppguide.html#Declaration_Order

[Yang, 2016/03/14 11:32:34]

Done.

+    DISCARD_DUPLICATE,
+    OVERWRITE_DUPLICATE,
+  };
+
+  void AddStatementPosition(
+      size_t bytecode_offset, int source_position,
+      OnDuplicateCodeOffset on_duplicate = DISCARD_DUPLICATE);
   void AddExpressionPosition(size_t bytecode_offset, int source_position);
   Handle<ByteArray> ToSourcePositionTable();
 
  private:
-  void AddEntry(const PositionTableEntry& entry);
+  void AddEntry(const PositionTableEntry& entry,
+                OnDuplicateCodeOffset on_duplicate = DISCARD_DUPLICATE);
+  void CommitEntry();
+
+  static const int kUninitializedCandidateOffset = -1;

[vogelheim, 2016/03/14 10:41:15]

Also style nitpick: consts also go before methods.

[Yang, 2016/03/14 11:32:34]

Done.

 
   Isolate* isolate_;
   ZoneVector<byte> bytes_;
 #ifdef ENABLE_SLOW_DCHECKS
   ZoneVector<PositionTableEntry> raw_entries_;
 #endif
+  PositionTableEntry candidate_;

[vogelheim, 2016/03/14 10:41:15]

Maybe add mini-comments on what these do, e.g.:

... candidate_;  // Next entry to be written, unless offset !=
kUninitializedCandidateOffset.
... previous_;  // Previously written entry, used to compute deltas.

[Yang, 2016/03/14 11:32:34]

Done.

   PositionTableEntry previous_;
 };
 
 class SourcePositionTableIterator {
  public:
   explicit SourcePositionTableIterator(ByteArray* byte_array);
 
   void Advance();
 
   int bytecode_offset() const {
@@ skipping 17 matching lines @@
   int index_;
   PositionTableEntry current_;
   DisallowHeapAllocation no_gc;
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_SOURCE_POSITION_TABLE_H_