[debugger] use handler table on unoptimized code for exception prediction.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index a9c2439e61bbf077ad484031025d9fff7d03369e..512167c2da59ef5dcfd8d308c56c567dd59fa2c3 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4448,6 +4448,82 @@ class NormalizedMapCache: public FixedArray {
   void set(int index, Object* value);
 };
 
+// HandlerTable is a fixed array containing entries for exception handlers in
+// the code object it is associated with. The tables comes in two flavors:
+// 1) Based on ranges: Used for unoptimized code. Contains one entry per
+//    exception handler and a range representing the try-block covered by that
+//    handler. Layout looks as follows:
+//      [ range-start , range-end , handler-offset , handler-data ]
+// 2) Based on return addresses: Used for turbofanned code. Contains one entry
+//    per call-site that could throw an exception. Layout looks as follows:
+//      [ return-address-offset , handler-offset ]
+class HandlerTable : public FixedArray {
+ public:
+  // Conservative prediction whether a given handler will locally catch an
+  // exception or cause a re-throw to outside the code boundary. Since this is
+  // undecidable it is merely an approximation (e.g. useful for debugger).
+  enum CatchPrediction {
+    UNCAUGHT,  // the handler will (likely) rethrow the exception.
+    CAUGHT,    // the exception will be caught by the handler.
+    PROMISE    // the exception will be caught and cause a promise rejection.
+  };
+
+  // Getters for handler table based on ranges.
+  inline int GetRangeStart(int index) const;
+  inline int GetRangeEnd(int index) const;
+  inline int GetRangeHandler(int index) const;
+  inline int GetRangeData(int index) const;
+
+  // Setters for handler table based on ranges.
+  inline void SetRangeStart(int index, int value);
+  inline void SetRangeEnd(int index, int value);
+  inline void SetRangeHandler(int index, int offset, CatchPrediction pred);
+  inline void SetRangeData(int index, int value);
+
+  // Setters for handler table based on return addresses.
+  inline void SetReturnOffset(int index, int value);
+  inline void SetReturnHandler(int index, int offset, CatchPrediction pred);
+
+  // Lookup handler in a table based on ranges.
+  int LookupRange(int pc_offset, int* data, CatchPrediction* prediction);
+
+  // Lookup handler in a table based on return addresses.
+  int LookupReturn(int pc_offset);
+
+  // Returns the conservative catch predication.
+  inline CatchPrediction GetRangePrediction(int index) const;
+
+  // Returns the number of entries in the table.
+  inline int NumberOfRangeEntries() const;
+
+  // Returns the required length of the underlying fixed array.
+  static int LengthForRange(int entries) { return entries * kRangeEntrySize; }
+  static int LengthForReturn(int entries) { return entries * kReturnEntrySize; }
+
+  DECLARE_CAST(HandlerTable)
+
+#ifdef ENABLE_DISASSEMBLER
+  void HandlerTableRangePrint(std::ostream& os);   // NOLINT
+  void HandlerTableReturnPrint(std::ostream& os);  // NOLINT
+#endif
+
+ private:
+  // Layout description for handler table based on ranges.
+  static const int kRangeStartIndex = 0;
+  static const int kRangeEndIndex = 1;
+  static const int kRangeHandlerIndex = 2;
+  static const int kRangeDataIndex = 3;
+  static const int kRangeEntrySize = 4;
+
+  // Layout description for handler table based on return addresses.
+  static const int kReturnOffsetIndex = 0;
+  static const int kReturnHandlerIndex = 1;
+  static const int kReturnEntrySize = 2;
+
+  // Encoding of the {handler} field.
+  class HandlerPredictionField : public BitField<CatchPrediction, 0, 2> {};
+  class HandlerOffsetField : public BitField<int, 2, 30> {};
+};
 
 // ByteArray represents fixed sized byte arrays.  Used for the relocation info
 // that is attached to code objects.
@@ -4571,6 +4647,9 @@ class BytecodeArray : public FixedArrayBase {
 
   void CopyBytecodesTo(BytecodeArray* to);
 
+  int LookupRangeInHandlerTable(int code_offset, int* context_register,

[Michael Starzinger, 2016/08/02 11:04:05]

nit: s/context_register/data/ here, because for FCG code this is the stack depth
and not the context register.

+                                HandlerTable::CatchPrediction* prediction);
+
   // Layout description.
   static const int kConstantPoolOffset = FixedArrayBase::kHeaderSize;
   static const int kHandlerTableOffset = kConstantPoolOffset + kPointerSize;
@@ -4878,83 +4957,6 @@ class LiteralsArray : public FixedArray {
 };
 
 
-// HandlerTable is a fixed array containing entries for exception handlers in
-// the code object it is associated with. The tables comes in two flavors:
-// 1) Based on ranges: Used for unoptimized code. Contains one entry per
-//    exception handler and a range representing the try-block covered by that
-//    handler. Layout looks as follows:
-//      [ range-start , range-end , handler-offset , handler-data ]
-// 2) Based on return addresses: Used for turbofanned code. Contains one entry
-//    per call-site that could throw an exception. Layout looks as follows:
-//      [ return-address-offset , handler-offset ]
-class HandlerTable : public FixedArray {
- public:
-  // Conservative prediction whether a given handler will locally catch an
-  // exception or cause a re-throw to outside the code boundary. Since this is
-  // undecidable it is merely an approximation (e.g. useful for debugger).
-  enum CatchPrediction {
-    UNCAUGHT,  // the handler will (likely) rethrow the exception.
-    CAUGHT,    // the exception will be caught by the handler.
-    PROMISE    // the exception will be caught and cause a promise rejection.
-  };
-
-  // Getters for handler table based on ranges.
-  inline int GetRangeStart(int index) const;
-  inline int GetRangeEnd(int index) const;
-  inline int GetRangeHandler(int index) const;
-  inline int GetRangeData(int index) const;
-
-  // Setters for handler table based on ranges.
-  inline void SetRangeStart(int index, int value);
-  inline void SetRangeEnd(int index, int value);
-  inline void SetRangeHandler(int index, int offset, CatchPrediction pred);
-  inline void SetRangeData(int index, int value);
-
-  // Setters for handler table based on return addresses.
-  inline void SetReturnOffset(int index, int value);
-  inline void SetReturnHandler(int index, int offset, CatchPrediction pred);
-
-  // Lookup handler in a table based on ranges.
-  int LookupRange(int pc_offset, int* data, CatchPrediction* prediction);
-
-  // Lookup handler in a table based on return addresses.
-  int LookupReturn(int pc_offset, CatchPrediction* prediction);
-
-  // Returns the conservative catch predication.
-  inline CatchPrediction GetRangePrediction(int index) const;
-
-  // Returns the number of entries in the table.
-  inline int NumberOfRangeEntries() const;
-
-  // Returns the required length of the underlying fixed array.
-  static int LengthForRange(int entries) { return entries * kRangeEntrySize; }
-  static int LengthForReturn(int entries) { return entries * kReturnEntrySize; }
-
-  DECLARE_CAST(HandlerTable)
-
-#ifdef ENABLE_DISASSEMBLER
-  void HandlerTableRangePrint(std::ostream& os);   // NOLINT
-  void HandlerTableReturnPrint(std::ostream& os);  // NOLINT
-#endif
-
- private:
-  // Layout description for handler table based on ranges.
-  static const int kRangeStartIndex = 0;
-  static const int kRangeEndIndex = 1;
-  static const int kRangeHandlerIndex = 2;
-  static const int kRangeDataIndex = 3;
-  static const int kRangeEntrySize = 4;
-
-  // Layout description for handler table based on return addresses.
-  static const int kReturnOffsetIndex = 0;
-  static const int kReturnHandlerIndex = 1;
-  static const int kReturnEntrySize = 2;
-
-  // Encoding of the {handler} field.
-  class HandlerPredictionField : public BitField<CatchPrediction, 0, 2> {};
-  class HandlerOffsetField : public BitField<int, 2, 30> {};
-};
-
 class TemplateList : public FixedArray {
  public:
   static Handle<TemplateList> New(Isolate* isolate, int size);
@@ -5341,6 +5343,9 @@ class Code: public HeapObject {
   BailoutId TranslatePcOffsetToAstId(uint32_t pc_offset);
   uint32_t TranslateAstIdToPcOffset(BailoutId ast_id);
 
+  int LookupRangeInHandlerTable(int code_offset, int* context_register,

[Michael Starzinger, 2016/08/02 11:04:05]

nit: s/context_register/data/

+                                HandlerTable::CatchPrediction* prediction);
+
 #define DECLARE_CODE_AGE_ENUM(X) k##X##CodeAge,
   enum Age {
     kToBeExecutedOnceCodeAge = -3,
@@ -5554,6 +5559,11 @@ class AbstractCode : public HeapObject {
   // Return the source position table.
   inline ByteArray* source_position_table();
 
+  // Return the exception handler table.
+  inline int LookupRangeInHandlerTable(
+      int code_offset, int* context_register,

[Michael Starzinger, 2016/08/02 11:04:05]

nit: s/context_register/data/

+      HandlerTable::CatchPrediction* prediction);
+
   // Returns the size of instructions and the metadata.
   inline int SizeIncludingMetadata();