Initial support for emitting unwinding information in perf jitdump.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index a7aabe23e0f856b18734e09f3fe4f40c7b4b508d..9e887e18540d2e4b77cd1ae131337d51ded33f18 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4910,6 +4910,10 @@ class Code: public HeapObject {
   inline int instruction_size() const;
   inline void set_instruction_size(int value);
 
+  // [unwinding_info_size]: Size of the unwinding information.
+  inline int unwinding_info_size() const;
+  inline void set_unwinding_info_size(int value);
+
   // [relocation_info]: Code relocation information
   DECL_ACCESSORS(relocation_info, ByteArray)
   void InvalidateRelocation();
@@ -4985,6 +4989,10 @@ class Code: public HeapObject {
   inline void set_raw_kind_specific_flags1(int value);
   inline void set_raw_kind_specific_flags2(int value);
 
+  // [has_unwinding_info]: Whether this code object has unwinding information.
+  // If it doesn't, unwinding_information_start() will point to invalid data.
+  DECL_BOOLEAN_ACCESSORS(has_unwinding_info)

[rmcilroy, 2016/06/21 13:47:44]

nit - move down to near unwinding_info_start.

Also, please add a simple diagram showing the layout of the unwinding info
(including that the first address is the length).

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+
   // Testers for interpreter builtins.
   inline bool is_interpreter_trampoline_builtin();
 
@@ -5135,6 +5143,12 @@ class Code: public HeapObject {
   // Returns the address of the first relocation info (read backwards!).
   inline byte* relocation_start();
 
+  // Returns the address of the unwinding information.

[rmcilroy, 2016/06/21 13:47:44]

information, if any.

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+  inline byte* unwinding_info_start();
+
+  // Returns the address past the end of the unwinding information.

[rmcilroy, 2016/06/21 13:47:44]

/s/past/right after/

[Stefano Sanfilippo, 2016/06/23 15:23:44]

Done.

+  inline byte* unwinding_info_end();
+
   // Code entry point.
   inline byte* entry();
 
@@ -5283,9 +5297,11 @@ class Code: public HeapObject {
       : public BitField<CacheHolderFlag, ICStateField::kNext, 2> {};
   class KindField : public BitField<Kind, CacheHolderField::kNext, 5> {};
   STATIC_ASSERT(NUMBER_OF_KINDS <= KindField::kMax);
-  class ExtraICStateField : public BitField<ExtraICState, KindField::kNext,
-                                            PlatformSmiTagging::kSmiValueSize -
-                                                KindField::kNext + 1> {};
+  class HasUnwindingInfoField : public BitField<bool, KindField::kNext, 1> {};
+  class ExtraICStateField
+      : public BitField<ExtraICState, HasUnwindingInfoField::kNext,
+                        PlatformSmiTagging::kSmiValueSize -
+                            HasUnwindingInfoField::kNext + 1> {};
 
   // KindSpecificFlags1 layout (STUB, BUILTIN and OPTIMIZED_FUNCTION)
   static const int kStackSlotsFirstBit = 0;