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 2b3ba1b222b933819c3f76dbc81e9da459f620dc..3cbee1eb87d2efc266b84c162791c7f4bf91b95e 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5129,7 +5129,8 @@ class Code: public HeapObject {
   // Returns the address right after the last instruction.
   inline byte* instruction_end();
 
-  // Returns the size of the instructions, padding, and relocation information.
+  // Returns the size of the instructions, padding, relocation and unwinding
+  // information.
   inline int body_size();
 
   // Returns the size of code and its metadata. This includes the size of code
@@ -5139,6 +5140,49 @@ class Code: public HeapObject {
   // Returns the address of the first relocation info (read backwards!).
   inline byte* relocation_start();
 
+  // [has_unwinding_info]: Whether this code object has unwinding information.
+  // If it doesn't, unwinding_information_start() will point to invalid data.
+  //
+  // The body of all code objects has the following layout.
+  //
+  //  +--------------------------+  <-- instruction_start()
+  //  |       instructions       |
+  //  |           ...            |
+  //  +--------------------------+
+  //  |      relocation info     |
+  //  |           ...            |
+  //  +--------------------------+  <-- instruction_end()
+  //
+  // If has_unwinding_info() is false, instruction_end() points to the first
+  // memory location after the end of the code object. Otherwise, the body
+  // continues as follows:
+  //
+  //  +--------------------------+
+  //  |    padding to the next   |
+  //  |  8-byte aligned address  |
+  //  +--------------------------+  <-- instruction_end()
+  //  |   [unwinding_info_size]  |
+  //  |        as uint64_t       |
+  //  +--------------------------+  <-- unwinding_info_start()
+  //  |       unwinding info     |
+  //  |            ...           |
+  //  +--------------------------+  <-- unwinding_info_end()
+  //
+  // and unwinding_info_end() points to the first memory location after the end
+  // of the code object.
+  //
+  DECL_BOOLEAN_ACCESSORS(has_unwinding_info)
+
+  // [unwinding_info_size]: Size of the unwinding information.
+  inline int unwinding_info_size() const;
+  inline void set_unwinding_info_size(int value);
+
+  // Returns the address of the unwinding information, if any.
+  inline byte* unwinding_info_start();
+
+  // Returns the address right after the end of the unwinding information.
+  inline byte* unwinding_info_end();
+
   // Code entry point.
   inline byte* entry();
 
@@ -5269,6 +5313,8 @@ class Code: public HeapObject {
   static const int kHeaderSize =
       (kHeaderPaddingStart + kCodeAlignmentMask) & ~kCodeAlignmentMask;
 
+  inline int GetUnwindingInfoSizeOffset() const;
+
   class BodyDescriptor;
 
   // Byte offsets within kKindSpecificFlags1Offset.
@@ -5287,9 +5333,11 @@ 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;