[Interpreter]: Basic support for iterating interpreter stack frames for GC.

src/frames.cc

Index: src/frames.cc
diff --git a/src/frames.cc b/src/frames.cc
index 7b847974fdc775ef619336a71603200c25c970fc..c6ee65dec6f9ab039ee4c0f7fc471df52bd13d10 100644
--- a/src/frames.cc
+++ b/src/frames.cc
@@ -439,6 +439,19 @@ StackFrame::Type StackFrame::ComputeType(const StackFrameIteratorBase* iterator,
         return JAVA_SCRIPT;
       case Code::OPTIMIZED_FUNCTION:
         return OPTIMIZED;
+      case Code::BUILTIN:

[titzer, 2015/10/15 17:01:55]

Are interpreter frames really only identifiable through the marker being a SMI,
or is there a more reliable way to detect them? E.g. by marking a bit on the
code object?

[rmcilroy, 2015/10/15 19:47:47]

The marker is not a SMI (it's a tagged JSFunction object, like other JavaScript
frames).  It is identified by the fact that the return address always points to
the InterpreterEntryTrampoline builtin for interpreted frames. 

If you want to make it more robust I could do the same trick as the
ArgumentsAdapter (put a SMI marker in the context slot and push the context
separately. Would this be better? What was your plan for WASM frames?

+        if (!marker->IsSmi()) {
+          if (StandardFrame::IsArgumentsAdaptorFrame(state->fp)) {
+            // An adapter frame has a special SMI constant for the context and
+            // is not distinguished through the marker.
+            return ARGUMENTS_ADAPTOR;
+          } else {
+            // The interpreter entry trampoline has a non-SMI marker.
+            DCHECK(code_obj->is_interpreter_entry_trampoline());
+            return INTERPRETED;
+          }
+        }
+        break;  // Marker encodes the frame type.
       case Code::HANDLER:
         if (!marker->IsSmi()) {
           // Only hydrogen code stub handlers can have a non-SMI marker.
@@ -451,12 +464,6 @@ StackFrame::Type StackFrame::ComputeType(const StackFrameIteratorBase* iterator,
     }
   }
 
-  if (StandardFrame::IsArgumentsAdaptorFrame(state->fp)) {
-    // An adapter frame has a special SMI constant for the context and
-    // is not distinguished through the marker.
-    return ARGUMENTS_ADAPTOR;
-  }
-
   // Didn't find a code object, or the code kind wasn't specific enough.
   // The marker should encode the frame type.
   return static_cast<StackFrame::Type>(Smi::cast(marker)->value());