[interpreter] Switch context during stack unwinding.

src/compiler/bytecode-graph-builder.cc

Index: src/compiler/bytecode-graph-builder.cc
diff --git a/src/compiler/bytecode-graph-builder.cc b/src/compiler/bytecode-graph-builder.cc
index 69f39f6ad5e5a98fc708d77d4372333d45827aab..a05e29110c9572e1befb2f7430395be41318afee 100644
--- a/src/compiler/bytecode-graph-builder.cc
+++ b/src/compiler/bytecode-graph-builder.cc
@@ -1666,7 +1666,8 @@ void BytecodeGraphBuilder::EnterAndExitExceptionHandlers(int current_offset) {
     if (current_offset < next_start) break;  // Not yet covered by range.
     int next_end = table->GetRangeEnd(current_exception_handler_);
     int next_handler = table->GetRangeHandler(current_exception_handler_);
-    exception_handlers_.push({next_start, next_end, next_handler});
+    int next_depth = table->GetRangeDepth(current_exception_handler_);

[Michael Starzinger, 2016/02/03 14:34:01]

disclosure: I understand that the naming of the HandlerTable::depth field is
off, because the interpreter is now "hijacking" it to hold the context register
index. However, I would like to do any potential renaming of that field in a
separate CL and not as part of this CL.

+    exception_handlers_.push({next_start, next_end, next_handler, next_depth});
     current_exception_handler_++;
   }
 }
@@ -1733,15 +1734,19 @@ Node* BytecodeGraphBuilder::MakeNode(const Operator* op, int value_input_count,
     // Add implicit exception continuation for throwing nodes.
     if (!result->op()->HasProperty(Operator::kNoThrow) && inside_handler) {
       int handler_offset = exception_handlers_.top().handler_offset_;
+      int context_index = exception_handlers_.top().context_register_;
+      interpreter::Register context_register(context_index);
       // TODO(mstarzinger): Thread through correct prediction!
       IfExceptionHint hint = IfExceptionHint::kLocallyCaught;
       Environment* success_env = environment()->CopyForConditional();
       const Operator* op = common()->IfException(hint);
       Node* effect = environment()->GetEffectDependency();
       Node* on_exception = graph()->NewNode(op, effect, result);
+      Node* context = environment()->LookupRegister(context_register);
       environment()->UpdateControlDependency(on_exception);
       environment()->UpdateEffectDependency(on_exception);
       environment()->BindAccumulator(on_exception);
+      environment()->SetContext(context);
       MergeIntoSuccessorEnvironment(handler_offset);
       set_environment(success_env);
     }