[Interpreter] Move context chain search loop to handler

src/interpreter/interpreter-assembler.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/interpreter/interpreter-assembler.h"
 
 #include <limits>
 #include <ostream>
 
 #include "src/code-factory.h"
@@ skipping 66 matching lines @@
 }
 
 Node* InterpreterAssembler::GetContext() {
   return LoadRegister(Register::current_context());
 }
 
 void InterpreterAssembler::SetContext(Node* value) {
   StoreRegister(value, Register::current_context());
 }
 
+Node* InterpreterAssembler::GetContextAtDepth(Node* context, Node* depth) {
+  Variable cur_context(this, MachineRepresentation::kTaggedPointer);
+  cur_context.Bind(context);
+
+  Variable cur_depth(this, MachineRepresentation::kWord32);
+  cur_depth.Bind(depth);
+
+  Label context_found(this);
+
+  Variable* context_search_loop_variables[2] = {&cur_depth, &cur_context};
+  Label context_search(this, 2, context_search_loop_variables);
+
+  // Fast path if the depth is 0.
+  BranchIfWord32Equal(depth, Int32Constant(0), &context_found, &context_search);
+
+  // Loop until the depth is 0.
+  Bind(&context_search);
+  {
+    cur_depth.Bind(Int32Sub(cur_depth.value(), Int32Constant(1)));
+    cur_context.Bind(
+        LoadContextSlot(cur_context.value(), Context::PREVIOUS_INDEX));
+
+    BranchIfWord32Equal(cur_depth.value(), Int32Constant(0), &context_found,
+                        &context_search);
+  }
+
+  Bind(&context_found);
+  return cur_context.value();
+}
+
 Node* InterpreterAssembler::BytecodeOffset() {
   return bytecode_offset_.value();
 }
 
 Node* InterpreterAssembler::BytecodeArrayTaggedPointer() {
   if (made_call_) {
     // If we have made a call, restore bytecode array from stack frame in case
     // the debugger has swapped us to the patched debugger bytecode array.
     return LoadRegister(Register::bytecode_array());
   } else {
@@ skipping 1227 matching lines @@
     Goto(&loop);
   }
   Bind(&done_loop);
 
   return array;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8