[runtime] Use "the hole" instead of smi 0 as sentinel for context extension.

src/compiler/ast-graph-builder.cc

 // Copyright 2014 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/compiler/ast-graph-builder.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
@@ skipping 3840 matching lines @@
     environment()->Pop();
     fast_block.BeginBlock();
 
     // Perform checks whether the fast mode applies, by looking for any
     // extension object which might shadow the optimistic declaration.
     for (int depth = 0; bitset != 0; bitset >>= 1, depth++) {
       if ((bitset & 1) == 0) continue;
       Node* load = NewNode(
           javascript()->LoadContext(depth, Context::EXTENSION_INDEX, false),
           current_context());
-      Node* check =
-          NewNode(javascript()->CallRuntime(Runtime::kInlineIsSmi, 1), load);
+      Node* check = NewNode(javascript()->StrictEqual(), load,
+                            jsgraph()->TheHoleConstant());
       fast_block.BreakUnless(check, BranchHint::kTrue);
     }
 
     // Fast case, because variable is not shadowed. Perform global slot load.
     Node* fast = BuildGlobalLoad(name, feedback, typeof_mode);
     states.AddToNode(fast, bailout_id, combine);
     environment()->Push(fast);
     slow_block.Break();
     environment()->Pop();
     fast_block.EndBlock();
@@ skipping 20 matching lines @@
     environment()->Pop();
     fast_block.BeginBlock();
 
     // Perform checks whether the fast mode applies, by looking for any
     // extension object which might shadow the optimistic declaration.
     for (int depth = 0; bitset != 0; bitset >>= 1, depth++) {
       if ((bitset & 1) == 0) continue;
       Node* load = NewNode(
           javascript()->LoadContext(depth, Context::EXTENSION_INDEX, false),
           current_context());
-      Node* check =
-          NewNode(javascript()->CallRuntime(Runtime::kInlineIsSmi, 1), load);
+      Node* check = NewNode(javascript()->StrictEqual(), load,
+                            jsgraph()->TheHoleConstant());
       fast_block.BreakUnless(check, BranchHint::kTrue);
     }
 
     // Fast case, because variable is not shadowed. Perform context slot load.
     Variable* local = variable->local_if_not_shadowed();
     DCHECK(local->location() == VariableLocation::CONTEXT);  // Must be context.
     Node* fast = BuildVariableLoad(local, bailout_id, states, feedback, combine,
                                    typeof_mode);
     environment()->Push(fast);
     slow_block.Break();
@@ skipping 389 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8