[turbofan] Optimize silent hole checks on legacy const context slots.

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/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
 #include "src/compiler/js-type-feedback.h"
@@ skipping 2710 matching lines @@
   DCHECK(rest->IsContextSlot() || rest->IsStackAllocated());
   // This should never lazy deopt, so it is fine to send invalid bailout id.
   BuildVariableAssignment(rest, object, Token::ASSIGN, BailoutId::None());
 
   return object;
 }
 
 
 Node* AstGraphBuilder::BuildHoleCheckSilent(Node* value, Node* for_hole,
                                             Node* not_hole) {
-  IfBuilder hole_check(this);
   Node* the_hole = jsgraph()->TheHoleConstant();
   Node* check = NewNode(javascript()->StrictEqual(), value, the_hole);
-  hole_check.If(check);
-  hole_check.Then();
-  environment()->Push(for_hole);
-  hole_check.Else();
-  environment()->Push(not_hole);
-  hole_check.End();
-  return environment()->Pop();
+  return NewNode(common()->Select(kMachAnyTagged, BranchHint::kFalse), check,
+                 for_hole, not_hole);
 }
 
 
 Node* AstGraphBuilder::BuildHoleCheckThrow(Node* value, Variable* variable,
                                            Node* not_hole,
                                            BailoutId bailout_id) {
   IfBuilder hole_check(this);
   Node* the_hole = jsgraph()->TheHoleConstant();
   Node* check = NewNode(javascript()->StrictEqual(), value, the_hole);
   hole_check.If(check);
@@ skipping 806 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