[turbofan] Ensure AstGraphBuilder::CheckOsrEntry hits once.

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/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/compilation-info.h"
 #include "src/compiler.h"
@@ skipping 3970 matching lines @@
       return input;
     default:
       break;
   }
   return nullptr;
 }
 
 
 bool AstGraphBuilder::CheckOsrEntry(IterationStatement* stmt) {
   if (info()->osr_ast_id() == stmt->OsrEntryId()) {
-    info()->set_osr_expr_stack_height(std::max(
-        environment()->stack_height(), info()->osr_expr_stack_height()));
+    DCHECK_EQ(-1, info()->osr_expr_stack_height());
+    info()->set_osr_expr_stack_height(environment()->stack_height());
     return true;
   }
   return false;
 }
 
 
 void AstGraphBuilder::PrepareFrameState(Node* node, BailoutId ast_id,
                                         OutputFrameStateCombine combine) {
   if (OperatorProperties::HasFrameStateInput(node->op())) {
     DCHECK(ast_id.IsNone() || info()->shared_info()->VerifyBailoutId(ast_id));
@@ skipping 321 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