[turbofan] Handle cyclic dependencies in context typing.

src/compiler/typer.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/bootstrapper.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 298 matching lines @@
   Bounds BoundsOrNone(Node* node) {
     return NodeProperties::IsTyped(node) ? NodeProperties::GetBounds(node)
                                          : Bounds(Type::None());
   }
 
   Bounds Operand(Node* node, int i) {
     Node* operand_node = NodeProperties::GetValueInput(node, i);
     return BoundsOrNone(operand_node);
   }
 
-  Bounds ContextOperand(Node* node) {
-    Bounds result = BoundsOrNone(NodeProperties::GetContextInput(node));
-    DCHECK(result.upper->Maybe(Type::Internal()));
-    // TODO(rossberg): More precisely, instead of the above assertion, we should
-    // back-propagate the constraint that it has to be a subtype of Internal.
-    return result;
-  }
-
+  Bounds WrapContextBoundsForInput(Node* node);
   Type* Weaken(Type* current_type, Type* previous_type);
 
   Zone* zone() { return typer_->zone(); }
   Isolate* isolate() { return typer_->isolate(); }
   Graph* graph() { return typer_->graph(); }
   MaybeHandle<Context> context() { return typer_->context(); }
 
   typedef Type* (*UnaryTyperFun)(Type*, Typer* t);
   typedef Type* (*BinaryTyperFun)(Type*, Type*, Typer* t);
 
@@ skipping 1037 matching lines @@
   }
 }
 
 
 Bounds Typer::Visitor::TypeJSStoreContext(Node* node) {
   UNREACHABLE();
   return Bounds();
 }
 
 
+Bounds Typer::Visitor::WrapContextBoundsForInput(Node* node) {
+  Bounds outer = BoundsOrNone(NodeProperties::GetContextInput(node));
+  if (outer.upper->Is(Type::None())) {
+    return Bounds(Type::None());
+  } else {
+    DCHECK(outer.upper->Maybe(Type::Internal()));
+    return Bounds(Type::Context(outer.upper, zone()));
+  }
+}
+
+
 Bounds Typer::Visitor::TypeJSCreateFunctionContext(Node* node) {
-  Bounds outer = ContextOperand(node);
-  return Bounds(Type::Context(outer.upper, zone()));
+  return WrapContextBoundsForInput(node);
 }
 
 
 Bounds Typer::Visitor::TypeJSCreateCatchContext(Node* node) {
-  Bounds outer = ContextOperand(node);
-  return Bounds(Type::Context(outer.upper, zone()));
+  return WrapContextBoundsForInput(node);
 }
 
 
 Bounds Typer::Visitor::TypeJSCreateWithContext(Node* node) {
-  Bounds outer = ContextOperand(node);
-  return Bounds(Type::Context(outer.upper, zone()));
+  return WrapContextBoundsForInput(node);
 }
 
 
 Bounds Typer::Visitor::TypeJSCreateBlockContext(Node* node) {
-  Bounds outer = ContextOperand(node);
-  return Bounds(Type::Context(outer.upper, zone()));
+  return WrapContextBoundsForInput(node);
 }
 
 
 Bounds Typer::Visitor::TypeJSCreateModuleContext(Node* node) {
   // TODO(rossberg): this is probably incorrect
-  Bounds outer = ContextOperand(node);
-  return Bounds(Type::Context(outer.upper, zone()));
+  return WrapContextBoundsForInput(node);
 }
 
 
 Bounds Typer::Visitor::TypeJSCreateScriptContext(Node* node) {
-  Bounds outer = ContextOperand(node);
-  return Bounds(Type::Context(outer.upper, zone()));
+  return WrapContextBoundsForInput(node);
 }
 
 
 // JS other operators.
 
 
 Bounds Typer::Visitor::TypeJSYield(Node* node) {
   return Bounds::Unbounded(zone());
 }
 
@@ skipping 689 matching lines @@
       TYPED_ARRAYS(TYPED_ARRAY_CASE)
 #undef TYPED_ARRAY_CASE
     }
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8