Add script context with context-allocated "const this"

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index 43d402094539cfae9c31dd3f2f3395888a17db86..05819cdce6cd393a1d31a0ca66e61e1566b8e29c 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -2420,37 +2420,17 @@ void AstGraphBuilder::VisitCall(Call* expr) {
     // Create node to ask for help resolving potential eval call. This will
     // provide a fully resolved callee and the corresponding receiver.
     Node* function = GetFunctionClosure();
-    // TODO(wingo): ResolvePossibleDirectEval doesn't really need a receiver,
-    // now that eval scopes don't have "this" declarations.  Remove this hack
-    // once ResolvePossibleDirectEval changes.
-    Node* receiver;
-    {
-      Variable* variable = info()->scope()->LookupThis();
-      if (variable->IsStackAllocated()) {
-        receiver = environment()->Lookup(variable);
-      } else {
-        DCHECK(variable->IsContextSlot());
-        int depth = current_scope()->ContextChainLength(variable->scope());
-        bool immutable = variable->maybe_assigned() == kNotAssigned;
-        const Operator* op =
-            javascript()->LoadContext(depth, variable->index(), immutable);
-        receiver = NewNode(op, current_context());
-      }
-    }
     Node* language = jsgraph()->Constant(language_mode());
     Node* position = jsgraph()->Constant(current_scope()->start_position());
     const Operator* op =
-        javascript()->CallRuntime(Runtime::kResolvePossiblyDirectEval, 6);
-    Node* pair =
-        NewNode(op, callee, source, function, receiver, language, position);
-    PrepareFrameState(pair, expr->EvalOrLookupId(),
+        javascript()->CallRuntime(Runtime::kResolvePossiblyDirectEval, 5);
+    Node* new_callee =
+        NewNode(op, callee, source, function, language, position);
+    PrepareFrameState(new_callee, expr->EvalOrLookupId(),
                       OutputFrameStateCombine::PokeAt(arg_count + 1));
-    Node* new_callee = NewNode(common()->Projection(0), pair);
-    Node* new_receiver = NewNode(common()->Projection(1), pair);
 
-    // Patch callee and receiver on the environment.
+    // Patch callee on the environment.
     environment()->Poke(arg_count + 1, new_callee);
-    environment()->Poke(arg_count + 0, new_receiver);
   }
 
   // Create node to perform the function call.
@@ -2873,7 +2853,13 @@ void AstGraphBuilder::VisitDelete(UnaryOperation* expr) {
     // Delete of an unqualified identifier is only allowed in classic mode but
     // deleting "this" is allowed in all language modes.
     Variable* variable = expr->expression()->AsVariableProxy()->var();
-    DCHECK(is_sloppy(language_mode()) || variable->is_this());
+    // Delete of an unqualified identifier is disallowed in strict mode but
+    // "delete this" is allowed.  (It could be that the "this" variable has

[Michael Starzinger, 2015/06/12 08:06:10]

nit: Can we merge this comment with the one two lines above, because it
basically tries to express the same thing.

+    // DYNAMIC resolution though so we haven't been able to map it to
+    // Variable::THIS, but regardless if its name is "this" then it is
+    // "this".)
+    DCHECK(is_sloppy(language_mode()) ||
+           *variable->name() == *isolate()->factory()->this_string());

[Michael Starzinger, 2015/06/12 08:06:10]

nit: This heavily relies on the fact that variable->name() is internalized. Can
we move this into a Variable::IsThisName(Isolate*) helper so that it not spread
across the codebase?

     value = BuildVariableDelete(variable, expr->id(),
                                 ast_context()->GetStateCombine());
   } else if (expr->expression()->IsProperty()) {
@@ -3321,9 +3307,11 @@ Node* AstGraphBuilder::BuildVariableDelete(Variable* variable,
     }
     case Variable::PARAMETER:
     case Variable::LOCAL:
-    case Variable::CONTEXT:
+    case Variable::CONTEXT: {
       // Local var, const, or let variable or context variable.
-      return jsgraph()->BooleanConstant(variable->is_this());
+      bool is_this = *variable->name() == *isolate()->factory()->this_string();

[Michael Starzinger, 2015/06/12 08:06:10]

nit: See comment above.

+      return jsgraph()->BooleanConstant(is_this);
+    }
     case Variable::LOOKUP: {
       // Dynamic lookup of context variable (anywhere in the chain).
       Node* name = jsgraph()->Constant(variable->name());