Resolve references to "this" the same way as normal variables

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 6828b5b0a86c7bb3e85ae2745c12401a1f5cc812..bf12869a93cb38f5eef583d080c029cccfa98d7f 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -468,9 +468,11 @@ bool AstGraphBuilder::CreateGraph(bool constant_context, bool stack_check) {
 
   // Build receiver check for sloppy mode if necessary.
   // TODO(mstarzinger/verwaest): Should this be moved back into the CallIC?
-  Node* original_receiver = env.Lookup(scope->receiver());
-  Node* patched_receiver = BuildPatchReceiverToGlobalProxy(original_receiver);
-  env.Bind(scope->receiver(), patched_receiver);
+  if (scope->has_this_declaration()) {
+    Node* original_receiver = env.Lookup(scope->receiver());
+    Node* patched_receiver = BuildPatchReceiverToGlobalProxy(original_receiver);
+    env.Bind(scope->receiver(), patched_receiver);
+  }
 
   // Build function context only if there are context allocated variables.
   int heap_slots = info()->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;
@@ -639,6 +641,13 @@ AstGraphBuilder::Environment::Environment(AstGraphBuilder::Environment* copy)
 
 
 void AstGraphBuilder::Environment::Bind(Variable* variable, Node* node) {
+  // "this" may be context-allocated, but it's possible for us to look it up and
+  // patch it on the stack before it has been hoisted to the context.
+  if (variable->is_this()) {

[Michael Starzinger, 2015/04/21 18:13:44]

AFAICT, this is only needed for patching the receiver to the global proxy in the
method prologue. Please don't "extend" Environment::Bind this way, but rather
adapt BuildPatchReceiverToGlobalProxy accordingly.

[wingo, 2015/04/22 08:04:00]

I had tried to do that, but I couldn't get at environment->values()->at(0), as
it's private.  I realize this is an awful hack and something different should go
in :)  I guess common()->Parameter(0) is the thing to use, then?

[Michael Starzinger, 2015/04/22 10:59:21]

Yes, I think for patching purposes Parameter(0) is always correct.

+    values()->at(0) = node;
+    return;
+  }
+
   DCHECK(variable->IsStackAllocated());
   if (variable->IsParameter()) {
     // The parameter indices are shifted by 1 (receiver is parameter
@@ -655,6 +664,12 @@ void AstGraphBuilder::Environment::Bind(Variable* variable, Node* node) {
 
 
 Node* AstGraphBuilder::Environment::Lookup(Variable* variable) {
+  // "this" may be context-allocated, but it's possible for us to look it up and
+  // patch it on the stack before it has been hoisted to the context.
+  if (variable->is_this()) {

[Michael Starzinger, 2015/04/21 18:13:44]

Likewise.

[wingo, 2015/04/22 08:04:00]

Acknowledged.

+    return values()->at(0);
+  }
+
   DCHECK(variable->IsStackAllocated());
   if (variable->IsParameter()) {
     // The parameter indices are shifted by 1 (receiver is parameter
@@ -2148,7 +2163,7 @@ 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();
-    Node* receiver = environment()->Lookup(info()->scope()->receiver());
+    Node* receiver = environment()->Lookup(info()->scope()->LookupThis());
     Node* language = jsgraph()->Constant(language_mode());
     Node* position = jsgraph()->Constant(info()->scope()->start_position());
     const Operator* op =
@@ -2651,8 +2666,10 @@ Node* AstGraphBuilder::BuildLocalFunctionContext(Node* context) {
 
   // Copy parameters into context if necessary.
   int num_parameters = info()->scope()->num_parameters();
-  for (int i = 0; i < num_parameters; i++) {
-    Variable* variable = info()->scope()->parameter(i);
+  int first_parameter = info()->scope()->has_this_declaration() ? -1 : 0;
+  for (int i = first_parameter; i < num_parameters; i++) {
+    Variable* variable =
+        (i == -1) ? info()->scope()->receiver() : info()->scope()->parameter(i);

[Michael Starzinger, 2015/04/21 18:13:44]

This is getting out of hand, please hoist handling of the receiver out into a
separate block (preferably placed at line 2666 above) and rather duplicate
creation of the StoreContext node below.

     if (!variable->IsContextSlot()) continue;
     // Temporary parameter node. The parameter indices are shifted by 1
     // (receiver is parameter index -1 but environment index 0).