First step in letting Crankshaft inline functions with a different context.

Use a special slot for HContext, and fetch the value from there each time it is used.  Allocate space for special slots in every HEnvironment.  Fill them with constant undefined.  Do not copy them to LEnvironment.

BUG=
TEST=

Review URL: http://codereview.chromium.org/6929066

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7807 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1015,6 +1015,8 @@ LEnvironment* LChunkBuilder::CreateEnvironment(HEnvironment* hydrogen_env) {
                                           outer);
   int argument_index = 0;
   for (int i = 0; i < value_count; ++i) {
+    if (hydrogen_env->is_special_index(i)) continue;
+
     HValue* value = hydrogen_env->values()->at(i);
     LOperand* op = NULL;
     if (value->IsArgumentsObject()) {

src/hydrogen-instructions.h

@@ -3311,7 +3311,7 @@ class HLoadKeyedSpecializedArrayElement: public HBinaryOperation {
 
 class HLoadKeyedGeneric: public HTemplateInstruction<3> {
  public:
-  HLoadKeyedGeneric(HContext* context, HValue* obj, HValue* key) {
+  HLoadKeyedGeneric(HValue* context, HValue* obj, HValue* key) {
     set_representation(Representation::Tagged());
     SetOperandAt(0, obj);
     SetOperandAt(1, key);

src/hydrogen.h

@@ -322,6 +322,7 @@ class HEnvironment: public ZoneObject {
     return &assigned_variables_;
   }
   int parameter_count() const { return parameter_count_; }
+  int specials_count() const { return specials_count_; }
   int local_count() const { return local_count_; }
   HEnvironment* outer() const { return outer_; }
   int pop_count() const { return pop_count_; }
@@ -331,6 +332,9 @@ class HEnvironment: public ZoneObject {
   void set_ast_id(int id) { ast_id_ = id; }
 
   int length() const { return values_.length(); }
+  bool is_special_index(int i) const {
+    return i >= parameter_count() && i < parameter_count() + specials_count();
+  }
 
   void Bind(Variable* variable, HValue* value) {
     Bind(IndexFor(variable), value);
@@ -338,6 +342,10 @@ class HEnvironment: public ZoneObject {
 
   void Bind(int index, HValue* value);
 
+  void BindContext(HValue* value) {
+    Bind(parameter_count(), value);
+  }
+
   HValue* Lookup(Variable* variable) const {
     return Lookup(IndexFor(variable));
   }
@@ -348,6 +356,11 @@ class HEnvironment: public ZoneObject {
     return result;
   }
 
+  HValue* LookupContext() const {
+    // Return first special.
+    return Lookup(parameter_count());
+  }
+
   void Push(HValue* value) {
     ASSERT(value != NULL);
     ++push_count_;
@@ -368,6 +381,8 @@ class HEnvironment: public ZoneObject {
 
   HValue* Top() const { return ExpressionStackAt(0); }
 
+  bool ExpressionStackIsEmpty() const;
+
   HValue* ExpressionStackAt(int index_from_top) const {
     int index = length() - index_from_top - 1;
     ASSERT(HasExpressionAt(index));
@@ -412,8 +427,6 @@ class HEnvironment: public ZoneObject {
   // True if index is included in the expression stack part of the environment.
   bool HasExpressionAt(int index) const;
 
-  bool ExpressionStackIsEmpty() const;
-
   void Initialize(int parameter_count, int local_count, int stack_height);
   void Initialize(const HEnvironment* other);
 
@@ -423,15 +436,18 @@ class HEnvironment: public ZoneObject {
   int IndexFor(Variable* variable) const {
     Slot* slot = variable->AsSlot();
     ASSERT(slot != NULL && slot->IsStackAllocated());
-    int shift = (slot->type() == Slot::PARAMETER) ? 1 : parameter_count_;
+    int shift = (slot->type() == Slot::PARAMETER)
+        ? 1
+        : parameter_count_ + specials_count_;
     return slot->index() + shift;
   }
 
   Handle<JSFunction> closure_;
-  // Value array [parameters] [locals] [temporaries].
+  // Value array [parameters] [specials] [locals] [temporaries].
   ZoneList<HValue*> values_;
   ZoneList<int> assigned_variables_;
   int parameter_count_;
+  int specials_count_;
   int local_count_;
   HEnvironment* outer_;
   int pop_count_;

src/ia32/lithium-ia32.cc

@@ -1010,6 +1010,8 @@ LEnvironment* LChunkBuilder::CreateEnvironment(HEnvironment* hydrogen_env) {
                                           outer);
   int argument_index = 0;
   for (int i = 0; i < value_count; ++i) {
+    if (hydrogen_env->is_special_index(i)) continue;
+
     HValue* value = hydrogen_env->values()->at(i);
     LOperand* op = NULL;
     if (value->IsArgumentsObject()) {

src/x64/lithium-x64.cc

@@ -1010,6 +1010,8 @@ LEnvironment* LChunkBuilder::CreateEnvironment(HEnvironment* hydrogen_env) {
                                           outer);
   int argument_index = 0;
   for (int i = 0; i < value_count; ++i) {
+    if (hydrogen_env->is_special_index(i)) continue;
+
     HValue* value = hydrogen_env->values()->at(i);
     LOperand* op = NULL;
     if (value->IsArgumentsObject()) {