Support for global var shortcuts in script contexts.

src/scopes.cc

 // Copyright 2012 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/v8.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
 #include "src/scopeinfo.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
 
+// TODO(ishell): remove this once compiler support is landed.
+bool enable_context_globals = false;
+
 // ----------------------------------------------------------------------------
 // Implementation of LocalsMap
 //
 // Note: We are storing the handle locations as key values in the hash map.
 //       When inserting a new variable via Declare(), we rely on the fact that
 //       the handle location remains alive for the duration of that variable
 //       use. Because a Variable holding a handle with the same location exists
 //       this is ensured.
 
 VariableMap::VariableMap(Zone* zone)
@@ skipping 145 matching lines @@
   language_mode_ = outer_scope != NULL ? outer_scope->language_mode_ : SLOPPY;
   outer_scope_calls_sloppy_eval_ = false;
   inner_scope_calls_eval_ = false;
   inner_scope_uses_arguments_ = false;
   force_eager_compilation_ = false;
   force_context_allocation_ = (outer_scope != NULL && !is_function_scope())
       ? outer_scope->has_forced_context_allocation() : false;
   num_var_or_const_ = 0;
   num_stack_slots_ = 0;
   num_heap_slots_ = 0;
+  num_global_slots_ = 0;
   num_modules_ = 0;
   module_var_ = NULL,
   rest_parameter_ = NULL;
   rest_index_ = -1;
   scope_info_ = scope_info;
   start_position_ = RelocInfo::kNoPosition;
   end_position_ = RelocInfo::kNoPosition;
   if (!scope_info.is_null()) {
     scope_calls_eval_ = scope_info->CallsEval();
     language_mode_ = scope_info->language_mode();
@@ skipping 191 matching lines @@
   Handle<String> name_handle = name->string();
   // The Scope is backed up by ScopeInfo. This means it cannot operate in a
   // heap-independent mode, and all strings must be internalized immediately. So
   // it's ok to get the Handle<String> here.
   // If we have a serialized scope info, we might find the variable there.
   // There should be no local slot with the given name.
   DCHECK(scope_info_->StackSlotIndex(*name_handle) < 0 || is_block_scope());
 
   // Check context slot lookup.
   VariableMode mode;
+  ContextSlotKindFlag slot_kind;
   Variable::Location location = Variable::CONTEXT;
   InitializationFlag init_flag;
   MaybeAssignedFlag maybe_assigned_flag;
-  int index = ScopeInfo::ContextSlotIndex(scope_info_, name_handle, &mode,
-                                          &init_flag, &maybe_assigned_flag);
+  int index =
+      ScopeInfo::ContextSlotIndex(scope_info_, name_handle, &mode, &slot_kind,
+                                  &init_flag, &maybe_assigned_flag);
   if (index < 0) {
     // Check parameters.
     index = scope_info_->ParameterIndex(*name_handle);
     if (index < 0) return NULL;
 
     mode = DYNAMIC;
     location = Variable::LOOKUP;
     init_flag = kCreatedInitialized;
     // Be conservative and flag parameters as maybe assigned. Better information
     // would require ScopeInfo to serialize the maybe_assigned bit also for
     // parameters.
     maybe_assigned_flag = kMaybeAssigned;
+
+  } else if (slot_kind == ContextSlotKindFlag::kGlobal) {
+    DCHECK(is_script_scope());
+    DCHECK(IsDeclaredVariableMode(mode) && !IsLexicalVariableMode(mode));
+    location = Variable::UNALLOCATED;
   }
 
   Variable::Kind kind = Variable::NORMAL;
   if (location == Variable::CONTEXT &&
       index == scope_info_->ReceiverContextSlotIndex()) {
     kind = Variable::THIS;
   }
   // TODO(marja, rossberg): Correctly declare FUNCTION, CLASS, NEW_TARGET, and
   // ARGUMENTS bindings as their corresponding Variable::Kind.
 
@@ skipping 178 matching lines @@
   }
 
  private:
   Variable* var_;
   int order_;
 };
 
 
 void Scope::CollectStackAndContextLocals(
     ZoneList<Variable*>* stack_locals, ZoneList<Variable*>* context_locals,
+    ZoneList<Variable*>* context_globals,
     ZoneList<Variable*>* strong_mode_free_variables) {
   DCHECK(stack_locals != NULL);
   DCHECK(context_locals != NULL);
+  DCHECK(context_globals != NULL);
 
   // Collect internals which are always allocated on the heap.
   for (int i = 0; i < internals_.length(); i++) {
     Variable* var = internals_[i];
     if (var->is_used()) {
       DCHECK(var->IsContextSlot());
       context_locals->Add(var, zone());
     }
   }
 
@@ skipping 28 matching lines @@
     }
   }
   vars.Sort(VarAndOrder::Compare);
   int var_count = vars.length();
   for (int i = 0; i < var_count; i++) {
     Variable* var = vars[i].var();
     if (var->IsStackLocal()) {
       stack_locals->Add(var, zone());
     } else if (var->IsContextSlot()) {
       context_locals->Add(var, zone());
+    } else if (enable_context_globals && var->IsStaticGlobalObjectProperty()) {
+      context_globals->Add(var, zone());
     }
   }
 }
 
 
 bool Scope::AllocateVariables(ParseInfo* info, AstNodeFactory* factory) {
   // 1) Propagate scope information.
   bool outer_scope_calls_sloppy_eval = false;
   if (outer_scope_ != NULL) {
     outer_scope_calls_sloppy_eval =
@@ skipping 19 matching lines @@
 
 
 bool Scope::HasTrivialContext() const {
   // A function scope has a trivial context if it always is the global
   // context. We iteratively scan out the context chain to see if
   // there is anything that makes this scope non-trivial; otherwise we
   // return true.
   for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) {
     if (scope->is_eval_scope()) return false;
     if (scope->scope_inside_with_) return false;
-    if (scope->num_heap_slots_ > 0) return false;
+    if (scope->ContextLocalCount() > 0) return false;
   }
   return true;
 }
 
 
 bool Scope::HasTrivialOuterContext() const {
   Scope* outer = outer_scope_;
   if (outer == NULL) return true;
   // Note that the outer context may be trivial in general, but the current
   // scope may be inside a 'with' statement in which case the outer context
@@ skipping 115 matching lines @@
 
 
 static void PrintName(const AstRawString* name) {
   PrintF("%.*s", name->length(), name->raw_data());
 }
 
 
 static void PrintLocation(Variable* var) {
   switch (var->location()) {
     case Variable::UNALLOCATED:
+      if (var->IsStaticGlobalObjectProperty()) {
+        PrintF("global[%d]", var->index());
+      }
       break;
     case Variable::PARAMETER:
       PrintF("parameter[%d]", var->index());
       break;
     case Variable::LOCAL:
       PrintF("local[%d]", var->index());
       break;
     case Variable::CONTEXT:
       PrintF("context[%d]", var->index());
       break;
     case Variable::LOOKUP:
       PrintF("lookup");
       break;
   }
 }
 
 
 static void PrintVar(int indent, Variable* var) {
-  if (var->is_used() || !var->IsUnallocated()) {
+  if (var->is_used() || !var->IsUnallocated() ||
+      var->IsStaticGlobalObjectProperty()) {
     Indent(indent, Variable::Mode2String(var->mode()));
     PrintF(" ");
     PrintName(var->raw_name());
     PrintF(";  // ");
     PrintLocation(var);
-    bool comma = !var->IsUnallocated();
+    bool comma = !var->IsUnallocated() || var->IsStaticGlobalObjectProperty();
     if (var->has_forced_context_allocation()) {
       if (comma) PrintF(", ");
       PrintF("forced context allocation");
       comma = true;
     }
     if (var->maybe_assigned() == kMaybeAssigned) {
       if (comma) PrintF(", ");
       PrintF("maybe assigned");
     }
     PrintF("\n");
   }
 }
 
 
 static void PrintMap(int indent, VariableMap* map) {
   for (VariableMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
     Variable* var = reinterpret_cast<Variable*>(p->value);
-    PrintVar(indent, var);
+    if (var == NULL) {
+      Indent(indent, "<?>\n");
+    } else {
+      PrintVar(indent, var);
+    }
   }
 }
 
 
 void Scope::Print(int n) {
   int n0 = (n > 0 ? n : 0);
   int n1 = n0 + 2;  // indentation
 
   // Print header.
   Indent(n0, Header(scope_type_));
@@ skipping 36 matching lines @@
   if (scope_uses_arguments_) Indent(n1, "// scope uses 'arguments'\n");
   if (scope_uses_super_property_)
     Indent(n1, "// scope uses 'super' property\n");
   if (inner_scope_uses_arguments_) {
     Indent(n1, "// inner scope uses 'arguments'\n");
   }
   if (outer_scope_calls_sloppy_eval_) {
     Indent(n1, "// outer scope calls 'eval' in sloppy context\n");
   }
   if (inner_scope_calls_eval_) Indent(n1, "// inner scope calls 'eval'\n");
-  if (num_stack_slots_ > 0) { Indent(n1, "// ");
-  PrintF("%d stack slots\n", num_stack_slots_); }
-  if (num_heap_slots_ > 0) { Indent(n1, "// ");
-  PrintF("%d heap slots\n", num_heap_slots_); }
+  if (num_stack_slots_ > 0) {
+    Indent(n1, "// ");
+    PrintF("%d stack slots\n", num_stack_slots_);
+  }
+  if (num_heap_slots_ > 0) {
+    Indent(n1, "// ");
+    PrintF("%d heap slots (including %d global slots)\n", num_heap_slots_,
+           num_global_slots_);
+  }
 
   // Print locals.
   if (function_ != NULL) {
     Indent(n1, "// function var:\n");
     PrintVar(n1, function_->proxy()->var());
   }
 
   if (temps_.length() > 0) {
     Indent(n1, "// temporary vars:\n");
     for (int i = 0; i < temps_.length(); i++) {
@@ skipping 466 matching lines @@
       DCHECK(var->IsUnallocated() || var->IsContextSlot());
       if (var->IsUnallocated()) {
         AllocateHeapSlot(var);
       }
     } else {
       DCHECK(var->IsUnallocated() || var->IsParameter());
       if (var->IsUnallocated()) {
         var->AllocateTo(Variable::PARAMETER, index);
       }
     }
+  } else {
+    DCHECK(!var->IsStaticGlobalObjectProperty());
   }
 }
 
 
 void Scope::AllocateReceiver() {
   DCHECK_NOT_NULL(receiver());
   DCHECK_EQ(receiver()->scope(), this);
 
   if (has_forced_context_allocation()) {
     // Force context allocation of the receiver.
@@ skipping 10 matching lines @@
   if (var->IsUnallocated() && MustAllocate(var)) {
     if (MustAllocateInContext(var)) {
       AllocateHeapSlot(var);
     } else {
       AllocateStackSlot(var);
     }
   }
 }
 
 
-void Scope::AllocateNonParameterLocals(Isolate* isolate) {
+void Scope::AllocateDeclaredGlobal(Isolate* isolate, Variable* var) {
+  DCHECK(var->scope() == this);
+  DCHECK(!var->IsVariable(isolate->factory()->dot_result_string()) ||
+         !var->IsStackLocal());
+  if (var->IsUnallocated() && var->IsStaticGlobalObjectProperty()) {
+    DCHECK_EQ(-1, var->index());
+    DCHECK(var->name()->IsString());
+    var->AllocateTo(Variable::UNALLOCATED, num_heap_slots_);
+    num_global_slots_++;
+    // Each global variable occupies two slots in the context: for reads
+    // and writes.
+    num_heap_slots_ += 2;
+  }
+}
+
+
+void Scope::AllocateNonParameterLocalsAndDeclaredGlobals(Isolate* isolate) {
   // All variables that have no rewrite yet are non-parameter locals.
   for (int i = 0; i < temps_.length(); i++) {
     AllocateNonParameterLocal(isolate, temps_[i]);
   }
 
   for (int i = 0; i < internals_.length(); i++) {
     AllocateNonParameterLocal(isolate, internals_[i]);
   }
 
   ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());
   for (VariableMap::Entry* p = variables_.Start();
        p != NULL;
        p = variables_.Next(p)) {
     Variable* var = reinterpret_cast<Variable*>(p->value);
     vars.Add(VarAndOrder(var, p->order), zone());
   }
   vars.Sort(VarAndOrder::Compare);
   int var_count = vars.length();
   for (int i = 0; i < var_count; i++) {
     AllocateNonParameterLocal(isolate, vars[i].var());
   }
 
+  if (enable_context_globals) {
+    for (int i = 0; i < var_count; i++) {
+      AllocateDeclaredGlobal(isolate, vars[i].var());
+    }
+  }
+
   // For now, function_ must be allocated at the very end.  If it gets
   // allocated in the context, it must be the last slot in the context,
   // because of the current ScopeInfo implementation (see
   // ScopeInfo::ScopeInfo(FunctionScope* scope) constructor).
   if (function_ != nullptr) {
     AllocateNonParameterLocal(isolate, function_->proxy()->var());
   }
 
   if (rest_parameter_ != nullptr) {
     AllocateNonParameterLocal(isolate, rest_parameter_);
@@ skipping 25 matching lines @@
   // If scope is already resolved, we still need to allocate
   // variables in inner scopes which might not had been resolved yet.
   if (already_resolved()) return;
   // The number of slots required for variables.
   num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
 
   // Allocate variables for this scope.
   // Parameters must be allocated first, if any.
   if (is_function_scope()) AllocateParameterLocals(isolate);
   if (has_this_declaration()) AllocateReceiver();
-  AllocateNonParameterLocals(isolate);
+  AllocateNonParameterLocalsAndDeclaredGlobals(isolate);
 
   // Force allocation of a context for this scope if necessary. For a 'with'
   // scope and for a function scope that makes an 'eval' call we need a context,
   // even if no local variables were statically allocated in the scope.
   // Likewise for modules.
   bool must_have_context = is_with_scope() || is_module_scope() ||
                            (is_function_scope() && calls_sloppy_eval());
 
   // If we didn't allocate any locals in the local context, then we only
   // need the minimal number of slots if we must have a context.
@@ skipping 23 matching lines @@
 
 
 int Scope::StackLocalCount() const {
   return num_stack_slots() -
       (function_ != NULL && function_->proxy()->var()->IsStackLocal() ? 1 : 0);
 }
 
 
 int Scope::ContextLocalCount() const {
   if (num_heap_slots() == 0) return 0;
+  bool is_function_var_in_context =
+      function_ != NULL && function_->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
-      (function_ != NULL && function_->proxy()->var()->IsContextSlot() ? 1 : 0);
+         2 * num_global_slots() - (is_function_var_in_context ? 1 : 0);
 }
+
+
+int Scope::ContextGlobalCount() const { return num_global_slots(); }
 }  // namespace internal
 }  // namespace v8