Track usage of "this" and "arguments" in Scope

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/scopes.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
@@ skipping 142 matching lines @@
   scope_type_ = scope_type;
   scope_name_ = ast_value_factory_->empty_string();
   dynamics_ = NULL;
   receiver_ = NULL;
   function_ = NULL;
   arguments_ = NULL;
   illegal_redecl_ = NULL;
   scope_inside_with_ = false;
   scope_contains_with_ = false;
   scope_calls_eval_ = false;
+  scope_uses_this_ = false;
+  scope_uses_arguments_ = false;
   // Inherit the strict mode from the parent scope.
   strict_mode_ = outer_scope != NULL ? outer_scope->strict_mode_ : SLOPPY;
   outer_scope_calls_sloppy_eval_ = false;
   inner_scope_calls_eval_ = false;
+  inner_scope_uses_this_ = 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_modules_ = 0;
   module_var_ = NULL,
   scope_info_ = scope_info;
   start_position_ = RelocInfo::kNoPosition;
@@ skipping 697 matching lines @@
   // Scope info.
   if (HasTrivialOuterContext()) {
     Indent(n1, "// scope has trivial outer context\n");
   }
   if (strict_mode() == STRICT) {
     Indent(n1, "// strict mode scope\n");
   }
   if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");
   if (scope_contains_with_) Indent(n1, "// scope contains 'with'\n");
   if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n");
+  if (scope_uses_this_) Indent(n1, "// scope uses 'this'\n");
+  if (scope_uses_arguments_) Indent(n1, "// scope uses 'arguments'\n");
+  if (inner_scope_uses_this_) Indent(n1, "// inner scope uses 'this'\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_); }
 
   // Print locals.
@@ skipping 261 matching lines @@
   }
 
   bool calls_sloppy_eval =
       this->calls_sloppy_eval() || outer_scope_calls_sloppy_eval_;
   for (int i = 0; i < inner_scopes_.length(); i++) {
     Scope* inner = inner_scopes_[i];
     inner->PropagateScopeInfo(calls_sloppy_eval);
     if (inner->scope_calls_eval_ || inner->inner_scope_calls_eval_) {
       inner_scope_calls_eval_ = true;
     }
+    if (inner->scope_uses_this_ || inner->inner_scope_uses_this_) {

[rossberg, 2014/09/10 06:33:56]

If inner is a function scope and not an arrow function, then both new flags must
not be propagated.

+      inner_scope_uses_this_ = true;
+    }
+    if (inner->scope_uses_arguments_ || inner->inner_scope_uses_arguments_) {
+      inner_scope_uses_arguments_ = true;
+    }
     if (inner->force_eager_compilation_) {
       force_eager_compilation_ = true;
     }
   }
 }
 
 
 bool Scope::MustAllocate(Variable* var) {
   // Give var a read/write use if there is a chance it might be accessed
   // via an eval() call.  This is only possible if the variable has a
@@ skipping 220 matching lines @@
 }
 
 
 int Scope::ContextLocalCount() const {
   if (num_heap_slots() == 0) return 0;
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
       (function_ != NULL && function_->proxy()->var()->IsContextSlot() ? 1 : 0);
 }
 
 } }  // namespace v8::internal