Stack allocate lexical locals + hoist stack slots

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"
@@ skipping 353 matching lines @@
 
   // Move unresolved variables
   for (int i = 0; i < unresolved_.length(); i++) {
     outer_scope()->unresolved_.Add(unresolved_[i], zone());
   }
 
   // Propagate usage flags to outer scope.
   if (uses_arguments()) outer_scope_->RecordArgumentsUsage();
   if (uses_super_property()) outer_scope_->RecordSuperPropertyUsage();
   if (uses_this()) outer_scope_->RecordThisUsage();
+  if (scope_calls_eval_) outer_scope_->RecordEvalCall();
 
   return NULL;
 }
 
 
 Variable* Scope::LookupLocal(const AstRawString* name) {
   Variable* result = variables_.Lookup(name);
   if (result != NULL || scope_info_.is_null()) {
     return result;
   }
+  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.
-  Handle<String> name_handle = name->string();
   // 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);
+  DCHECK(scope_info_->StackSlotIndex(*name_handle) < 0 || is_block_scope());
 
   // Check context slot lookup.
   VariableMode mode;
   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);
   if (index < 0) {
     // Check parameters.
@@ skipping 296 matching lines @@
 bool Scope::HasLazyCompilableOuterContext() const {
   Scope* outer = outer_scope_;
   if (outer == NULL) return true;
   // We have to prevent lazy compilation if this scope is inside a with scope
   // and all declaration scopes between them have empty contexts. Such
   // declaration scopes may become invisible during scope info deserialization.
   outer = outer->DeclarationScope();
   bool found_non_trivial_declarations = false;
   for (const Scope* scope = outer; scope != NULL; scope = scope->outer_scope_) {
     if (scope->is_with_scope() && !found_non_trivial_declarations) return false;
+    if (scope->is_block_scope() && !scope->decls_.is_empty()) return false;
     if (scope->is_declaration_scope() && scope->num_heap_slots() > 0) {
       found_non_trivial_declarations = true;
     }
   }
   return true;
 }
 
 
 bool Scope::AllowsLazyCompilation() const {
   return !force_eager_compilation_ && HasLazyCompilableOuterContext();
@@ skipping 562 matching lines @@
   // an eval() call or a runtime with lookup), it must be allocated in the
   // context.
   //
   // Exceptions: If the scope as a whole has forced context allocation, all
   // variables will have context allocation, even temporaries.  Otherwise
   // temporary variables are always stack-allocated.  Catch-bound variables are
   // always context-allocated.
   if (has_forced_context_allocation()) return true;
   if (var->mode() == TEMPORARY) return false;
   if (var->mode() == INTERNAL) return true;
-  if (is_catch_scope() || is_block_scope() || is_module_scope()) return true;
+  if (is_catch_scope() || is_module_scope()) return true;
   if (is_script_scope() && IsLexicalVariableMode(var->mode())) return true;
   return var->has_forced_context_allocation() ||
       scope_calls_eval_ ||
       inner_scope_calls_eval_ ||
       scope_contains_with_;
 }
 
 
 bool Scope::HasArgumentsParameter(Isolate* isolate) {
   for (int i = 0; i < params_.length(); i++) {
     if (params_[i]->name().is_identical_to(
             isolate->factory()->arguments_string())) {
       return true;
     }
   }
   return false;
 }
 
 
 void Scope::AllocateStackSlot(Variable* var) {
-  var->AllocateTo(Variable::LOCAL, num_stack_slots_++);
+  if (is_block_scope()) {
+    auto decl_scope = DeclarationScope();

[rossberg, 2015/04/21 14:41:02]

Nit: inline into next line

[Dmitry Lomov (no reviews), 2015/04/22 12:24:30]

Done.

+    decl_scope->AllocateStackSlot(var);
+  } else {
+    var->AllocateTo(Variable::LOCAL, num_stack_slots_++);
+  }
 }
 
 
 void Scope::AllocateHeapSlot(Variable* var) {
   var->AllocateTo(Variable::CONTEXT, num_heap_slots_++);
 }
 
 
 void Scope::AllocateParameterLocals(Isolate* isolate) {
   DCHECK(is_function_scope());
@@ skipping 104 matching lines @@
     AllocateNonParameterLocal(isolate, function_->proxy()->var());
   }
 
   if (rest_parameter_) {
     AllocateNonParameterLocal(isolate, rest_parameter_);
   }
 }
 
 
 void Scope::AllocateVariablesRecursively(Isolate* isolate) {
+  if (!already_resolved()) {
+    num_stack_slots_ = 0;
+  }
   // Allocate variables for inner scopes.
   for (int i = 0; i < inner_scopes_.length(); i++) {
     inner_scopes_[i]->AllocateVariablesRecursively(isolate);
   }
 
   // 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_stack_slots_ = 0;
   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);
   AllocateNonParameterLocals(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.
@@ skipping 33 matching lines @@
       (function_ != NULL && function_->proxy()->var()->IsStackLocal() ? 1 : 0);
 }
 
 
 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