[Interpreter] Adds support for variable/function declarations in lookup slots.

src/interpreter/bytecode-generator.cc

 // Copyright 2015 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/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-register-allocator.h"
 #include "src/interpreter/control-flow-builders.h"
@@ skipping 427 matching lines @@
     } else {
       VisitDeclarations(stmt->scope()->declarations());
       VisitStatements(stmt->statements());
     }
   }
   if (stmt->labels() != nullptr) block_builder.EndBlock();
 }
 
 
 void BytecodeGenerator::VisitVariableDeclaration(VariableDeclaration* decl) {
+  RegisterAllocationScope register_scope(this);

[rmcilroy, 2016/01/15 14:17:20]

Instead of adding these, could you instead modify VisitDeclarations such that
you replace the line: AstVisitor::VisitDeclarations() with the following:

for (int i = 0; i < declarations->length(); i++) {
  RegisterAllocationScope register_scope(this);
  Visit(declarations->at(i));
}

Thanks.

[mythria, 2016/01/15 17:10:36]

Done.

+
   Variable* variable = decl->proxy()->var();
   VariableMode mode = decl->mode();
   // Const and let variables are initialized with the hole so that we can
   // check that they are only assigned once.
   bool hole_init = mode == CONST || mode == CONST_LEGACY || mode == LET;
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       Handle<Oddball> value = variable->binding_needs_init()
                                   ? isolate()->factory()->the_hole_value()
@@ skipping 15 matching lines @@
         Register destination(builder()->Parameter(variable->index() + 1));
         builder()->LoadTheHole().StoreAccumulatorInRegister(destination);
       }
       break;
     case VariableLocation::CONTEXT:
       if (hole_init) {
         builder()->LoadTheHole().StoreContextSlot(execution_context()->reg(),
                                                   variable->index());
       }
       break;
-    case VariableLocation::LOOKUP:
-      UNIMPLEMENTED();
+    case VariableLocation::LOOKUP: {
+      DCHECK(IsDeclaredVariableMode(mode));
+
+      register_allocator()->PrepareForConsecutiveAllocations(3);
+      Register name = register_allocator()->NextConsecutiveRegister();
+      Register init_value = register_allocator()->NextConsecutiveRegister();
+      Register attributes = register_allocator()->NextConsecutiveRegister();
+
+      builder()->LoadLiteral(variable->name()).StoreAccumulatorInRegister(name);
+      if (hole_init) {
+        builder()->LoadTheHole().StoreAccumulatorInRegister(init_value);
+      } else {
+        // For variables, we must not use an initial value (such as 'undefined')
+        // because we may have a (legal) redeclaration and we must not destroy
+        // the current value.
+        builder()
+            ->LoadLiteral(Smi::FromInt(0))
+            .StoreAccumulatorInRegister(init_value);
+      }
+      builder()
+          ->LoadLiteral(Smi::FromInt(variable->DeclarationPropertyAttributes()))
+          .StoreAccumulatorInRegister(attributes)
+          .CallRuntime(Runtime::kDeclareLookupSlot, name, 3);
       break;
+    }
   }
 }
 
 
 void BytecodeGenerator::VisitFunctionDeclaration(FunctionDeclaration* decl) {
+  RegisterAllocationScope register_scope(this);

[rmcilroy, 2016/01/15 14:17:20]

Also remove this once the above comment is done.

[mythria, 2016/01/15 17:10:36]

Done.

+
   Variable* variable = decl->proxy()->var();
   switch (variable->location()) {
     case VariableLocation::GLOBAL:
     case VariableLocation::UNALLOCATED: {
       Handle<SharedFunctionInfo> function = Compiler::GetSharedFunctionInfo(
           decl->fun(), info()->script(), info());
       // Check for stack-overflow exception.
       if (function.is_null()) return SetStackOverflow();
       globals()->push_back(variable->name());
       globals()->push_back(function);
       break;
     }
     case VariableLocation::PARAMETER:
     case VariableLocation::LOCAL: {
       VisitForAccumulatorValue(decl->fun());
       VisitVariableAssignment(variable, FeedbackVectorSlot::Invalid());
       break;
     }
     case VariableLocation::CONTEXT: {
       DCHECK_EQ(0, execution_context()->ContextChainDepth(variable->scope()));
       VisitForAccumulatorValue(decl->fun());
       builder()->StoreContextSlot(execution_context()->reg(),
                                   variable->index());
       break;
     }
-    case VariableLocation::LOOKUP:
-      UNIMPLEMENTED();
+    case VariableLocation::LOOKUP: {
+      register_allocator()->PrepareForConsecutiveAllocations(3);
+      Register name = register_allocator()->NextConsecutiveRegister();
+      Register literal = register_allocator()->NextConsecutiveRegister();
+      Register attributes = register_allocator()->NextConsecutiveRegister();
+      builder()->LoadLiteral(variable->name()).StoreAccumulatorInRegister(name);
+
+      VisitForAccumulatorValue(decl->fun());
+      builder()
+          ->StoreAccumulatorInRegister(literal)
+          .LoadLiteral(Smi::FromInt(variable->DeclarationPropertyAttributes()))
+          .StoreAccumulatorInRegister(attributes)
+          .CallRuntime(Runtime::kDeclareLookupSlot, name, 3);
+    }
   }
 }
 
 
 void BytecodeGenerator::VisitImportDeclaration(ImportDeclaration* decl) {
   UNIMPLEMENTED();
 }
 
 
 void BytecodeGenerator::VisitExportDeclaration(ExportDeclaration* decl) {
@@ skipping 784 matching lines @@
           builder()
               ->LoadContextSlot(context_reg, Context::PREVIOUS_INDEX)
               .StoreAccumulatorInRegister(context_reg);
         }
         builder()->LoadAccumulatorWithRegister(value_temp);
       }
       builder()->StoreContextSlot(context_reg, variable->index());
       break;
     }
     case VariableLocation::LOOKUP: {
+      // TODO(mythria): Use Runtime::kInitializeLegacyConstLookupSlot for
+      // initializations of const declarations.
       builder()->StoreLookupSlot(variable->name(), language_mode());
       break;
     }
   }
 }
 
 
 void BytecodeGenerator::VisitAssignment(Assignment* expr) {
   DCHECK(expr->target()->IsValidReferenceExpression());
   Register object, key;
@@ skipping 220 matching lines @@
       if (callee_expr->AsVariableProxy()->var()->IsLookupSlot()) {
         RegisterAllocationScope inner_register_scope(this);
         register_allocator()->PrepareForConsecutiveAllocations(2);
         Register context = register_allocator()->NextConsecutiveRegister();
         Register name = register_allocator()->NextConsecutiveRegister();
 
         // Call LoadLookupSlot to get the callee and receiver.
         DCHECK(Register::AreContiguous(callee, receiver));
         Variable* variable = callee_expr->AsVariableProxy()->var();
         builder()
-            ->MoveRegister(Register::function_context(), context)
+            ->MoveRegister(execution_context()->reg(), context)
             .LoadLiteral(variable->name())
             .StoreAccumulatorInRegister(name)
             .CallRuntimeForPair(Runtime::kLoadLookupSlot, context, 2, callee);
         break;
       }
       // Fall through.
       DCHECK_EQ(call_type, Call::POSSIBLY_EVAL_CALL);
     }
     case Call::OTHER_CALL: {
       builder()->LoadUndefined().StoreAccumulatorInRegister(receiver);
@@ skipping 600 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8