[modules] Basic support of exports

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/code-stubs.h"
 #include "src/compilation-info.h"
 #include "src/compiler.h"
@@ skipping 725 matching lines @@
   // Initialize control scope.
   ControlScopeForTopLevel control(this);
 
   RegisterAllocationScope register_scope(this);
 
   if (IsResumableFunction(info()->literal()->kind())) {
     generator_state_ = register_allocator()->NewRegister();
     VisitGeneratorPrologue();
   }
 
-  // Build function context only if there are context allocated variables.

[neis, 2016/09/02 12:06:07]

This comment was not quite right: a scope may not have any context-allocated
variables but still require a context.

   if (scope()->NeedsContext()) {
     // Push a new inner context scope for the function.
     VisitNewLocalFunctionContext();

[neis, 2016/09/02 12:06:07]

I'm not happy with this name, as it can also create a ScriptContext and (now) a
ModuleContext, not just a FunctionContext. Any suggestions?

[adamk, 2016/09/02 17:51:51]

BuildNewContext?

[rmcilroy, 2016/09/05 11:36:07]

Could we do a rename pass on all the context creation functions to make them
consistent. How about:
 
 VisitNewLocalFunctionContext -> BuildNewLocalActivationContext
 VisitBuildLocalActivationContext -> BuildLocalActivationContextInitialization
 VisitNewLocalBlockContext -> BuildNewLocalBlockContext
 VisitNewLocalWithContext -> BuildNewLocalCatchContext
 VisitNewLocalCatchContext -> BuildNewLocalCatchContext

     ContextScope local_function_context(this, scope(), false);
     VisitBuildLocalActivationContext();
     GenerateBytecodeBody();
   } else {
     GenerateBytecodeBody();
   }
 
   // In generator functions, we may not have visited every yield in the AST
   // since we skip some obviously dead code. Hence the generated bytecode may
   // contain jumps to unbound labels (resume points that will never be used).
@@ skipping 173 matching lines @@
 
       Register name = register_allocator()->NewRegister();
 
       builder()
           ->LoadLiteral(variable->name())
           .StoreAccumulatorInRegister(name)
           .CallRuntime(Runtime::kDeclareEvalVar, name, 1);
       break;
     }
     case VariableLocation::MODULE:
-      UNREACHABLE();
+      // Nothing to do here.
+      break;
   }
 }
 
 void BytecodeGenerator::VisitFunctionDeclaration(FunctionDeclaration* decl) {
   Variable* variable = decl->proxy()->var();
   switch (variable->location()) {
     case VariableLocation::UNALLOCATED: {
       FeedbackVectorSlot slot = decl->proxy()->VariableFeedbackSlot();
       globals_builder()->AddFunctionDeclaration(slot, decl->fun());
       break;
@@ skipping 19 matching lines @@
       Register name = register_allocator()->NextConsecutiveRegister();
       Register literal = register_allocator()->NextConsecutiveRegister();
       builder()->LoadLiteral(variable->name()).StoreAccumulatorInRegister(name);
 
       VisitForAccumulatorValue(decl->fun());
       builder()->StoreAccumulatorInRegister(literal).CallRuntime(
           Runtime::kDeclareEvalFunction, name, 2);
       break;
     }
     case VariableLocation::MODULE:
-      UNREACHABLE();
+      DCHECK(variable->mode() == LET);
+      VisitForAccumulatorValue(decl->fun());
+      VisitVariableAssignment(variable, Token::INIT,
+                              FeedbackVectorSlot::Invalid());
+      break;
   }
 }
 
 void BytecodeGenerator::VisitDeclarations(
     ZoneList<Declaration*>* declarations) {
   RegisterAllocationScope register_scope(this);
   DCHECK(globals_builder()->empty());
   for (int i = 0; i < declarations->length(); i++) {
     RegisterAllocationScope register_scope(this);
     Visit(declarations->at(i));
@@ skipping 985 matching lines @@
       }
 
       builder()->LoadContextSlot(context_reg, variable->index());
       BuildHoleCheckForVariableLoad(variable);
       break;
     }
     case VariableLocation::LOOKUP: {
       builder()->LoadLookupSlot(variable->name(), typeof_mode);
       break;
     }
-    case VariableLocation::MODULE:
-      UNREACHABLE();
+    case VariableLocation::MODULE: {
+      ModuleDescriptor* descriptor = scope()->GetModuleScope()->module();
+      if (variable->IsExport()) {
+        auto it = descriptor->regular_exports().find(variable->raw_name());
+        DCHECK(it != descriptor->regular_exports().end());
+        Register export_name = register_allocator()->NewRegister();
+        builder()
+            ->LoadLiteral(it->second->export_name->string())
+            .StoreAccumulatorInRegister(export_name)
+            .CallRuntime(Runtime::kLoadModuleExport, export_name, 1);
+      } else {
+        UNIMPLEMENTED();
+      }
+      break;
+    }
   }
   execution_result()->SetResultInAccumulator();
 }
 
 void BytecodeGenerator::VisitVariableLoadForAccumulatorValue(
     Variable* variable, FeedbackVectorSlot slot, TypeofMode typeof_mode) {
   AccumulatorResultScope accumulator_result(this);
   VisitVariableLoad(variable, slot, typeof_mode);
 }
 
@@ skipping 177 matching lines @@
         builder()->StoreContextSlot(context_reg, variable->index());
       } else if (variable->throw_on_const_assignment(language_mode())) {
         builder()->CallRuntime(Runtime::kThrowConstAssignError, Register(), 0);
       }
       break;
     }
     case VariableLocation::LOOKUP: {
       builder()->StoreLookupSlot(variable->name(), language_mode());
       break;
     }
-    case VariableLocation::MODULE:
-      UNREACHABLE();
+    case VariableLocation::MODULE: {
+      DCHECK(IsDeclaredVariableMode(mode));
+
+      if (mode == CONST && op != Token::INIT) {
+        builder()->CallRuntime(Runtime::kThrowConstAssignError, Register(), 0);
+        break;
+      }
+
+      // If we don't throw above, we know that we're dealing with an
+      // export because imports are const and we do not generate initializing
+      // assignments for them.
+      DCHECK(variable->IsExport());
+
+      ModuleDescriptor* mod = scope()->GetModuleScope()->module();
+      auto it = mod->regular_exports().find(variable->raw_name());
+      DCHECK(it != mod->regular_exports().end());
+
+      register_allocator()->PrepareForConsecutiveAllocations(2);
+      Register export_name = register_allocator()->NextConsecutiveRegister();
+      Register value = register_allocator()->NextConsecutiveRegister();
+      builder()
+          ->StoreAccumulatorInRegister(value)
+          .LoadLiteral(it->second->export_name->string())
+          .StoreAccumulatorInRegister(export_name)
+          .CallRuntime(Runtime::kStoreModuleExport, export_name, 2);
+      break;
+    }
   }
 }
 
 void BytecodeGenerator::VisitAssignment(Assignment* expr) {
   DCHECK(expr->target()->IsValidReferenceExpressionOrThis());
   Register object, key, home_object, value;
   Handle<String> name;
 
   // Left-hand side can only be a property, a global or a variable slot.
   Property* property = expr->target()->AsProperty();
@@ skipping 936 matching lines @@
 }
 
 void BytecodeGenerator::VisitRewritableExpression(RewritableExpression* expr) {
   Visit(expr->expression());
 }
 
 void BytecodeGenerator::VisitNewLocalFunctionContext() {
   AccumulatorResultScope accumulator_execution_result(this);
   Scope* scope = this->scope();
 
-  // Allocate a new local context.
-  if (scope->is_script_scope()) {
+  // Create the appropriate context.
+  if (scope->is_module_scope()) {
+    // We don't need to do anything for the outer script scope.
+    DCHECK(scope->outer_scope()->is_script_scope());
+
+    RegisterAllocationScope register_scope(this);
+    Register module = register_allocator()->NewRegister();
+    Register closure = register_allocator()->NewRegister();
+    Register scope_info = register_allocator()->NewRegister();
+    DCHECK(Register::AreContiguous(module, closure, scope_info));

[rmcilroy, 2016/09/05 11:36:07]

Please use PrepareForConsecutiveAllocations / NextConsecutiveRegister (also if
you could update the script scope case below that would be great, thanks).

+    // A JSFunction representing a module is called with the module object as
+    // its sole argument, which we pass on to PushModuleContext.
+    builder()
+        ->MoveRegister(builder()->Parameter(1), module)
+        .LoadAccumulatorWithRegister(Register::function_closure())
+        .StoreAccumulatorInRegister(closure)

[rmcilroy, 2016/09/05 11:36:07]

.MoveRegister(Register::function_closure(), closure)

(also below in script scope too please)

+        .LoadLiteral(scope->scope_info())
+        .StoreAccumulatorInRegister(scope_info)
+        .CallRuntime(Runtime::kPushModuleContext, module, 3);
+  } else if (scope->is_script_scope()) {

[rmcilroy, 2016/09/05 11:36:07]

nit - could we do script scope first.

     RegisterAllocationScope register_scope(this);
     Register closure = register_allocator()->NewRegister();
     Register scope_info = register_allocator()->NewRegister();
     DCHECK(Register::AreContiguous(closure, scope_info));
     builder()
         ->LoadAccumulatorWithRegister(Register::function_closure())
         .StoreAccumulatorInRegister(closure)
         .LoadLiteral(scope->scope_info())
         .StoreAccumulatorInRegister(scope_info)
         .CallRuntime(Runtime::kNewScriptContext, closure, 2);
@@ skipping 127 matching lines @@
 
   // Store the new target we were called with in the given variable.
   builder()->LoadAccumulatorWithRegister(Register::new_target());
   VisitVariableAssignment(variable, Token::INIT, FeedbackVectorSlot::Invalid());
 }
 
 void BytecodeGenerator::VisitFunctionClosureForContext() {
   AccumulatorResultScope accumulator_execution_result(this);
   DeclarationScope* closure_scope =
       execution_context()->scope()->GetClosureScope();
-  if (closure_scope->is_script_scope() ||
-      closure_scope->is_module_scope()) {
+  if (closure_scope->is_script_scope()) {
     // Contexts nested in the native context have a canonical empty function as
     // their closure, not the anonymous closure containing the global code.
     Register native_context = register_allocator()->NewRegister();
     builder()
         ->LoadContextSlot(execution_context()->reg(),
                           Context::NATIVE_CONTEXT_INDEX)
         .StoreAccumulatorInRegister(native_context)
         .LoadContextSlot(native_context, Context::CLOSURE_INDEX);
   } else if (closure_scope->is_eval_scope()) {
     // Contexts created by a call to eval have the same closure as the
     // context calling eval, not the anonymous closure containing the eval
     // code. Fetch it from the context.
     builder()->LoadContextSlot(execution_context()->reg(),
                                Context::CLOSURE_INDEX);
   } else {
-    DCHECK(closure_scope->is_function_scope());
+    DCHECK(closure_scope->is_function_scope() ||
+           closure_scope->is_module_scope());
     builder()->LoadAccumulatorWithRegister(Register::function_closure());
   }
   execution_result()->SetResultInAccumulator();
 }
 
 // Visits the expression |expr| and places the result in the accumulator.
 void BytecodeGenerator::VisitForAccumulatorValue(Expression* expr) {
   AccumulatorResultScope accumulator_scope(this);
   Visit(expr);
 }
@@ skipping 69 matching lines @@
   return execution_context()->scope()->language_mode();
 }
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return TypeFeedbackVector::GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8