Eliminate temporary locals for some expressions

runtime/vm/parser.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
@@ skipping 98 matching lines @@
 }
 
 
 LocalVariable* ParsedFunction::CreateExpressionTempVar(intptr_t token_pos) {
   return new LocalVariable(token_pos,
                            Symbols::ExprTemp(),
                            Type::ZoneHandle(Type::DynamicType()));
 }
 
 
-LocalVariable* ParsedFunction::CreateArrayLiteralVar(intptr_t token_pos) {
-  return new LocalVariable(token_pos,
-                           Symbols::ArrayLiteralVar(),
-                           Type::ZoneHandle(Type::ArrayType()));
-}
-
-
 void ParsedFunction::SetNodeSequence(SequenceNode* node_sequence) {
   ASSERT(node_sequence_ == NULL);
   ASSERT(node_sequence != NULL);
   node_sequence_ = node_sequence;
 }
 
 
 LocalVariable* ParsedFunction::GetSavedArgumentsDescriptorVar() const {
   const int num_parameters = function().NumParameters();
   LocalScope* scope = node_sequence()->scope();
@@ skipping 645 matching lines @@
     case RawFunction::kConstImplicitGetter:
       node_sequence = parser.ParseStaticConstGetter(func);
       break;
     case RawFunction::kMethodExtractor:
       node_sequence = parser.ParseMethodExtractor(func);
       break;
     default:
       UNREACHABLE();
   }
 
-  parsed_function->set_array_literal_var(
-      ParsedFunction::CreateArrayLiteralVar(func.token_pos()));
-  node_sequence->scope()->AddVariable(parsed_function->array_literal_var());
-
   if (!HasReturnNode(node_sequence)) {
     // Add implicit return node.
     node_sequence->Add(new ReturnNode(func.end_token_pos()));
   }
   if (parsed_function->has_expression_temp_var()) {
     node_sequence->scope()->AddVariable(parsed_function->expression_temp_var());
   }
   if (parsed_function->has_saved_current_context_var()) {
     node_sequence->scope()->AddVariable(
         parsed_function->saved_current_context_var());
@@ skipping 597 matching lines @@
 }
 
 
 static const String& PrivateCoreLibName(const String& str) {
   const Library& core_lib = Library::Handle(Library::CoreLibrary());
   const String& private_name = String::ZoneHandle(core_lib.PrivateName(str));
   return private_name;
 }
 
 
-LocalVariable* Parser::BuildArrayTempLocal(intptr_t token_pos) {
-  char name[64];
-  OS::SNPrint(name, 64, ":arrlit%"Pd, token_pos);
-  LocalVariable* temp =
-      new LocalVariable(token_pos,
-                        String::ZoneHandle(Symbols::New(name)),
-                        Type::ZoneHandle(Type::ArrayType()));
-  current_block_->scope->AddVariable(temp);
-  return temp;
-}
-
-
 StaticCallNode* Parser::BuildInvocationMirrorAllocation(
     intptr_t call_pos,
     const String& function_name,
     const ArgumentListNode& function_args) {
   const intptr_t args_pos = function_args.token_pos();
   // Build arguments to the call to the static
   // InvocationMirror._allocateInvocationMirror method.
   ArgumentListNode* arguments = new ArgumentListNode(args_pos);
   // The first argument is the original function name.
   arguments->Add(new LiteralNode(args_pos, function_name));
   // The second argument is the arguments descriptor of the original function.
   const Array& args_descriptor =
       Array::ZoneHandle(ArgumentsDescriptor::New(function_args.length(),
                                                  function_args.names()));
   arguments->Add(new LiteralNode(args_pos, args_descriptor));
   // The third argument is an array containing the original function arguments,
   // including the receiver.
-  ArrayNode* args_array = new ArrayNode(
-      args_pos, Type::ZoneHandle(Type::ArrayType()),
-      *BuildArrayTempLocal(call_pos));
+  ArrayNode* args_array =
+      new ArrayNode(args_pos, Type::ZoneHandle(Type::ArrayType()));
   for (intptr_t i = 0; i < function_args.length(); i++) {
     args_array->AddElement(function_args.NodeAt(i));
   }
   arguments->Add(args_array);
   // Lookup the static InvocationMirror._allocateInvocationMirror method.
   const Class& mirror_class =
       Class::Handle(LookupCoreClass(Symbols::InvocationMirror()));
   ASSERT(!mirror_class.IsNull());
   const Function& allocation_function = Function::ZoneHandle(
       mirror_class.LookupStaticFunction(
@@ skipping 5567 matching lines @@
   if (expr->IsLiteralNode()) {
     return expr;
   }
   if (expr->EvalConstExpr() == NULL) {
     ErrorMsg(expr_pos, "expression must be a compile-time constant");
   }
   return new LiteralNode(expr_pos, EvaluateConstExpr(expr));
 }
 
 
-// A compound assignment consists of a store and a load part. In order
-// to control inputs with potential side effects, the store part stores any
-// side effect creating inputs into locals. The load part reads then from
-// those locals. If expr may have side effects, it will be split into two new
-// left and right nodes. 'expr' becomes the right node, left node is returned as
-// result.
-AstNode* Parser::PrepareCompoundAssignmentNodes(AstNode** expr) {
+LetNode* Parser::PrepareCompoundAssignmentNodes(AstNode** expr) {
   AstNode* node = *expr;
+  intptr_t token_pos = node->token_pos();
+  LetNode* result = new LetNode(token_pos);
   if (node->IsLoadIndexedNode()) {
-    LoadIndexedNode* left_node = node->AsLoadIndexedNode();
-    LoadIndexedNode* right_node = left_node;
-    intptr_t token_pos = node->token_pos();
-    node = NULL;  // Do not use it.
-    if (!IsSimpleLocalOrLiteralNode(left_node->array())) {
-      LocalVariable* temp =
-          CreateTempConstVariable(token_pos, "lia");
-      StoreLocalNode* save =
-          new StoreLocalNode(token_pos, temp, left_node->array());
-      left_node = new LoadIndexedNode(token_pos,
-                                      save,
-                                      left_node->index_expr(),
-                                      left_node->super_class());
-      right_node = new LoadIndexedNode(token_pos,
-                                       new LoadLocalNode(token_pos, temp),
-                                       right_node->index_expr(),
-                                       right_node->super_class());
+    LoadIndexedNode* load_indexed = node->AsLoadIndexedNode();
+    AstNode* array = load_indexed->array();
+    AstNode* index = load_indexed->index_expr();
+    if (!IsSimpleLocalOrLiteralNode(load_indexed->array())) {
+      LocalVariable* t0 = result->AddInitializer(load_indexed->array());
+      array = new LoadLocalNode(token_pos, t0);
     }
-    if (!IsSimpleLocalOrLiteralNode(left_node->index_expr())) {
-      LocalVariable* temp =
-          CreateTempConstVariable(token_pos, "lix");
-      StoreLocalNode* save =
-          new StoreLocalNode(token_pos, temp, left_node->index_expr());
-      left_node = new LoadIndexedNode(token_pos,
-                                      left_node->array(),
-                                      save,
-                                      left_node->super_class());
-      right_node = new LoadIndexedNode(token_pos,
-                                       right_node->array(),
-                                       new LoadLocalNode(token_pos, temp),
-                                       right_node->super_class());
+    if (!IsSimpleLocalOrLiteralNode(load_indexed->index_expr())) {
+      LocalVariable* t1 = result->AddInitializer(
+          load_indexed->index_expr());
+      index = new LoadLocalNode(token_pos, t1);
     }
-    *expr = right_node;
-    return left_node;
+    *expr = new LoadIndexedNode(token_pos,
+                                array,
+                                index,
+                                load_indexed->super_class());
+    return result;
   }
   if (node->IsInstanceGetterNode()) {
-    InstanceGetterNode* left_node = node->AsInstanceGetterNode();
-    InstanceGetterNode* right_node = left_node;
-    intptr_t token_pos = node->token_pos();
-    node = NULL;  // Do not use it.
-    if (!IsSimpleLocalOrLiteralNode(left_node->receiver())) {
-      LocalVariable* temp =
-          CreateTempConstVariable(token_pos, "igr");
-      StoreLocalNode* save =
-          new StoreLocalNode(token_pos, temp, left_node->receiver());
-      left_node = new InstanceGetterNode(token_pos,
-                                         save,
-                                         left_node->field_name());
-      right_node = new InstanceGetterNode(token_pos,
-                                          new LoadLocalNode(token_pos, temp),
-                                          right_node->field_name());
+    InstanceGetterNode* getter = node->AsInstanceGetterNode();
+    AstNode* receiver = getter->receiver();
+    if (!IsSimpleLocalOrLiteralNode(getter->receiver())) {
+      LocalVariable* t0 = result->AddInitializer(getter->receiver());
+      receiver = new LoadLocalNode(token_pos, t0);
     }
-    *expr = right_node;
-    return left_node;
+    *expr = new InstanceGetterNode(token_pos,
+                                   receiver,
+                                   getter->field_name());
+    return result;
   }
-  return *expr;
+  return result;
 }
 
 
 // Ensure that the expression temp is allocated for nodes that may need it.
 AstNode* Parser::CreateAssignmentNode(AstNode* original, AstNode* rhs) {
   AstNode* result = original->MakeAssignmentNode(rhs);
   if ((result == NULL) && original->IsTypeNode()) {
     const String& type_name = String::ZoneHandle(
         original->AsTypeNode()->type().ClassName());
     // TODO(tball): determine whether NoSuchMethod should be called instead.
@@ skipping 10 matching lines @@
        result->IsStoreStaticFieldNode() ||
        result->IsStoreLocalNode())) {
     EnsureExpressionTemp();
   }
   return result;
 }
 
 
 AstNode* Parser::ParseCascades(AstNode* expr) {
   intptr_t cascade_pos = TokenPos();
-  LocalVariable* cascade_receiver_var =
-      CreateTempConstVariable(cascade_pos, "casc");
+  LetNode* result = new LetNode(cascade_pos);
+  LocalVariable* cascade_receiver_var = result->AddInitializer(expr);
+  // TODO(fschneider): Make LetNode support more than one body node and
+  // replace the SequenceNode here and CommaNode here and in postfix
+  // expressions.
   SequenceNode* cascade = new SequenceNode(cascade_pos, NULL);
-  StoreLocalNode* save_cascade =
-      new StoreLocalNode(cascade_pos, cascade_receiver_var, expr);
-  cascade->Add(save_cascade);
   while (CurrentToken() == Token::kCASCADE) {
     cascade_pos = TokenPos();
     LoadLocalNode* load_cascade_receiver =
         new LoadLocalNode(cascade_pos, cascade_receiver_var);
     if (Token::IsIdentifier(LookaheadToken(1))) {
       // Replace .. with . for ParseSelectors().
       token_kind_ = Token::kPERIOD;
     } else if (LookaheadToken(1) == Token::kLBRACK) {
       ConsumeToken();
     } else {
       ErrorMsg("identifier or [ expected after ..");
     }
     expr = ParseSelectors(load_cascade_receiver, true);
 
     // Assignments after a cascade are part of the cascade. The
     // assigned expression must not contain cascades.
     if (Token::IsAssignmentOperator(CurrentToken())) {
       Token::Kind assignment_op = CurrentToken();
       const intptr_t assignment_pos = TokenPos();
       ConsumeToken();
       AstNode* right_expr = ParseExpr(kAllowConst, kNoCascades);
-      AstNode* left_expr = expr;
       if (assignment_op != Token::kASSIGN) {
         // Compound assignment: store inputs with side effects into
         // temporary locals.
-        left_expr = PrepareCompoundAssignmentNodes(&expr);
+        LetNode* let_expr = PrepareCompoundAssignmentNodes(&expr);
+        right_expr =
+            ExpandAssignableOp(assignment_pos, assignment_op, expr, right_expr);
+        AstNode* assign_expr = CreateAssignmentNode(expr, right_expr);
+        if (assign_expr == NULL) {
+          ErrorMsg(assignment_pos,
+                   "left hand side of '%s' is not assignable",
+                   Token::Str(assignment_op));
+        }
+        let_expr->set_body(assign_expr);
+        expr = let_expr;
+      } else {
+        right_expr =
+            ExpandAssignableOp(assignment_pos, assignment_op, expr, right_expr);
+        AstNode* assign_expr = CreateAssignmentNode(expr, right_expr);
+        if (assign_expr == NULL) {
+          ErrorMsg(assignment_pos,
+                   "left hand side of '%s' is not assignable",
+                   Token::Str(assignment_op));
+        }
+        expr = assign_expr;
       }
-      right_expr =
-          ExpandAssignableOp(assignment_pos, assignment_op, expr, right_expr);
-      AstNode* assign_expr = CreateAssignmentNode(left_expr, right_expr);
-      if (assign_expr == NULL) {
-        ErrorMsg(assignment_pos,
-                 "left hand side of '%s' is not assignable",
-                 Token::Str(assignment_op));
-      }
-      expr = assign_expr;
     }
     cascade->Add(expr);
   }
   // The result is a pair of the (side effects of the) cascade sequence
   // followed by the (value of the) receiver temp variable load.
-  return new CommaNode(
+  CommaNode* body = new CommaNode(
       cascade_pos,
       cascade,
       new LoadLocalNode(cascade_pos, cascade_receiver_var));
+  result->set_body(body);
+  return result;
 }
 
 
 AstNode* Parser::ParseExpr(bool require_compiletime_const,
                            bool consume_cascades) {
   TRACE_PARSER("ParseExpr");
   const intptr_t expr_pos = TokenPos();
 
   if (CurrentToken() == Token::kTHROW) {
     ConsumeToken();
@@ skipping 13 matching lines @@
   }
   // Assignment expressions.
   Token::Kind assignment_op = CurrentToken();
   const intptr_t assignment_pos = TokenPos();
   ConsumeToken();
   const intptr_t right_expr_pos = TokenPos();
   if (require_compiletime_const && (assignment_op != Token::kASSIGN)) {
     ErrorMsg(right_expr_pos, "expression must be a compile-time constant");
   }
   AstNode* right_expr = ParseExpr(require_compiletime_const, consume_cascades);
-  AstNode* left_expr = expr;
   if (assignment_op != Token::kASSIGN) {
     // Compound assignment: store inputs with side effects into temp. locals.
-    left_expr = PrepareCompoundAssignmentNodes(&expr);
+    LetNode* let_expr = PrepareCompoundAssignmentNodes(&expr);
+    AstNode* assigned_value =
+        ExpandAssignableOp(assignment_pos, assignment_op, expr, right_expr);
+    AstNode* assign_expr = CreateAssignmentNode(expr, assigned_value);
+    if (assign_expr == NULL) {
+      ErrorMsg(assignment_pos,
+               "left hand side of '%s' is not assignable",
+               Token::Str(assignment_op));
+    }
+    let_expr->set_body(assign_expr);
+    return let_expr;
+  } else {
+    AstNode* assigned_value =
+        ExpandAssignableOp(assignment_pos, assignment_op, expr, right_expr);
+    AstNode* assign_expr = CreateAssignmentNode(expr, assigned_value);
+    if (assign_expr == NULL) {
+      ErrorMsg(assignment_pos,
+               "left hand side of '%s' is not assignable",
+               Token::Str(assignment_op));
+    }
+    return assign_expr;
   }
-  right_expr =
-      ExpandAssignableOp(assignment_pos, assignment_op, expr, right_expr);
-  AstNode* assign_expr = CreateAssignmentNode(left_expr, right_expr);
-  if (assign_expr == NULL) {
-    ErrorMsg(assignment_pos,
-             "left hand side of '%s' is not assignable",
-             Token::Str(assignment_op));
-  }
-  return assign_expr;
 }
 
 
 LiteralNode* Parser::ParseConstExpr() {
   TRACE_PARSER("ParseConstExpr");
   AstNode* expr = ParseExpr(kRequireConst, kNoCascades);
   ASSERT(expr->IsLiteralNode());
   return expr->AsLiteralNode();
 }
 
@@ skipping 37 matching lines @@
       expr = UnaryOpNode::UnaryOpOrLiteral(op_pos, unary_op, expr);
     }
   } else if (IsIncrementOperator(CurrentToken())) {
     Token::Kind incr_op = CurrentToken();
     ConsumeToken();
     expr = ParseUnaryExpr();
     if (!IsAssignableExpr(expr)) {
       ErrorMsg("expression is not assignable");
     }
     // Is prefix.
-    AstNode* left_expr = PrepareCompoundAssignmentNodes(&expr);
+    LetNode* let_expr = PrepareCompoundAssignmentNodes(&expr);
     Token::Kind binary_op =
         (incr_op == Token::kINCR) ? Token::kADD : Token::kSUB;
     BinaryOpNode* add = new BinaryOpNode(
         op_pos,
         binary_op,
         expr,
         new LiteralNode(op_pos, Smi::ZoneHandle(Smi::New(1))));
-    AstNode* store = CreateAssignmentNode(left_expr, add);
+    AstNode* store = CreateAssignmentNode(expr, add);
     ASSERT(store != NULL);
-    expr = store;
+    let_expr->set_body(store);
+    expr = let_expr;
   } else {
     expr = ParsePostfixExpr();
   }
   return expr;
 }
 
 
 ArgumentListNode* Parser::ParseActualParameters(
                               ArgumentListNode* implicit_arguments,
                               bool require_const) {
@@ skipping 461 matching lines @@
   AstNode* postfix_expr = ParsePrimary();
   postfix_expr = ParseSelectors(postfix_expr, false);
   if (IsIncrementOperator(CurrentToken())) {
     TRACE_PARSER("IncrementOperator");
     Token::Kind incr_op = CurrentToken();
     if (!IsAssignableExpr(postfix_expr)) {
       ErrorMsg("expression is not assignable");
     }
     ConsumeToken();
     // Not prefix.
-    AstNode* left_expr = PrepareCompoundAssignmentNodes(&postfix_expr);
-    const LocalVariable* temp = GetIncrementTempLocal();
-    AstNode* save =
-        new StoreLocalNode(postfix_expr_pos, temp, postfix_expr);
+    LetNode* let_expr = PrepareCompoundAssignmentNodes(&postfix_expr);
+    LocalVariable* temp = let_expr->AddInitializer(postfix_expr);
     Token::Kind binary_op =
         (incr_op == Token::kINCR) ? Token::kADD : Token::kSUB;
     BinaryOpNode* add = new BinaryOpNode(
         postfix_expr_pos,
         binary_op,
-        save,
+        new LoadLocalNode(postfix_expr_pos, temp),
         new LiteralNode(postfix_expr_pos, Smi::ZoneHandle(Smi::New(1))));
-    AstNode* store = CreateAssignmentNode(left_expr, add);
+    AstNode* store = CreateAssignmentNode(postfix_expr, add);
+    ASSERT(store != NULL);
     // The result is a pair of the (side effects of the) store followed by
     // the (value of the) initial value temp variable load.
-    return new CommaNode(
+    let_expr->set_body(new CommaNode(
         postfix_expr_pos,
         store,
-        new LoadLocalNode(postfix_expr_pos, temp));
+        new LoadLocalNode(postfix_expr_pos, temp)));
+    return let_expr;
   }
   return postfix_expr;
 }
 
 
 // Resolve the given type and its type arguments from the given scope class
 // according to the given type finalization mode.
 // If the given scope class is null, use the current library, but do not try to
 // resolve type parameters.
 // Not all involved type classes may get resolved yet, but at least the type
@@ skipping 1054 matching lines @@
     }
     factory_type_args = factory_type_args.Canonicalize();
     ArgumentListNode* factory_param = new ArgumentListNode(literal_pos);
     if (element_list.length() == 0) {
       // TODO(srdjan): Use Object::empty_array once issue 9871 has been fixed.
       Array& empty_array = Array::ZoneHandle(Object::empty_array().raw());
       LiteralNode* empty_array_literal =
           new LiteralNode(TokenPos(), empty_array);
       factory_param->Add(empty_array_literal);
     } else {
-      const LocalVariable& temp_local = *BuildArrayTempLocal(type_pos);
-      ArrayNode* list =
-          new ArrayNode(TokenPos(), type, temp_local, element_list);
+      ArrayNode* list = new ArrayNode(TokenPos(), type, element_list);
       factory_param->Add(list);
     }
     return CreateConstructorCallNode(literal_pos,
                                      factory_type_args,
                                      factory_method,
                                      factory_param);
   }
 }
 
 
 ConstructorCallNode* Parser::CreateConstructorCallNode(
     intptr_t token_pos,
     const AbstractTypeArguments& type_arguments,
     const Function& constructor,
     ArgumentListNode* arguments) {
   if (!type_arguments.IsNull() && !type_arguments.IsInstantiated()) {
     EnsureExpressionTemp();
   }
-  LocalVariable* allocated =
-      CreateTempConstVariable(token_pos, "alloc");
   return new ConstructorCallNode(token_pos,
                                  type_arguments,
                                  constructor,
-                                 arguments,
-                                 allocated);
+                                 arguments);
 }
 
 
 static void AddKeyValuePair(GrowableArray<AstNode*>* pairs,
                             bool is_const,
                             AstNode* key,
                             AstNode* value) {
   if (is_const) {
     ASSERT(key->IsLiteralNode());
     ASSERT(key->AsLiteralNode()->literal().IsString());
@@ skipping 177 matching lines @@
       factory_type_args = factory_type.arguments();
       ASSERT(factory_type_args.Length() == factory_class.NumTypeArguments());
     }
     factory_type_args = factory_type_args.Canonicalize();
     ArgumentListNode* factory_param = new ArgumentListNode(literal_pos);
     // The kv_pair array is temporary and of element type dynamic. It is passed
     // to the factory to initialize a properly typed map.
     ArrayNode* kv_pairs = new ArrayNode(
         TokenPos(),
         Type::ZoneHandle(Type::ArrayType()),
-        *BuildArrayTempLocal(type_pos),
         kv_pairs_list);
     factory_param->Add(kv_pairs);
     return CreateConstructorCallNode(literal_pos,
                                      factory_type_args,
                                      factory_method,
                                      factory_param);
   }
 }
 
 
@@ skipping 366 matching lines @@
       values_list.Add(expr);
     }
   }
   if (is_compiletime_const) {
     primary = new LiteralNode(literal_start, Interpolate(values_list));
   } else {
     ArgumentListNode* interpolate_arg = new ArgumentListNode(TokenPos());
     ArrayNode* values = new ArrayNode(
         TokenPos(),
         Type::ZoneHandle(Type::ArrayType()),
-        *BuildArrayTempLocal(TokenPos()),
         values_list);
     interpolate_arg->Add(values);
     primary = MakeStaticCall(Symbols::StringBase(),
                              PrivateCoreLibName(Symbols::Interpolate()),
                              interpolate_arg);
   }
   return primary;
 }
 
 
@@ skipping 500 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart