[torque] Refactored functions to prevent unnecessary copies

Bug: v8:8015
Change-Id: Ice0c5994ff5695c06be307c3e37d90daf14c643c
Reviewed-on: https://chromium-review.googlesource.com/1209763
Commit-Queue: Florian Sattler <sattlerf@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55691}

src/torque/implementation-visitor.cc

@@ -1399,7 +1399,8 @@ LocationReference ImplementationVisitor::GetLocationReference(
   return LocationReference(nullptr, result, {});
 }
 
-std::string ImplementationVisitor::RValueFlattenStructs(VisitResult result) {
+std::string ImplementationVisitor::RValueFlattenStructs(
+    const VisitResult& result) {
   if (result.declarable()) {
     const Value* value = *result.declarable();
     const Type* type = value->type();
@@ -1422,7 +1423,7 @@ std::string ImplementationVisitor::RValueFlattenStructs(VisitResult result) {
 }
 
 VisitResult ImplementationVisitor::GenerateFetchFromLocation(
-    LocationExpression* location, LocationReference reference) {
+    LocationExpression* location, const LocationReference& reference) {
   switch (location->kind) {
     case AstNode::Kind::kIdentifierExpression:
       return GenerateFetchFromLocation(
@@ -1439,7 +1440,7 @@ VisitResult ImplementationVisitor::GenerateFetchFromLocation(
 }
 
 VisitResult ImplementationVisitor::GenerateFetchFromLocation(
-    FieldAccessExpression* expr, LocationReference reference) {
+    FieldAccessExpression* expr, const LocationReference& reference) {
   if (reference.value != nullptr) {
     return GenerateFetchFromLocation(reference);
   }
@@ -1455,7 +1456,7 @@ VisitResult ImplementationVisitor::GenerateFetchFromLocation(
 }
 
 void ImplementationVisitor::GenerateAssignToVariable(Variable* var,
-                                                     VisitResult value) {
+                                                     const VisitResult& value) {
   if (var->type()->IsStructType()) {
     if (value.type() != var->type()) {
       std::stringstream s;
@@ -1491,7 +1492,7 @@ void ImplementationVisitor::GenerateAssignToVariable(Variable* var,
 
 void ImplementationVisitor::GenerateAssignToLocation(
     LocationExpression* location, const LocationReference& reference,
-    VisitResult assignment_value) {
+    const VisitResult& assignment_value) {
   if (reference.value != nullptr) {
     Value* value = reference.value;
     if (value->IsConst()) {
@@ -1998,6 +1999,7 @@ void ImplementationVisitor::GenerateLabelGoto(Label* label) {
 std::vector<Label*> ImplementationVisitor::LabelsFromIdentifiers(
     const std::vector<std::string>& names) {
   std::vector<Label*> result;
+  result.reserve(names.size());
   for (const auto& name : names) {
     result.push_back(declarations()->LookupLabel(name));
   }

src/torque/implementation-visitor.h

@@ -48,22 +48,22 @@ class ImplementationVisitor : public FileVisitor {
     return LocationReference({}, Visit(expr->array), Visit(expr->index));
   }
 
-  std::string RValueFlattenStructs(VisitResult result);
+  std::string RValueFlattenStructs(const VisitResult& result);
 
-  VisitResult GenerateFetchFromLocation(LocationReference reference) {
+  VisitResult GenerateFetchFromLocation(const LocationReference& reference) {
     const Value* value = reference.value;
     return VisitResult(value->type(), value);
   }
   VisitResult GenerateFetchFromLocation(LocationExpression* location,
-                                        LocationReference reference);
+                                        const LocationReference& reference);
   VisitResult GenerateFetchFromLocation(IdentifierExpression* expr,
-                                        LocationReference reference) {
+                                        const LocationReference& reference) {
     return GenerateFetchFromLocation(reference);
   }
   VisitResult GenerateFetchFromLocation(FieldAccessExpression* expr,
-                                        LocationReference reference);
+                                        const LocationReference& reference);
   VisitResult GenerateFetchFromLocation(ElementAccessExpression* expr,
-                                        LocationReference reference) {
+                                        const LocationReference& reference) {
     Arguments arguments;
     arguments.parameters = {reference.base, reference.index};
     return GenerateCall("[]", arguments);
@@ -183,11 +183,11 @@ class ImplementationVisitor : public FileVisitor {
 
   VisitResult GenerateCopy(const VisitResult& to_copy);
 
-  void GenerateAssignToVariable(Variable* var, VisitResult value);
+  void GenerateAssignToVariable(Variable* var, const VisitResult& value);
 
   void GenerateAssignToLocation(LocationExpression* location,
                                 const LocationReference& reference,
-                                VisitResult assignment_value);
+                                const VisitResult& assignment_value);
 
   void GenerateVariableDeclaration(const Variable* var);
 

src/torque/torque-parser.cc

@@ -987,7 +987,7 @@ struct TorqueGrammar : Grammar {
            MakeParameterListFromNameAndTypeList<true>)};
 
   // Result: std::string
-  Symbol* OneOf(std::vector<std::string> alternatives) {
+  Symbol* OneOf(const std::vector<std::string>& alternatives) {
     Symbol* result = NewSymbol();
     for (const std::string& s : alternatives) {
       result->AddRule(Rule({Token(s)}, YieldMatchedInput));