Rollback of r15267, r15263, r15193 in trunk branch in preparation for 3.19 branch

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 6865465694402841779541ca516682cb3c8f2924..170f5eda6c51d8eb60b137eb6f8c275b5d7d7a85 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1155,12 +1155,8 @@ void HBoundsCheck::InferRepresentation(HInferRepresentation* h_infer) {
   HValue* actual_length = length()->ActualValue();
   Representation index_rep = actual_index->representation();
   Representation length_rep = actual_length->representation();
-  if (index_rep.IsTagged() && actual_index->type().IsSmi()) {
-    index_rep = Representation::Smi();
-  }
-  if (length_rep.IsTagged() && actual_length->type().IsSmi()) {
-    length_rep = Representation::Smi();
-  }
+  if (index_rep.IsTagged()) index_rep = Representation::Smi();
+  if (length_rep.IsTagged()) length_rep = Representation::Smi();
   Representation r = index_rep.generalize(length_rep);
   if (r.is_more_general_than(Representation::Integer32())) {
     r = Representation::Integer32();
@@ -3327,9 +3323,10 @@ HInstruction* HStringAdd::New(
     HConstant* c_right = HConstant::cast(right);
     HConstant* c_left = HConstant::cast(left);
     if (c_left->HasStringValue() && c_right->HasStringValue()) {
-      Handle<String> concat = zone->isolate()->factory()->NewFlatConcatString(
-          c_left->StringValue(), c_right->StringValue());
-      return new(zone) HConstant(concat, Representation::Tagged());
+      Factory* factory = Isolate::Current()->factory();
+      return new(zone) HConstant(factory->NewConsString(c_left->StringValue(),
+                                                        c_right->StringValue()),
+                                 Representation::Tagged());
     }
   }
   return new(zone) HStringAdd(context, left, right);