[turbofan] Optimize tagged conversion based on type.

src/compiler/typer.cc

 // Copyright 2014 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/compiler/typer.h"
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/common-operator.h"
@@ skipping 1853 matching lines @@
   return ChangeRepresentation(arg, Type::UntaggedIntegral32(), zone());
 }
 
 
 Type* Typer::Visitor::TypeChangeTaggedToFloat64(Node* node) {
   Type* arg = Operand(node, 0);
   // TODO(neis): DCHECK(arg->Is(Type::Number()));
   return ChangeRepresentation(arg, Type::UntaggedFloat64(), zone());
 }
 
+Type* Typer::Visitor::TypeChangeInt31ToTagged(Node* node) {
+  Type* arg = Operand(node, 0);
+  // TODO(neis): DCHECK(arg->Is(Type::Signed31()));
+  Type* rep =
+      arg->Is(Type::SignedSmall()) ? Type::TaggedSigned() : Type::Tagged();
+  return ChangeRepresentation(arg, rep, zone());
+}
 
 Type* Typer::Visitor::TypeChangeInt32ToTagged(Node* node) {
   Type* arg = Operand(node, 0);
   // TODO(neis): DCHECK(arg->Is(Type::Signed32()));
   Type* rep =
       arg->Is(Type::SignedSmall()) ? Type::TaggedSigned() : Type::Tagged();
   return ChangeRepresentation(arg, rep, zone());
 }
 
 
@@ skipping 679 matching lines @@
   }
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8