[turbofan] Use the typer to statically detect Smis.

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/base/flags.h"
 #include "src/bootstrapper.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-properties.h"
@@ skipping 1598 matching lines @@
 Bounds Typer::Visitor::TypeStringLessThanOrEqual(Node* node) {
   return Bounds(Type::None(zone()), Type::Boolean(zone()));
 }
 
 
 Bounds Typer::Visitor::TypeStringAdd(Node* node) {
   return Bounds(Type::None(zone()), Type::String(zone()));
 }
 
 
-static Type* ChangeRepresentation(Type* type, Type* rep, Zone* zone) {
-  // TODO(neis): Enable when expressible.
-  /*
-  return Type::Union(
-      Type::Intersect(type, Type::Semantic(), zone),
-      Type::Intersect(rep, Type::Representation(), zone), zone);
-  */
-  return type;
+namespace {
+
+Type* ChangeRepresentation(Type* type, Type* rep, Zone* zone) {
+  return Type::Union(Type::Semantic(type, zone),
+                     Type::Representation(rep, zone), zone);
 }
 
+}  // namespace
+
 
 Bounds Typer::Visitor::TypeChangeTaggedToInt32(Node* node) {
   Bounds arg = Operand(node, 0);
   // TODO(neis): DCHECK(arg.upper->Is(Type::Signed32()));
   return Bounds(
       ChangeRepresentation(arg.lower, Type::UntaggedSigned32(), zone()),
       ChangeRepresentation(arg.upper, Type::UntaggedSigned32(), zone()));
 }
 
 
@@ skipping 11 matching lines @@
   // TODO(neis): DCHECK(arg.upper->Is(Type::Number()));
   return Bounds(
       ChangeRepresentation(arg.lower, Type::UntaggedFloat64(), zone()),
       ChangeRepresentation(arg.upper, Type::UntaggedFloat64(), zone()));
 }
 
 
 Bounds Typer::Visitor::TypeChangeInt32ToTagged(Node* node) {
   Bounds arg = Operand(node, 0);
   // TODO(neis): DCHECK(arg.upper->Is(Type::Signed32()));
-  return Bounds(
-      ChangeRepresentation(arg.lower, Type::Tagged(), zone()),
-      ChangeRepresentation(arg.upper, Type::Tagged(), zone()));
+  Type* lower_rep = arg.lower->Is(Type::SignedSmall()) ? Type::TaggedSigned()
+                                                       : Type::Tagged();
+  Type* upper_rep = arg.upper->Is(Type::SignedSmall()) ? Type::TaggedSigned()
+                                                       : Type::Tagged();
+  return Bounds(ChangeRepresentation(arg.lower, lower_rep, zone()),
+                ChangeRepresentation(arg.upper, upper_rep, zone()));
 }
 
 
 Bounds Typer::Visitor::TypeChangeUint32ToTagged(Node* node) {
   Bounds arg = Operand(node, 0);
   // TODO(neis): DCHECK(arg.upper->Is(Type::Unsigned32()));
   return Bounds(
       ChangeRepresentation(arg.lower, Type::Tagged(), zone()),
       ChangeRepresentation(arg.upper, Type::Tagged(), zone()));
 }
@@ skipping 511 matching lines @@
       TYPED_ARRAYS(TYPED_ARRAY_CASE)
 #undef TYPED_ARRAY_CASE
     }
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8