Use Representation::Integer32() for smi types on 32-bit-tagged systems.

src/types.cc

Index: src/types.cc
diff --git a/src/types.cc b/src/types.cc
index 3840e6fd223f72c0210b49a386e3ca4462ef4a0b..dedfeadb46ac0003f032e9cc0276e8fd1a2171d3 100644
--- a/src/types.cc
+++ b/src/types.cc
@@ -568,7 +568,8 @@ typename TypeImpl<Config>::TypeHandle TypeImpl<Config>::Convert(
 // TODO(rossberg): this does not belong here.
 Representation Representation::FromType(Type* type) {
   if (type->Is(Type::None())) return Representation::None();
-  if (type->Is(Type::Smi())) return Representation::Smi();
+  if (type->Is(Type::Smi())) return SmiValuesAre31Bits()
+      ? Representation::Smi() : Representation::Integer32();
   if (type->Is(Type::Signed32())) return Representation::Integer32();
   if (type->Is(Type::Number())) return Representation::Double();
   return Representation::Tagged();