[turbofan] Compute more precise type for ObjectIsSmi if possible.

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/base/lazy-instance.h"
 #include "src/bootstrapper.h"
 #include "src/compiler/common-operator.h"
@@ skipping 1639 matching lines @@
   return nullptr;
 }
 
 
 Type* Typer::Visitor::TypeStoreElement(Node* node) {
   UNREACHABLE();
   return nullptr;
 }
 
 
-Type* Typer::Visitor::TypeObjectIsSmi(Node* node) { return Type::Boolean(); }
+Type* Typer::Visitor::TypeObjectIsSmi(Node* node) {
+  Type* arg = Operand(node, 0);
+  if (arg->Is(Type::None())) return Type::None();
+  if (arg->Is(Type::TaggedSigned())) return typer_->singleton_true_;
+  if (arg->Is(Type::TaggedPointer())) return typer_->singleton_false_;
+  return Type::Boolean();
+}
 
 
 // Machine operators.
 
 Type* Typer::Visitor::TypeLoad(Node* node) { return Type::Any(); }
 
 
 Type* Typer::Visitor::TypeStore(Node* node) {
   UNREACHABLE();
   return nullptr;
@@ skipping 434 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