[turbofan] Improve representation selection for Smi checking.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 7db9a05079453b6b227dc70236876abc5878b715..e33b7764567881f149e760262b26a9a58f2b1f87 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1571,6 +1571,16 @@ Type* Typer::Visitor::TypeCheckBounds(Node* node) {
   return Type::Range(min, max, zone());
 }
 
+Type* Typer::Visitor::TypeCheckHeapObject(Node* node) {
+  Type* type = Operand(node, 0);
+  return type;
+}
+
+Type* Typer::Visitor::TypeCheckIf(Node* node) {
+  UNREACHABLE();
+  return nullptr;
+}
+
 Type* Typer::Visitor::TypeCheckMaps(Node* node) {
   UNREACHABLE();
   return nullptr;
@@ -1581,24 +1591,14 @@ Type* Typer::Visitor::TypeCheckNumber(Node* node) {
   return Type::Intersect(arg, Type::Number(), zone());
 }
 
-Type* Typer::Visitor::TypeCheckString(Node* node) {
+Type* Typer::Visitor::TypeCheckSmi(Node* node) {
   Type* arg = Operand(node, 0);
-  return Type::Intersect(arg, Type::String(), zone());
+  return Type::Intersect(arg, Type::SignedSmall(), zone());
 }
 
-Type* Typer::Visitor::TypeCheckIf(Node* node) {
-  UNREACHABLE();
-  return nullptr;
-}
-
-Type* Typer::Visitor::TypeCheckTaggedPointer(Node* node) {
-  Type* type = Operand(node, 0);
-  return type;
-}
-
-Type* Typer::Visitor::TypeCheckTaggedSigned(Node* node) {
+Type* Typer::Visitor::TypeCheckString(Node* node) {
   Type* arg = Operand(node, 0);
-  return Type::Intersect(arg, typer_->cache_.kSmi, zone());
+  return Type::Intersect(arg, Type::String(), zone());
 }
 
 Type* Typer::Visitor::TypeCheckFloat64Hole(Node* node) {