[turbofan] Osr value typing + dynamic type checks on entry.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index e33b7764567881f149e760262b26a9a58f2b1f87..bcacff55d9bcfd5af76fafe7e5cfe239e14dcef0 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -550,6 +550,19 @@ Type* Typer::Visitor::TypeParameter(Node* node) { return Type::Any(); }
 
 Type* Typer::Visitor::TypeOsrValue(Node* node) { return Type::Any(); }
 
+Type* Typer::Visitor::TypeOsrGuard(Node* node) {
+  switch (OsrGuardTypeOf(node->op())) {
+    case OsrGuardType::kUninitialized:
+      return Type::None();
+    case OsrGuardType::kSignedSmall:
+      return Type::SignedSmall();
+    case OsrGuardType::kAny:
+      return Type::Any();
+  }
+  UNREACHABLE();
+  return nullptr;
+}
+
 Type* Typer::Visitor::TypeRetain(Node* node) {
   UNREACHABLE();
   return nullptr;