When HBranch sees Smi, it sees Smi.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 53d92d7a2178a5cd636cb564a817c1fe0d4b9884..02d0da40587191602105861feea905794228655d 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -1286,7 +1286,7 @@ Representation HBranch::observed_input_representation(int index) {
   } else if (expected_input_types_.Contains(ToBooleanStub::HEAP_NUMBER)) {
     return Representation::Double();
   } else if (expected_input_types_.Contains(ToBooleanStub::SMI)) {
-    return Representation::Integer32();
+    return Representation::Smi();
   } else {
     return Representation::None();
   }