[turbofan] Distinguish between change- and truncate-tagged-to-float64.

test/cctest/compiler/test-representation-change.cc

Index: test/cctest/compiler/test-representation-change.cc
diff --git a/test/cctest/compiler/test-representation-change.cc b/test/cctest/compiler/test-representation-change.cc
index 76aa390491a700bb152596c5eb23ea753676efdd..6b57244015b9c3032e486195bb8d53df4b37a966 100644
--- a/test/cctest/compiler/test-representation-change.cc
+++ b/test/cctest/compiler/test-representation-change.cc
@@ -473,7 +473,10 @@ TEST(SingleChanges) {
   CheckChange(IrOpcode::kChangeTaggedToFloat64, MachineRepresentation::kTagged,
               Type::Number(), MachineRepresentation::kFloat64);
   CheckChange(IrOpcode::kChangeTaggedToFloat64, MachineRepresentation::kTagged,
-              Type::NumberOrUndefined(), MachineRepresentation::kFloat64);
+              Type::Number(), MachineRepresentation::kFloat64);
+  CheckChange(IrOpcode::kTruncateTaggedToFloat64,
+              MachineRepresentation::kTagged, Type::NumberOrUndefined(),
+              MachineRepresentation::kFloat64);
   CheckTwoChanges(IrOpcode::kChangeTaggedSignedToInt32,
                   IrOpcode::kChangeInt32ToFloat64,
                   MachineRepresentation::kTagged, Type::TaggedSigned(),