Convert EqualityCompare to StrictCompare if reciever is either null or guaranteed to have default e…

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 0c64c347fe51721707a272bef7e638cfb00ed102..c897711bdadefdf01ece556fa2a4c6515df32112 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -1316,16 +1316,7 @@ Instruction* CheckClassInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
     return this;
   }
 
-  const intptr_t num_checks = unary_checks().NumberOfChecks();
-
-  for (intptr_t i = 0; i < num_checks; i++) {
-    if (value_cid == unary_checks().GetReceiverClassIdAt(i)) {
-      // No checks needed.
-      return NULL;
-    }
-  }
-
-  return this;
+  return unary_checks().HasReceiverClassId(value_cid) ? NULL : this;
 }