Reapply "Fix misoptimization of 'is' test""

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index fdcca2fa4ea8fbe13c630dba90970158b4411fbf..c4c8932832f053a386c95419ff56178635a8a4d5 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -3104,21 +3104,19 @@ class TestSmiInstr : public TemplateComparison<2, NoThrow, Pure> {
 
 
 // Checks the input value cid against cids stored in a table and returns either
-// a result or deoptimizes.
+// a result or deoptimizes.  If the cid is not in the list and there is a deopt
+// id, then the instruction deoptimizes.  If there is no deopt id, all the
+// results must be the same (all true or all false) and the instruction returns
+// the opposite for cids not on the list.  The first element in the table must
+// always be the result for the Smi class-id and is allowed to differ from the
+// other results even in the no-deopt case.
 class TestCidsInstr : public TemplateComparison<1, NoThrow, Pure> {
  public:
   TestCidsInstr(TokenPosition token_pos,
                 Token::Kind kind,
                 Value* value,
                 const ZoneGrowableArray<intptr_t>& cid_results,
-                intptr_t deopt_id)
-      : TemplateComparison(token_pos, kind, deopt_id),
-        cid_results_(cid_results),
-        licm_hoisted_(false) {
-    ASSERT((kind == Token::kIS) || (kind == Token::kISNOT));
-    SetInputAt(0, value);
-    set_operation_cid(kObjectCid);
-  }
+                intptr_t deopt_id);
 
   const ZoneGrowableArray<intptr_t>& cid_results() const {
     return cid_results_;