Fix misoptimization of 'is' test

runtime/vm/aot_optimizer.cc

Index: runtime/vm/aot_optimizer.cc
diff --git a/runtime/vm/aot_optimizer.cc b/runtime/vm/aot_optimizer.cc
index 513936c56eb1692baf4aace5b803d29e1262e1f9..9f359d35c03782f569c8d5e937d30ffbf1814af1 100644
--- a/runtime/vm/aot_optimizer.cc
+++ b/runtime/vm/aot_optimizer.cc
@@ -17,10 +17,11 @@
 #include "vm/flow_graph_range_analysis.h"
 #include "vm/hash_map.h"
 #include "vm/il_printer.h"
-#include "vm/jit_optimizer.h"
 #include "vm/intermediate_language.h"
+#include "vm/jit_optimizer.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
+#include "vm/optimizer.h"
 #include "vm/parser.h"
 #include "vm/precompiler.h"
 #include "vm/resolver.h"
@@ -1348,73 +1349,6 @@ bool AotOptimizer::TypeCheckAsClassEquality(const AbstractType& type) {
 }
 
 
-static bool CidTestResultsContains(const ZoneGrowableArray<intptr_t>& results,
-                                   intptr_t test_cid) {
-  for (intptr_t i = 0; i < results.length(); i += 2) {
-    if (results[i] == test_cid) return true;
-  }
-  return false;
-}
-
-
-static void TryAddTest(ZoneGrowableArray<intptr_t>* results,
-                       intptr_t test_cid,
-                       bool result) {
-  if (!CidTestResultsContains(*results, test_cid)) {
-    results->Add(test_cid);
-    results->Add(result);
-  }
-}
-
-
-// Tries to add cid tests to 'results' so that no deoptimization is
-// necessary.
-// TODO(srdjan): Do also for other than 'int' type.
-static bool TryExpandTestCidsResult(ZoneGrowableArray<intptr_t>* results,
-                                    const AbstractType& type) {
-  ASSERT(results->length() >= 2);  // At least on entry.
-  const ClassTable& class_table = *Isolate::Current()->class_table();
-  if ((*results)[0] != kSmiCid) {
-    const Class& cls = Class::Handle(class_table.At(kSmiCid));
-    const Class& type_class = Class::Handle(type.type_class());
-    const bool smi_is_subtype =
-        cls.IsSubtypeOf(Object::null_type_arguments(), type_class,
-                        Object::null_type_arguments(), NULL, NULL, Heap::kOld);
-    results->Add((*results)[results->length() - 2]);
-    results->Add((*results)[results->length() - 2]);
-    for (intptr_t i = results->length() - 3; i > 1; --i) {
-      (*results)[i] = (*results)[i - 2];
-    }
-    (*results)[0] = kSmiCid;
-    (*results)[1] = smi_is_subtype;
-  }
-
-  ASSERT(type.IsInstantiated() && !type.IsMalformedOrMalbounded());
-  ASSERT(results->length() >= 2);
-  if (type.IsSmiType()) {
-    ASSERT((*results)[0] == kSmiCid);
-    return false;
-  } else if (type.IsIntType()) {
-    ASSERT((*results)[0] == kSmiCid);
-    TryAddTest(results, kMintCid, true);
-    TryAddTest(results, kBigintCid, true);
-    // Cannot deoptimize since all tests returning true have been added.
-    return false;
-  } else if (type.IsNumberType()) {
-    ASSERT((*results)[0] == kSmiCid);
-    TryAddTest(results, kMintCid, true);
-    TryAddTest(results, kBigintCid, true);
-    TryAddTest(results, kDoubleCid, true);
-    return false;
-  } else if (type.IsDoubleType()) {
-    ASSERT((*results)[0] == kSmiCid);
-    TryAddTest(results, kDoubleCid, true);
-    return false;
-  }
-  return true;  // May deoptimize since we have not identified all 'true' tests.
-}
-
-
 // TODO(srdjan): Use ICData to check if always true or false.
 void AotOptimizer::ReplaceWithInstanceOf(InstanceCallInstr* call) {
   ASSERT(Token::IsTypeTestOperator(call->token_kind()));
@@ -1511,7 +1445,9 @@ void AotOptimizer::ReplaceWithInstanceOf(InstanceCallInstr* call) {
         new (Z) ZoneGrowableArray<intptr_t>(number_of_checks * 2);
     InstanceOfAsBool(unary_checks, type, results);
     if (results->length() == number_of_checks * 2) {
-      const bool can_deopt = TryExpandTestCidsResult(results, type);
+      bool int_type_only = false;

[Vyacheslav Egorov (Google), 2017/05/23 16:00:31]

const kIntTypeOnly = false;

[erikcorry, 2017/05/24 13:37:15]

Looking at the performance bot, it seems the effect of this flag is
indistinguishable from noise, so I will get rid of it instead.

+      const bool can_deopt =
+          Optimizer::TryExpandTestCidsResult(results, type, int_type_only);
       if (can_deopt && !IsAllowedForInlining(call->deopt_id())) {
         // Guard against repeated speculative inlining.
         return;