Revert "Fix misoptimization of 'is' test"

runtime/vm/optimizer.cc

-// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#include "vm/optimizer.h"
-
-#include "vm/intermediate_language.h"
-#include "vm/object.h"
-
-namespace dart {
-
-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);
-  }
-}
-
-
-// Used when we only need the positive result because we return false by
-// default.
-static void PurgeNegativeTestCidsEntries(ZoneGrowableArray<intptr_t>* results) {
-  // We can't purge the Smi entry at the beginning since it is used in the
-  // Smi check before the Cid is loaded.
-  int dest = 2;
-  for (intptr_t i = 2; i < results->length(); i += 2) {
-    if (results->At(i + 1) != 0) {
-      (*results)[dest++] = results->At(i);
-      (*results)[dest++] = results->At(i + 1);
-    }
-  }
-  results->SetLength(dest);
-}
-
-
-bool Optimizer::SpecializeTestCidsForNumericTypes(
-    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);
-    PurgeNegativeTestCidsEntries(results);
-    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.
-    PurgeNegativeTestCidsEntries(results);
-    return false;
-  } else if (type.IsNumberType()) {
-    ASSERT((*results)[0] == kSmiCid);
-    TryAddTest(results, kMintCid, true);
-    TryAddTest(results, kBigintCid, true);
-    TryAddTest(results, kDoubleCid, true);
-    PurgeNegativeTestCidsEntries(results);
-    return false;
-  } else if (type.IsDoubleType()) {
-    ASSERT((*results)[0] == kSmiCid);
-    TryAddTest(results, kDoubleCid, true);
-    PurgeNegativeTestCidsEntries(results);
-    return false;
-  }
-  return true;  // May deoptimize since we have not identified all 'true' tests.
-}
-
-}  // namespace dart