Handle LoadClassId(obj) === cid during type propagation.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, 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/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/constant_propagator.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 134 matching lines @@
     // TODO(fschneider): Make sure ic_data are sorted to hit more cases.
     if (unary_checks().GetReceiverClassIdAt(i) !=
         other_check->unary_checks().GetReceiverClassIdAt(i)) {
       return false;
     }
   }
   return true;
 }
 
 
+bool CheckClassInstr::IsImmutableClassId(intptr_t cid) {
+  switch (cid) {
+    case kOneByteStringCid:
+    case kTwoByteStringCid:
+      return false;
+    default:
+      return true;
+  }
+}
+
+
+static bool AreAllChecksImmutable(const ICData& checks) {
+  const intptr_t len = checks.NumberOfChecks();
+  for (intptr_t i = 0; i < len; i++) {
+    if (checks.IsUsedAt(i)) {
+      if (!CheckClassInstr::IsImmutableClassId(
+              checks.GetReceiverClassIdAt(i))) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+
 EffectSet CheckClassInstr::Dependencies() const {
   // Externalization of strings via the API can change the class-id.
-  const bool externalizable =
-      unary_checks().HasReceiverClassId(kOneByteStringCid) ||
-      unary_checks().HasReceiverClassId(kTwoByteStringCid);
-  return externalizable ? EffectSet::Externalization() : EffectSet::None();
+  return !AreAllChecksImmutable(unary_checks()) ?
+      EffectSet::Externalization() : EffectSet::None();
 }
 
 
 EffectSet CheckClassIdInstr::Dependencies() const {
   // Externalization of strings via the API can change the class-id.
-  const bool externalizable =
-      cid_ == kOneByteStringCid || cid_ == kTwoByteStringCid;
-  return externalizable ? EffectSet::Externalization() : EffectSet::None();
+  return !CheckClassInstr::IsImmutableClassId(cid_) ?
+      EffectSet::Externalization() : EffectSet::None();
 }
 
 
 bool CheckClassInstr::IsNullCheck() const {
   if (unary_checks().NumberOfChecks() != 1) {
     return false;
   }
   CompileType* in_type = value()->Type();
   const intptr_t cid = unary_checks().GetCidAt(0);
   // Performance check: use CheckSmiInstr instead.
@@ skipping 3289 matching lines @@
     case Token::kTRUNCDIV: return 0;
     case Token::kMOD: return 1;
     default: UNIMPLEMENTED(); return -1;
   }
 }
 
 
 #undef __
 
 }  // namespace dart