Optimize "smi or old" filter in scavenger.

runtime/vm/raw_object.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 274 matching lines @@
     }
   };
 
   class ClassIdTag :
       public BitField<intptr_t, kClassIdTagPos, kClassIdTagSize> {};  // NOLINT
 
   bool IsHeapObject() const {
     uword value = reinterpret_cast<uword>(this);
     return (value & kSmiTagMask) == kHeapObjectTag;
   }
-
+  // Assumes this is a heap object.
   bool IsNewObject() const {
     ASSERT(IsHeapObject());
     uword addr = reinterpret_cast<uword>(this);
     return (addr & kNewObjectAlignmentOffset) == kNewObjectAlignmentOffset;
   }
+  // Assumes this is a heap object.
   bool IsOldObject() const {
     ASSERT(IsHeapObject());
     uword addr = reinterpret_cast<uword>(this);
     return (addr & kNewObjectAlignmentOffset) == kOldObjectAlignmentOffset;
   }
+  // Assumes this is a heap object.
   bool IsVMHeapObject() const;
 
+  // Like !IsHeapObject() || IsOldObject(), but compiles to a single branch.
+  bool IsSmiOrOldObject() const {
+    COMPILE_ASSERT(kHeapObjectTag == 1);
+    COMPILE_ASSERT(kNewObjectAlignmentOffset == kWordSize);
+    static const uword kNewObjectBits =
+        (kNewObjectAlignmentOffset | kHeapObjectTag);
+    const uword addr = reinterpret_cast<uword>(this);
+    return (addr & kNewObjectBits) != kNewObjectBits;
+  }
+
   // Support for GC marking bit.
   bool IsMarked() const {
     return MarkBit::decode(ptr()->tags_);
   }
   void SetMarkBit() {
     ASSERT(!IsMarked());
     uword tags = ptr()->tags_;
     ptr()->tags_ = MarkBit::update(true, tags);
   }
   void ClearMarkBit() {
@@ skipping 1667 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_