Put live register bits in stackmaps.

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 797 matching lines @@
 // live object index starting from the base of the frame.
 //
 // The Stackmap also consists of a link to the code object corresponding to
 // the frame which the stack map is describing.  The bit map representation
 // is optimized for dense and small bit maps, without any upper bound.
 class RawStackmap : public RawObject {
   RAW_HEAP_OBJECT_IMPLEMENTATION(Stackmap);
 
   RawCode* code_;  // Code object corresponding to the frame described.
 
+  // TODO(kmillikin): We need a small number of bits to encode the register
+  // count.  Consider packing them in with the length.
   intptr_t length_;  // Length of payload, in bits.
+  intptr_t register_count_;  // Count of live registers, included in length_.
+
   uword pc_;  // PC corresponding to this stack map representation.
 
   // Variable length data follows here (bitmap of the stack layout).
   uint8_t data_[0];
 };
 
 
 class RawLocalVarDescriptors : public RawObject {
  public:
   enum VarInfoKind {
@@ skipping 751 matching lines @@
          kExternalUint64ArrayCid == kByteArrayCid + 18 &&
          kExternalFloat32ArrayCid == kByteArrayCid + 19 &&
          kExternalFloat64ArrayCid == kByteArrayCid + 20 &&
          kStacktraceCid == kByteArrayCid + 21);
   return (index >= kByteArrayCid && index <= kExternalFloat64ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_