Re-landing of "replace TrySync with Metadata".

runtime/vm/exceptions.h

 // Copyright (c) 2011, 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 RUNTIME_VM_EXCEPTIONS_H_
 #define RUNTIME_VM_EXCEPTIONS_H_
 
 #include "vm/allocation.h"
 #include "vm/token_position.h"
 
@@ skipping 84 matching lines @@
 // The index into the ExceptionHandlers table corresponds to
 // the try_index of the handler.
 struct ExceptionHandlerInfo {
   uint32_t handler_pc_offset;  // PC offset value of handler.
   int16_t outer_try_index;     // Try block index of enclosing try block.
   int8_t needs_stacktrace;     // True if a stacktrace is needed.
   int8_t has_catch_all;        // Catches all exceptions.
   int8_t is_generated;         // True if this is a generated handler.
 };
 
+
+class CatchEntryState {
+ public:
+  enum { kCatchEntryStateIsMove = 1, kCatchEntryStateDestShift = 1 };
+
+  CatchEntryState() : data_(NULL), ref_count_(NULL) {}
+  explicit CatchEntryState(intptr_t* data)
+      : data_(data), ref_count_(new intptr_t(1)) {}
+
+  CatchEntryState(const CatchEntryState& state) { Copy(state); }
+
+  ~CatchEntryState() { Destroy(); }
+
+  CatchEntryState& operator=(const CatchEntryState& state) {
+    Destroy();
+    Copy(state);
+    return *this;
+  }
+
+  bool Empty() { return ref_count_ == NULL; }
+
+  intptr_t Pairs() { return data_[0]; }
+
+  intptr_t Src(intptr_t i) { return data_[1 + 2 * i]; }
+
+  intptr_t Dest(intptr_t i) {
+    return data_[2 + 2 * i] >> kCatchEntryStateDestShift;
+  }
+
+  bool isMove(intptr_t i) { return data_[2 + 2 * i] & kCatchEntryStateIsMove; }
+
+ private:
+  void Destroy() {
+    if (ref_count_ != NULL) {
+      (*ref_count_)--;
+      if (*ref_count_ == 0) {
+        delete ref_count_;
+        delete[] data_;
+      }
+    }
+  }
+
+  void Copy(const CatchEntryState& state) {
+    data_ = state.data_;
+    ref_count_ = state.ref_count_;
+    if (ref_count_ != NULL) {
+      (*ref_count_)++;
+    }
+  }
+
+  // data_ has the following format:
+  // 0 - number of pairs in this state
+  // 1-2 - 1st encoded src,dest pair
+  // 3-4 - 2nd pair
+  // ....
+  intptr_t* data_;
+  intptr_t* ref_count_;
+};
+
 }  // namespace dart
 
 #endif  // RUNTIME_VM_EXCEPTIONS_H_