A simpler scheme for garbage collection of ureachable phi inputs.

runtime/vm/flow_graph_builder.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_FLOW_GRAPH_BUILDER_H_
 #define VM_FLOW_GRAPH_BUILDER_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 16 matching lines @@
     kEffectContext,
     kTestContext
   };
 
   FlowGraph* BuildGraph(InliningContext context);
 
   const ParsedFunction& parsed_function() const { return parsed_function_; }
 
   void Bailout(const char* reason);
 
+  intptr_t AllocateBlockId() { return ++last_used_block_id_; }
+
   void set_context_level(intptr_t value) { context_level_ = value; }
   intptr_t context_level() const { return context_level_; }
 
   // Each try in this function gets its own try index.
   intptr_t AllocateTryIndex() { return ++last_used_try_index_; }
 
   // Manage the currently active try index.
   void set_try_index(intptr_t value) { try_index_ = value; }
   intptr_t try_index() const { return try_index_; }
 
@@ skipping 24 matching lines @@
   intptr_t variable_count() const {
     return parameter_count() + num_stack_locals_;
   }
 
   const ParsedFunction& parsed_function_;
 
   const intptr_t num_copied_params_;
   const intptr_t num_non_copied_params_;
   const intptr_t num_stack_locals_;  // Does not include any parameters.
 
+  intptr_t last_used_block_id_;
   intptr_t context_level_;
   intptr_t last_used_try_index_;
   intptr_t try_index_;
   GraphEntryInstr* graph_entry_;
   InliningContext inlining_context_;
   ZoneGrowableArray<ReturnInstr*>* exits_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FlowGraphBuilder);
 };
 
@@ skipping 297 matching lines @@
   // Output parameters.
   GrowableArray<TargetEntryInstr**> true_successor_addresses_;
   GrowableArray<TargetEntryInstr**> false_successor_addresses_;
 
   intptr_t condition_token_pos_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_BUILDER_H_