Compute preorder as well as postorder basic block orderings.

runtime/vm/flow_graph_compiler_x64.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_COMPILER_X64_H_
 #define VM_FLOW_GRAPH_COMPILER_X64_H_
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #error Include flow_graph_compiler.h instead of flow_graph_compiler_x64.h.
 #endif
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/intermediate_language.h"
 
 namespace dart {
 
 class Code;
 template <typename T> class GrowableArray;
 class ParsedFunction;
 
 class FlowGraphCompiler : public FlowGraphVisitor {
  public:
   FlowGraphCompiler(Assembler* assembler,
                     const ParsedFunction& parsed_function,
-                    const GrowableArray<BlockEntryInstr*>* blocks);
+                    const GrowableArray<BlockEntryInstr*>& block_order);
 
   virtual ~FlowGraphCompiler();
 
   void CompileGraph();
 
   // Infrastructure copied from class CodeGenerator or stubbed out.
   void FinalizePcDescriptors(const Code& code);
   void FinalizeVarDescriptors(const Code& code);
   void FinalizeExceptionHandlers(const Code& code);
 
  private:
   struct BlockInfo : public ZoneAllocated {
    public:
     BlockInfo() : label() { }
 
     Label label;
   };
 
   BlockEntryInstr* current_block() const { return current_block_; }
 
   // Bail out of the flow graph compiler.  Does not return to the caller.
   void Bailout(const char* reason);
 
-  virtual void VisitBlocks(const GrowableArray<BlockEntryInstr*>& blocks);
+  virtual void VisitBlocks();
 
   // Emit code to perform a computation, leaving its value in RAX.
 #define DECLARE_VISIT_COMPUTATION(ShortName, ClassName)                        \
   virtual void Visit##ShortName(ClassName* comp);
 
   // Each visit function compiles a type of instruction.
 #define DECLARE_VISIT_INSTRUCTION(ShortName)                                   \
   virtual void Visit##ShortName(ShortName##Instr* instr);
 
   FOR_EACH_COMPUTATION(DECLARE_VISIT_COMPUTATION)
@@ skipping 35 matching lines @@
                           bool negate_result);
 
   void GenerateInstantiatorTypeArguments(intptr_t token_index);
 
   void CopyParameters();
 
   intptr_t StackSize() const;
 
   Assembler* assembler_;
   const ParsedFunction& parsed_function_;
-  const GrowableArray<BlockEntryInstr*>* blocks_;
 
-  // Compiler specific per-block state.  Indexed by block number, so not
-  // necessarily the same order as the array of blocks.
+  // Compiler specific per-block state.  Indexed by postorder block number
+  // for convenience.  This is not the block's index in the block order,
+  // which is reverse postorder.
   GrowableArray<BlockInfo*> block_info_;
 
   BlockEntryInstr* current_block_;
 
   CodeGenerator::DescriptorList* pc_descriptors_list_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_X64_H_