Compute preorder as well as postorder basic block orderings.

runtime/vm/compiler.cc

 // 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.
 
 #include "vm/compiler.h"
 
 #include "vm/assembler.h"
 #include "vm/ast_printer.h"
 #include "vm/code_generator.h"
 #include "vm/code_index_table.h"
@@ skipping 124 matching lines @@
     if (FLAG_use_new_compiler) {
       ASSERT(!optimized);
       LongJump* old_base = isolate->long_jump_base();
       LongJump bailout_jump;
       isolate->set_long_jump_base(&bailout_jump);
       if (setjmp(*bailout_jump.Set()) == 0) {
         FlowGraphBuilder graph_builder(parsed_function);
         graph_builder.BuildGraph();
 
         Assembler assembler;
-        FlowGraphCompiler graph_compiler(&assembler,
-                                         parsed_function,
-                                         graph_builder.blocks());
+        // The non-optimizing compiler compiles blocks in reverse postorder,
+        // because it is a 'natural' order for the human reader of the
+        // generated code.
+        intptr_t length = graph_builder.postorder_block_entries().length();
+        GrowableArray<BlockEntryInstr*> block_order(length);
+        for (intptr_t i = length - 1; i >= 0; --i) {
+          block_order.Add(graph_builder.postorder_block_entries()[i]);
+        }
+        FlowGraphCompiler graph_compiler(&assembler, parsed_function,
+                                         block_order);
         graph_compiler.CompileGraph();
         const Code& code =
             Code::Handle(Code::FinalizeCode(function_fullname, &assembler));
         code.set_is_optimized(false);
         graph_compiler.FinalizePcDescriptors(code);
         graph_compiler.FinalizeVarDescriptors(code);
         graph_compiler.FinalizeExceptionHandlers(code);
         function.set_unoptimized_code(code);
         function.SetCode(code);
         ASSERT(CodePatcher::CodeIsPatchable(code));
@@ skipping 238 matching lines @@
   } else {
     result = isolate->object_store()->sticky_error();
     isolate->object_store()->clear_sticky_error();
   }
   isolate->set_long_jump_base(base);
   return result.raw();
 }
 
 
 }  // namespace dart