Collect edge count profiling data and reorder basic blocks.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 9864e56417d311aea71e32c282ffa19e55b98662..a50bf18a53fcb9d98c50690091f4645b66328d8e 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -7,6 +7,7 @@
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
+#include "vm/block_scheduler.h"
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
 #include "vm/dart_entry.h"
@@ -52,6 +53,7 @@ DEFINE_FLAG(int, deoptimization_counter_licm_threshold, 8,
     "How many times we allow deoptimization before we disable LICM.");
 DEFINE_FLAG(bool, use_inlining, true, "Enable call-site inlining");
 DEFINE_FLAG(bool, range_analysis, true, "Enable range analysis");
+DEFINE_FLAG(bool, reorder_basic_blocks, true, "Enable basic-block reordering.");
 DEFINE_FLAG(bool, verify_compiler, false,
     "Enable compiler verification assertions");
 DECLARE_FLAG(bool, print_flow_graph);
@@ -305,6 +307,11 @@ static bool CompileParsedFunctionHelper(ParsedFunction* parsed_function,
         }
       }
 
+      BlockScheduler block_scheduler(flow_graph);
+      if (optimized && FLAG_reorder_basic_blocks) {
+        block_scheduler.AssignEdgeWeights();
+      }
+
       if (optimized) {
         TimerScope timer(FLAG_compiler_stats,
                          &CompilerStats::ssa_timer,
@@ -317,7 +324,6 @@ static bool CompileParsedFunctionHelper(ParsedFunction* parsed_function,
         }
       }
 
-
       // Collect all instance fields that are loaded in the graph and
       // have non-generic type feedback attached to them that can
       // potentially affect optimizations.
@@ -504,6 +510,7 @@ static bool CompileParsedFunctionHelper(ParsedFunction* parsed_function,
         // Perform register allocation on the SSA graph.
         FlowGraphAllocator allocator(*flow_graph);
         allocator.AllocateRegisters();
+        if (FLAG_reorder_basic_blocks) block_scheduler.ReorderBlocks();
 
         if (FLAG_print_flow_graph || FLAG_print_flow_graph_optimized) {
           FlowGraphPrinter::PrintGraph("After Optimizations", flow_graph);
@@ -511,9 +518,7 @@ static bool CompileParsedFunctionHelper(ParsedFunction* parsed_function,
       }
 
       Assembler assembler(use_far_branches);
-      FlowGraphCompiler graph_compiler(&assembler,
-                                       *flow_graph,
-                                       optimized);
+      FlowGraphCompiler graph_compiler(&assembler, flow_graph, optimized);
       {
         TimerScope timer(FLAG_compiler_stats,
                          &CompilerStats::graphcompiler_timer,