VM: Reduce the number of edge counters in generated code.

runtime/vm/block_scheduler.cc

 // Copyright (c) 2013, 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/block_scheduler.h"
 
 #include "vm/allocation.h"
 #include "vm/code_patcher.h"
 #include "vm/flow_graph.h"
 
@@ skipping 19 matching lines @@
 
 
 // There is an edge from instruction->successor.  Set its weight (edge count
 // per function entry).
 static void SetEdgeWeight(Instruction* instruction,
                           BlockEntryInstr* successor,
                           const Code& unoptimized_code,
                           intptr_t entry_count) {
   TargetEntryInstr* target = successor->AsTargetEntry();
   if (target != NULL) {
-    intptr_t count = ComputeEdgeCount(unoptimized_code, target->deopt_id());
+    // If this block ends in a goto, the edge count of this edge is the same
+    // as the count on the single outgoing edge. This is true as long as the
+    // block does not throw an exception.
+    GotoInstr* jump = target->last_instruction()->AsGoto();
+    const intptr_t deopt_id =
+        (jump != NULL)  ? jump->deopt_id() : target->deopt_id();
+    intptr_t count = ComputeEdgeCount(unoptimized_code, deopt_id);
     if ((count >= 0) && (entry_count != 0)) {
       double weight =
           static_cast<double>(count) / static_cast<double>(entry_count);
       target->set_edge_weight(weight);
     }
   } else {
     GotoInstr* jump = instruction->AsGoto();
     if (jump != NULL) {
       intptr_t count = ComputeEdgeCount(unoptimized_code, jump->deopt_id());
       if ((count >= 0) && (entry_count != 0)) {
@@ skipping 151 matching lines @@
   for (intptr_t i = block_count - 1; i >= 0; --i) {
     if (chains[i]->first->block == flow_graph()->postorder()[i]) {
       for (Link* link = chains[i]->first; link != NULL; link = link->next) {
         flow_graph()->CodegenBlockOrder(true)->Add(link->block);
       }
     }
   }
 }
 
 }  // namespace dart