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

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
===================================================================
--- runtime/vm/flow_graph_compiler.cc	(revision 37078)
+++ runtime/vm/flow_graph_compiler.cc	(working copy)
@@ -27,6 +27,7 @@
 DECLARE_FLAG(bool, code_comments);
 DECLARE_FLAG(bool, disassemble);
 DECLARE_FLAG(bool, disassemble_optimized);
+DECLARE_FLAG(bool, emit_edge_counters);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, intrinsify);
 DECLARE_FLAG(bool, propagate_ic_data);
@@ -961,6 +962,15 @@
 }
 
 
+bool FlowGraphCompiler::NeedsEdgeCounter(TargetEntryInstr* block) {
+  // Only emit an edge counter if there is not goto at the end of the block,
+  // except for the entry block.
+  return (FLAG_emit_edge_counters
+      && (!block->last_instruction()->IsGoto()
+          || (block == flow_graph().graph_entry()->normal_entry())));
+}
+
+
 // Allocate a register that is not explicitly blocked.
 static Register AllocateFreeRegister(bool* blocked_registers) {
   for (intptr_t regno = 0; regno < kNumberOfCpuRegisters; regno++) {