Add flag —enable-debugger (default true) in order to disable debugger single stepping code.

runtime/vm/intermediate_language_x64.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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/locations.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
 #define __ compiler->assembler()->
 
 namespace dart {
 
+DECLARE_FLAG(bool, emit_edge_counters);
 DECLARE_FLAG(int, optimization_counter_threshold);
 DECLARE_FLAG(bool, propagate_ic_data);
 DECLARE_FLAG(bool, throw_on_javascript_int_overflow);
 DECLARE_FLAG(bool, use_osr);
 
 // Generic summary for call instructions that have all arguments pushed
 // on the stack and return the result in a fixed register RAX.
 LocationSummary* Instruction::MakeCallSummary() {
   LocationSummary* result = new LocationSummary(0, 0, LocationSummary::kCall);
   result->set_out(0, Location::RegisterLocation(RAX));
@@ skipping 5523 matching lines @@
 void GraphEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   if (!compiler->CanFallThroughTo(normal_entry())) {
     __ jmp(compiler->GetJumpLabel(normal_entry()));
   }
 }
 
 
 void TargetEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ Bind(compiler->GetJumpLabel(this));
   if (!compiler->is_optimizing()) {
-    compiler->EmitEdgeCounter();
+    if (FLAG_emit_edge_counters) {
+      compiler->EmitEdgeCounter();
+    }
     // The deoptimization descriptor points after the edge counter code for
     // uniformity with ARM and MIPS, where we can reuse pattern matching
     // code that matches backwards from the end of the pattern.
     compiler->AddCurrentDescriptor(PcDescriptors::kDeopt,
                                    deopt_id_,
                                    Scanner::kNoSourcePos);
   }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
   }
 }
 
 
 LocationSummary* GotoInstr::MakeLocationSummary(bool opt) const {
   return new LocationSummary(0, 0, LocationSummary::kNoCall);
 }
 
 
 void GotoInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   if (!compiler->is_optimizing()) {
-    compiler->EmitEdgeCounter();
+    if (FLAG_emit_edge_counters) {
+      compiler->EmitEdgeCounter();
+    }
     // Add a deoptimization descriptor for deoptimizing instructions that
     // may be inserted before this instruction.  This descriptor points
     // after the edge counter for uniformity with ARM and MIPS, where we can
     // reuse pattern matching that matches backwards from the end of the
     // pattern.
     compiler->AddCurrentDescriptor(PcDescriptors::kDeopt,
                                    GetDeoptId(),
                                    Scanner::kNoSourcePos);
   }
   if (HasParallelMove()) {
@@ skipping 184 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64