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

runtime/vm/stub_code_mips.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"
 #if defined(TARGET_ARCH_MIPS)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/heap.h"
 #include "vm/instructions.h"
 #include "vm/object_store.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/tags.h"
 
 #define __ assembler->
 
 namespace dart {
 
 DEFINE_FLAG(bool, inline_alloc, true, "Inline allocation of objects.");
 DEFINE_FLAG(bool, use_slow_path, false,
     "Set to true for debugging & verifying the slow paths.");
 DECLARE_FLAG(bool, trace_optimized_ic_calls);
 
+DECLARE_FLAG(bool, enable_debugger);
 
 // Input parameters:
 //   RA : return address.
 //   SP : address of last argument in argument array.
 //   SP + 4*S4 - 4 : address of first argument in argument array.
 //   SP + 4*S4 : address of return value.
 //   S5 : address of the runtime function to call.
 //   S4 : number of arguments to the call.
 void StubCode::GenerateCallToRuntimeStub(Assembler* assembler) {
   const intptr_t isolate_offset = NativeArguments::isolate_offset();
@@ skipping 1378 matching lines @@
     __ lw(T0, FieldAddress(S5, ICData::state_bits_offset()));
     ASSERT(ICData::NumArgsTestedShift() == 0);  // No shift needed.
     __ andi(T0, T0, Immediate(ICData::NumArgsTestedMask()));
     __ BranchEqual(T0, num_args, &ok);
     __ Stop("Incorrect stub for IC data");
     __ Bind(&ok);
   }
 #endif  // DEBUG
 
 
-  // Check single stepping.
-  Label not_stepping;
-  __ lw(T0, FieldAddress(CTX, Context::isolate_offset()));
-  __ lbu(T0, Address(T0, Isolate::single_step_offset()));
-  __ BranchEqual(T0, 0, &not_stepping);
-  // Call single step callback in debugger.
-  __ EnterStubFrame();
-  __ addiu(SP, SP, Immediate(-2 * kWordSize));
-  __ sw(S5, Address(SP, 1 * kWordSize));  // Preserve IC data.
-  __ sw(RA, Address(SP, 0 * kWordSize));  // Return address.
-  __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
-  __ lw(RA, Address(SP, 0 * kWordSize));
-  __ lw(S5, Address(SP, 1 * kWordSize));
-  __ addiu(SP, SP, Immediate(2 * kWordSize));
-  __ LeaveStubFrame();
-  __ Bind(&not_stepping);
+  if (FLAG_enable_debugger) {
+    // Check single stepping.
+    Label not_stepping;
+    __ lw(T0, FieldAddress(CTX, Context::isolate_offset()));
+    __ lbu(T0, Address(T0, Isolate::single_step_offset()));
+    __ BranchEqual(T0, 0, &not_stepping);
+    // Call single step callback in debugger.
+    __ EnterStubFrame();
+    __ addiu(SP, SP, Immediate(-2 * kWordSize));
+    __ sw(S5, Address(SP, 1 * kWordSize));  // Preserve IC data.
+    __ sw(RA, Address(SP, 0 * kWordSize));  // Return address.
+    __ CallRuntime(kSingleStepHandlerRuntimeEntry, 0);
+    __ lw(RA, Address(SP, 0 * kWordSize));
+    __ lw(S5, Address(SP, 1 * kWordSize));
+    __ addiu(SP, SP, Immediate(2 * kWordSize));
+    __ LeaveStubFrame();
+    __ Bind(&not_stepping);
+  }
 
   // Load argument descriptor into S4.
   __ lw(S4, FieldAddress(S5, ICData::arguments_descriptor_offset()));
   // Preserve return address, since RA is needed for subroutine call.
   __ mov(T2, RA);
   // Loop that checks if there is an IC data match.
   Label loop, update, test, found, get_class_id_as_smi;
   // S5: IC data object (preserved).
   __ lw(T0, FieldAddress(S5, ICData::ic_data_offset()));
   // T0: ic_data_array with check entries: classes and target functions.
@@ skipping 638 matching lines @@
   const Register right = T0;
   __ lw(left, Address(SP, 1 * kWordSize));
   __ lw(right, Address(SP, 0 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp1, temp2);
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS