[es6] Don't disable ES6 tail call elimination when Debugger is on.

src/arm/builtins-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 1915 matching lines @@
 // |  f()'s arg 1
 // |  f()'s receiver arg   <- sp (f()'s caller pc is not on the stack yet!)
 // ----------------------
 //
 void PrepareForTailCall(MacroAssembler* masm, Register args_reg,
                         Register scratch1, Register scratch2,
                         Register scratch3) {
   DCHECK(!AreAliased(args_reg, scratch1, scratch2, scratch3));
   Comment cmnt(masm, "[ PrepareForTailCall");
 
-  // Prepare for tail call only if the debugger is not active.
-  Label done;
-  ExternalReference debug_is_active =
-      ExternalReference::debug_is_active_address(masm->isolate());
-  __ mov(scratch1, Operand(debug_is_active));
-  __ ldrb(scratch1, MemOperand(scratch1));
-  __ cmp(scratch1, Operand(0));
-  __ b(ne, &done);
-
   // Drop possible interpreter handler/stub frame.
   {
     Label no_interpreter_frame;
     __ ldr(scratch3,
            MemOperand(fp, CommonFrameConstants::kContextOrFrameTypeOffset));
     __ cmp(scratch3, Operand(Smi::FromInt(StackFrame::STUB)));
     __ b(ne, &no_interpreter_frame);
     __ ldr(fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
     __ bind(&no_interpreter_frame);
   }
@@ skipping 23 matching lines @@
   __ ldr(caller_args_count_reg,
          FieldMemOperand(scratch1,
                          SharedFunctionInfo::kFormalParameterCountOffset));
   __ SmiUntag(caller_args_count_reg);
 
   __ bind(&formal_parameter_count_loaded);
 
   ParameterCount callee_args_count(args_reg);
   __ PrepareForTailCall(callee_args_count, caller_args_count_reg, scratch2,
                         scratch3);
-  __ bind(&done);
 }
 }  // namespace
 
 // static
 void Builtins::Generate_CallFunction(MacroAssembler* masm,
                                      ConvertReceiverMode mode,
                                      TailCallMode tail_call_mode) {
   // ----------- S t a t e -------------
   //  -- r0 : the number of arguments (not including the receiver)
   //  -- r1 : the function to call (checked to be a JSFunction)
@@ skipping 512 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM