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

src/arm64/builtins-arm64.cc

 // Copyright 2013 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_ARM64
 
 #include "src/arm64/frames-arm64.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 1959 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 20 matching lines @@
   __ Ldr(scratch1,
          FieldMemOperand(scratch1, JSFunction::kSharedFunctionInfoOffset));
   __ Ldrsw(caller_args_count_reg,
            FieldMemOperand(scratch1,
                            SharedFunctionInfo::kFormalParameterCountOffset));
   __ 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) {
   ASM_LOCATION("Builtins::Generate_CallFunction");
   // ----------- S t a t e -------------
   //  -- x0 : the number of arguments (not including the receiver)
@@ skipping 612 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM