Remove --check-stack flag from V8.

src/x64/regexp-macro-assembler-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1191 matching lines @@
   __ cmpq(rsp, rax);
   __ j(above, &no_preempt);
 
   SafeCall(&check_preempt_label_);
 
   __ bind(&no_preempt);
 }
 
 
 void RegExpMacroAssemblerX64::CheckStackLimit() {
-  if (FLAG_check_stack) {
-    Label no_stack_overflow;
-    ExternalReference stack_limit =
-        ExternalReference::address_of_regexp_stack_limit();
-    __ load_rax(stack_limit);
-    __ cmpq(backtrack_stackpointer(), rax);
-    __ j(above, &no_stack_overflow);
+  Label no_stack_overflow;
+  ExternalReference stack_limit =
+      ExternalReference::address_of_regexp_stack_limit();
+  __ load_rax(stack_limit);
+  __ cmpq(backtrack_stackpointer(), rax);
+  __ j(above, &no_stack_overflow);
 
-    SafeCall(&stack_overflow_label_);
+  SafeCall(&stack_overflow_label_);
 
-    __ bind(&no_stack_overflow);
-  }
+  __ bind(&no_stack_overflow);
 }
 
 
 void RegExpMacroAssemblerX64::FrameAlign(int num_arguments) {
   // TODO(lrn): Since we no longer use the system stack arbitrarily (but we do
   // use it, e.g., for SafeCall), we know the number of elements on the stack
   // since the last frame alignment. We might be able to do this simpler then.
   int frameAlignment = OS::ActivationFrameAlignment();
   ASSERT(frameAlignment != 0);
   // Make stack end at alignment and make room for num_arguments pointers
@@ skipping 51 matching lines @@
                  Operand(rsi, rdi, times_1, cp_offset * sizeof(uc16)));
     }
   }
 }
 
 #undef __
 
 #endif  // V8_NATIVE_REGEXP
 
 }}  // namespace v8::internal