PPC64: Adjust simulator stack safety margin.

src/ppc/simulator-ppc.h

 // Copyright 2014 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.
 
 
 // Declares a Simulator for PPC instructions if we are not generating a native
 // PPC binary. This Simulator allows us to run and debug PPC code generation on
 // regular desktop machines.
 // V8 calls into generated code by "calling" the CALL_GENERATED_CODE macro,
 // which will start execution in the Simulator or forwards to the real entry
@@ skipping 333 matching lines @@
   int32_t fp_condition_reg_;
   intptr_t special_reg_lr_;
   intptr_t special_reg_pc_;
   intptr_t special_reg_ctr_;
   int32_t special_reg_xer_;
 
   int64_t fp_registers_[kNumFPRs];
 
   // Simulator support.
   char* stack_;
+  static const size_t stack_protection_size_ = 256 * kPointerSize;
   bool pc_modified_;
   int icount_;
 
   // Debugger input.
   char* last_debugger_input_;
 
   // Icache simulation
   v8::internal::HashMap* i_cache_;
 
   // Registered breakpoints.
@@ skipping 54 matching lines @@
 
   static inline void UnregisterCTryCatch() {
     Simulator::current(Isolate::Current())->PopAddress();
   }
 };
 }
 }  // namespace v8::internal
 
 #endif  // !defined(USE_SIMULATOR)
 #endif  // V8_PPC_SIMULATOR_PPC_H_