Fix mozilla regress-398085-01 failure on windows.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 102 matching lines @@
 
   // Copy the string before recording it in the assembler to avoid
   // issues when the stack allocated buffer goes out of scope.
   int length = builder.position();
   Vector<char> copy = Vector<char>::New(length + 1);
   OS::MemCopy(copy.start(), builder.Finalize(), copy.length());
   masm()->RecordComment(copy.start());
 }
 
 
+#ifdef _MSC_VER
+void LCodeGen::MakeSureStackPagesMapped(int offset) {
+  const int kPageSize = 4 * KB;
+  for (offset -= kPageSize; offset > 0; offset -= kPageSize) {
+    __ movq(Operand(rsp, offset), rax);
+  }
+}
+#endif
+
+
 bool LCodeGen::GeneratePrologue() {
   ASSERT(is_generating());
 
   if (info()->IsOptimizing()) {
     ProfileEntryHookStub::MaybeCallEntryHook(masm_);
 
 #ifdef DEBUG
     if (strlen(FLAG_stop_at) > 0 &&
         info_->function()->name()->IsUtf8EqualTo(CStrVector(FLAG_stop_at))) {
       __ int3();
@@ skipping 29 matching lines @@
       __ push(rdi);  // Callee's JS function.
     }
     info()->AddNoFrameRange(0, masm_->pc_offset());
   }
 
   // Reserve space for the stack slots needed by the code.
   int slots = GetStackSlotCount();
   if (slots > 0) {
     if (FLAG_debug_code) {
       __ subq(rsp, Immediate(slots * kPointerSize));
+#ifdef _MSC_VER
+      MakeSureStackPagesMapped(slots * kPointerSize);
+#endif
       __ push(rax);
       __ Set(rax, slots);
       __ movq(kScratchRegister, kSlotsZapValue, RelocInfo::NONE64);
       Label loop;
       __ bind(&loop);
       __ movq(MemOperand(rsp, rax, times_pointer_size, 0),
               kScratchRegister);
       __ decl(rax);
       __ j(not_zero, &loop);
       __ pop(rax);
     } else {
       __ subq(rsp, Immediate(slots * kPointerSize));
 #ifdef _MSC_VER
-      // On windows, you may not access the stack more than one page below
-      // the most recently mapped page. To make the allocated area randomly
-      // accessible, we write to each page in turn (the value is irrelevant).
-      const int kPageSize = 4 * KB;
-      for (int offset = slots * kPointerSize - kPageSize;
-           offset > 0;
-           offset -= kPageSize) {
-        __ movq(Operand(rsp, offset), rax);
-      }
+      MakeSureStackPagesMapped(slots * kPointerSize);
 #endif
     }
 
     if (info()->saves_caller_doubles()) {
       Comment(";;; Save clobbered callee double registers");
       int count = 0;
       BitVector* doubles = chunk()->allocated_double_registers();
       BitVector::Iterator save_iterator(doubles);
       while (!save_iterator.Done()) {
         __ movsd(MemOperand(rsp, count * kDoubleSize),
@@ skipping 5355 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64