Small change to stack checks in unoptimized code.

src/ia32/deoptimizer-ia32.cc

-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 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
 //       with the distribution.
@@ skipping 86 matching lines @@
   if (FLAG_trace_deopt) {
     PrintF("[forced deoptimization: ");
     function->PrintName();
     PrintF(" / %x]\n", reinterpret_cast<uint32_t>(function));
   }
 }
 
 
 void Deoptimizer::PatchStackCheckCode(RelocInfo* rinfo,
                                       Code* replacement_code) {
-  // The stack check code matches the pattern (on ia32, for example):
+  // The stack check code matches the pattern:
   //
   //     cmp esp, <limit>
   //     jae ok
   //     call <stack guard>
+  //     test eax, <loop nesting depth>
   // ok: ...
   //
-  // We will patch the code to:
+  // We will patch away the branch so the code is:
   //
   //     cmp esp, <limit>  ;; Not changed
   //     nop
   //     nop
   //     call <on-stack replacment>
+  //     test eax, <loop nesting depth>
   // ok:
   Address call_target_address = rinfo->pc();
   ASSERT(*(call_target_address - 3) == 0x73 &&  // jae
-         *(call_target_address - 2) == 0x05 &&  // offset
+         *(call_target_address - 2) == 0x07 &&  // offset
          *(call_target_address - 1) == 0xe8);   // call
   *(call_target_address - 3) = 0x90;  // nop
   *(call_target_address - 2) = 0x90;  // nop
   rinfo->set_target_address(replacement_code->entry());
 }
 
 
 void Deoptimizer::RevertStackCheckCode(RelocInfo* rinfo, Code* check_code) {
+  // Replace the nops from patching (Deoptimizer::PatchStackCheckCode) to
+  // restore the conditional branch.
   Address call_target_address = rinfo->pc();
   ASSERT(*(call_target_address - 3) == 0x90 &&  // nop
          *(call_target_address - 2) == 0x90 &&  // nop
          *(call_target_address - 1) == 0xe8);   // call
   *(call_target_address - 3) = 0x73;  // jae
-  *(call_target_address - 2) = 0x05;  // offset
+  *(call_target_address - 2) = 0x07;  // offset
   rinfo->set_target_address(check_code->entry());
 }
 
 
 static int LookupBailoutId(DeoptimizationInputData* data, unsigned ast_id) {
   ByteArray* translations = data->TranslationByteArray();
   int length = data->DeoptCount();
   for (int i = 0; i < length; i++) {
     if (static_cast<unsigned>(data->AstId(i)->value()) == ast_id) {
       TranslationIterator it(translations,  data->TranslationIndex(i)->value());
@@ skipping 457 matching lines @@
     __ jmp(&done);
     ASSERT(masm()->pc_offset() - start == table_entry_size_);
   }
   __ bind(&done);
 }
 
 #undef __
 
 
 } }  // namespace v8::internal