X64: Optimize access to external references.

src/x64/deoptimizer-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 739 matching lines @@
     // Do not restore rsp, simply pop the value into the next register
     // and overwrite this afterwards.
     if (r.is(rsp)) {
       ASSERT(i > 0);
       r = Register::toRegister(i - 1);
     }
     __ pop(r);
   }
 
   // Set up the roots register.
-  ExternalReference roots_address = ExternalReference::roots_address();

[William Hesse, 2011/03/22 14:05:08]

Could this be necessary for serialization reasons?

[Lasse Reichstein, 2011/03/22 14:12:21]

I don't see how. It's a local variable that isn't used anywhere.
I think it's just a leftover from when InitializeRootRegister was introduced.

   __ InitializeRootRegister();
   __ InitializeSmiConstantRegister();
 
   // Return to the continuation point.
   __ ret(0);
 }
 
 
 void Deoptimizer::TableEntryGenerator::GeneratePrologue() {
   // Create a sequence of deoptimization entries.
   Label done;
   for (int i = 0; i < count(); i++) {
     int start = masm()->pc_offset();
     USE(start);
     __ push_imm32(i);
     __ jmp(&done);
     ASSERT(masm()->pc_offset() - start == table_entry_size_);
   }
   __ bind(&done);
 }
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64