MIPS: Fix and simplify code aging.

src/mips/builtins-mips.cc

 // Copyright 2012 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 795 matching lines @@
 }
 
 
 static void GenerateMakeCodeYoungAgainCommon(MacroAssembler* masm) {
   // For now, we are relying on the fact that make_code_young doesn't do any
   // garbage collection which allows us to save/restore the registers without
   // worrying about which of them contain pointers. We also don't build an
   // internal frame to make the code faster, since we shouldn't have to do stack
   // crawls in MakeCodeYoung. This seems a bit fragile.
 
-  __ mov(a0, ra);
-  // Adjust a0 to point to the head of the PlatformCodeAge sequence
+  // Set a0 to point to the head of the PlatformCodeAge sequence.
   __ Subu(a0, a0,
       Operand((kNoCodeAgeSequenceLength - 1) * Assembler::kInstrSize));
-  // Restore the original return address of the function
-  __ mov(ra, at);
 
   // The following registers must be saved and restored when calling through to
   // the runtime:
   //   a0 - contains return address (beginning of patch sequence)
   //   a1 - isolate
   RegList saved_regs =
       (a0.bit() | a1.bit() | ra.bit() | fp.bit()) & ~sp.bit();
   FrameScope scope(masm, StackFrame::MANUAL);
   __ MultiPush(saved_regs);
   __ PrepareCallCFunction(1, 0, a2);
@@ skipping 16 matching lines @@
 CODE_AGE_LIST(DEFINE_CODE_AGE_BUILTIN_GENERATOR)
 #undef DEFINE_CODE_AGE_BUILTIN_GENERATOR
 
 
 void Builtins::Generate_MarkCodeAsExecutedOnce(MacroAssembler* masm) {
   // For now, as in GenerateMakeCodeYoungAgainCommon, we are relying on the fact
   // that make_code_young doesn't do any garbage collection which allows us to
   // save/restore the registers without worrying about which of them contain
   // pointers.
 
-  __ mov(a0, ra);
-  // Adjust a0 to point to the head of the PlatformCodeAge sequence
+  // Set a0 to point to the head of the PlatformCodeAge sequence.
   __ Subu(a0, a0,
       Operand((kNoCodeAgeSequenceLength - 1) * Assembler::kInstrSize));
-  // Restore the original return address of the function
-  __ mov(ra, at);
 
   // The following registers must be saved and restored when calling through to
   // the runtime:
   //   a0 - contains return address (beginning of patch sequence)
   //   a1 - isolate
   RegList saved_regs =
       (a0.bit() | a1.bit() | ra.bit() | fp.bit()) & ~sp.bit();
   FrameScope scope(masm, StackFrame::MANUAL);
   __ MultiPush(saved_regs);
   __ PrepareCallCFunction(1, 0, a2);
@@ skipping 650 matching lines @@
   __ bind(&dont_adapt_arguments);
   __ Jump(a3);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS