MIPS: Fix and simplify code aging.

src/mips/builtins-mips.cc

Index: src/mips/builtins-mips.cc
diff --git a/src/mips/builtins-mips.cc b/src/mips/builtins-mips.cc
index d2641df6e675dcc5f08d4812874e723a493bc80a..19f3cdf4ff81bc837b7ba0958f2da6a63118ee90 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -813,12 +813,9 @@ static void GenerateMakeCodeYoungAgainCommon(MacroAssembler* masm) {
   // 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:
@@ -855,12 +852,9 @@ void Builtins::Generate_MarkCodeAsExecutedOnce(MacroAssembler* masm) {
   // 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: