MIPS: Add code again to allow reclaiming old unexecuted functions.

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 1237 matching lines @@
     __ pop(a1);
 
     // Tear down temporary frame.
   }
 
   // Do a tail-call of the compiled function.
   __ Jump(t9);
 }
 
 
-// Just a dummy for now, so snapshot generation works.
 static void GenerateMakeCodeYoungAgainCommon(MacroAssembler* masm) {
-  __ Ret();
+  // 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
+  __ 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 - function object
+  RegList saved_regs =
+      (a0.bit() | a1.bit() | ra.bit() | fp.bit()) & ~sp.bit();
+  FrameScope scope(masm, StackFrame::MANUAL);
+  __ MultiPush(saved_regs);
+  __ PrepareCallCFunction(1, 0, a1);
+  __ CallCFunction(
+      ExternalReference::get_make_code_young_function(masm->isolate()), 1);
+  __ MultiPop(saved_regs);
+  __ Jump(a0);
 }
 
-
 #define DEFINE_CODE_AGE_BUILTIN_GENERATOR(C)                 \
 void Builtins::Generate_Make##C##CodeYoungAgainEvenMarking(  \
     MacroAssembler* masm) {                                  \
   GenerateMakeCodeYoungAgainCommon(masm);                    \
 }                                                            \
 void Builtins::Generate_Make##C##CodeYoungAgainOddMarking(   \
     MacroAssembler* masm) {                                  \
   GenerateMakeCodeYoungAgainCommon(masm);                    \
 }
 CODE_AGE_LIST(DEFINE_CODE_AGE_BUILTIN_GENERATOR)
@@ skipping 581 matching lines @@
   __ bind(&dont_adapt_arguments);
   __ Jump(a3);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS