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

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 5a21230c91b460b49a264382019e37a87af68d05..b2348fca20f150474874e700bcc4d2e6c1e85750 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -1255,12 +1255,35 @@ void Builtins::Generate_LazyRecompile(MacroAssembler* masm) {
 }
 
 
-// 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) {                                  \