MIPS: Avoid use of a0 as return address in jalr.

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 b5a67b47dc59892991d1f785619f6191d77b8631..20b19295eb94ed8e46c2deb4d9581cc54c132a1a 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -1024,9 +1024,12 @@ 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.
 
-  // Set a0 to point to the head of the PlatformCodeAge sequence.
+  // Set a0 to point to the head of the PlatformCodeAge sequence, using ret adr.
+  __ mov(a0, ra);
   __ Subu(a0, a0,
       Operand(kNoCodeAgeSequenceLength - 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:
@@ -1063,9 +1066,12 @@ void Builtins::Generate_MarkCodeAsExecutedOnce(MacroAssembler* masm) {
   // save/restore the registers without worrying about which of them contain
   // pointers.
 
-  // Set a0 to point to the head of the PlatformCodeAge sequence.
+  // Set a0 to point to the head of the PlatformCodeAge sequence, using ret adr.
+  __ mov(a0, ra);
   __ Subu(a0, a0,
       Operand(kNoCodeAgeSequenceLength - 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: