Fix clobbered register when setting this_function variable.

src/mips/full-codegen-mips.cc

Index: src/mips/full-codegen-mips.cc
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index 08a39a1400b2a872c8fb6ef9818d6b38cdcade48..5f2ed7534f3f97b0ee99620e8591ecc1c98c2346 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -252,6 +252,10 @@ void FullCodeGenerator::Generate() {
   Variable* this_function_var = scope()->this_function_var();
   if (this_function_var != nullptr) {
     Comment cmnt(masm_, "[ This function");
+    if (!function_in_register) {
+      __ lw(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+      // The write barrier clobbers register again, keep is marked as such.
+    }
     SetVar(this_function_var, a1, a2, a3);
   }