Fix clobbered register when setting this_function variable.

src/ppc/full-codegen-ppc.cc

Index: src/ppc/full-codegen-ppc.cc
diff --git a/src/ppc/full-codegen-ppc.cc b/src/ppc/full-codegen-ppc.cc
index 533e097fc379ebbb1453ca3a91133b0c1bf44d1b..cd6e7e60ab82fb38895e30e485de1d77c499829e 100644
--- a/src/ppc/full-codegen-ppc.cc
+++ b/src/ppc/full-codegen-ppc.cc
@@ -248,6 +248,10 @@ 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) {
+      __ LoadP(r4, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+      // The write barrier clobbers register again, keep is marked as such.
+    }
     SetVar(this_function_var, r4, r3, r5);
   }