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 ebd7efe8fbdb5534631ed245aa7fae530a2f119f..493a1f9c7246226bc60f0b8a30f9a9fa1e14f7ae 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));
+      function_in_register = true;
+    }
     SetVar(this_function_var, r4, r3, r5);
   }