A64: Tidy up a few TODOs.

src/a64/macro-assembler-a64.h

Index: src/a64/macro-assembler-a64.h
diff --git a/src/a64/macro-assembler-a64.h b/src/a64/macro-assembler-a64.h
index f5fa14f7dac1dd3483a981fb631a94bcc5f1c440..a9cf18909036c330d5f35dfac4c90c33783a83e7 100644
--- a/src/a64/macro-assembler-a64.h
+++ b/src/a64/macro-assembler-a64.h
@@ -1047,7 +1047,6 @@ class MacroAssembler : public Assembler {
     CallRuntime(Runtime::FunctionForId(id), num_arguments, save_doubles);
   }
 
-  // TODO(all): Why does this variant save FP regs unconditionally?
   void CallRuntimeSaveDoubles(Runtime::FunctionId id) {
     const Runtime::Function* function = Runtime::FunctionForId(id);
     CallRuntime(function, function->nargs, kSaveFPRegs);
@@ -1110,9 +1109,10 @@ class MacroAssembler : public Assembler {
                      const CallWrapper& call_wrapper = NullCallWrapper());
 
   // Store the code object for the given builtin in the target register and
-  // setup the function in x1.
-  // TODO(all): Can we use another register than x1?
-  void GetBuiltinEntry(Register target, Builtins::JavaScript id);
+  // setup the function in the function register.
+  void GetBuiltinEntry(Register target,
+                       Register function,
+                       Builtins::JavaScript id);
 
   // Store the function for the given builtin in the target register.
   void GetBuiltinFunction(Register target, Builtins::JavaScript id);