[extend] special case ext_call "->"

might be a worthwile optimization. however:
16.589294527 0.13% => 16.612686915 0.21% on parrot-bench linux
similar on darwin, but darwin bench is more noisy

src/extend.c

@@ -149,17 +149,24 @@ Parrot_ext_call(PARROT_INTERP, ARGIN(Parrot_PMC sub_pmc),
     PMC  *call_obj = NULL;
     const char *arg_sig = NULL, *ret_sig = NULL;
     PMC * old_call_obj = Parrot_pcc_get_signature(interp, CURRENT_CONTEXT(interp));
-    Parrot_pcc_split_signature_string(signature, &arg_sig, &ret_sig);
 
-    va_start(args, signature);
-    call_obj = Parrot_pcc_build_call_from_varargs(interp, PMCNULL,
-        arg_sig, &args);
+    if (0 == strcmp(signature, "->")) {
+        call_obj = Parrot_pmc_new(interp, enum_class_CallContext);
+        Parrot_pcc_invoke_from_sig_object(interp, sub_pmc, call_obj);
+    }
+    else {
+        Parrot_pcc_split_signature_string(signature, &arg_sig, &ret_sig);
+
+        va_start(args, signature);
+        call_obj = Parrot_pcc_build_call_from_varargs(interp, PMCNULL,
+            arg_sig, &args);
 
-    Parrot_pcc_invoke_from_sig_object(interp, sub_pmc, call_obj);
-    call_obj = Parrot_pcc_get_signature(interp, CURRENT_CONTEXT(interp));
-    Parrot_pcc_fill_params_from_varargs(interp, call_obj, ret_sig, &args,
+        Parrot_pcc_invoke_from_sig_object(interp, sub_pmc, call_obj);
+        call_obj = Parrot_pcc_get_signature(interp, CURRENT_CONTEXT(interp));
+        Parrot_pcc_fill_params_from_varargs(interp, call_obj, ret_sig, &args,
             PARROT_ERRORS_RESULT_COUNT_FLAG);
-    va_end(args);
+        va_end(args);
+    }
     Parrot_pcc_set_signature(interp, CURRENT_CONTEXT(interp), old_call_obj);
 }