Avoid array allocation for empty ruby2_keywords flagged keyword hash

If the method being called does not have a positional splat
parameter, there is no point in allocating the array, as
decrementing given_argc is sufficient to ensure the empty keyword
hash is not considered an argument, assuming that we are calling
a method/lambda and not a regular proc.

1 files changed, 5 insertions, 2 deletions

diff --git a/vm_args.c b/vm_args.c
index 1db62dc7e2..0c1a26cfad 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -693,8 +693,11 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
                 args->rest_dupped = false;
 
                 if (ignore_keyword_hash_p(rest_last, iseq, &kw_flag, &converted_keyword_hash)) {
-                    arg_rest_dup(args);
-                    rb_ary_pop(args->rest);
+                    if (ISEQ_BODY(iseq)->param.flags.has_rest || arg_setup_type != arg_setup_method) {
+                        // Only duplicate/modify splat array if it will be used
+                        arg_rest_dup(args);
+                        rb_ary_pop(args->rest);
+                    }
                     given_argc--;
                     kw_flag &= ~(VM_CALL_KW_SPLAT | VM_CALL_KW_SPLAT_MUT);
                 }