Avoid array allocation for f(*r2k_ary) when def f(x)

When calling a method that does not accept a positional splat
parameter with a splatted array with a ruby2_keywords flagged hash,
there is no need to duplicate the splatted array.  Previously,
Ruby would duplicate the splatted array and potentially modify
it before flattening it to the VM stack

Use a similar approach as the f(*ary, **hash) optimization,
flattening the splatted array to the VM stack without modifying
it, and make any modifications needed to the VM stack.

1 files changed, 26 insertions, 0 deletions

diff --git a/vm_args.c b/vm_args.c
index abd9cf75f6..84ffd2e983 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -734,6 +734,32 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
                     }
                     given_argc--;
                 }
+                else if (!ISEQ_BODY(iseq)->param.flags.has_rest) {
+                    // Avoid duping rest when not necessary
+                    // Copy rest elements and converted keyword hash directly to VM stack
+                    const VALUE *argv = RARRAY_CONST_PTR(args->rest);
+                    int j, i=args->argc, rest_len = RARRAY_LENINT(args->rest)-1;
+                    args->argc += rest_len;
+                    if (rest_len) {
+                        CHECK_VM_STACK_OVERFLOW(ec->cfp, rest_len+1);
+                        for (i, j=0; rest_len > 0; rest_len--, i++, j++) {
+                            locals[i] = argv[j];
+                        }
+                    }
+                    args->rest = Qfalse;
+                    ci_flag &= ~VM_CALL_ARGS_SPLAT;
+
+                    if (ISEQ_BODY(iseq)->param.flags.has_kw || ISEQ_BODY(iseq)->param.flags.has_kwrest) {
+                        given_argc--;
+                        keyword_hash = converted_keyword_hash;
+                    }
+                    else {
+                        args->argc += 1;
+                        locals[i] = converted_keyword_hash;
+                        keyword_hash = Qnil;
+                        kw_flag = 0;
+                    }
+                }
                 else {
                     if (rest_last != converted_keyword_hash) {
                         rest_last = converted_keyword_hash;