The `f(arg, *arg, **arg, **arg)` case was previously not optimized. The optimizer didn't optimize this case because of the multiple keyword splats, and the compiler didn't optimize it because the `f(*arg, **arg, **arg)` optimization added in 0ee3960685e283d8e75149a8777eb0109d41509a didn't apply. I found it difficult to apply this optimization without changing the `setup_args_core` API, since by the time you get to the ARGSCAT case, you don't know whether you were called recursively or directly, so I'm not sure if it was possible to know at that point whether the array allocation could be avoided. This changes the dup_rest argument in `setup_args_core` from an int to a pointer to int. This allows us to track whether we have allocated a caller side array for multiple splats or splat+post across recursive calls. Check the pointed value (*dup_rest) to determine the `splatarray` argument. If dup_rest is 1, then use `splatarray true` (caller-side array allocation), then set *dup_rest back to 0, ensuring only a single `splatarray true` per method call. Before calling `setup_args_core`, check whether the array allocation can be avoided safely using `splatarray false`. Optimizable cases are: ``` // f(*arg) SPLAT // f(1, *arg) ARGSCAT LIST // f(*arg, **arg) ARGSPUSH SPLAT HASH nd_brace=0 // f(1, *arg, **arg) ARGSPUSH ARGSCAT LIST HASH nd_brace=0 ``` If so, dup_rest is set to 0 instead of 1 to avoid the allocation. After calling `setup_args_core`, check the flag. If the flag includes `VM_CALL_ARGS_SPLAT`, and the pointed value has changed, indicating `splatarray true` was used, then also set `VM_CALL_ARGS_SPLAT_MUT` in the flag. My initial attempt at this broke the `f(*ary, &ary.pop)` test, because we were not duplicating the ary in the splat even though it was modified later (evaluation order issue). The initial attempt would also break `f(*ary, **ary.pop)` or `f(*ary, kw: ary.pop)` cases for the same reason. I added test cases for those evaluation order issues. Add setup_args_dup_rest_p static function that checks that a given node is safe. Call that on the block pass node to determine if the block pass node is safe. Also call it on each of the hash key/value nodes to test that they are safe. If any are not safe, then set dup_rest = 1 so that `splatarray true` will be used to avoid the evaluation order issue. This new approach has the affect of optimizing most cases of literal keywords after positional splats. Previously, only static keyword hashes after positional splats avoided array allocation for the splat. Now, most dynamic keyword hashes after positional splats also avoid array allocation. Add allocation tests for dynamic keyword keyword hashes after positional splats. setup_args_dup_rest_p is currently fairly conservative. It could definitely be expanded to handle additional node types to reduce allocations in additional cases.