Add VM_CALL_ARGS_SPLAT_MUT callinfo flag

This flag is set when the caller has already created a new array to
handle a splat, such as for `f(*a, b)` and `f(*a, *b)`.  Previously,
if `f` was defined as `def f(*a)`, these calls would create an extra
array on the callee side, instead of using the new array created
by the caller.

This modifies `setup_args_core` to set the flag whenver it would add
a `splatarray true` instruction.  However, when `splatarray true` is
changed to `splatarray false` in the peephole optimizer, to avoid
unnecessary allocations on the caller side, the flag must be removed.
Add `optimize_args_splat_no_copy` and have the peephole optimizer call
that.  This significantly simplifies the related peephole optimizer
code.

On the callee side, in `setup_parameters_complex`, set
`args->rest_dupped` to true if the flag is set.

This takes a similar approach for optimizing regular splats that was
previiously used for keyword splats in
d2c41b1bff1f3102544bb0d03d4e82356d034d33 (via VM_CALL_KW_SPLAT_MUT).

1 files changed, 1 insertions, 1 deletions

diff --git a/vm_args.c b/vm_args.c
index 37b765a41d..8171dcb8e0 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -510,7 +510,7 @@ setup_parameters_complex(rb_execution_context_t * const ec, const rb_iseq_t * co
     args = &args_body;
     given_argc = args->argc = calling->argc;
     args->argv = locals;
-    args->rest_dupped = FALSE;
+    args->rest_dupped = vm_ci_flag(ci) & VM_CALL_ARGS_SPLAT_MUT;
 
     if (kw_flag & VM_CALL_KWARG) {
         args->kw_arg = vm_ci_kwarg(ci);