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, 2 insertions, 0 deletions

diff --git a/vm_callinfo.h b/vm_callinfo.h
index 8437f2176c..2165582a2f 100644
--- a/vm_callinfo.h
+++ b/vm_callinfo.h
@@ -25,6 +25,7 @@ enum vm_call_flag_bits {
     VM_CALL_ZSUPER_bit,         // zsuper
     VM_CALL_OPT_SEND_bit,       // internal flag
     VM_CALL_KW_SPLAT_MUT_bit,   // kw splat hash can be modified (to avoid allocating a new one)
+    VM_CALL_ARGS_SPLAT_MUT_bit, // args splat can be modified (to avoid allocating a new one)
     VM_CALL__END
 };
 
@@ -40,6 +41,7 @@ enum vm_call_flag_bits {
 #define VM_CALL_ZSUPER          (0x01 << VM_CALL_ZSUPER_bit)
 #define VM_CALL_OPT_SEND        (0x01 << VM_CALL_OPT_SEND_bit)
 #define VM_CALL_KW_SPLAT_MUT    (0x01 << VM_CALL_KW_SPLAT_MUT_bit)
+#define VM_CALL_ARGS_SPLAT_MUT  (0x01 << VM_CALL_ARGS_SPLAT_MUT_bit)
 
 struct rb_callinfo_kwarg {
     int keyword_len;