ffi: elide useless by-value in calls.

We can avoid calling in methods in the by-value nuance
(copy == 0) on types known not to have by-value in semantics.
Basic types have no by-value in.
Pointers inherently have by-value in.
An aggregate has by-value in semantics if any of one
of its members does, otherwise not.

* ffi.c (struct txr_ffi_type): New bitfield member,
by_value_in.
(ffi_ptr_in_in, ffi_ptr_in_d_in): Elite in call if target
type's by_value_in flag is clear.
(ffi_struct_in): Short-circuit to a return if doing by-value,
and the FFI struct type has no by-value semantics.
(ffi_array_in_common): Likewise. In this code change, we
just have to replace the test whether the element type has
an in method with a test of its by_value_in flag.
(make_ffi_type_pointer): Set by_value_in flag to 1, since
pointers have by value in semantics. This is true also of
ptr-in, because a structure passed as an in parameter to a
function via ptr-in could itself contain ptr or ptr-out
elements.
(make_ffi_type_struct): Set the type's by_value_in if
any element type's by_value_in is true.
(make_ffi_type_array): Propagate the by_value_in flag from
the element type to the array type.
(ffi_call_wrap): Calculate the in_pass_needed local flag
from the by_value_in flags of the arguments, not from whether
or not they have an in function. Only call the in function
for arguments which have the flag set.

0 files changed, 0 insertions, 0 deletions