https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102281
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
__builtin_clear_padding when folded emits a series of memory stores rather than
BIT_INSERT_EXPR etc., so that wouldn't work.
But, IMNSHO, -ftrivial-auto-var-init* shouldn't be adding
__builtin_clear_padding calls at all for objects of types that can't have any
padding.
Currently one can do e.g. what my
r12-3455-g8122fbff770bcff183a9c3c72e8092c0ca32150b does for OpenMP atomics,
+ bool clear_padding = false;
+ if (BITS_PER_UNIT == 8 && CHAR_BIT == 8)
+ {
+ HOST_WIDE_INT sz = int_size_in_bytes (cmptype), i;
+ gcc_assert (sz > 0);
+ unsigned char *buf = XALLOCAVEC (unsigned char, sz);
+ memset (buf, ~0, sz);
+ clear_type_padding_in_mask (cmptype, buf);
+ for (i = 0; i < sz; i++)
+ if (buf[i] != (unsigned char) ~0)
+ {
+ clear_padding = true;
+ break;
+ }
+ }
so that when nothing needs to be padded (the usual case for non-struct/union
types unless they have extended long double), the builtin isn't added at all.
I doubt we support vectors of long double, so it is mainly whether returning of
long double or _Complex long double works fine.
