https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113576
--- Comment #32 from Richard Biener <rguenth at gcc dot gnu.org> ---
Btw, AVX512 knotb will invert all 8 bits and there's no knot just affecting
the lowest 4 or 2 bits.
It all feels like desaster waiting to happen ;)
For example BIT_NOT_EXPR is RTL expanded like
case BIT_NOT_EXPR:
op0 = expand_expr (treeop0, subtarget,
VOIDmode, EXPAND_NORMAL);
if (modifier == EXPAND_STACK_PARM)
target = 0;
/* In case we have to reduce the result to bitfield precision
for unsigned bitfield expand this as XOR with a proper constant
instead. */
if (reduce_bit_field && TYPE_UNSIGNED (type))
{
int_mode = SCALAR_INT_TYPE_MODE (type);
wide_int mask = wi::mask (TYPE_PRECISION (type),
false, GET_MODE_PRECISION (int_mode));
temp = expand_binop (int_mode, xor_optab, op0,
immed_wide_int_const (mask, int_mode),
target, 1, OPTAB_LIB_WIDEN);
so we could, for VECTOR_BOOLEAN_TYPE_P with integer mode and
effective bit-precision set reduce_bit_field and fixup the fallout
(not sure why the above is only for TYPE_UNSIGNED).
At least it feels similar and doing things the opposite for vectors
(fixing up at uses) would be odd?
