isel: Fold more in gimple_expand_vec_cond_expr with andc and iorc [PR115659]

isel: Fold more in gimple_expand_vec_cond_expr with andc and iorc [PR115659]

As PR115659 shows, assuming c = x CMP y, there are some
folding chances for patterns r = c ? 0/z : z/-1:
  - for r = c ? 0 : z, it can be folded into r = ~c & z.
  - for r = c ? z : -1, it can be folded into r = ~c | z.

But BIT_AND/BIT_IOR applied on one BIT_NOT operand is a
compound operation, it's arguable to consider it beats
vector selection.  So this patch is to introduce new
optabs andc, iorc and its corresponding internal functions
BIT_{ANDC,IORC}, and if targets defines such optabs for
vector modes, it means targets support these hardware
insns and should be not worse than vector selection.

	PR tree-optimization/115659

gcc/ChangeLog:

	* doc/md.texi: Document andcm3 and iorcm3.
	* gimple-isel.cc (gimple_expand_vec_cond_expr): Add more foldings for
	patterns x CMP y ? 0 : z and x CMP y ? z : -1.
	* internal-fn.def (BIT_ANDC): New internal function.
	(BIT_IORC): Likewise.
	* optabs.def (andc, iorc): New optab.