VN: Canonicalize compares before calling vn_nary_op_lookup_pieces

VN: Canonicalize compares before calling vn_nary_op_lookup_pieces

This is the followup as mentioned in
https://gcc.gnu.org/pipermail/gcc-patches/2024-November/667987.html .
We need to canonicalize the compares using tree_swap_operands_p instead
of checking CONSTANT_CLASS_P.

Bootstrapped and tested on x86_64-linux-gnu.

gcc/ChangeLog:

	* tree-ssa-sccvn.cc (visit_phi): Swap the operands
	before calling vn_nary_op_lookup_pieces if
	tree_swap_operands_p returns true.
	(insert_predicates_for_cond): Use tree_swap_operands_p
	instead of checking for CONSTANT_CLASS_P.
	(process_bb): Swap the comparison and operands
	if tree_swap_operands_p returns true.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>