Make more use of VECTOR_CST_ENCODED_ELT

Make more use of VECTOR_CST_ENCODED_ELT

This patch makes various bits of code operate directly on the new
VECTOR_CST encoding, instead of using VECTOR_CST_ELT on all elements
of the vector.

Previous patches handled operations that produce a new VECTOR_CST,
while this patch handles things like predicates.  It also makes
print_node dump the encoding instead of the full vector that
the encoding represents.

2017-12-07  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree-vector-builder.h
	(tree_vector_builder::binary_encoded_nelts): Declare.
	* tree-vector-builder.c
	(tree_vector_builder::binary_encoded_nelts): New function.
	* fold-const.c (negate_expr_p): Likewise.
	(operand_equal_p, fold_checksum_tree): Likewise.
	* tree-loop-distribution.c (const_with_all_bytes_same): Likewise.
	* tree.c (integer_zerop, integer_onep, integer_all_onesp, real_zerop)
	(real_onep, real_minus_onep, add_expr, initializer_zerop): Likewise.
	(uniform_vector_p): Likewise.
	* varasm.c (const_hash_1, compare_constant): Likewise.
	* tree-ssa-ccp.c: Include tree-vector-builder.h.
	(valid_lattice_transition): Operate directly on the VECTOR_CST
	encoding.
	* ipa-icf.c: Include tree-vector-builder.h.
	(sem_variable::equals): Operate directly on the VECTOR_CST encoding.
	* print-tree.c (print_node): Print encoding of VECTOR_CSTs.

From-SVN: r255480