This RFC patch changes the type of predicates to bool. However, some
of the targets (e.g. x86) use indirect functions to call the
predicates, so without the local change, the build fails. Putting the
patch through CI bots should weed out the problems, but I have no
infrastructure to do it myself.

2021-06-30  Uroš Bizjak  <ubizjak@gmail.com>

gcc/
    * genpreds.c (write_predicate_subfunction):
    Change the type of written subfunction to bool.
    (write_one_predicate_function):
    Change the type of written function to bool.
    (write_tm_preds_h): Ditto.
    * recog.h (*insn_operand_predicate_fn): Change the type to bool.
    * recog.c (general_operand): Change the type to bool.
    (address_operand): Ditto.
    (register_operand): Ditto.
    (pmode_register_operand): Ditto.
    (scratch_operand): Ditto.
    (immediate_operand): Ditto.
    (const_int_operand): Ditto.
    (const_scalar_int_operand): Ditto.
    (const_double_operand): Ditto.
    (nonimmediate_operand): Ditto.
    (nonmemory_operand): Ditto.
    (push_operand): Ditto.
    (pop_operand): Ditto.
    (memory_operand): Ditto.
    (indirect_operand): Ditto.
    (ordered_comparison_operator): Ditto.
    (comparison_operator): Ditto.

    * config/i386/i386-expand.c (ix86_expand_sse_cmp):
    Change the type of indirect predicate function to bool.

Patch was bootstrapped on x86_64-linux-gnu.

Comments welcome.

Uros.