Replace IFN_TRAP with BUILT_IN_UNREACHABLE_TRAP [PR107300]

For PR106099 I've added IFN_TRAP as an alternative to __builtin_trap
meant for __builtin_unreachable purposes (e.g. with -funreachable-traps
or some sanitizers) which doesn't need vops because __builtin_unreachable
doesn't need them either.  This works in various cases, but unfortunately
IPA likes to decide on the redirection to unreachable just by tweaking
the cgraph edge to point to a different FUNCTION_DECL.  As internal
functions don't have a decl, this causes problems like in the following
testcase.

The following patch fixes it by removing IFN_TRAP again and replacing
it with user inaccessible BUILT_IN_UNREACHABLE_TRAP, so that e.g.
builtin_decl_unreachable can return it directly and we don't need to tweak
it later in wherever we actually replace the call stmt.

2023-02-02  Jakub Jelinek  <jakub@redhat.com>

	PR ipa/107300
	* builtins.def (BUILT_IN_UNREACHABLE_TRAP): New builtin.
	* internal-fn.def (TRAP): Remove.
	* internal-fn.cc (expand_TRAP): Remove.
	* tree.cc (build_common_builtin_nodes): Define
	BUILT_IN_UNREACHABLE_TRAP if not yet defined.
	(builtin_decl_unreachable): Use BUILT_IN_UNREACHABLE_TRAP
	instead of BUILT_IN_TRAP.
	* gimple.cc (gimple_build_builtin_unreachable): Remove
	emitting internal function for BUILT_IN_TRAP.
	* asan.cc (maybe_instrument_call): Handle BUILT_IN_UNREACHABLE_TRAP.
	* cgraph.cc (cgraph_edge::verify_corresponds_to_fndecl): Handle
	BUILT_IN_UNREACHABLE_TRAP instead of BUILT_IN_TRAP.
	* ipa-devirt.cc (possible_polymorphic_call_target_p): Handle
	BUILT_IN_UNREACHABLE_TRAP.
	* builtins.cc (expand_builtin, is_inexpensive_builtin): Likewise.
	* tree-cfg.cc (verify_gimple_call,
	pass_warn_function_return::execute): Likewise.
	* attribs.cc (decl_attributes): Don't report exclusions on
	BUILT_IN_UNREACHABLE_TRAP either.

	* gcc.dg/pr107300.c: New test.