hardcfr: support checking at abnormal edges [PR111943]

hardcfr: support checking at abnormal edges [PR111943]

Control flow redundancy may choose abnormal edges for early checking,
but that breaks because we can't insert checks on such edges.

Introduce conditional checking on the dest block of abnormal edges,
and leave it for the optimizer to drop the conditional.

for  gcc/ChangeLog

	PR tree-optimization/111943
	* gimple-harden-control-flow.cc: Adjust copyright year.
	(rt_bb_visited): Add vfalse and vtrue data members.
	Zero-initialize them in the ctor.
	(rt_bb_visited::insert_exit_check_on_edge): Upon encountering
	abnormal edges, insert initializers for vfalse and vtrue on
	entry, and insert the check sequence guarded by a conditional
	in the dest block.

for  libgcc/ChangeLog

	* hardcfr.c: Adjust copyright year.

for  gcc/testsuite/ChangeLog

	PR tree-optimization/111943
	* gcc.dg/harden-cfr-pr111943.c: New.