ch: Fix detection of non-executed loop exit

ch: Fix detection of non-executed loop exit

After r16-6104-gb5c64db0a49d46, we try to duplicate bb's
that contain loop exit that have "never exit" but we check
against the propability of the exit to very_unlikely. If we
have PGO, then a loop exit might be very unlikely to be taken
if we interate the loop more than 2000 times.
The problem is the check for very_unlikely is just wrong. It should
just be never. So let's remove that.

Also adds a testcase for __builtin_abort instead of __builtin_unreachable
since there are slightly different pathes to get the probilities.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/122734
gcc/ChangeLog:

	* tree-ssa-loop-ch.cc (should_duplicate_loop_header_p): Remove
	check on very_unlikely probability.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/copy-headers-13.c: New test.

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>