cfgcleanup: Protect latches always [PR123417]

cfgcleanup: Protect latches always [PR123417]

So it turns out LOOPS_MAY_HAVE_MULTIPLE_LATCHES is set in places
along compiling. Setting it only means there might be multiple
latches currently. It does not mean let's go in an delete them
all; which is what remove_forwarder_block does currently. This
was happening before my set of patches too but since it was
only happening in merge_phi pass, latches were not cleared away
al of the time and then recreated.

This solves the problem by protecting latches all of the time
instead of depedent on LOOPS_MAY_HAVE_MULTIPLE_LATCHES not being set.

vect-uncounted_7.c needs to be xfailed here because we no longer
vectorize the code. Note the IR between GCC 15 and after this patch
is the same so I think this was just a case were the testcase
was added after the remove forwarder changes and should not have
vectorized (or vectorize differently).

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/123417
gcc/ChangeLog:

	* tree-cfgcleanup.cc (maybe_remove_forwarder_block): Always
	protect latches.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/vect-uncounted_7.c: xfail vect test.

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