cfgcleanup: Fix -fcompare-debug issue in outgoing_edges_match [PR100254]

cfgcleanup: Fix -fcompare-debug issue in outgoing_edges_match [PR100254]

The following testcase fails with -fcompare-debug.  The problem is that
outgoing_edges_match behaves differently between -g0 and -g, if
some load/store with REG_EH_REGION is followed by DEBUG_INSNs, the
REG_EH_REGION check is not done, while when there are no DEBUG_INSNs, it is
done.

We already compute last1 and last2 as BB_END (bb{1,2}) with skipped debug
insns and notes, so this patch just uses those.

2021-04-27  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/100254
	* cfgcleanup.c (outgoing_edges_match): Check REG_EH_REGION on
	last1 and last2 insns rather than BB_END (bb1) and BB_END (bb2) insns.

	* g++.dg/opt/pr100254.C: New test.

(cherry picked from commit e600df51a15b2ec7a72731921a2464ffe59cf5ab)