Copy EH phi args for throwing hardened compares

Copy EH phi args for throwing hardened compares

When we duplicate a throwing compare for hardening, the EH edge from
the original compare gets duplicated for the inverted compare, but we
failed to adjust any PHI nodes in the EH block.  This patch adds the
needed adjustment, copying the PHI args from those of the preexisting
edge.

for  gcc/ChangeLog

	PR tree-optimization/103856
	* gimple-harden-conditionals.cc (non_eh_succ_edge): Enable the
	eh edge to be requested through an extra parameter.
	(pass_harden_compares::execute): Copy PHI args in the EH dest
	block for the new EH edge added for the inverted compare.

for  gcc/testsuite/ChangeLog

	PR tree-optimization/103856
	* g++.dg/pr103856.C: New.