[PR67828] don't unswitch on default defs of non-parms

[PR67828] don't unswitch on default defs of non-parms

for  gcc/ChangeLog

	PR rtl-optimizatoin/67828
	* tree-ssa-loop-unswitch.c: Include tree-ssa.h.
	(tree_may_unswitch_on): Don't unswitch on expressions
	involving undefined values.

for  gcc/testsuite/ChangeLog

	PR rtl-optimization/67828
	* gcc.dg/torture/pr67828.c: New.

From-SVN: r228650