Check if dependency is valid before using in may_recompute_p.

Check if dependency is valid before using in may_recompute_p.

When the IL is rewritten after a statement has been processed and
dependencies cached, its possible that an ssa-name in the dependency
cache is no longer in the IL.  Check this before trying to recompute.

	PR tree-optimization/109417
	gcc/
	* gimple-range-gori.cc (gori_compute::may_recompute_p): Check if
	dependency is in SSA_NAME_FREE_LIST.

	gcc/testsuite/
	* gcc.dg/pr109417.c: New.