re PR ipa/68672 (g++.dg/torture/pr68470.C: ICE: cannot update SSA form: statement...

re PR ipa/68672 (g++.dg/torture/pr68470.C: ICE: cannot update SSA form: statement uses released SSA name)

	PR ipa/68672
	* ipa-split.c (split_function): Don't compute/use main_part_return_p.
	Compute retval and retbnd early in all cases if split_part_return_p
	and return_bb is not EXIT.  Remove all clobber stmts and reset
	all debug stmts that refer to SSA_NAMEs defined in split part,
	except if it is retval, in that case replace the old retval with the
	lhs of the call to the split part.

	* g++.dg/ipa/pr68672-1.C: New test.
	* g++.dg/ipa/pr68672-2.C: New test.
	* g++.dg/ipa/pr68672-3.C: New test.

From-SVN: r233374