tree-optimization/98786 - fix issue with phiopt and abnormals

tree-optimization/98786 - fix issue with phiopt and abnormals

This fixes factor_out_conditional_conversion to avoid creating overlapping
lifetimes for abnormals.  It also makes sure we do deal with a conditional
conversion (at least for one PHI arg def) - for the testcase that wasn't the case.

2021-01-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/98786
	* tree-ssa-phiopt.c (factor_out_conditional_conversion): Avoid
	adding new uses of abnormals.  Verify we deal with a conditional
	conversion.

	* gcc.dg/torture/pr98786.c: New testcase.