tree-optimization/98513 - fix bug in range intersection code

tree-optimization/98513 - fix bug in range intersection code

This fixes a premature optimization in the range intersection code
which assumes earlier branches have to be taken, not taking into
account that for symbolic ranges we cannot always compare endpoints.
The fix is to instantiate the compare deemed redundant (which then
fails as undecidable for the testcase).

2021-01-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/98513
	* value-range.cc (intersect_ranges): Compare the upper bounds
	for the expected relation.

	* gcc.dg/tree-ssa/pr98513.c: New testcase.

(cherry picked from commit a05cc70a6c1ae0e5b22e16f4d8d13995a38ea1f9)