tree-optimization/97953 - fix bougs range recorded by EVRP

tree-optimization/97953 - fix bougs range recorded by EVRP

EVRP records some ranges from asserts into SSA_NAME_RANGE_INFO
but fails to assert that the condition the range is derived from
is always true after the SSA names definition.  The patch implements
the simplest post-dominance check, basic-block equality.

2020-11-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97953
	* gimple-ssa-evrp-analyze.c
	(evrp_range_analyzer::record_ranges_from_incoming_edge): Make
	sure the condition post-dominates the SSA definition before
	recording into SSA_NAME_RANGE_INFO.

	* gcc.dg/pr97953.c: New testcase.

(cherry picked from commit c76b3f9e83353a4cd437ca137c1fb835c9b5c21f)