re PR tree-optimization/78496 (Missed opportunities for jump threading)

re PR tree-optimization/78496 (Missed opportunities for jump threading)

	PR tree-optimizatin/78496
	* gimple-ssa-evrp-analyze.h
	(evrp_range_analyzer::get_vr_values): Simplify.
	* gimple-ssa-evrp-analyze.c: Corresponding changes.
	* tree-ssa-dom.c: Include alloc-pool.h, tree-vrp.h, vr-values.h
	and gimple-ssa-evrp-analyze.h.
	(dom_opt_dom_walker class): Add evrp_range_analyzer member.
	(simplify_stmt_for_jump_threading): Copy a blob of code from
	tree-vrp.c to use ranges to simplify statements.
	(dom_opt_dom_walker::before_dom_children): Call
	evrp_range_analyzer::{enter,record_ranges_from_stmt} methods.
	(dom_opt_dom_walker::after_dom_children): Similarly for
	evrp_range_analyzer::leave.
	(dom_opt_dom_walker::optimize_stmt): Use EVRP ranges to optimize
	conditionals.

	PR tree-optimization/78496
	* gcc.dg/builtin-unreachable-6.c: Disable DOM.
	* gcc.dg/builtin-unreachable-6a.c: New test.
	* gcc.dg/tree-ssa/20030922-1.c: No longer XFAIL.
	* gcc.dg/ssa-dom-branch-1.c: Tweak expected output.

From-SVN: r255387