re PR tree-optimization/71437 (Performance regression after r235817)

re PR tree-optimization/71437 (Performance regression after r235817)

	PR tree-optimization/71437
	* tree-vrp.c (simplify_stmt_for_jump_threading): Lookup the
	conditional in the hash table first.
	(vrp_dom_walker::before_dom_children): Extract condition from
	ASSERT_EXPR.  Record condition, its inverion and any implied
	conditions as well.

	PR tree-optimization/71437
	* gcc.dg/tree-ssa/pr71437.c: New test.
	* gcc.dg/tree-ssa/20040305-1.c: Test earlier dump.
	* gcc.dg/tree-ssa/ssa-dom-thread-4.c: Adjust for jump threads
	now caught by VRP, but which were previously caught by DOM.

From-SVN: r246225