PR tree-optimization/19105

	PR tree-optimization/19105
	PR tree-optimization/21643
	PR tree-optimization/46309
	* tree-ssa-reassoc.c (init_range_entry): Add STMT argument
	and use it if EXP is NULL.
	(update_range_test): Handle OPCODE equal to ERROR_MARK
	and oe->op NULL.
	(optimize_range_tests): Likewise.
	(final_range_test_p, suitable_cond_bb, no_side_effect_bb, get_ops,
	maybe_optimize_range_tests): New functions.
	(reassociate_bb): Call maybe_optimize_range_tests if last
	stmt of bb is GIMPLE_COND that hasn't been visited yet.

	* gcc.dg/pr19105.c: New test.
	* gcc.dg/pr21643.c: New test.
	* gcc.dg/pr46309-2.c: New test.
	* gcc.c-torture/execute/pr46309.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@193028 138bc75d-0d04-0410-961f-82ee72b054a4