re PR tree-optimization/15255 ([tree-ssa] a * 2 + a * 2 is not converted to a * 4)

re PR tree-optimization/15255 ([tree-ssa] a * 2 + a * 2 is not converted to a * 4)

2008-08-13  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/15255
	* tree-ssa-reassoc.c (linearize_expr_tree): Declare.
	(struct oecount_s): New struct and VEC types.
	(cvec): New global.
	(oecount_hash): New function.
	(oecount_eq): Likewise.
	(oecount_cmp): Likewise.
	(zero_one_operation): New function.
	(build_and_add_sum): Likewise.
	(undistribute_ops_list): Perform un-distribution of multiplication
	and division on the chain of summands.
	(should_break_up_subtract): Also break up subtracts for factors.
	(reassociate_bb): Delete dead visited statements.
	Call undistribute_ops_list.  Re-sort and optimize if it did something.
	* passes.c (init_optimization_passes): Move DSE before
	reassociation.
	* tree-ssa-loop-niter.c (stmt_dominates_stmt_p): Correctly handle
	PHI nodes.

	* gcc.dg/tree-ssa/reassoc-14.c: New testcase.
	* gcc.dg/tree-ssa/reassoc-15.c: Likewise.
	* gcc.dg/tree-ssa/reassoc-16.c: Likewise.
	* gcc.dg/torture/reassoc-1.c: Likewise.
	* gcc.dg/tree-ssa/recip-2.c: Adjust.
	* gcc.dg/tree-ssa/recip-6.c: Likewise.
	* gcc.dg/tree-ssa/recip-7.c: Likewise.
	* gfortran.dg/reassoc_4.f: Likewise.

From-SVN: r139048