re PR tree-optimization/20256 (Perfect nest transformation not conservative enough)

re PR tree-optimization/20256 (Perfect nest transformation not conservative enough)

	PR middle-end/20256
	PR middle-end/26435
	* tree-loop-linear.c (linear_transform_loops): Don't test perfect_nest_p.
	Call rewrite_into_loop_closed_ssa only when something changed.
	* lambda.h (gcc_loopnest_to_lambda_loopnest): Update declaration.
	* lambda-code.c (can_convert_to_perfect_nest): Declared.
	(gcc_loopnest_to_lambda_loopnest): Removed need_perfect_nest parameter.
	Test for perfect_nest_p here.  Fix formating.
	(replace_uses_equiv_to_x_with_y): Fix formating.
	(stmt_uses_op): Removed.
	(can_convert_to_perfect_nest): Removed loopivs parameter.
	Complete the test by checking the scalar dependences.
	(perfect_nestify): Remove the test for can_convert_to_perfect_nest.
	Fix formating.

From-SVN: r113862