tree-optimization/97623 - Avoid PRE hoist insertion iteration

tree-optimization/97623 - Avoid PRE hoist insertion iteration

The recent previous change in this area limited hoist insertion
iteration via a param but the following is IMHO better since
we are not really interested in PRE opportunities exposed by
hoisting but only the other way around.  So this moves hoist
insertion after PRE iteration finished and removes hoist
insertion iteration alltogether.

2020-11-11  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97623
	* params.opt (-param=max-pre-hoist-insert-iterations): Remove
	again.
	* doc/invoke.texi (max-pre-hoist-insert-iterations): Likewise.
	* tree-ssa-pre.c (insert): Move hoist insertion after PRE
	insertion iteration and do not iterate it.

	* gcc.dg/tree-ssa/ssa-hoist-3.c: Adjust.
	* gcc.dg/tree-ssa/ssa-hoist-7.c: Likewise.
	* gcc.dg/tree-ssa/ssa-pre-30.c: Likewise.