re PR target/42495 (redundant memory load)

re PR target/42495 (redundant memory load)

	PR target/42495
	PR middle-end/42574
	* basic-block.h (get_dominated_to_depth): Declare.
	* dominance.c (get_dominated_to_depth): New function, use
	get_all_dominated_blocks as a base.
	(get_all_dominated_blocks): Use get_dominated_to_depth.

	* gcse.c (occr_t, VEC (occr_t, heap)): Define.
	(hoist_exprs): Remove.
	(alloc_code_hoist_mem, free_code_hoist_mem): Update.
	(compute_code_hoist_vbeinout): Add debug print outs.
	(hoist_code): Partially rewrite, simplify.  Use get_dominated_to_depth.

	* params.def (PARAM_MAX_HOIST_DEPTH): New parameter to avoid
	quadratic behavior.
	* params.h (MAX_HOIST_DEPTH): New macro.
	* doc/invoke.texi (max-hoist-depth): Document.

From-SVN: r162597