re PR tree-optimization/83518 (Missing optimization: useless instructions should...

re PR tree-optimization/83518 (Missing optimization: useless instructions should be dropped)

2019-07-08  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/83518
	* tree-ssa-sccvn.c: Include splay-tree.h.
	(struct pd_range, struct pd_data): New.
	(struct vn_walk_cb_data): Add data to track partial definitions.
	(vn_walk_cb_data::~vn_walk_cb_data): New.
	(vn_walk_cb_data::push_partial_def): New.
	(pd_tree_alloc, pd_tree_dealloc, pd_range_compare): New.
	(vn_reference_lookup_2): When partial defs are registered give up.
	(vn_reference_lookup_3): Track partial defs for memset and
	constructor zeroing and for defs from constants.

	* gcc.dg/tree-ssa/ssa-fre-73.c: New testcase.
	* gcc.dg/tree-ssa/ssa-fre-74.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-75.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-76.c: Likewise.
	* g++.dg/tree-ssa/pr83518.C: Likewise.

From-SVN: r273194