PR tree-optimization/90883
	* tree-ssa-alias.c (stmt_kills_ref_p): Handle BUILT_IN_CALLOC.
	* tree-ssa-dse.c: Update various comments to distinguish between
	dead and redundant stores.
	(initialize_ao_ref_for_dse): Handle BUILT_IN_CALLOC.
	(dse_optimize_redundant_stores): New function.
	(delete_dead_or_redundant_call): Renamed from delete_dead_call.
	Distinguish between dead and redundant calls in dump output.  All
	callers updated.
	(delete_dead_or_redundant_assignment): Similarly for assignments.
	(dse_optimize_stmt): Handle _CHK variants.  For statements which
	store 0 into multiple memory locations, try to prove a subsequent
	store is redundant.

        PR tree-optimization/90883
	* g++.dg/tree-ssa/pr90883.C: New test.
	* gcc.dg/tree-ssa/ssa-dse-36.c: New test.

From-SVN: r272717