2018-05-16  Richard Biener  <rguenther@suse.de>

	* params.def (PARAM_DSE_MAX_ALIAS_QUERIES_PER_STORE): New param.
	* doc/invoke.texi (dse-max-alias-queries-per-store): Document.
	* tree-ssa-dse.c: Include tree-ssa-loop.h.
	(check_name): New callback.
	(dse_classify_store): Track cycles via a visited bitmap of PHI
	defs and simplify handling of in-loop and across loop dead stores
	and properly fail for loop-variant refs.  Handle byte-tracking with
	multiple defs.  Use PARAM_DSE_MAX_ALIAS_QUERIES_PER_STORE for
	limiting the walk.

	* gcc.dg/tree-ssa/ssa-dse-32.c: New testcase.
	* gcc.dg/tree-ssa/ssa-dse-33.c: Likewise.
	* gcc.dg/uninit-pr81897-2.c: Use -fno-tree-dse.

From-SVN: r260288