PR tree-optimization/20933

	PR tree-optimization/20933
	* tree-ssa-alias.c (compute_flow_insensitive_aliasing): Move
	logic to reject aliases between read-only and writable
	variables ...
	(may_alias_p): ... here.
	(get_tmt_for): Do not associate read-only tags to pointers
	whose pointed-to type is not read-only.
	* tree-ssa.c (verify_ssa): Check that memory stores have at
	least one V_MAY_DEF or V_MUST_DEF.

testsuite/ChangeLog

	PR tree-optimization/20933
	* gcc.dg/tree-ssa/pr20933.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@97988 138bc75d-0d04-0410-961f-82ee72b054a4