* tree-flow-inline.h (op_iter_next_must_and_may_def): New.
	(op_iter_init_must_and_may_def): Likewise.
	(unmodifiable_var_p): Move to a later point in the file.
	* tree-ssa-operands.h (FOR_EACH_SSA_MUST_AND_MAY_DEF_OPERAND): New.
	* tree-ssa-dse.c (need_imm_uses_for): Remove, no longer needed.
	(dse_record_phis): Directly check for virtual operands rather than
	using need_imm_uses_for.
	(dse_optimize_stmt): Handle V_MUST_DEF operands.  Handle case where
	store has multiple V_{MAY,MUST}_DEF operands.

From-SVN: r98780