* common.opt (ftree-fre): New flag.
	* flags.h (flag_tree_fre): Declare.
	* opts.c (decode_options): Set.
	* timevar.def (TV_TREE_FRE): Define.
	* tree-flow-inline.h (may_propagate_copy): Re-arrange for
	readability.  Handle destinations that are not SSA_NAMEs.
	* tree-flow.h (struct ptr_info_def): Move from tree.h
	(cprop_into_stmt, cprop_into_successor_phis): Remove.
	(vn_compute, vn_lookup_or_add, vn_add, vn_lookup): Add
	vuse_optype parameter.
	* tree-pass.h (pass_fre): Declare.
	* tree-ssa-copy.c (cprop_operand): Move to tree-ssa-dom.c
	(cprop_into_stmt): Likewise.
	(cprop_into_successor_phis): Likewise.
	* tree-ssa-dom.c (eliminate_redundant_computations): Fix
	argument ordering in call to may_propagate_copy.
	* tree-ssa-pre.c (is_undefined_value): Assume hard registers
	to be always defined.
	(add_to_sets): New local function.
	(create_value_expr_from): New local function.
	(compute_avail): Call them.
	(eliminate): Don't ignore statements with virtual operands.
	(init_pre): New local function.
	(fini_pre): New local function.
	(execute_pre): Call them.
	Add argument DO_FRE.  Don't do insertion if DO_FRE is true.
	(do_pre): New function.
	(do_fre): New function.
	(gate_fre): New function.
	(pass_fre): Declare.
	* tree-ssa.c (init_tree_ssa): Don't call vn_init.
	(delete_tree_ssa): Don't call vn_delete.
	* tree-vn.c (val_expr_pair_d): Add documentation.
	(vn_compute): Add VUSES argument to incorporate in computing
	hash values.  Update all callers.
	(expressions_equal_p): Call operand_equal_p with
	OEP_PURE_SAME.
	(vn_add): Add VUSES argument.  Update all callers.
	(vn_lookup): Likewise.
	(vn_lookup_or_add): Likewise.
	* doc/invoke.texi: Document -ftree-fre and -fdump-tree-fre.

From-SVN: r83837