re PR middle-end/20623 (ICE: fold check: original tree changed by fold with --enable...

re PR middle-end/20623 (ICE: fold check: original tree changed by fold with --enable-checking=fold)

	PR middle-end/20623
	* tree.h (debug_fold_checksum): Declared.
	* fold-const.c (build_fold_addr_expr_with_type_1): New.
	(build_fold_addr_expr_with_type, build_fold_addr_expr): Use
	build_fold_addr_expr_with_type_1.
	(fold_addr_expr, debug_fold_checksum): New.
	(fold_checksum_tree): Don't fold TREE_CHAIN of an SSA_NAME.
	(fold_unary, fold_comparison, split_address_to_core_and_offset):
	Use fold_addr_expr.

From-SVN: r125929