2006-06-16  Richard Guenther  <rguenther@suse.de>

	PR middle-end/27116
	* fold-const.c (negate_expr_p): Do not introduce undefined
	overflow in negating INTEGER_CSTs.
	(fold_negate_expr): Rename from negate_expr.  Revert last
	change for folding BIT_NOT_EXPR.  Change semantics to
	return NULL_TREE for non-simplified negations.  Do not
	strip type conversions and unify type handling.
	(negate_expr): New function, wrap around fold_negate_expr
	but ensure building a tree always.  Strip type conversions
	here, fold to result type.
	(fold_unary): Use fold_negate_expr for folding NEGATE_EXPR.

	* gcc.dg/pr15785-1.c: Revert last change.
	* gcc.dg/torture/pr27116-2.c: New testcase.

From-SVN: r114723