* expr.c (check_max_integer_computation_mode): New function.
        (expand_expr): Avoid integer computations in modes wider than
        MAX_INTEGER_COMPUTATION_MODE.
        * fold-const.c (fold): Likewise.
        * tree.h (check_max_integer_computation_mode): Declare.
        * tm.texi (MAX_INTEGER_COMPUTATION_MODE): Document it.

From-SVN: r20538