* toplev.c (rest_of_compilation): Don't call optimize_mode_switching
        unless OPTIMIZE_MODE_SWITCHING.  Conditionally set no_new_pseudos.
        Don't call recompute_reg_usage if no_new_pseudos is true.
        * lcm.c (optimize_mode_switching): Move ifdefs outside function.
        Return true if we did work; update global life information.
        * basic-block.h (optimize_mode_switching): Update decl.

From-SVN: r33965