tcg: Introduce goto_ptr opcode and tcg_gen_lookup_and_goto_ptr

tcg: Introduce goto_ptr opcode and tcg_gen_lookup_and_goto_ptr

Instead of exporting goto_ptr directly to TCG frontends, export
tcg_gen_lookup_and_goto_ptr(), which calls goto_ptr with the pointer
returned by the lookup_tb_ptr() helper. This is the only use case
we have for goto_ptr and lookup_tb_ptr, so having this function is
very convenient. Furthermore, it trivially allows us to avoid calling
the lookup helper if goto_ptr is not implemented by the backend.

Reviewed-by: Alex Bennée <[email protected]>
Signed-off-by: Emilio G. Cota <[email protected]>
Message-Id: <1493263764[email protected]>
Message-Id: <1493263764[email protected]>
Message-Id: <1493263764[email protected]>
Message-Id: <1493263764[email protected]>
[rth: Squashed 4 related commits.]
Signed-off-by: Richard Henderson <[email protected]>