On 07/11/2017 09:20 AM, Alex Bennée wrote:
Richard Henderson <r...@twiddle.net> writes:
On 07/11/2017 07:59 AM, Alex Bennée wrote:
if (use_goto_tb(s, dest)) {
tcg_gen_goto_tb(n);
gen_set_pc_im(s, dest);
tcg_gen_exit_tb((uintptr_t)s->tb + n);
+ s->is_jmp = DISAS_TB_JUMP;
} else {
gen_set_pc_im(s, dest);
gen_goto_ptr();
+ s->is_jmp = DISAS_JUMP;
}
I think DISAS_TB_JUMP is appropriate for both cases. When not using
goto_tb, the jump is still static and we still chain to the next TB
via goto_ptr.
OK - I guess we need to nail down what the essential difference is
between the two. I understood DISAS_TB_JUMP as a static known PC which
can be patched in the generated code because we know the two addresses
are in the same page - whereas DISAS_JUMP is a "computed" jump although
in this case the PC is already known.
Does making a distinction between computed and non-computer inter-page
jumps make any sense anyway?
*shrug* probably not.
Honestly, the only thing that's really interesting here is that is_jmp indicate
that we have already exited the TB and that all following code is dead.
As a response to one of Lluis' threads, I suggested that the generic term for
this be DISAS_NORETURN. Which also covers exiting the TB via calling a helper
that does not return, e.g. throwing an illegal opcode exception, aka DISAS_EXC
in the current target/arm sources.
r~
