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Re: [Qemu-devel] [RFC 38/48] translator: implement 2-pass translation
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [RFC 38/48] translator: implement 2-pass translation |
Date: |
Mon, 26 Nov 2018 15:16:00 +0000 |
User-agent: |
mu4e 1.1.0; emacs 26.1.90 |
Emilio G. Cota <address@hidden> writes:
> The second pass only occurs when a plugin has subscribed to
> TB translation events.
>
> Signed-off-by: Emilio G. Cota <address@hidden>
> ---
> tcg/tcg.h | 8 ++++
> accel/tcg/translator.c | 91 +++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 97 insertions(+), 2 deletions(-)
>
> diff --git a/tcg/tcg.h b/tcg/tcg.h
> index d5afe25c97..479b57d65f 100644
> --- a/tcg/tcg.h
> +++ b/tcg/tcg.h
> @@ -720,6 +720,14 @@ struct TCGContext {
>
> TCGLabel *exitreq_label;
>
<snip>
> }
>
> + if (tb_trans_cb && first_pass) {
> + qemu_plugin_tb_trans_cb(cpu, plugin_tb);
> + first_pass = false;
> + goto translate;
> + }
> +
So the only reason we are doing this two pass tango is to ensure the
plugin can insert TCG ops before the actual translation has occurred?
I think we can do better, especially as the internal structures of
TCGops are implemented as a list so ops and be inserted before and after
other ops. This is currently only done by the optimiser at the moment,
see:
TCGOp *tcg_op_insert_before(TCGContext *s, TCGOp *op, TCGOpcode opc, int
narg);
TCGOp *tcg_op_insert_after(TCGContext *s, TCGOp *op, TCGOpcode opc, int narg);
and all the base tcg ops end up going to tcg_emit_op which just appends
to the tail. But if we can come up with a neater way to track the op
used before the current translated expression we could do away with two
phases translation completely.
> /* Emit code to exit the TB, as indicated by db->is_jmp. */
> ops->tb_stop(db, cpu);
> gen_tb_end(db->tb, db->num_insns - bp_insn);
--
Alex Bennée
- Re: [Qemu-devel] [RFC 38/48] translator: implement 2-pass translation,
Alex Bennée <=