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Re: [Qemu-devel] Shifts, ppc[64], xtensa
From: |
malc |
Subject: |
Re: [Qemu-devel] Shifts, ppc[64], xtensa |
Date: |
Fri, 21 Sep 2012 02:53:41 +0400 (MSK) |
User-agent: |
Alpine 2.00 (LNX 1167 2008-08-23) |
On Thu, 20 Sep 2012, Max Filippov wrote:
> On Wed, Sep 19, 2012 at 11:53 PM, Richard Henderson <address@hidden> wrote:
> > On 09/19/2012 11:30 AM, Peter Maydell wrote:
> >> ...but on the other hand that ought to work for PPC too, so
> >> presumably my analysis is wrong somewhere.
> >
> > It isn't. It's a target-xtensa bug.
> >
[..snip..]
>
> This code is generated when TB ends on LEND
> (zero-overhead loop ending) with branching instruction.
> So, in addition to 3 way branch there's extra looping code
> generated by unconditional gen_check_loop_end(dc, 0);
> at the end of disas_xtensa_insn. I was pretty sure that this
> dead code would make no harm. --enable-debug-tcg says
> nothing on x86_64 host. The following should fix that:
It does, once the commit message is fixed i can apply it.
>
> -- >8 --
> From: Max Filippov <address@hidden>
> Date: Thu, 20 Sep 2012 04:07:20 +0400
> Subject: [PATCH] target-xtensa: don't emit extra gen_check_loop_end
>
> Unconditional gen_check_loop_end at the end of disas_xtensa_insn
> can emit tcg_gen_goto_tb with slot id already used in the TB (e.g. when
> TB ends at LEND with a branch). Not all tcg backends can handle that.
>
> Signed-off-by: Max Filippov <address@hidden>
> ---
> target-xtensa/translate.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/target-xtensa/translate.c b/target-xtensa/translate.c
> index 63b37b3..57a2b6f 100644
> --- a/target-xtensa/translate.c
> +++ b/target-xtensa/translate.c
> @@ -2502,7 +2502,9 @@ static void disas_xtensa_insn(DisasContext *dc)
> break;
> }
>
> - gen_check_loop_end(dc, 0);
> + if (dc->is_jmp == DISAS_NEXT) {
> + gen_check_loop_end(dc, 0);
> + }
> dc->pc = dc->next_pc;
>
> return;
>
--
mailto:address@hidden
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, (continued)
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Aurelien Jarno, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Peter Maydell, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Peter Maydell, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Max Filippov, 2012/09/19
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Richard Henderson, 2012/09/20
- Re: [Qemu-devel] Shifts, ppc[64], xtensa, Max Filippov, 2012/09/20
- Re: [Qemu-devel] Shifts, ppc[64], xtensa,
malc <=