Re: [Qemu-devel] [PATCH v3 2/6] Add copy and constant propagation.

[Stefan Weil <weil@mail.berlios.de>]

Am 07.07.2011 14:37, schrieb Kirill Batuzov:
> Make tcg_constant_folding do copy and constant propagation. It is a
> preparational work before actual constant folding.
>
> Signed-off-by: Kirill Batuzov<batuzovk@ispras.ru>
> ---
>   tcg/optimize.c |  182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>   1 files changed, 180 insertions(+), 2 deletions(-)
>
> diff --git a/tcg/optimize.c b/tcg/optimize.c
> index c7c7da9..f8afe71 100644
> --- a/tcg/optimize.c
> +++ b/tcg/optimize.c
>    
...

This patch breaks QEMU on 32 bit hosts (tested on 386 Linux
and w32 hosts). Simply running qemu (BIOS only) terminates
with abort(). As the error is easy to reproduce, I don't provide
a stack frame here.

> +static void tcg_opt_gen_mov(TCGArg *gen_args, TCGArg dst, TCGArg src,
> +                            int nb_temps, int nb_globals)
> +{
> +        reset_temp(dst, nb_temps, nb_globals);
> +        assert(temps[src].state != TCG_TEMP_COPY);
> +        if (src>= nb_globals) {
> +            assert(temps[src].state != TCG_TEMP_CONST);
> +            if (temps[src].state != TCG_TEMP_HAS_COPY) {
> +                temps[src].state = TCG_TEMP_HAS_COPY;
> +                temps[src].next_copy = src;
> +                temps[src].prev_copy = src;
> +            }
> +            temps[dst].state = TCG_TEMP_COPY;
> +            temps[dst].val = src;
> +            temps[dst].next_copy = temps[src].next_copy;
> +            temps[dst].prev_copy = src;
> +            temps[temps[dst].next_copy].prev_copy = dst;
> +            temps[src].next_copy = dst;
> +        }
> +        gen_args[0] = dst;
> +        gen_args[1] = src;
> +}
>    

QEMU with a modified tcg_opt_gen_mov() (without the if block) works.

Kind regards,
Stefan Weil