Re: [Qemu-devel] [PATCH] cpu: Move tcg_exit_req to the end of CPUState

[Richard Henderson <rth@twiddle.net>]

Ping?  This is a significant TCG code size regression
for ARM, AArch64, and Sparc hosts.  It helps x86 too,
though that's not as severe.


r~

On 03/14/2014 03:30 PM, Richard Henderson wrote:
> Reverse an increase in the size of generated code.
> 
> Cc: Andreas Färber <afaerber@suse.de>
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  include/qom/cpu.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 06ee263..f99885a 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -227,7 +227,6 @@ struct CPUState {
>      bool stop;
>      bool stopped;
>      volatile sig_atomic_t exit_request;
> -    volatile sig_atomic_t tcg_exit_req;
>      uint32_t interrupt_request;
>      int singlestep_enabled;
>      int64_t icount_extra;
> @@ -272,6 +271,12 @@ struct CPUState {
>      } icount_decr;
>      uint32_t can_do_io;
>      int32_t exception_index; /* used by m68k TCG */
> +
> +    /* Note that this is accessed at the start of every TB via a negative
> +       offset from AREG0.  Leave this field at the end so as to make the
> +       (absolute value) offset as small as possible.  This reduces code
> +       size, especially for hosts without large memory offsets.  */
> +    volatile sig_atomic_t tcg_exit_req;
>  };
>  
>  QTAILQ_HEAD(CPUTailQ, CPUState);
>