Re: [Qemu-devel] [PATCH] Clean up definition of MAX_OPC_PARAM

[Blue Swirl <blauwirbel@gmail.com>]

Thanks, applied.

On 4/28/10, Stuart Brady <sdb@zubnet.me.uk> wrote:
> MAX_OPC_PARAM is intended to refer to the maximum number of entries used
>  in gen_opparam_buf[] for any single helper call.  It is currently defined
>  as 10, but for 32-bit archs, the correct value (with a maximum for four
>  helper arguments) is 14, and for 64-bit archs, only 9 entries are needed.
>
>  tcg_gen_callN() fills four entries with the function address, flags,
>  number of args, etc. and on 32-bit archs uses a further two entries per
>  argument (with a maximum of four helper arguments), plus two more for the
>  return value.  On 64-bit archs, only half as many entries are used for the
>  args and the return value.
>
>  In reality, TBs tend not to consist purely of helper calls exceeding the
>  stated 10 gen_opparam_buf[] entries, so this would never actually be a
>  problem on 32-bit archs, but the definition is still rather confusing.
>
>  Signed-off-by: Stuart Brady <sdb@zubnet.me.uk>
>  ---
>  diff --git a/exec-all.h b/exec-all.h
>  index 4bae1e2..1016de2 100644
>  --- a/exec-all.h
>  +++ b/exec-all.h
>  @@ -44,8 +44,20 @@ typedef struct TranslationBlock TranslationBlock;
>
>   /* XXX: make safe guess about sizes */
>   #define MAX_OP_PER_INSTR 96
>  -/* A Call op needs up to 6 + 2N parameters (N = number of arguments).  */
>  -#define MAX_OPC_PARAM 10
>  +
>  +#if HOST_LONG_BITS == 32
>  +#define MAX_OPC_PARAM_PER_ARG 2
>  +#else
>  +#define MAX_OPC_PARAM_PER_ARG 1
>  +#endif
>  +#define MAX_OPC_PARAM_IARGS 4
>  +#define MAX_OPC_PARAM_OARGS 1
>  +#define MAX_OPC_PARAM_ARGS (MAX_OPC_PARAM_IARGS + MAX_OPC_PARAM_OARGS)
>  +
>  +/* A Call op needs up to 4 + 2N parameters on 32-bit archs,
>  + * and up to 4 + N parameters on 64-bit archs
>  + * (N = number of input arguments + output arguments).  */
>  +#define MAX_OPC_PARAM (4 + (MAX_OPC_PARAM_PER_ARG * MAX_OPC_PARAM_ARGS))
>   #define OPC_BUF_SIZE 640
>   #define OPC_MAX_SIZE (OPC_BUF_SIZE - MAX_OP_PER_INSTR)
>
>
>
>