Re: [PATCH] bpf: Forces __buildin_memcmp not to generate a call upto 1024 bytes.

["Jose E. Marchesi" <jose.marchesi@oracle.com>]

Hi Cuper.

Sorry, I missed this patch last week.
This is OK.

Thanks!

> This patch forces __builtin_memcmp calls upto data sizes of 1024 to
> become inline in caller.
> This is a requirement by BPF and it mimics the default behaviour of the
> clang BPF implementation.
>
> gcc/ChangeLog:
> 	* config/bpf/bpf.cc (bpf_use_by_pieces_infrastructure_p): Added
> 	function to bypass default behaviour.
> 	* config/bpf/bpf.h (COMPARE_MAX_PIECES): Defined to 1024 bytes.
> ---
>  gcc/config/bpf/bpf.cc | 16 ++++++++++++++++
>  gcc/config/bpf/bpf.h  |  5 +++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
> index a0956a069729..764a3e487cb6 100644
> --- a/gcc/config/bpf/bpf.cc
> +++ b/gcc/config/bpf/bpf.cc
> @@ -1115,6 +1115,22 @@ bpf_small_register_classes_for_mode_p (machine_mode mode)
>  #define TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P \
>    bpf_small_register_classes_for_mode_p
>  
> +static bool
> +bpf_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT size,
> +				    unsigned int align ATTRIBUTE_UNUSED,
> +				    enum by_pieces_operation op,
> +				    bool speed_p)
> +{
> +  if (op != COMPARE_BY_PIECES)
> +    return default_use_by_pieces_infrastructure_p (size, align, op, speed_p);
> +
> +  return size <= COMPARE_MAX_PIECES;
> +}
> +
> +#undef TARGET_USE_BY_PIECES_INFRASTRUCTURE_P
> +#define TARGET_USE_BY_PIECES_INFRASTRUCTURE_P \
> +  bpf_use_by_pieces_infrastructure_p
> +
>  /* Finally, build the GCC target.  */
>  
>  struct gcc_target targetm = TARGET_INITIALIZER;
> diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
> index 82702aa7b6ba..1f177ec4c4ef 100644
> --- a/gcc/config/bpf/bpf.h
> +++ b/gcc/config/bpf/bpf.h
> @@ -489,6 +489,11 @@ enum reg_class
>     locations.  */
>  #define MOVE_MAX 8
>  
> +/* Allow upto 1024 bytes moves to occur using by_pieces
> +   infrastructure.  This mimics clang behaviour when using
> +   __builtin_memcmp.  */
> +#define COMPARE_MAX_PIECES 1024
> +
>  /* An alias for the machine mode for pointers.  */
>  #define Pmode DImode