[PATCH 2/2] rs6000: tune loop size for cunroll at O2

[Jiufu Guo]

Jiufu Guo <guojiufu@linux.ibm.com> writes:

> Hi,
>
> This patch check the size of a loop to be unrolled/peeled completely,
> and set the limits to a number (24).  This prevents large loop from
> being unrolled, then avoid binary size increasing, and this limit keeps
> performance.
>
> Bootstrap&regtest pass on powerpc64le, ok for trunk?
>
> Jiufu

ChangeLog
2020-05-20  Jiufu Guo   <guojiufu@cn.ibm.com>

	PR target/95018
	* config/rs6000/rs6000.c (num_stmt_in_loop): New function.
	(rs6000_loop_allow_unroll_completely_peel): Call num_stmt_in_loop.

>
> ---
>  gcc/config/rs6000/rs6000.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> index a1a3f9cb583..f3abb92d046 100644
> --- a/gcc/config/rs6000/rs6000.c
> +++ b/gcc/config/rs6000/rs6000.c
> @@ -5142,6 +5142,22 @@ rs6000_loop_unroll_adjust (unsigned nunroll, struct loop *loop)
>    return nunroll;
>  }
>  
> +/* Count the number of statements in LOOP.  */
> +
> +static int
> +num_stmt_in_loop (class loop *loop)
> +{
> +  int res = 0;
> +  basic_block *bbs = get_loop_body (loop);
> +  for (unsigned i = 0; i < loop->num_nodes; i++)
> +    for (gimple_stmt_iterator bsi = gsi_start_bb (bbs[i]); !gsi_end_p (bsi);
> +	 gsi_next (&bsi))
> +      if (!is_gimple_debug (gsi_stmt (bsi)))
> +	res++;
> +
> +  return res;
> +}
> +
>  /* Implement targetm.loop_allow_unroll_completely_peel.  */
>  
>  static bool
> @@ -5151,7 +5167,8 @@ rs6000_loop_allow_unroll_completely_peel (HOST_WIDE_INT maxiter, tree niter,
>    if (unroll_only_small_loops && optimize == 2)
>      {
>        if (maxiter >= 4
> -	  && !(TREE_CODE (niter) == INTEGER_CST && single_exit (loop)))
> +	  && !(TREE_CODE (niter) == INTEGER_CST && num_stmt_in_loop (loop) < 24
> +	       && single_exit (loop)))
>  	return false;
>      }