Re: [PATCH] libgccjit: Handle truncation and extension for casts [PR 95498]

[Andrea Corallo <andrea.corallo@arm.com>]

Hi Antoni,

a couple of nits and some thoughts.

Antoni Boucher via Gcc-patches <gcc-patches@gcc.gnu.org> writes:

> 2020-07-12  Antoni Boucher  <bouanto@zoho.com>
> 
> gcc/jit/
> 	PR target/95498
> 	* jit-playback.c: Add support to handle truncation and extension
                       ^^^
                       here we usually add the function that gets
modified, you can look at other changelog entries as example.

> diff --git a/gcc/jit/jit-playback.c b/gcc/jit/jit-playback.c
> index 0fddf04da87..4f4a1080c36 100644
> --- a/gcc/jit/jit-playback.c
> +++ b/gcc/jit/jit-playback.c
> @@ -61,22 +61,39 @@ along with GCC; see the file COPYING3.  If not see
>  
>  /* gcc::jit::playback::context::build_cast uses the convert.h API,
>     which in turn requires the frontend to provide a "convert"
> -   function, apparently as a fallback.
> -
> -   Hence we provide this dummy one, with the requirement that any casts
> -   are handled before reaching this.  */
> +   function, apparently as a fallback for casts that can be simplified
> +   (truncation, extension). */
>  extern tree convert (tree type, tree expr);
>  
>  tree
>  convert (tree dst_type, tree expr)
>  {
> -  gcc_assert (gcc::jit::active_playback_ctxt);
> -  gcc::jit::active_playback_ctxt->add_error (NULL, "unhandled conversion");
> -  fprintf (stderr, "input expression:\n");
> -  debug_tree (expr);
> -  fprintf (stderr, "requested type:\n");
> -  debug_tree (dst_type);
> -  return error_mark_node;
> +  tree t_ret = NULL;
> +  t_ret = targetm.convert_to_type (dst_type, expr);
> +  if (t_ret)
> +      return t_ret;
        ^^^
        indent nit
> +  enum tree_code dst_code = TREE_CODE (dst_type);
> +  switch (dst_code)
> +    {
> +    case INTEGER_TYPE:
> +    case ENUMERAL_TYPE:
> +      t_ret = convert_to_integer (dst_type, expr);
> +      goto maybe_fold;
> +
> +    default:
> +      gcc_assert (gcc::jit::active_playback_ctxt);
> +      gcc::jit::active_playback_ctxt->add_error (NULL, "unhandled conversion");
> +      fprintf (stderr, "input expression:\n");
> +      debug_tree (expr);
> +      fprintf (stderr, "requested type:\n");
> +      debug_tree (dst_type);
> +      return error_mark_node;
> +
> +    maybe_fold:
> +      if (TREE_CODE (t_ret) != C_MAYBE_CONST_EXPR)
> +	t_ret = fold (t_ret);
> +      return t_ret;
> +    }
>  }

Looking at 'convert' at c-convert.c:66 the INTEGER_TYPE case here looks
good, but given the set of casts we accept as input I guess we should
handle also POINTER_TYPE, BOOLEAN_TYPE and REAL_TYPE.  What do you think
about?

Hope it helps

Bests

  Andrea