Re: [PATCH] Refactor handle_section_attribute to reduce nesting and distinguish error cases

[Andrew Pinski <pinskia at gmail dot com>]

On Sun, Aug 24, 2014 at 1:42 PM, Josh Triplett <josh@joshtriplett.org> wrote:
> handle_section_attribute contains many levels of nested conditionals and
> branching code flow paths, with the error cases sometimes in the else
> case and sometimes in the if case.  Simplify the code flow into a series
> of potential failure cases ending with the successful path, with no
> nesting and no else clauses.
> ---
>
> I started to work on an extension to the section attribute, and found
> myself cleaning up the logic in handle_section_attribute; I wanted to
> send this cleanup patch separately.
>
> I'm not a GCC committer, so I'm looking both for review and for someone
> to commit this patch.
>
>  gcc/ChangeLog           |  5 +++
>  gcc/c-family/c-common.c | 91 +++++++++++++++++++++++++------------------------
>  2 files changed, 51 insertions(+), 45 deletions(-)
>
> diff --git a/gcc/ChangeLog b/gcc/ChangeLog
> index 703a489..0286bfb 100644
> --- a/gcc/ChangeLog
> +++ b/gcc/ChangeLog
> @@ -1,3 +1,8 @@
> +2014-08-24  Josh Triplett  <josh@joshtriplett.org>
> +
> +       * c-family/c-common.c (handle_section_attribute): Refactor to reduce
> +       nesting and distinguish between error cases.
> +
>  2014-08-24  Oleg Endo  <olegendo@gcc.gnu.org>
>
>         PR target/61996
> diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
> index 58b9763..a63eedf 100644
> --- a/gcc/c-family/c-common.c
> +++ b/gcc/c-family/c-common.c
> @@ -7387,58 +7387,59 @@ handle_section_attribute (tree *node, tree ARG_UNUSED (name), tree args,
>  {
>    tree decl = *node;
>
> -  if (targetm_common.have_named_sections)
> +  if (!targetm_common.have_named_sections)
>      {
> -      user_defined_section_attribute = true;
> +      error_at (DECL_SOURCE_LOCATION (*node),
> +               "section attributes are not supported for this target");
> +      goto fail;

Why not move this to a different function and then do:

if (function(...))
  set_decl_section_name (decl, TREE_STRING_POINTER (TREE_VALUE (args)));
else
  *no_add_attrs = true;

return NULL_TREE;

This is a way to get away from using gotos.

Thanks,
Andrew


> +    }
>
> -      if ((TREE_CODE (decl) == FUNCTION_DECL
> -          || TREE_CODE (decl) == VAR_DECL)
> -         && TREE_CODE (TREE_VALUE (args)) == STRING_CST)
> -       {
> -         if (TREE_CODE (decl) == VAR_DECL
> -             && current_function_decl != NULL_TREE
> -             && !TREE_STATIC (decl))
> -           {
> -             error_at (DECL_SOURCE_LOCATION (decl),
> -                       "section attribute cannot be specified for "
> -                       "local variables");
> -             *no_add_attrs = true;
> -           }
> +  user_defined_section_attribute = true;
>
> -         /* The decl may have already been given a section attribute
> -            from a previous declaration.  Ensure they match.  */
> -         else if (DECL_SECTION_NAME (decl) != NULL
> -                  && strcmp (DECL_SECTION_NAME (decl),
> -                             TREE_STRING_POINTER (TREE_VALUE (args))) != 0)
> -           {
> -             error ("section of %q+D conflicts with previous declaration",
> -                    *node);
> -             *no_add_attrs = true;
> -           }
> -         else if (TREE_CODE (decl) == VAR_DECL
> -                  && !targetm.have_tls && targetm.emutls.tmpl_section
> -                  && DECL_THREAD_LOCAL_P (decl))
> -           {
> -             error ("section of %q+D cannot be overridden", *node);
> -             *no_add_attrs = true;
> -           }
> -         else
> -           set_decl_section_name (decl,
> -                                  TREE_STRING_POINTER (TREE_VALUE (args)));
> -       }
> -      else
> -       {
> -         error ("section attribute not allowed for %q+D", *node);
> -         *no_add_attrs = true;
> -       }
> +  if (TREE_CODE (decl) != FUNCTION_DECL && TREE_CODE (decl) != VAR_DECL)
> +    {
> +      error ("section attribute not allowed for %q+D", *node);
> +      goto fail;
>      }
> -  else
> +
> +  if (TREE_CODE (TREE_VALUE (args)) != STRING_CST)
>      {
> -      error_at (DECL_SOURCE_LOCATION (*node),
> -               "section attributes are not supported for this target");
> -      *no_add_attrs = true;
> +      error ("section attribute argument not a string constant");
> +      goto fail;
> +    }
> +
> +  if (TREE_CODE (decl) == VAR_DECL
> +      && current_function_decl != NULL_TREE
> +      && !TREE_STATIC (decl))
> +    {
> +      error_at (DECL_SOURCE_LOCATION (decl),
> +                "section attribute cannot be specified for local variables");
> +      goto fail;
>      }
>
> +  /* The decl may have already been given a section attribute
> +     from a previous declaration.  Ensure they match.  */
> +  if (DECL_SECTION_NAME (decl) != NULL
> +      && strcmp (DECL_SECTION_NAME (decl),
> +                 TREE_STRING_POINTER (TREE_VALUE (args))) != 0)
> +    {
> +      error ("section of %q+D conflicts with previous declaration", *node);
> +      goto fail;
> +    }
> +
> +  if (TREE_CODE (decl) == VAR_DECL
> +      && !targetm.have_tls && targetm.emutls.tmpl_section
> +      && DECL_THREAD_LOCAL_P (decl))
> +    {
> +      error ("section of %q+D cannot be overridden", *node);
> +      goto fail;
> +    }
> +
> +  set_decl_section_name (decl, TREE_STRING_POINTER (TREE_VALUE (args)));
> +  return NULL_TREE;
> +
> +fail:
> +  *no_add_attrs = true;
>    return NULL_TREE;
>  }
>
> --
> 2.1.0
>