Re: PATCH [3/n] X32: Promote pointers to Pmode

[Uros Bizjak <ubizjak at gmail dot com>]

On Sat, Jul 9, 2011 at 11:28 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:

> X32 psABI requires promoting pointers to Pmode when passing/returning
> in registers. ?OK for trunk?
>
> Thanks.
>
> H.J.
> --
> 2011-07-09 ?H.J. Lu ?<hongjiu.lu@intel.com>
>
> ? ? ? ?* config/i386/i386.c (ix86_promote_function_mode): New.
> ? ? ? ?(TARGET_PROMOTE_FUNCTION_MODE): Likewise.
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 04cb07d..c852719 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -7052,6 +7061,23 @@ ix86_function_value (const_tree valtype, const_tree fntype_or_decl,
> ? return ix86_function_value_1 (valtype, fntype_or_decl, orig_mode, mode);
> ?}
>
> +/* Pointer function arguments and return values are promoted to
> + ? Pmode. ?*/
> +
> +static enum machine_mode
> +ix86_promote_function_mode (const_tree type, enum machine_mode mode,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? int *punsignedp, const_tree fntype,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? int for_return)
> +{
> + ?if (for_return != 1 && type != NULL_TREE && POINTER_TYPE_P (type))
> + ? ?{
> + ? ? ?*punsignedp = POINTERS_EXTEND_UNSIGNED;
> + ? ? ?return Pmode;
> + ? ?}
> + ?return default_promote_function_mode (type, mode, punsignedp, fntype,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? for_return);
> +}

Please rewrite the condition to:

if (for_return == 1)
  /* Do not promote function return values.  */
  ;
else if (type != NULL_TREE && ...)

Also, please add some comments.

Your comment also says that pointer return arguments are promoted to
Pmode. The documentation says that:

     FOR_RETURN allows to distinguish the promotion of arguments and
     return values.  If it is `1', a return value is being promoted and
     `TARGET_FUNCTION_VALUE' must perform the same promotions done here.
     If it is `2', the returned mode should be that of the register in
     which an incoming parameter is copied, or the outgoing result is
     computed; then the hook should return the same mode as
     `promote_mode', though the signedness may be different.

You bypass promotions when FOR_RETURN is 1.

Uros.