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

[H.J. Lu]

On Wed, Jul 13, 2011 at 8:37 AM, Richard Henderson <rth@redhat.com> wrote:
> On 07/13/2011 08:35 AM, H.J. Lu wrote:
>> On Wed, Jul 13, 2011 at 8:27 AM, Richard Henderson <rth@redhat.com> wrote:
>>> On 07/13/2011 07:02 AM, H.J. Lu wrote:
>>>> Hi Richard,
>>>>
>>>> Is my patch OK?
>>>
>>> No, I don't think it is.
>>>
>>
>> What is your suggestion?
>
> Promote the return value.  If that means it doesn't match function_value,
> then I suggest that function_value is wrong.
>
>

static enum machine_mode
ix86_promote_function_mode (const_tree type, enum machine_mode mode,
                            int *punsignedp, const_tree fntype,
                            int for_return)
{
  if (type != NULL_TREE && POINTER_TYPE_P (type))
    {
      *punsignedp = POINTERS_EXTEND_UNSIGNED;
      return Pmode;
    }
  return default_promote_function_mode (type, mode, punsignedp, fntype,
                                        for_return);
}

doesn't work.  I got

In file included from
/export/gnu/import/git/gcc-x32/libgcc/config/libbid/bid_div_macros.h:27:0,
                 from
/export/gnu/import/git/gcc-x32/libgcc/config/libbid/bid128_div.c:25:
/export/gnu/import/git/gcc-x32/libgcc/config/libbid/bid_internal.h: In
function \u2018handle_UF_128.constprop.7\u2019:
/export/gnu/import/git/gcc-x32/libgcc/config/libbid/bid_internal.h:1626:1:
internal compiler error: in emit_move_insn, at expr.c:3349
Please submit a full bug report,
with preprocessed source if appropriate.

TARGET_FUNCTION_VALUE shouldn't promote pointers to Pmode
since it will also promote pointers passed in memory, which aren't
needed nor desired.

Since x86-64 processors ALWAYS zero-extend 32bit to 64bit
when writing 32bit registers, it is OK not to promote pointers
in TARGET_FUNCTION_VALUE.  We only need to promote
pointers to

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)
    /* Do not promote function return values.  */
    ;
  else if (type != NULL_TREE && POINTER_TYPE_P (type))
    {
      *punsignedp = POINTERS_EXTEND_UNSIGNED;
      return Pmode;
    }
  return default_promote_function_mode (type, mode, punsignedp, fntype,
                                        for_return);
}

Richard, can you tell me what the real problem with my approach is?

Thanks.


-- 
H.J.