[Ada] Avoid unnecessarily overaligned access types

[Eric Botcazou]

This changes the default alignment of all access types to that of access types
with standard size (Standard'Address_Size) on non-strict-alignment platforms.
This in particular means that access-to-unconstrained-array types, whose size
is twice as large as that of regular access types, are not overaligned by
default anymore and therefore don't cause unnecessary padding in record types.

The following program must run quietly on these platforms:

procedure P is
  type Array_T is array (Positive range <>) of Integer;
  type Access_Array_T is access Array_T;
  type Thin_Access_Array_T is access Array_T;
  for Thin_Access_Array_T'Size use Standard'Address_Size;
begin
  if Access_Array_T'Alignment /= Thin_Access_Array_T'Alignment then
    raise Program_Error;
  end if;
end;

Tested on x86_64-suse-linux, applied on the mainline.


2012-08-19  Eric Botcazou  <ebotcazou@adacore.com>

	* layout.adb (Set_Elem_Alignment): Cap the alignment of access types to
	that of a regular access type for non-strict-alignment platforms.
	* gcc-interface/utils.c (finish_fat_pointer_type): Do not set the
	alignment for non-strict-alignment platforms.


-- 
Eric Botcazou
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