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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                         G N A T . A L T I V E C                          --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 2004-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

-------------------------

-- General description --

-------------------------

--  This is the root of a package hierarchy offering an Ada binding to the

--  PowerPC AltiVec extensions. These extensions basically consist in a set of

--  128bit vector types together with a set of subprograms operating on such

--  vectors. On a real Altivec capable target, vector objects map to hardware

--  vector registers and the subprograms map to a set of specific hardware

--  instructions.

--  Relevant documents are:

--  o AltiVec Technology, Programming Interface Manual (1999-06)

--    to which we will refer as [PIM], describes the data types, the

--    functional interface and the ABI conventions.

--  o AltiVec Technology, Programming Environments Manual (2002-02)

--    to which we will refer as [PEM], describes the hardware architecture

--    and instruction set.

--  These documents, as well as a number of others of general interest on the

--  AltiVec technology, are available from the Motorola/AltiVec Web site at

--  http://www.motorola.com/altivec

--  We offer two versions of this binding: one for real AltiVec capable

--  targets, and one for other targets. In the latter case, everything is

--  emulated in software. We will refer to the two bindings as:

--  o The Hard binding for AltiVec capable targets (with the appropriate

--    hardware support and corresponding instruction set)

--  o The Soft binding for other targets (with the low level primitives

--    emulated in software).

--  The two versions of the binding are expected to be equivalent from the

--  functional standpoint. The same client application code should observe no

--  difference in operation results, even if the Soft version is used on a

--  non-powerpc target. The Hard binding is naturally expected to run faster

--  than the Soft version on the same target.

--  We also offer interfaces not strictly part of the base AltiVec API, such

--  as vector conversions to/from array representations, which are of interest

--  for client applications (e.g. for vector initialization purposes) and may

--  also be used as implementation facilities.

-----------------------------------------

-- General package architecture survey --

-----------------------------------------

--  The various vector representations are all "containers" of elementary

--  values, the possible types of which are declared in this root package to

--  be generally accessible.

--  From the user standpoint, the two versions of the binding are available

--  through a consistent hierarchy of units providing identical services:

--                             GNAT.Altivec

--                           (component types)

--                                   |

--          o----------------o----------------o-------------o

--          |                |                |             |

--    Vector_Types   Vector_Operations   Vector_Views   Conversions

--  The user can manipulate vectors through two families of types: Vector

--  types and View types.

--  Vector types are defined in the GNAT.Altivec.Vector_Types package

--  On these types, the user can apply the Altivec operations defined in

--  GNAT.Altivec.Vector_Operations. Their layout is opaque and may vary across

--  configurations, for it is typically target-endianness dependant.

--  Vector_Types and Vector_Operations implement the core binding to the

--  AltiVec API, as described in [PIM-2.1 data types] and [PIM-4 AltiVec

--  operations and predicates].

--  View types are defined in the GNAT.Altivec.Vector_Views package

--  These types do not represent Altivec vectors per se, in the sense that the

--  Altivec_Operations are not available for them. They are intended to allow

--  Vector initializations as well as access to the Vector component values.

--  The GNAT.Altivec.Conversions package is provided to convert a View to the

--  corresponding Vector and vice-versa.

--  The two versions of the binding rely on a low level internal interface,

--  and switching from one version to the other amounts to select one low

--  level implementation instead of the other.

--  The bindings are provided as a set of sources together with a project file

--  (altivec.gpr). The hard/soft binding selection is controlled by a project

--  variable on targets where switching makes sense. See the example usage

--  section below.

---------------------------

-- Underlying principles --

---------------------------

--  The general organization sketched above has been devised from a number

--  of driving ideas:

--  o From the clients standpoint, the two versions of the binding should be

--    as easily exchangeable as possible,

--  o From the maintenance standpoint, we want to avoid as much code

--    duplication as possible.

--  o From both standpoints above, we want to maintain a clear interface

--    separation between the base bindings to the Motorola API and the

--    additional facilities.

--  The identification of the low level interface is directly inspired by the

--  the base API organization, basically consisting of a rich set of functions

--  around a core of low level primitives mapping to AltiVec instructions.

--  See for instance "vec_add" in [PIM-4.4 Generic and Specific AltiVec

--  operations]: no less than six result/arguments combinations of byte vector

--  types map to "vaddubm".

--  The "hard" version of the low level primitives map to real AltiVec

--  instructions via the corresponding GCC builtins. The "soft" version is

--  a software emulation of those.

-------------------

-- Example usage --

-------------------

--  Here is a sample program declaring and initializing two vectors, 'add'ing

--  them and displaying the result components:

--  with GNAT.Altivec.Vector_Types;      use GNAT.Altivec.Vector_Types;

--  with GNAT.Altivec.Vector_Operations; use GNAT.Altivec.Vector_Operations;

--  with GNAT.Altivec.Vector_Views;      use GNAT.Altivec.Vector_Views;

--  with GNAT.Altivec.Conversions;       use GNAT.Altivec.Conversions;

--  use GNAT.Altivec;

--  procedure Sample is

--     Va : Vector_Unsigned_Int := To_Vector ((Values => (1, 2, 3, 4)));

--     Vb : Vector_Unsigned_Int := To_Vector ((Values => (1, 2, 3, 4)));

--     Vs : Vector_Unsigned_Int;

--     Vs_View : VUI_View;

--  begin

--     Vs := Vec_Add (Va, Vb);

--     Vs_View := To_View (Vs);

--     for I in Vs_View.Values'Range loop

--        Put_Line (Unsigned_Int'Image (Vs_View.Values (I)));

--     end loop;

--  end;

--  This currently requires the GNAT project management facilities to compile,

--  to automatically retrieve the set of necessary sources and switches

--  depending on your configuration. For the example above, customizing the

--  switches to include -g also, this would be something like:

--  sample.gpr

--

--  with "altivec.gpr";

--

--  project Sample is

--    for Source_Dirs use (".");

--    for Main use ("sample");

--    package Compiler is

--       for Default_Switches ("Ada") use

--           Altivec.Compiler'Default_Switches ("Ada") & "-g";

--    end Compiler;

--  end Sample;

--  $ gnatmake -Psample

--  [...]

--  $ ./sample

--  2

--  4

--  6

--  8

------------------------------------------------------------------------------

with System;

package GNAT.Altivec is

   --  Definitions of constants and vector/array component types common to all

   --  the versions of the binding.

   --  All the vector types are 128bits

   VECTOR_BIT : constant := 128;

   -------------------------------------------

   -- [PIM-2.3.1 Alignment of vector types] --

   -------------------------------------------

   --  "A defined data item of any vector data type in memory is always

   --  aligned on a 16-byte boundary. A pointer to any vector data type always

   --  points to a 16-byte boundary. The compiler is responsible for aligning

   --  vector data types on 16-byte boundaries."

   VECTOR_ALIGNMENT : constant := Natural'Min (16, Standard'Maximum_Alignment);

   --  This value is used to set the alignment of vector datatypes in both the

   --  hard and the soft binding implementations.

   --

   --  We want this value to never be greater than 16, because none of the

   --  binding implementations requires larger alignments and such a value

   --  would cause useless space to be allocated/wasted for vector objects.

   --  Furthermore, the alignment of 16 matches the hard binding leading to

   --  a more faithful emulation.

   --

   --  It needs to be exactly 16 for the hard binding, and the initializing

   --  expression is just right for this purpose since Maximum_Alignment is

   --  expected to be 16 for the real Altivec ABI.

   --

   --  The soft binding doesn't rely on strict 16byte alignment, and we want

   --  the value to be no greater than Standard'Maximum_Alignment in this case

   --  to ensure it is supported on every possible target.

   -------------------------------------------------------

   -- [PIM-2.1] Data Types - Interpretation of contents --

   -------------------------------------------------------

   ---------------------

   -- char components --

   ---------------------

   CHAR_BIT    : constant := 8;

   SCHAR_MIN   : constant := -2 ** (CHAR_BIT - 1);

   SCHAR_MAX   : constant := 2 ** (CHAR_BIT - 1) - 1;

   UCHAR_MAX   : constant := 2 ** CHAR_BIT - 1;

   type unsigned_char is mod UCHAR_MAX + 1;

   for unsigned_char'Size use CHAR_BIT;

   type signed_char is range SCHAR_MIN .. SCHAR_MAX;

   for signed_char'Size use CHAR_BIT;

   subtype bool_char is unsigned_char;

   --  ??? There is a difference here between what the Altivec Technology

   --  Programming Interface Manual says and what GCC says. In the manual,

   --  vector_bool_char is a vector_unsigned_char, while in altivec.h it

   --  is a vector_signed_char.

   bool_char_True  : constant bool_char := bool_char'Last;

   bool_char_False : constant bool_char := 0;

   ----------------------

   -- short components --

   ----------------------

   SHORT_BIT   : constant := 16;

   SSHORT_MIN  : constant := -2 ** (SHORT_BIT - 1);

   SSHORT_MAX  : constant := 2 ** (SHORT_BIT - 1) - 1;

   USHORT_MAX  : constant := 2 ** SHORT_BIT - 1;

   type unsigned_short is mod USHORT_MAX + 1;

   for unsigned_short'Size use SHORT_BIT;

   subtype unsigned_short_int is unsigned_short;

   type signed_short is range SSHORT_MIN .. SSHORT_MAX;

   for signed_short'Size use SHORT_BIT;

   subtype signed_short_int is signed_short;

   subtype bool_short is unsigned_short;

   --  ??? See bool_char

   bool_short_True  : constant bool_short := bool_short'Last;

   bool_short_False : constant bool_short := 0;

   subtype bool_short_int is bool_short;

   --------------------

   -- int components --

   --------------------

   INT_BIT     : constant := 32;

   SINT_MIN    : constant := -2 ** (INT_BIT - 1);

   SINT_MAX    : constant := 2 ** (INT_BIT - 1) - 1;

   UINT_MAX    : constant := 2 ** INT_BIT - 1;

   type unsigned_int is mod UINT_MAX + 1;

   for unsigned_int'Size use INT_BIT;

   type signed_int is range SINT_MIN .. SINT_MAX;

   for signed_int'Size use INT_BIT;

   subtype bool_int is unsigned_int;

   --  ??? See bool_char

   bool_int_True  : constant bool_int := bool_int'Last;

   bool_int_False : constant bool_int := 0;

   ----------------------

   -- float components --

   ----------------------

   FLOAT_BIT   : constant := 32;

   FLOAT_DIGIT : constant := 6;

   FLOAT_MIN   : constant := -16#0.FFFF_FF#E+32;

   FLOAT_MAX   : constant := 16#0.FFFF_FF#E+32;

   type C_float is digits FLOAT_DIGIT range FLOAT_MIN .. FLOAT_MAX;

   for C_float'Size use FLOAT_BIT;

   --  Altivec operations always use the standard native floating-point

   --  support of the target. Note that this means that there may be

   --  minor differences in results between targets when the floating-

   --  point implementations are slightly different, as would happen

   --  with normal non-Altivec floating-point operations. In particular

   --  the Altivec simulations may yield slightly different results

   --  from those obtained on a true hardware Altivec target if the

   --  floating-point implementation is not 100% compatible.

   ----------------------

   -- pixel components --

   ----------------------

   subtype pixel is unsigned_short;

   -----------------------------------------------------------

   -- Subtypes for variants found in the GCC implementation --

   -----------------------------------------------------------

   subtype c_int is signed_int;

   subtype c_short is c_int;

   LONG_BIT  : constant := 32;

   --  Some of the GCC builtins are built with "long" arguments and

   --  expect SImode to come in.

   SLONG_MIN : constant := -2 ** (LONG_BIT - 1);

   SLONG_MAX : constant :=  2 ** (LONG_BIT - 1) - 1;

   ULONG_MAX : constant :=  2 ** LONG_BIT - 1;

   type signed_long   is range SLONG_MIN .. SLONG_MAX;

   type unsigned_long is mod ULONG_MAX + 1;

   subtype c_long is signed_long;

   subtype c_ptr is System.Address;

   ---------------------------------------------------------

   -- Access types, for the sake of some argument passing --

   ---------------------------------------------------------

   type signed_char_ptr    is access all signed_char;

   type unsigned_char_ptr  is access all unsigned_char;

   type short_ptr          is access all c_short;

   type signed_short_ptr   is access all signed_short;

   type unsigned_short_ptr is access all unsigned_short;

   type int_ptr            is access all c_int;

   type signed_int_ptr     is access all signed_int;

   type unsigned_int_ptr   is access all unsigned_int;

   type long_ptr           is access all c_long;

   type signed_long_ptr    is access all signed_long;

   type unsigned_long_ptr  is access all unsigned_long;

   type float_ptr          is access all Float;

   --

   type const_signed_char_ptr    is access constant signed_char;

   type const_unsigned_char_ptr  is access constant unsigned_char;

   type const_short_ptr          is access constant c_short;

   type const_signed_short_ptr   is access constant signed_short;

   type const_unsigned_short_ptr is access constant unsigned_short;

   type const_int_ptr            is access constant c_int;

   type const_signed_int_ptr     is access constant signed_int;

   type const_unsigned_int_ptr   is access constant unsigned_int;

   type const_long_ptr           is access constant c_long;

   type const_signed_long_ptr    is access constant signed_long;

   type const_unsigned_long_ptr  is access constant unsigned_long;

   type const_float_ptr          is access constant Float;

   --  Access to const volatile arguments need specialized types

   type volatile_float is new Float;

   pragma Volatile (volatile_float);

   type volatile_signed_char is new signed_char;

   pragma Volatile (volatile_signed_char);

   type volatile_unsigned_char is new unsigned_char;

   pragma Volatile (volatile_unsigned_char);

   type volatile_signed_short is new signed_short;

   pragma Volatile (volatile_signed_short);

   type volatile_unsigned_short is new unsigned_short;

   pragma Volatile (volatile_unsigned_short);

   type volatile_signed_int is new signed_int;

   pragma Volatile (volatile_signed_int);

   type volatile_unsigned_int is new unsigned_int;

   pragma Volatile (volatile_unsigned_int);

   type volatile_signed_long is new signed_long;

   pragma Volatile (volatile_signed_long);

   type volatile_unsigned_long is new unsigned_long;

   pragma Volatile (volatile_unsigned_long);

   type constv_char_ptr           is access constant volatile_signed_char;

   type constv_signed_char_ptr    is access constant volatile_signed_char;

   type constv_unsigned_char_ptr  is access constant volatile_unsigned_char;

   type constv_short_ptr          is access constant volatile_signed_short;

   type constv_signed_short_ptr   is access constant volatile_signed_short;

   type constv_unsigned_short_ptr is access constant volatile_unsigned_short;

   type constv_int_ptr            is access constant volatile_signed_int;

   type constv_signed_int_ptr     is access constant volatile_signed_int;

   type constv_unsigned_int_ptr   is access constant volatile_unsigned_int;

   type constv_long_ptr           is access constant volatile_signed_long;

   type constv_signed_long_ptr    is access constant volatile_signed_long;

   type constv_unsigned_long_ptr  is access constant volatile_unsigned_long;

   type constv_float_ptr  is access constant volatile_float;

private

   -----------------------

   -- Various constants --

   -----------------------

   CR6_EQ     : constant := 0;

   CR6_EQ_REV : constant := 1;

   CR6_LT     : constant := 2;

   CR6_LT_REV : constant := 3;

end GNAT.Altivec;