Subversion Repositories openrisc_2011-10-31

-- C490002.A
--
--                             Grant of Unlimited Rights
--
--     Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,
--     F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained
--     unlimited rights in the software and documentation contained herein.
--     Unlimited rights are defined in DFAR 252.227-7013(a)(19).  By making
--     this public release, the Government intends to confer upon all
--     recipients unlimited rights  equal to those held by the Government.
--     These rights include rights to use, duplicate, release or disclose the
--     released technical data and computer software in whole or in part, in
--     any manner and for any purpose whatsoever, and to have or permit others
--     to do so.
--
--                                    DISCLAIMER
--
--     ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR
--     DISCLOSED ARE AS IS.  THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED
--     WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE
--     SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE
--     OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A
--     PARTICULAR PURPOSE OF SAID MATERIAL.
--*
--
-- OBJECTIVE:
--      Check that, for a real static expression that is not part of a larger
--      static expression, and whose expected type T is an ordinary fixed
--      point type that is not a descendant of a formal scalar type, the value
--      is rounded to the nearest integral multiple of the small of T if
--      T'Machine_Rounds is true, and is truncated otherwise. Check that if
--      rounding is performed, and the value is exactly halfway between two
--      multiples of the small, one of the two multiples of small is used.
--
-- TEST DESCRIPTION:
--      The test obtains an integral multiple M1 of the small of an ordinary
--      fixed point subtype S by dividing a real literal by S'Small, and then
--      truncating the result using 'Truncation. It then obtains an adjacent
--      multiple M2 of the small by using S'Succ (or S'Pred). It then
--      constructs values which lie between these multiples: one (A) which is
--      closer to M1, one (B) which is exactly halfway between M1 and M2, and
--      one (C) which is closer to M2. This is done for both positive and
--      negative multiples of the small.
--
--      Let M1 be closer to zero than M2. Then if S'Machine_Rounds is true,
--      C must be rounded to M2, A must be rounded to M1, and B must be rounded
--      to either M1 or M2. If S'Machine_Rounds is false, all the values must
--      be truncated to M1.
--
--      A, B, and C are constructed using the following static expressions:
--
--         A: constant S := M1 + (M2 - M1)/Z; -- Z slightly more than 2.0.
--         B: constant S := M1 + (M2 - M1)/Z; -- Z equals 2.0.
--         C: constant S := M1 + (M2 - M1)/Z; -- Z slightly less than 2.0.
--
--      Since these are static expressions, they must be evaluated exactly,
--      and no rounding may occur until the final result is calculated.
--
--      The checks for equality between the members of (A, B, C) and (M1, M2)
--      are performed at run-time within the body of a subprogram.
--
--      The test performs additional checks that the rounding performed on
--      real literals is consistent for ordinary fixed point subtypes. A
--      named number (initialized with a literal) is assigned to a constant of
--      a fixed point subtype S. The same literal is then passed to a
--      subprogram, along with the constant, and an equality check is
--      performed within the body of the subprogram.
--
--
-- CHANGE HISTORY:
--      26 Sep 95   SAIC    Initial prerelease version.
--
--!

package C490002_0 is

   type My_Fix is delta 0.0625 range -1000.0 .. 1000.0;

   Small : constant := My_Fix'Small;                      -- Named number.

   procedure Fixed_Subtest (A, B: in My_Fix; Msg: in String);

   procedure Fixed_Subtest (A, B, C: in My_Fix; Msg: in String);


--
-- Positive cases:
--

   --  |----|-------------|-----------------|-------------------|-----------|
   --  |    |             |                 |                   |           |
   --  0   P_M1  Less_Pos_Than_Half  Pos_Exactly_Half  More_Pos_Than_Half  P_M2


   Positive_Real  : constant := 0.11433;          -- Named number.
   Pos_Multiplier : constant := Float'Truncation(Positive_Real/Small);

   -- Pos_Multiplier is the number of integral multiples of small contained
   -- in Positive_Real. P_M1 is thus the largest integral multiple of
   -- small less than or equal to Positive_Real. Note that since Positive_Real
   -- is a named number and not a fixed point object, P_M1 is generated
   -- without assuming that rounding is performed correctly for fixed point
   -- subtypes.

   Positive_Fixed : constant My_Fix := Positive_Real;

   P_M1 : constant My_Fix := Pos_Multiplier * Small;
   P_M2 : constant My_Fix := My_Fix'Succ(P_M1);

   -- P_M1 and P_M2 are adjacent multiples of the small of My_Fix. Note that
   -- 0.11433 either equals P_M1 (if it is an integral multiple of the small)
   -- or lies between P_M1 and P_M2 (since truncation was forced in
   -- generating Pos_Multiplier). It is not certain, however, exactly where
   -- it lies between them (halfway, less than halfway, more than halfway).
   -- This fact is irrelevant to the test.


   -- The following entities are used to verify that rounding is performed
   -- according to the value of 'Machine_Rounds. If language rules are
   -- obeyed, the intermediate expressions in the following static
   -- initialization expressions will not be rounded; all calculations will
   -- be performed exactly. The final result, however, will be rounded to
   -- an integral multiple of the small (either P_M1 or P_M2, depending on the
   -- value of My_Fix'Machine_Rounds). Thus, the value of each constant below
   -- will equal that of P_M1 or P_M2.

   Less_Pos_Than_Half : constant My_Fix := P_M1 + ((P_M2 - P_M1)/2.050);
   Pos_Exactly_Half   : constant My_Fix := P_M1 + ((P_M2 - P_M1)/2.000);
   More_Pos_Than_Half : constant My_Fix := P_M1 + ((P_M2 - P_M1)/1.975);


--
-- Negative cases:
--

   --  -|-------------|-----------------|-------------------|-----------|----|
   --   |             |                 |                   |           |    |
   --  N_M2  More_Neg_Than_Half  Neg_Exactly_Half  Less_Neg_Than_Half  N_M1  0


   -- The descriptions for the positive cases above apply to the negative
   -- cases below as well. Note that, for N_M2, 'Pred is used rather than
   -- 'Succ. Thus, N_M2 is further from 0.0 (i.e. more negative) than N_M1.

   Negative_Real  : constant := -467.13988;       -- Named number.
   Neg_Multiplier : constant := Float'Truncation(Negative_Real/Small);

   Negative_Fixed : constant My_Fix := Negative_Real;

   N_M1 : constant My_Fix := Neg_Multiplier * Small;
   N_M2 : constant My_Fix := My_Fix'Pred(N_M1);

   More_Neg_Than_Half : constant My_Fix := N_M1 + ((N_M2 - N_M1)/1.980);
   Neg_Exactly_Half   : constant My_Fix := N_M1 + ((N_M2 - N_M1)/2.000);
   Less_Neg_Than_Half : constant My_Fix := N_M1 + ((N_M2 - N_M1)/2.033);

end C490002_0;


     --==================================================================--


with TCTouch;
package body C490002_0 is

   procedure Fixed_Subtest (A, B: in My_Fix; Msg: in String) is
   begin
       TCTouch.Assert (A = B, Msg);
   end Fixed_Subtest;

   procedure Fixed_Subtest (A, B, C: in My_Fix; Msg: in String) is
   begin
       TCTouch.Assert (A = B or A = C, Msg);
   end Fixed_Subtest;

end C490002_0;


     --==================================================================--


with C490002_0;  -- Fixed point support.
use  C490002_0;

with Report;
procedure C490002 is
begin
   Report.Test ("C490002", "Rounding of real static expressions: " &
                "ordinary fixed point subtypes");


   -- Literal cases: If the named numbers used to initialize Positive_Fixed
   -- and Negative_Fixed are rounded to an integral multiple of the small
   -- prior to assignment (as expected), then Positive_Fixed and
   -- Negative_Fixed are already integral multiples of the small, and
   -- equal either P_M1 or P_M2 (resp., N_M1 or N_M2). An equality check
   -- can determine in which direction rounding occurred. For example:
   --
   --        if (Positive_Fixed = P_M1) then -- Rounding was toward 0.0.
   --
   -- Check here that the rounding direction is consistent for literals:

   if (Positive_Fixed = P_M1) then
      Fixed_Subtest (0.11433, P_M1, "Positive Fixed: literal");
   else
      Fixed_Subtest (0.11433, P_M2, "Positive Fixed: literal");
   end if;

   if (Negative_Fixed = N_M1) then
      Fixed_Subtest (-467.13988, N_M1, "Negative Fixed: literal");
   else
      Fixed_Subtest (-467.13988, N_M2, "Negative Fixed: literal");
   end if;


   -- Now check that rounding is performed correctly for values between
   -- multiples of the small, according to the value of 'Machine_Rounds:

   if My_Fix'Machine_Rounds then
      Fixed_Subtest (Pos_Exactly_Half,   P_M1, P_M2, "Positive Fixed: = half");
      Fixed_Subtest (More_Pos_Than_Half, P_M2, "Positive Fixed: > half");
      Fixed_Subtest (Less_Pos_Than_Half, P_M1, "Positive Fixed: < half");

      Fixed_Subtest (Neg_Exactly_Half,   N_M1, N_M2, "Negative Fixed: = half");
      Fixed_Subtest (More_Neg_Than_Half, N_M2, "Negative Fixed: > half");
      Fixed_Subtest (Less_Neg_Than_Half, N_M1, "Negative Fixed: < half");
   else
      Fixed_Subtest (Pos_Exactly_Half,   P_M1, "Positive Fixed: = half");
      Fixed_Subtest (More_Pos_Than_Half, P_M1, "Positive Fixed: > half");
      Fixed_Subtest (Less_Pos_Than_Half, P_M1, "Positive Fixed: < half");

      Fixed_Subtest (Neg_Exactly_Half,   N_M1, "Negative Fixed: = half");
      Fixed_Subtest (More_Neg_Than_Half, N_M1, "Negative Fixed: > half");
      Fixed_Subtest (Less_Neg_Than_Half, N_M1, "Negative Fixed: < half");
   end if;


   Report.Result;
end C490002;