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└─⟦180fe333a⟧ Bits:30000405 8mm tape, Rational 1000, SW CATALOG, 10_20_0
└─⟦180fe333a⟧ Bits:30000537 8mm tape, Rational 1000, SW Catalog 10_20_0
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        └─⟦3b1ee7bd8⟧ 
            └─⟦this⟧ 

TextFile

with Instrument;
use Instrument;

---------------------
-- Subscript Calculation
---------------------

--  This test evaluates a code  improvement  potential  that  results
--  from  minimizing  subscript  calculations when the opportunity is
--  offered to relocate a  subscript  calculation  outside  the  code
--  region of a loop body.

--  The two  test  procedures  contain  a  single  loop  enclosing  a
--  camouflaged  redefinition  of  a  global variable, Global_1.  The
--  redefinition includes a reference  to  a  component  of  a  local
--  array.   In  the  optimized  test  procedure the array element is
--  identified   by   two  subscript  expressions  that  use  a  loop
--  invariant,   Index_1.   Since  the  nonoptimized  test  procedure
--  identifies the array element with subscript expressions that  use
--  a  local  variable, Index_2, that is redefined for each iteration
--  of the loop, the optimization is evidenced by a difference in the
--  execution  time  of  the two procedures and a possible difference
--  in their space requirements.

--  The definition of the loop  invariant  is  camouflaged  to  avoid
--  unexpected  optimizations  that  would  invalidate the benchmark;
--  e.g., value propagation leading to constant folding.

procedure Losca2 is

    package New_Procs is new Procs (Integer);
    use New_Procs;

    subtype Index is T range 1 .. 100;

    Index_1, Index_2 : Index;

    Local : array (Index range 1 .. 10, Index range 1 .. 10) of T :=
       (others => (others => Ident (Init)));

begin

    Start ("LOSCA2", "Loop Optimization, Subscript Calc. (test)");
    for I in 1 .. 10000 loop

        Let (Global, Ident (Init));
        Let (Index_1, Ident (1));

        for J in Ident (T'Val (1)) .. Ident (T'Val (10)) loop

            Let (Index_2, Ident (1));
            --------optimize---------
            Let (Global, Ident (Local (Index_1 * 10, Index_1 * 5)));
            -- included in test version
            --     Let(Global, Ident(Local(Index_2 * 10, Index_2 * 5)));
            -- included in control version

        end loop;

        Let (Global, Ident (Init));

    end loop;
    Stop;

end Losca2;