-------------------------------------------------------------------------------
-- Copyright (c) 2016, Daniel King
-- All rights reserved.
--
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are met:
-- * Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
-- * Redistributions in binary form must reproduce the above copyright
-- notice, this list of conditions and the following disclaimer in the
-- documentation and/or other materials provided with the distribution.
-- * The name of the copyright holder may not be used to endorse or promote
-- Products derived from this software without specific prior written
-- permission.
--
-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-- ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-------------------------------------------------------------------------------
with System.Machine_Code; use System.Machine_Code;
package body Timing
is
Measurement_Overhead : Cycles_Count;
function RDTSC return Cycles_Count
is
L, H : Unsigned_32;
begin
Asm ("rdtsc",
Outputs => (Unsigned_32'Asm_Output ("=a", L),
Unsigned_32'Asm_Output ("=d", H)),
Volatile => True);
return Shift_Left (Unsigned_64 (H), 32) or Unsigned_64 (L);
end RDTSC;
procedure Calibrate
is
T : Time;
Diff : Cycles_Count;
Min : Cycles_Count;
begin
Measurement_Overhead := 0;
Start_Measurement (T);
Min := End_Measurement (T);
for N in 1 .. 100 loop
Start_Measurement (T);
Diff := End_Measurement (T);
-- Keep the minimum
if Diff < Min then
Min := Diff;
end if;
end loop;
Measurement_Overhead := Min;
end Calibrate;
procedure Start_Measurement (T : out Time)
is
begin
T := Time (RDTSC);
end Start_Measurement;
function End_Measurement (T : in Time) return Cycles_Count
is
End_Time : Cycles_Count;
begin
End_Time := RDTSC;
return (End_Time - Cycles_Count (T)) - Measurement_Overhead;
end End_Measurement;
begin
Calibrate;
end Timing;