So someone reached out to me directly again asking for an FPC
optimisation. Now I want to see if this is possible to optimise and
won't break something or be annoying specific.
Gareth aka. Kit
-------- Forwarded Message --------
Subject: Re: An optimization suggestion for FPC
Date: Sun, 28 Jun 2020 11:30:09 +0100
From: J. Gareth Moreton <gar...@moreton-family.com>
To: Okoba <okobapat...@protonmail.com>
Heh, I'm honoured you came to me directly. I'll see if I can work
anything out. A lot of it is down to where the record is stored. If
it's on the stack, an optimisation shouldn't be difficult, but if it's
on the heap somewhere, then it will be a bit more difficult. Do you
have your C++ example, and which C++ compiler did you use?
Gareth aka. Kit
On 28/06/2020 11:06, Okoba wrote:
Hi,
It seems you are interested in optimizing FPC and I have a trouble
with it and wanted to check it with you if I may.
I like to have a way to pass the record variable and inc it without
losing speed. I wrote a sample and ran it with FPC trunk in Win64 and
the times are commented. I should say the times for Delphi for the
same target is the same. And tried a C++ version and all the times are
almost the same and near 250.
I tried many ways including absolute, pointer, custom asm functions,
custom functions with const and var params and the are almost always
slower than the first loop.
So is there anyway to have a custom Inc function that get he record
variable and inc it without losing speed in compare to the system inc?
Regards.
program Project1;
uses
SysUtils;
type
TTest = record
P: int64;
end;
procedure Test;
var
V: TTest;
P: int64;
T: UInt64;
i, C: integer;
begin
C := 1000 * 1000 * 1000;
T := GetTickCount64;
P := 1;
for i := 1 to C do
Inc(P);
WriteLn(GetTickCount64 - T); //266
T := GetTickCount64;
V.P := 1;
for i := 1 to C do
Inc(V.P);
WriteLn(GetTickCount64 - T); //1400
T := GetTickCount64;
V.P := 1;
P := V.P;
for i := 1 to C do
Inc(P);
P := V.P;
WriteLn(GetTickCount64 - T); //250
end;
begin
Test;
ReadLn;
end.
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
fpc-devel maillist - fpc-devel@lists.freepascal.org
https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
