[fpc-pascal] fast integer multiplication and one asm questio
Gerhard Scholz
gs at g--s.de
Tue Aug 2 20:16:18 CEST 2005
For learning some basics of assembler you should download the NASM, it is
bundled with a documentation; more documentation should be found at the intel
sides. Or e.g. try http://www.agner.org/assem
But keep in mind that the exact syntax differs from assembler to assembler.
Also a good idea is to compile (little) pascal programs and look at the
generated code (compile with the option "-al")
A general assembler tutorial here would overflow this mail list.
Gerhard
-----Ursprüngliche Nachricht-----
Von: "Pianoman" <pianoman at centrum.sk>
An: <fpc-pascal at lists.freepascal.org>
Gesendet: Dienstag, 2. August 2005 17:22
Betreff: [fpc-pascal] fast integer multiplication and one asm questio
> Hi, the UI32x32To64 function is great but is amazingly short. How can I
> Specify which varriables in function will be accessed. In this function for
> example it accesses a and b but source says mull (I don't know why not mul I
> didnt find mull instruction in any assembly book) and %eax why mull %eax
> multiplies a,b is it on the stack or why? If i would like to multiply a,b,c
> what would look source code then? Thanx for response to those quite stupid
> assembly question(I am only beginner in asm :)
> Pianoman
> ----- Original Message -----
> From: <fpc-pascal-request at lists.freepascal.org>
> To: <fpc-pascal at lists.freepascal.org>
> Sent: Tuesday, August 02, 2005 12:00 PM
> Subject: fpc-pascal Digest, Vol 12, Issue 2
>
>
> Send fpc-pascal mailing list submissions to
> fpc-pascal at lists.freepascal.org
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://lists.freepascal.org/mailman/listinfo/fpc-pascal
> or, via email, send a message with subject or body 'help' to
> fpc-pascal-request at lists.freepascal.org
>
> You can reach the person managing the list at
> fpc-pascal-owner at lists.freepascal.org
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of fpc-pascal digest..."
>
>
> Today's Topics:
>
> 1. Re: lazarus crash at start (Jesus Reyes)
> 2. Re: fast integer multiplication (Gerhard Scholz)
> 3. Can a program find out how it was started?
> (miller at psy.otago.ac.nz)
> 4. Re: Can a program find out how it was started? (Moz)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 1 Aug 2005 11:21:10 -0500 (CDT)
> From: Jesus Reyes <jesusrmx at yahoo.com.mx>
> Subject: Re: [fpc-pascal] lazarus crash at start
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <20050801162111.68197.qmail at web52306.mail.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
>
> --- Peter Vreman <peter at freepascal.org> escribió:
>
> > At 01:12 1-8-2005, you wrote:
> > >Trying to find why lazarus crashes at start in win98 I found a
> > courious
> > >problem, global variable IsConsole is true when it should be false
> > as
> > >lazarus is built as a gui application.
> > >
> > >Digging I found that IsConsole is set in two functions in
> > wprt0.as:
> > >_mainCRTStartup sets to true and _WinMainCRTStartup sets to False,
> > this
> > >cause a wrong setup of standard Output that DebugLn (lclprocs.pas)
> > use to
> > >emit debug messages.
> > >
> > >It seems that this functions are 'used' in the linker script, for
> > example
> > >ld .--verbose shows that by default a ENTRY(_mainCRTStartup) it's
> > used. I
> > >looked into the generated lazarus link.res file and didn't find a
> > ENTRY
> > >section so I guess it uses the default and that's why even when
> > lazarus is
> > >a gui app, it's linked as a console app.
> > >
> > >To demostrate this I modified the link.res script to inculde
> > >ENTRY(_WinMainCRTStartup) section and then linked, the resulting
> > >lazarus.exe file now behaves as a gui app and won't crash at
> > start.
> > >
> > >It seems that WriteResponseFile lacks the code to add the ENTRY
> > section to
> > >the link.res script but I don't know if it's supposed to be there
> > or
> > >should it be in another stage, any comments?
> >
> > You need to use {$apptype gui} or use the -WG parameter. For the
> > compiler
> > it is not known if the application needs a console or not.
> >
> >
> > Peter
> >
>
> Lazarus is already compiled with -WG
>
> Jesus Reyes A.
>
>
> __________________________________________________
> Correo Yahoo!
> Espacio para todos tus mensajes, antivirus y antispam ¡gratis!
> Regístrate ya - http://correo.yahoo.com.mx/
>
>
>
> ------------------------------
>
> Message: 2
> Date: Mon, 1 Aug 2005 23:58:04 +0200
> From: "Gerhard Scholz" <gs at g--s.de>
> Subject: Re: [fpc-pascal] fast integer multiplication
> To: "FPC-Pascal users discussions" <fpc-pascal at lists.freepascal.org>
> Message-ID: <04d601c596e4$1aef7de0$f7dcb9d9 at es>
> Content-Type: text/plain; charset="iso-8859-1"
>
> ...
> >>The code generated for the above sample is:
> >># [16] c:=a*b;
> >> movl U_P$PROJECT1_A,%edx
> >> movl U_P$PROJECT1_B,%eax
> >> mull %edx
> >> movl $0,%edx
> >> movl %eax,U_P$PROJECT1_C
> >> movl %edx,U_P$PROJECT1_C+4
> >>
> >>What I want is the above code, but without the "movl $0,%edx"
> >>instruction. Is there a way to do this (wihtout using fpc_mul_qword).
> >
> >
> > Only assembler for now. Any suggestions how the compiler could be told
> > to generate such code?
> ...
> >function UI32x32To64(A,B: Longword): QWord;
> >assembler; register; nostackframe;
> >asm
> > mull %edx
> >end;
> >
> >It is fast but certainly much less than if it were inlined.
>
> My suggestion would be:
>
> FUNCTION lmul ( CONST a,
> b : LongInt ) : int64 ; inline ;
>
> BEGIN
> {$ifdef cpu86}
> ASM
> movl a,%eax
> imull b
> movl %eax,lmul
> movl %edx,lmul+4
> END ;
> {$else}
> {$ifdef cpu68k}
> lmul := int64 ( a ) * b ;
> {$else}
> {$ifdef cpusparc}
> lmul := int64 ( a ) * b ;
> {$else}
> {$ifdef cpualpha}
> lmul := int64 ( a ) * b ;
> {$else}
> {$ifdef cpupowerpc}
> lmul := int64 ( a ) * b ;
> {$else}
> lmul := int64 ( a ) * b ;
> {$endif}
> {$endif}
> {$endif}
> {$endif}
> {$endif}
> END ;
>
> and similar for unsigned mul.
>
> (shortened here; full code in ulmul.pas; liitle test in tmuls.pas, timing
> routines in
> wtimer/tdrsc1)
>
> Is portable so code doesn't need to be rewritten when compiled for other
> processors (but not optimal then)
>
> Tested only on i386.
>
> Seems to be faster than standard multiplication (interesting: significantly
> faster for signed mul than for unsigned mul), can be assembly-coded in the
> branches for the other cpus
> (if there are opcodes for such a multiplication - I don't know), could go to
> unit math.pp.
>
> It seems that routines which contain assembler are not inlined; on the day
> somebody finds a trick to inline such code they should be really fast.
>
> Gerhard
> -------------- next part --------------
> A non-text attachment was scrubbed...
> Name: ULMUL.pas
> Type: application/octet-stream
> Size: 2604 bytes
> Desc: not available
> Url :
> http://lists.freepascal.org/pipermail/fpc-pascal/attachments/20050801/86cde0
> 70/ULMUL-0001.obj
> -------------- next part --------------
> A non-text attachment was scrubbed...
> Name: tmuls.pas
> Type: application/octet-stream
> Size: 1291 bytes
> Desc: not available
> Url :
> http://lists.freepascal.org/pipermail/fpc-pascal/attachments/20050801/86cde0
> 70/tmuls-0001.obj
> -------------- next part --------------
> A non-text attachment was scrubbed...
> Name: WTIMER.pas
> Type: application/octet-stream
> Size: 1645 bytes
> Desc: not available
> Url :
> http://lists.freepascal.org/pipermail/fpc-pascal/attachments/20050801/86cde0
> 70/WTIMER-0001.obj
> -------------- next part --------------
> A non-text attachment was scrubbed...
> Name: TDRSC1.pas
> Type: application/octet-stream
> Size: 2879 bytes
> Desc: not available
> Url :
> http://lists.freepascal.org/pipermail/fpc-pascal/attachments/20050801/86cde0
> 70/TDRSC1-0001.obj
>
> ------------------------------
>
> Message: 3
> Date: Tue, 2 Aug 2005 22:03:45 +1200
> From: miller at psy.otago.ac.nz
> Subject: [fpc-pascal] Can a program find out how it was started?
> To: fpc-pascal at lists.freepascal.org
> Message-ID: <1122977025.42ef45014673a at www.psy.otago.ac.nz>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Greetings from New Zealand,
>
> I use fpc to compile programs intended to be run from the command line in a
> cmd
> window (Windows 2000, etc). Sometimes, though, new users try to start the
> programs by double-clicking on the exe file (application icon). When the
> program starts, I would like to be able to tell if they have done that,
> so that I can present a special error message.
>
> So my question is:
> Is it possible for a program to tell whether it was started from
> the command line or started by double-clicking on the application icon?
>
> I tried checking ParamStr(0) and DOSVersion, but these have the same values
> regardless of how the program was started.
>
> Any suggestions?
>
> Thank you for your time,
>
> Jeff Miller
>
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 2 Aug 2005 19:25:13 +1000
> From: Moz <list at moz.geek.nz>
> Subject: Re: [fpc-pascal] Can a program find out how it was started?
> To: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Message-ID: <1412152272.20050802192513 at moz.geek.nz>
> Content-Type: text/plain; charset=us-ascii
>
> miller at psy.otago.ac.nz said:
> > Sometimes, though, new users try to start the programs by
> > double-clicking on the exe file (application icon). When the program
> > starts, I would like to be able to tell if they have done that, so
> > that I can present a special error message.
>
> One trivial solution is to drop a readline at the end of the help
> routine. That way the cmd window stays open until they hit enter
> (which you should tell them to do). Mildly annoying for people at the
> command line if there's only a few lines of help, but solves the
> problem.
>
> Moz
>
>
>
>
> ------------------------------
>
> _______________________________________________
> fpc-pascal maillist - fpc-pascal at lists.freepascal.org
> http://lists.freepascal.org/mailman/listinfo/fpc-pascal
>
>
> End of fpc-pascal Digest, Vol 12, Issue 2
> *****************************************
>
>
> __________ Informacia od NOD32 1.977 (20050120) __________
>
> Tato sprava bola preverena antivirusovym systemom NOD32.
> http://www.eset.sk
>
>
>
>
> _______________________________________________
> fpc-pascal maillist - fpc-pascal at lists.freepascal.org
> http://lists.freepascal.org/mailman/listinfo/fpc-pascal
>
More information about the fpc-pascal
mailing list