Re: ?DUP

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From	Bernd Paysan <bernd.paysan@gmx.de>
Newsgroups	comp.lang.forth
Subject	Re: ?DUP
Date	Tue, 29 Oct 2013 20:00:09 +0100
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Albert van der Horst wrote:
> I'd hate to have special code just for ?DUP apart from dropping ?DUP
> if the argument is known to be non-zero.
> 
> Think about it this way:
>    - DUP? is a conditional, WHILE is a conditional.
>    - An optimisation is possible whenever two conditionals are known
>        to use the same condition.
> 
> That is probably much more worth the effort.

Yes, that should work.  GCC can combine two conditionals that either have 
the same or the opposite condition into one single branch, too.

So the definition of ?DUP is just

: ?dup ( n / 0 -- n n / 0 )  dup if dup then ;

and the control flow handling should figure out what to do.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/

Thread

Floating Point : To Stack or Not To Stack rickman <gnuarm@gmail.com> - 2013-10-14 16:18 -0400
  Re: Floating Point : To Stack or Not To Stack "Elizabeth D. Rather" <erather@forth.com> - 2013-10-14 10:34 -1000
    Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-14 15:41 -0500
    Re: Floating Point : To Stack or Not To Stack Paul Rubin <no.email@nospam.invalid> - 2013-10-14 20:32 -0700
      Re: Floating Point : To Stack or Not To Stack rickman <gnuarm@gmail.com> - 2013-10-15 17:14 -0400
    Re: Floating Point : To Stack or Not To Stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-15 16:22 +0000
  Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-14 15:42 -0500
    Re: Floating Point : To Stack or Not To Stack Hans Bezemer <the.beez.speaks@gmail.com> - 2013-10-16 11:16 +0200
  Re: Floating Point : To Stack or Not To Stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-15 16:09 +0000
  Re: Floating Point : To Stack or Not To Stack krishna.myneni@ccreweb.org - 2013-10-15 18:51 -0700
    Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-16 03:47 -0500
    Re: Floating Point : To Stack or Not To Stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-16 12:27 +0000
      Re: Floating Point : To Stack or Not To Stack rickman <gnuarm@gmail.com> - 2013-10-25 14:20 -0400
        Re: Floating Point : To Stack or Not To Stack Paul Rubin <no.email@nospam.invalid> - 2013-10-25 12:08 -0700
          Re: Floating Point : To Stack or Not To Stack rickman <gnuarm@gmail.com> - 2013-10-26 02:34 -0400
            Re: Floating Point : To Stack or Not To Stack Paul Rubin <no.email@nospam.invalid> - 2013-10-26 00:13 -0700
              Re: Floating Point : To Stack or Not To Stack "Elizabeth D. Rather" <erather@forth.com> - 2013-10-25 21:49 -1000
                Re: Floating Point : To Stack or Not To Stack Paul Rubin <no.email@nospam.invalid> - 2013-10-26 01:26 -0700
                Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-26 05:45 -0500
                Re: Floating Point : To Stack or Not To Stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-26 13:48 +0000
                Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-26 14:28 -0500
                Re: Floating Point : To Stack or Not To Stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-27 12:41 +0000
                Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-27 08:31 -0500
                ?DUP (was: Floating Point : To Stack or Not To Stack) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-28 15:19 +0000
                Re: ?DUP Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-28 13:54 -0500
                Re: ?DUP "Rod Pemberton" <dont_use_email@xnohavenotit.cnm> - 2013-10-28 16:30 -0400
                Re: ?DUP "Elizabeth D. Rather" <erather@forth.com> - 2013-10-28 11:11 -1000
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-29 11:51 +0000
                Re: ?DUP Bernd Paysan <bernd.paysan@gmx.de> - 2013-10-29 16:48 +0100
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-29 16:10 +0000
                Re: ?DUP albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-29 16:24 +0000
                Re: ?DUP Bernd Paysan <bernd.paysan@gmx.de> - 2013-10-29 20:00 +0100
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-30 07:44 +0000
                Re: ?DUP Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-29 16:29 -0500
                Re: ?DUP "Rod Pemberton" <dont_use_email@xnohavenotit.cnm> - 2013-10-29 18:58 -0400
                Re: ?DUP Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-30 03:15 -0500
                Re: ?DUP albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-30 01:14 +0000
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-30 08:22 +0000
                Re: ?DUP "Rod Pemberton" <dont_use_email@xnohavenotit.cnm> - 2013-10-30 08:03 -0400
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-30 12:24 +0000
                Re: ?DUP Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-30 12:44 -0500
                Re: ?DUP "Alex McDonald" <blog@rivadpm.com> - 2013-10-30 22:43 +0000
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-31 12:09 +0000
                Re: ?DUP Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-31 12:23 -0500
                Re: ?DUP (was: Floating Point : To Stack or Not To Stack) "Rod Pemberton" <dont_use_email@xnohavenotit.cnm> - 2013-10-28 16:30 -0400
                Re: ?DUP "Elizabeth D. Rather" <erather@forth.com> - 2013-10-28 11:16 -1000
                Re: ?DUP Bernd Paysan <bernd.paysan@gmx.de> - 2013-10-29 01:58 +0100
                Re: ?DUP Stefan Mauerhofer <smauerhofer@androsoft.ch> - 2013-10-28 18:41 -0700
                Re: ?DUP Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-29 04:37 -0500
                Re: ?DUP m.a.m.hendrix@tue.nl - 2013-10-29 04:27 -0700
                Re: ?DUP anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-29 12:51 +0000
              Re: Floating Point : To Stack or Not To Stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-26 09:45 +0000
                Re: Floating Point : To Stack or Not To Stack albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-26 11:30 +0000
                Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-26 08:05 -0500
                Re: Floating Point : To Stack or Not To Stack mhx@iae.nl - 2013-10-26 06:09 -0700
                Re: Floating Point : To Stack or Not To Stack "Rod Pemberton" <dont_use_email@nohavenotit.com> - 2013-10-27 03:01 -0400
                Re: Floating Point : To Stack or Not To Stack "Elizabeth D. Rather" <erather@forth.com> - 2013-10-26 22:23 -1000
            Re: Floating Point : To Stack or Not To Stack albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-26 09:39 +0000
              Re: Floating Point : To Stack or Not To Stack albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-26 09:44 +0000
  Re: Floating Point : To Stack or Not To Stack "Ed" <invalid@invalid.com> - 2013-10-18 14:09 +1000
    Re: Floating Point : To Stack or Not To Stack "Elizabeth D. Rather" <erather@forth.com> - 2013-10-17 21:21 -1000
      Re: Floating Point : To Stack or Not To Stack "Ed" <invalid@invalid.com> - 2013-10-19 12:14 +1000
        Re: Floating Point : To Stack or Not To Stack "Elizabeth D. Rather" <erather@forth.com> - 2013-10-18 17:17 -1000
          Re: Floating Point : To Stack or Not To Stack Paul Rubin <no.email@nospam.invalid> - 2013-10-19 02:58 -0700
          Re: Floating Point : To Stack or Not To Stack "Ed" <invalid@invalid.com> - 2013-10-27 22:33 +1100
            Re: Floating Point : To Stack or Not To Stack mhx@iae.nl - 2013-10-27 06:21 -0700
              Re: Floating Point : To Stack or Not To Stack "Ed" <invalid@invalid.com> - 2013-10-29 22:40 +1100
            Re: Floating Point : To Stack or Not To Stack Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-10-27 08:23 -0500
  Re: Floating Point : To Stack or Not To Stack Stefan Mauerhofer <smauerhofer@androsoft.ch> - 2013-10-28 18:38 -0700

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