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Re: ?DUP

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On Wed, 30 Oct 2013 04:22:13 -0400, Anton Ertl  
<anton@mips.complang.tuwien.ac.at> wrote:
> Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>> Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:

>>> Not "optimizing" ROT would not simplify the compiler.
>>
>> Why not?  Surely if you don't recognize ROT, but simply code
>> it as a call to a definition, the optimizer is simpler.
>
> Even a definition of ROT as a colon definition would result in
> optimizing ROT.

Are you two talking about different things here?

ISTM, that Anton is discussing optimization down to the
assembly level for a Forth that compiles, but Andrew might
be discussing optimization which stops at the level of
low-level words, e.g., for a thread-code interpreted Forth.
In one case, everything is optimized, both high- and low-level
Forth words.  In the other, just the high-level words.

> And it's not really simpler than a more direct
> definition of ROT:
>
> Colon definition:
>
> : myrot >r swap r> swap ;
>
> A direct definition would look maybe like this:
>
> c: rot rot ; : rot rot ;
>

Interesting, but is there really a need for "c:" definition?

I.e., if you're just defining "rot" to be "rot", what's the
purpose of "c:" ?  Symbolic?

Anyway, how ROT is defined depends on what you have available.

If you have >R and SWAP , then ">R SWAP >R SWAP" works.

Of course, you could also implement ROT in assembly or C, etc
as a low-level word.

Or, you could use one of many other high-level definitions:

: ROT 2 ROLL ;
: ROT TUCK 2SWAP DROP ;
: ROT NUP 2SWAP DROP ;
: ROT >R SWAP >R 2R> ;
: ROT >R 2>R R> 2R> ;
etc...

E.g., ROT using one register A:
: ROT >R >R A! R> R> A@ ;
: ROT A! SWAP A@ SWAP ;

E.g., ROT using two registers A and B:
: ROT A! B! >R B@ A@ R> ;

If you have more precise stack control, other definitions
are possible, but likely longer sequences.

Of course, you really want to pick whatever is fastest,
or that which optimizes the best, not necessarily that
which is the shortest.  That could mean using operations
that you wouldn't normally choose.


Rod Pemberton

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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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