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Re: What about code blocks (not Forth blocks)?

From anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups comp.lang.forth
Subject Re: What about code blocks (not Forth blocks)?
Date 2013-12-29 15:25 +0000
Organization Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID <2013Dec29.162528@mips.complang.tuwien.ac.at> (permalink)
References (1 earlier) <2013Dec19.165803@mips.complang.tuwien.ac.at> <7xfvpoaf8j.fsf@ruckus.brouhaha.com> <l8vjmk$l6a$1@dont-email.me> <7xfvpod1j3.fsf@ruckus.brouhaha.com> <gu2dnXofQshAgCLPnZ2dnUVZ_rednZ2d@supernews.com>

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Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>Paul Rubin <no.email@nospam.invalid> wrote:
>> "Alex McDonald" <blog@rivadpm.com> writes:
>>> : [:  postpone ahead  here ; immediate
>> 
>> Hmm, does that mean the quotation is compiled inline with the rest of
>> the function, and branched around during execution?  I guess that's
>> simple enough, though it adds a little overhead.
>
>On 32-bit x86 native code, it may even be the fastest way to do it: a
>CALL insn pushes the start address of the quotation onto the system
>stack.  If the system stack is the data stack, you're done; if not,
>you have to do a push.

That may be a relatively short way to do it (but doing a PUSH imm32,
or MOV reg32, imm32 is just as short), but it is everything but fast.
It poisons the CPU-internal return stack (not the Forth return stack)
with spurious return addresses, so the return branch prediction will
fail (resulting in a misprediction penalty of around 10 cycles on
current CPUs) whenever returning from a word that contains a quotation
and all words that call such words, directly or indirectly.  In
contrast, the branch around the quotation will be perfectly predicted
(it's an unconditional absolute branch, after all) and therefore quite
cheap.

Putting the code for the quotation elsewhere would remove the
branch-around overhead (both size and space), and is perfectly
standard.  However, the overhead is small enough and the frequency of
quotations is also small enough that other things probably deserve
more attention than optimizing this.

By contrast, code should be put in a different place than writable
data.  The overheads caused by failing to do that are often huge.
While the system implementors are at it, they might consider adding
multiple code spaces to deal with quotations without introducing extra
branches.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2013: http://www.euroforth.org/ef13/

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Thread

What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-17 23:56 -0800
  Re: What about code blocks (not Forth blocks)? mhx@iae.nl - 2013-12-18 01:14 -0800
    Re: What about code blocks (not Forth blocks)? Mark Wills <markrobertwills@yahoo.co.uk> - 2013-12-18 01:34 -0800
    Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 02:33 -0800
      Re: What about code blocks (not Forth blocks)? Coos Haak <chforth@hccnet.nl> - 2013-12-18 14:36 +0100
        Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 06:24 -0800
          Re: What about code blocks (not Forth blocks)? Coos Haak <chforth@hccnet.nl> - 2013-12-19 02:54 +0100
            Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 22:12 -0800
      Re: What about code blocks (not Forth blocks)? mhx@iae.nl - 2013-12-18 05:43 -0800
  Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-12-18 11:21 +0000
    Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 04:31 -0800
      Re: What about code blocks (not Forth blocks)? Ilya Tarasov <ilya74.tarasov@gmail.com> - 2013-12-18 04:49 -0800
        Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 05:12 -0800
  Re: What about code blocks (not Forth blocks)? "Elizabeth D. Rather" <erather@forth.com> - 2013-12-18 08:26 -1000
    Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-18 11:03 -0800
      Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 11:21 -0800
    Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 11:19 -0800
      Re: What about code blocks (not Forth blocks)? "Elizabeth D. Rather" <erather@forth.com> - 2013-12-18 10:08 -1000
        Re: What about code blocks (not Forth blocks)? Bernd Paysan <bernd.paysan@gmx.de> - 2013-12-18 21:58 +0100
          Re: What about code blocks (not Forth blocks)? "Ed" <invalid@invalid.com> - 2013-12-19 14:15 +1100
            Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-19 13:32 +0000
              Re: What about code blocks (not Forth blocks)? "Ed" <invalid@invalid.com> - 2013-12-20 21:07 +1100
                Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-20 12:35 +0000
                Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-20 13:02 +0000
                Re: What about code blocks (not Forth blocks)? "Ed" <invalid@invalid.com> - 2013-12-22 14:19 +1100
                Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-22 10:15 +0000
                Re: What about code blocks (not Forth blocks)? "Ed" <invalid@invalid.com> - 2013-12-24 12:30 +1100
                Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-12-24 16:48 +0000
                Re: What about code blocks (not Forth blocks)? "Ed" <invalid@invalid.com> - 2013-12-28 11:08 +1100
                Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-12-28 11:40 +0000
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-26 18:03 +0000
                Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-26 10:34 -0800
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-27 15:53 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-28 17:26 +0000
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-28 17:53 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-28 18:21 +0000
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-29 14:49 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-29 20:45 +0000
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-30 17:08 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-30 20:00 +0000
                Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-12-28 18:04 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-28 18:47 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-28 19:12 +0000
                Re: What about code blocks (not Forth blocks)? "Ed" <invalid@invalid.com> - 2013-12-28 11:09 +1100
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-28 13:45 +0000
          Re: What about code blocks (not Forth blocks)? Elizabeth D Rather <erather@forth.com> - 2013-12-18 19:04 -1000
            Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-19 09:25 +0000
            Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-19 05:00 -0800
        Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-18 23:41 -0800
        Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-19 01:00 -0800
        Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-19 02:47 -0800
          Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-19 11:23 +0000
            Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-19 03:52 -0800
  Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-19 15:58 +0000
    Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-19 10:05 -0800
      Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-19 20:07 +0000
        Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-19 12:33 -0800
          Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-19 20:33 +0000
            Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-12-19 20:52 +0000
            Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-19 18:52 -0800
          Re: What about code blocks (not Forth blocks)? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-12-28 12:52 -0600
            Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-28 11:47 -0800
              Re: What about code blocks (not Forth blocks)? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-12-29 07:39 -0600
                Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-29 08:11 -0800
            Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-29 15:25 +0000
              Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-29 08:15 -0800
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-29 16:03 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-29 20:54 +0000
                Re: What about code blocks (not Forth blocks)? mhx@iae.nl - 2013-12-29 13:38 -0800
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-30 17:04 +0000
                Re: What about code blocks (not Forth blocks)? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2013-12-30 20:05 +0000
                Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2013-12-30 16:49 -0800
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-01-02 17:27 +0000
              Re: What about code blocks (not Forth blocks)? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-12-29 16:40 -0600
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-30 16:51 +0000
                Re: What about code blocks (not Forth blocks)? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-12-30 11:15 -0600
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-30 17:37 +0000
                Re: What about code blocks (not Forth blocks)? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-12-30 12:07 -0600
        Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-20 13:50 +0000
      Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2013-12-19 21:49 -0800
        Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2013-12-20 08:56 +0000
          Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-04-03 19:13 -0700
        Re: What about code blocks (not Forth blocks)? "WJ" <w_a_x_man@yahoo.com> - 2014-03-11 05:35 +0000
          Re: What about code blocks (not Forth blocks)? Bernd Paysan <bernd.paysan@gmx.de> - 2014-03-11 12:59 +0100
            Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-03-11 23:44 -0700
              Re: What about code blocks (not Forth blocks)? Julian Fondren <ayrnieu@gmail.com> - 2014-03-12 11:48 -0700
                Re: What about code blocks (not Forth blocks)? Bernd Paysan <bernd.paysan@gmx.de> - 2014-03-12 20:21 +0100
                Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-03-12 23:35 -0700
                Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2014-03-14 14:25 +0000
                Re: What about code blocks (not Forth blocks)? Bernd Paysan <bernd.paysan@gmx.de> - 2014-03-14 16:36 +0100
                Re: What about code blocks (not Forth blocks)? mhx@iae.nl - 2014-03-14 11:27 -0700
                Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-03-16 17:38 -0700
                Re: What about code blocks (not Forth blocks)? "Rod Pemberton" <dont_use_email@xnothavet.cqm> - 2014-03-17 03:35 -0400
                Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2014-03-17 20:36 -0700
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-03-18 13:13 +0000
                Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-03-18 14:28 +0000
                Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2014-03-18 10:10 -0700
                Re: What about code blocks (not Forth blocks)? Paul Rubin <no.email@nospam.invalid> - 2014-03-25 12:54 -0700
                Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-03-25 23:09 -0700
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-03-26 13:49 +0000
                Re: What about code blocks (not Forth blocks)? Bernd Paysan <bernd.paysan@gmx.de> - 2014-03-26 22:07 +0100
                Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-03-20 22:11 -0700
                Re: What about code blocks (not Forth blocks)? hughaguilar96@yahoo.com - 2014-03-28 22:18 -0700
                Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2014-03-29 10:57 +0000
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-03-13 16:42 +0000
          Re: What about code blocks (not Forth blocks)? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-03-11 12:51 +0000
            Re: What about code blocks (not Forth blocks)? "Alex McDonald" <blog@rivadpm.com> - 2014-03-11 14:54 +0000
    Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-19 21:36 -0800
      Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-20 16:56 +0000
    Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-19 23:24 -0800
      Re: What about code blocks (not Forth blocks)? mhx@iae.nl - 2013-12-20 02:05 -0800
      Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-20 12:41 +0000
        Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-20 17:46 +0000
          Re: What about code blocks (not Forth blocks)? Alexander Skobelev <al.skobelev@gmail.com> - 2013-12-21 08:11 -0800
            Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-23 10:07 +0000
              Re: What about code blocks (not Forth blocks)? Bernd Paysan <bernd.paysan@gmx.de> - 2013-12-23 19:31 +0100
                Re: What about code blocks (not Forth blocks)? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-12-26 17:45 +0000

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