Return-address manipulation (was: Would ?EXIT ...)

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Return-address manipulation (was: Would ?EXIT ...)
Date	2017-05-15 08:47 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2017May15.104722@mips.complang.tuwien.ac.at> (permalink)
References	<13e6c647-fd9a-4d77-89e3-2cc977f3bd5b@googlegroups.com> <f6c15651-b5bf-4b4c-9493-f738bfb75b67@googlegroups.com> <cbfcad08-8820-4161-af67-fad48b93e078@googlegroups.com>

Show all headers | View raw

lehs <skydda.barnen@gmail.com> writes:
>In the ever expanding Forth the return addresses could defined to be on the=
> return stack. If there is no need for a hardware stack there is no need fo=
>r hidden return addresses.

There are other reasons, too; they were not as prominent at the time
of Forth-94 standardization, but now they are:

* Forth systems use tail-call elimination and inlining; both
  optimizations mean that the return address that a traditional system
  would put on the return stack is not there.

* Locals need to be cleaned up if present.

Some people propose putting in a lot of effort to make return-address
manipulation work in the presence of these issues.

In particular, Bernd Paysan proposed to deal with tail-call
elimination and inlining by doing data-flow analysis of the return
addresses and then using that information to implement the control
flow intended by the programmer.

One problem with that is that there are cases where you do not get
precise information out of the data-flow analysis (e.g., in connection
with EXECUTE; you can solve some of these cases with more data-flow
analysis, but not all).

The other issue is that we end up with a lot of complex mechanism to
preserve the behaviour of an implementation model that our compilers
no longer follow.  Is this the Forth way?

Or should we rather use programming techniques that fit our
implementation techniques better, e.g., THROW for multi-level exits,
and quotations for some other uses of return-address manipulation?
Or, alternatively, turn off tail-call elimination and inlining, and
take a significant performance hit, in order to continue to use
return-address manipulation?

For dealing with locals, Bernd Paysan proposed UNLOCAL (similar to
UNLOOP), so you would write

: foo {: ... :} 
   ... ?do
   ... if
      unloop unlocal r> drop unloop unlocal exit then
   ... loop
   ... ;

: bar {: ... :}
   ... ?do
      ... foo ... loop
   ... ;

in order to perform a two-level exit from FOO to the caller of BAR.

We implemented UNLOCAL in connection with our attempt to make 

['] exit execute

work
<http://www.complang.tuwien.ac.at/anton/euroforth/ef15/papers/ertl.pdf>

Despite revising the implementation quite a lot, there remained a
mismatch between the implementation and the programming model that led
to complications in the implementation and wrong behaviour in corner
cases.  Fixing that would have required even more implementation
complexity, or a slower implementation even for code that does not use
return-address manipulation.  Eventually (after the paper linked above
was published) Bernd Paysan himself ripped much of the complications
out again.  ['] EXIT EXECUTE reverted to not performing the execution
semantics of EXIT, and UNLOCAL did not work properly in many cases, so
I then ripped that out.

Conclusion: supporting return-address manipulation constrains you a
lot in the rest of the Forth system, in particular when it comes to
performance-enhancing techniques.  Is this feature worth this price,
or are we better off using alternative programming techniques that do
not put as heavy constraints on the system?

- 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 2017: http://www.euroforth.org/ef17/

Thread

Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-10 08:21 -0700
  Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-10 16:39 +0100
    Re: Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-10 08:46 -0700
    Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-10 16:04 +0000
    Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-11 04:22 -0500
      Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-11 10:35 +0100
        Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-11 05:08 -0500
          Re: Would ?EXIT work in all ANS-Forth systems? Julian Fondren <julian.fondren@gmail.com> - 2017-05-11 03:51 -0700
            Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-11 07:02 -0500
            Re: Would ?EXIT work in all ANS-Forth systems? rickman <gnuarm@gmail.com> - 2017-05-13 11:55 -0400
        Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 09:32 -0500
          Re: Would ?EXIT work in all ANS-Forth systems? Cecil Bayona <cbayona@cbayona.com> - 2017-05-15 11:56 -0500
            Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 12:20 -0500
              Re: Would ?EXIT work in all ANS-Forth systems? Cecil Bayona <cbayona@cbayona.com> - 2017-05-15 12:31 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 15:50 -0500
  Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-10 16:49 +0000
    Re: Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-10 12:04 -0700
  Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-11 01:08 -0700
    Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-11 09:13 +0100
      Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-11 01:48 -0700
        Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-11 09:59 +0100
  Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-12 14:20 +0000
    Re: Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-12 17:01 -0700
      Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-12 22:18 -0700
        Re: Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-13 03:09 -0700
        Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-13 21:07 +1000
        Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-13 14:20 +0000
          Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-14 11:59 +1000
            Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-14 09:21 -0500
              Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-14 10:43 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-14 18:35 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Lars Brinkhoff <lars.spam@nocrew.org> - 2017-05-15 07:11 +0200
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 04:35 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Julian Fondren <julian.fondren@gmail.com> - 2017-05-15 03:54 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? mhx@iae.nl - 2017-05-15 04:07 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 06:23 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Julian Fondren <julian.fondren@gmail.com> - 2017-05-15 06:53 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 09:18 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-14 22:44 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-15 04:16 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-16 02:00 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-16 02:43 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-16 05:08 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-16 12:11 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? NN <november.nihal@gmail.com> - 2017-05-17 05:24 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-17 07:35 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-17 14:59 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-17 13:30 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-15 11:09 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-14 21:17 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Lars Brinkhoff <lars.spam@nocrew.org> - 2017-05-15 07:13 +0200
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-16 10:24 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-16 01:13 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-16 12:26 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-17 01:58 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-17 16:45 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? obi65537@gmail.com - 2017-05-25 12:04 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-26 10:02 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-26 07:46 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-26 13:53 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-26 10:14 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Cecil Bayona <cbayona@cbayona.com> - 2017-05-26 10:16 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-26 08:59 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Cecil Bayona <cbayona@cbayona.com> - 2017-05-26 11:27 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-26 10:19 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Lars Brinkhoff <lars.spam@nocrew.org> - 2017-05-26 20:20 +0200
                Re: Would ?EXIT work in all ANS-Forth systems? Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-26 21:38 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? Cecil Bayona <cbayona@cbayona.com> - 2017-05-26 14:06 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-26 22:00 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-26 17:06 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? hum9 <obi65537@gmail.com> - 2017-05-27 01:15 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-28 14:17 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-27 17:40 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-24 15:46 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <obi65537@gmail.com> - 2017-05-25 11:51 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <obi65537@gmail.com> - 2017-05-25 20:38 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? obi65537@gmail.com - 2017-05-25 22:03 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? obi65537@gmail.com - 2017-05-25 22:09 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-26 21:56 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-26 13:30 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-27 15:04 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-27 17:33 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-29 12:17 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? hum9 <obi65537@gmail.com> - 2017-05-27 00:33 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-27 14:53 +1000
                READ-FILE over-specified? "HAA" <someone@microsoft.com> - 2017-05-27 21:28 +1000
                Re: READ-FILE over-specified? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-27 13:11 +0000
                Re: READ-FILE over-specified? "HAA" <someone@microsoft.com> - 2017-05-29 13:47 +1000
                Re: READ-FILE over-specified? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-28 09:44 +0200
                Re: READ-FILE over-specified? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-28 13:41 +0000
                Re: READ-FILE over-specified? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-28 19:59 +0200
                Re: Would ?EXIT work in all ANS-Forth systems? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2017-05-16 09:42 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-16 09:53 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-16 04:53 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-16 12:32 +0200
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-16 12:35 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-16 10:48 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-16 18:23 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-17 04:33 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-17 12:29 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-16 10:28 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-16 10:43 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-16 16:34 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-16 12:41 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-17 16:14 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-18 03:05 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-18 16:33 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-18 12:43 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-18 04:01 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-18 15:41 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-18 11:58 -0500
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-18 22:57 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? "HAA" <someone@microsoft.com> - 2017-05-17 00:32 +1000
                Re: Would ?EXIT work in all ANS-Forth systems? Alex <alex@rivadpm.com> - 2017-05-16 15:53 +0100
                Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-15 05:29 +0000
                Re: Would ?EXIT work in all ANS-Forth systems? humptydumpty <ouatubi@gmail.com> - 2017-05-14 23:00 -0700
                Re: Would ?EXIT work in all ANS-Forth systems? rickman <gnuarm@gmail.com> - 2017-05-17 12:27 -0400
            Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-15 09:16 +0000
            Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-15 09:55 +0000
        Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-13 14:25 +0000
          Re: Would ?EXIT work in all ANS-Forth systems? Julian Fondren <julian.fondren@gmail.com> - 2017-05-13 07:49 -0700
            Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-15 09:59 +0000
            Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-15 12:22 +0000
      Re: Would ?EXIT work in all ANS-Forth systems? "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-05-13 14:19 +0000
  Re: Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-14 23:23 -0700
    Re: Would ?EXIT work in all ANS-Forth systems? Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-15 00:10 -0700
      Re: Would ?EXIT work in all ANS-Forth systems? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-15 09:35 +0000
    Re: Would ?EXIT work in all ANS-Forth systems? lehs <skydda.barnen@gmail.com> - 2017-05-15 00:54 -0700
      Return-address manipulation (was: Would ?EXIT ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-15 08:47 +0000
        Re: Return-address manipulation (was: Would ?EXIT ...) stephen@mpeforth.com (Stephen Pelc) - 2017-05-15 11:53 +0000
          Re: Return-address manipulation (was: Would ?EXIT ...) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-05-16 13:03 +0000
            Re: Return-address manipulation (was: Would ?EXIT ...) Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-16 07:06 -0700
              Re: Return-address manipulation (was: Would ?EXIT ...) Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-16 07:14 -0700
    Re: Would ?EXIT work in all ANS-Forth systems? "Elizabeth D. Rather" <erather@forth.com> - 2017-05-14 21:58 -1000
      Re: Would ?EXIT work in all ANS-Forth systems? stephen@mpeforth.com (Stephen Pelc) - 2017-05-15 11:23 +0000

csiph-web