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SEE (was: Umm...help?)

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"Elizabeth D. Rather" <erather@forth.com> writes:
>On 5/5/14 1:06 AM, Bernd Paysan wrote:
>> Elizabeth D. Rather wrote:
>>> It's harder than you might think. There are different sequences of
>>> high-level words that can compile the same few machine instructions, and
>>> how would you know whence they came?
>>
>> Search and display the most likely result.  SEE in bigForth is not always
>> 100% accurate, either.  Example: If you have DUP +, you can optimize that to
>> 2*.  A SEE that reports 2* would be fine for me.  Or when you do constant
>> folding, just display the results (e.g. 1 2 + would result in 3).
>>
>> How easy that is depends on how many optimizations you do.
>
>We do a lot more than that.

Is there a paper on it?  The last I heard about SwiftForth compilation
technique is that it combines sequences of primitives into optimized
primitives.  That is relatively straightforward to decompile, even if
you get synonymous code sometimes.

>If you want to see source, why not see it? Actual source is surely more 
>useful than an attempted reconstruction, which is almost certainly flawed.

Decompiled code (to the Forth level) is useful for seeing whether,
e.g., macros worked as intended.

And with enough effort, it is certainly not flawed.  The question is
whether the benefit justifies the effort.  For SwiftForth customers,
apparently not.  For gforth-fast other things are also higher on the
to-do list.

>The Forth200x definition of SEE is pretty opaque, IMO: "Display a 
>human-readable representation of the named word’s definition. The source
>of the representation (object-code decompilation, source block, etc.) 
>and the particular form of the display is implementation defined."
>
>It would be much more useful if it clarified whether it shows what has 
>been compiled (which to me is most useful) vs. an attempted reconstruction.

Your proposal on that will be welcome.  BTW, IIRC this wording came
unchanged from Forth-94.

In Gforth we have a number of code inspection words:

SEE tries to reconstruct something close to source.

SIMPLE-SEE tries to reconstruct the primitives and their arguments.

SEE-CODE is like SIMPLE-SEE, but shows the native code for the
  primitives that has been copied into dynamic superinstructions.

Sure, one might rename SEE into SEE-FORTH and SEE-CODE into SEE, but
does it really matter?  Portable programs don't depend on it, and what
the programmers want depends on the occasion.

Here's an example of input and output (for a somewhat extreme example):

: foo ." hello" ;  ok

see foo          
: foo  
  .\" hello" ; ok

simple-see foo   
$F7255F10 branch
$F7255F14 <-148545760> 
$F7255F18 <1819043176> 
$F7255F1C <538976367> 
$F7255F20 lit
$F7255F24 <-148545768> 
$F7255F28 lit
$F7255F2C <5> 
$F7255F30 lit-perform
$F7255F34 <type> 
$F7255F38 ;s ok

see-code foo     
$F7255F10 branch
$F7255F14 <-148545760> 
$F7255F18 <1819043176> 
$F7255F1C <538976367> 
( $F7213306 )  mov     dword ptr 806256C , ebx  \ $89 $1D $6C $25 $6 $8 
( $F721330C )  mov     ebx , dword ptr [ebx]  \ $8B $1B 
( $F721330E )  add     ebx , # 4  \ $83 $C3 $4 
( $F7213311 )  mov     eax , dword ptr FC [ebx]  \ $8B $43 $FC 
( $F7213314 )  jmp     eax  \ $FF $E0 
$F7255F20 lit
$F7255F24 <-148545768> 
( $F7213316 )  mov     dword ptr 806256C , ebx  \ $89 $1D $6C $25 $6 $8 
( $F721331C )  mov     eax , dword ptr [ebx]  \ $8B $3 
( $F721331E )  add     ebx , # 4  \ $83 $C3 $4 
( $F7213321 )  add     esi , # -4  \ $83 $C6 $FC 
( $F7213324 )  add     ebx , # 4  \ $83 $C3 $4 
( $F7213327 )  mov     dword ptr [esi] , eax  \ $89 $6 
$F7255F28 lit
$F7255F2C <5> 
( $F7213329 )  mov     dword ptr 806256C , ebx  \ $89 $1D $6C $25 $6 $8 
( $F721332F )  mov     eax , dword ptr [ebx]  \ $8B $3 
( $F7213331 )  add     ebx , # 4  \ $83 $C3 $4 
( $F7213334 )  add     esi , # -4  \ $83 $C6 $FC 
( $F7213337 )  add     ebx , # 4  \ $83 $C3 $4 
( $F721333A )  mov     dword ptr [esi] , eax  \ $89 $6 
$F7255F30 lit-perform
$F7255F34 <type> 
( $F721333C )  mov     dword ptr 806256C , ebx  \ $89 $1D $6C $25 $6 $8 
( $F7213342 )  mov     eax , dword ptr [ebx]  \ $8B $3 
( $F7213344 )  add     ebx , # 4  \ $83 $C3 $4 
( $F7213347 )  mov     edx , dword ptr [eax]  \ $8B $10 
( $F7213349 )  mov     eax , dword ptr [edx]  \ $8B $2 
( $F721334B )  xchg     eax, eax  \ $90 
( $F721334C )  jmp     eax  \ $FF $E0 
( $F721334E )  d16: \ $66 
( $F721334F )  xchg     eax, ax  \ $90 
$F7255F38 ;s ok

- 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 2014: http://www.euroforth.org/ef14/

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Umm...help? David J <skamolex@gmail.com> - 2014-04-29 18:46 -0700
  Re: Umm...help? Julian Fondren <ayrnieu@gmail.com> - 2014-04-29 19:32 -0700
    Re: Umm...help? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-04-30 10:21 +0000
      Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-01 15:39 -0700
        Re: Umm...help? Coos Haak <chforth@hccnet.nl> - 2014-05-02 10:13 +0200
        Re: Umm...help? Mark Wills <markwills1970@gmail.com> - 2014-05-02 02:06 -0700
          Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-08 16:04 -0700
          Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-08 16:10 -0700
            Re: Umm...help? rickman <gnuarm@gmail.com> - 2014-05-09 14:18 -0400
              Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-19 14:20 -0700
  Re: Umm...help? "Elizabeth D. Rather" <erather@forth.com> - 2014-04-29 16:51 -1000
    Re: Umm...help? David J <skamolex@gmail.com> - 2014-04-29 20:03 -0700
      Re: Umm...help? "Elizabeth D. Rather" <erather@forth.com> - 2014-04-29 17:41 -1000
        Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-01 15:29 -0700
  Re: Umm...help? David J <skamolex@gmail.com> - 2014-04-29 19:51 -0700
  Re: Umm...help? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-04-30 08:49 +0000
    Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-01 15:32 -0700
      Re: Umm...help? stephenXXX@mpeforth.com (Stephen Pelc) - 2014-05-02 09:03 +0000
      Re: Umm...help? Torfinn Ingolfsen <tingo@home.no> - 2014-05-02 13:33 +0200
        Re: Umm...help? rickman <gnuarm@gmail.com> - 2014-05-04 15:11 -0400
          Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-08 16:15 -0700
        Re: Umm...help? David J <skamolex@gmail.com> - 2014-05-08 16:11 -0700
  Re: Umm...help? David Hume <David.Hume@example.com> - 2014-05-04 20:35 +0100
    Re: Umm...help? "Elizabeth D. Rather" <erather@forth.com> - 2014-05-04 12:47 -1000
      Re: Umm...help? Bernd Paysan <bernd.paysan@gmx.de> - 2014-05-05 01:59 +0200
        Re: Umm...help? "Elizabeth D. Rather" <erather@forth.com> - 2014-05-04 15:05 -1000
          Re: Umm...help? Bernd Paysan <bernd.paysan@gmx.de> - 2014-05-05 13:06 +0200
            Re: Umm...help? "Elizabeth D. Rather" <erather@forth.com> - 2014-05-05 08:07 -1000
              SEE (was: Umm...help?) anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-06 16:30 +0000
                Re: SEE "Elizabeth D. Rather" <erather@forth.com> - 2014-05-06 09:24 -1000
                Re: SEE Bernd Paysan <bernd.paysan@gmx.de> - 2014-05-06 21:53 +0200
                no more ASS cracks? (was Re: SEE) all2001@spambog.com (Wolfgang Allinger) - 2014-05-06 19:48 -0400
                Re: SEE anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2014-05-10 17:11 +0000
            Re: Umm...help? Assad Ebrahim <assad.ebrahim@alum.swarthmore.edu> - 2014-05-10 15:47 +0100
              Re: Umm...help? Assad Ebrahim <assad.ebrahim@alum.swarthmore.edu> - 2014-05-10 16:06 +0100

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