[M3commit] [M3devel] m3back using Target.Int in place of INTEGER a lot now

[Jay K]

Hm. Ok. TInt.Multiply allows aliasing but TWord.Multiply does not.

 

 

MODULE Main;
IMPORT RTIO, Target, TInt, TWord;

VAR a,b:Target.Int;
BEGIN
EVAL TInt.FromInt(1, BYTESIZE(INTEGER), a);
EVAL TInt.FromInt(1, BYTESIZE(INTEGER), b);
TWord.Multiply(a, b, a);
RTIO.PutText(TInt.ToText(a));
RTIO.Flush();
END Main.


 

prints 0.

 

The code in m3back:

 

 

PROCEDURE doindex_address (t: T; shift, size: INTEGER; neg: BOOLEAN) =
...

        (* Beware TWord.Multiply: x * 1 = 0 *)

        IF NOT TInt.Multiply(stop0.imm, tsize, stop0.imm) THEN
          t.Err("doindex_address: multiply overflowed");
        END;


 

 

 - Jay

 


From: hosking at cs.purdue.edu
Date: Wed, 20 Jan 2010 20:00:39 -0500
To: hosking at cs.purdue.edu
CC: m3devel at elegosoft.com; m3commit at elegosoft.com; jay.krell at cornell.edu
Subject: Re: [M3devel] [M3commit] m3back using Target.Int in place of INTEGER a lot now


Jay, I don't know what you are talking about there being a bug in TWord.Multiply.


This little program prints out 2, as would be expected:



MODULE Main;
IMPORT RTIO, TInt, TWord, Target;


VAR i := TInt.Two;
    j: Target.Int;
    buf: ARRAY[0..10] OF CHAR;
BEGIN
  TWord.Multiply (i, TInt.One, j);
  FOR k := 0 TO TInt.ToChars (i, buf) DO
    RTIO.PutChar(buf[k]);
  END;
  RTIO.PutChar('\n');
  RTIO.Flush();
END Main.




On 20 Jan 2010, at 18:59, Tony Hosking wrote:

Where's the bug in TWord.Multiply?
If there were a bug we would have seen it by now surely?




Antony Hosking | Associate Professor | Computer Science | Purdue University
305 N. University Street | West Lafayette | IN 47907 | USA
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On 20 Jan 2010, at 10:05, Jay K wrote:

This is fairly large and tedious. If anyone has the patience to look at every single line, please do. Thanks.
I did look through pretty much every single line in search of the one bug I saw working on it.
It turns out the bug was in TWord though. TWord.Multiply(x, 1) = 0.
Which broke INC, it was adding 0 instead 1.
You could see the bug in RTIO.PutString where it just kept outputing the first character.
So I use TInt.Multiply instead.
 
 - Jay
 


From: jay.krell at cornell.edu
To: jkrell at elego.de; m3commit at elegosoft.com
Date: Wed, 20 Jan 2010 15:02:27 +0000
Subject: Re: [M3commit] CVS Update: cm3

diff attached





 
> Date: Wed, 20 Jan 2010 16:01:32 +0000
> To: m3commit at elegosoft.com
> From: jkrell at elego.de
> Subject: [M3commit] CVS Update: cm3
> 
> CVSROOT: /usr/cvs
> Changes by: jkrell at birch. 10/01/20 16:01:32
> 
> Modified files:
> cm3/m3-sys/m3back/src/: Codex86.i3 Codex86.m3 M3x86.m3 
> M3x86Rep.i3 Stackx86.i3 Stackx86.m3 
> cm3/m3-sys/m3middle/src/: TInt.i3 TInt.m3 
> 
> Log message:
> convert much of m3back to use Target.Int instead of INTEGER
> This should at least allow it to propagate constant LONGINTs
> as well as perhaps otherwise help with implementing LONGINT,
> since the virtual stack is now of Target.Int instead of INTEGER
> 
> Beware that TWord.Multiply(x, 1) = 0, so I use TInt.Multiply instead
> 
> Also note that there's still a lot of "INTEGER" used.
> 


 		 	   		  
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