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From: umueller@iiic.ethz.ch (Urban Dominik Mueller)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Manx 5.0d bug (-sr optimization error)
Summary: Check your Manx 5.0d version
Keywords: manx bug
Message-ID: <25118@neptune.inf.ethz.ch>
Date: 16 Feb 91 01:28:21 GMT
References: <7536@jhunix.HCF.JHU.EDU>
Sender: news@neptune.inf.ethz.ch
Reply-To: umueller@iiic.ethz.ch (Urban Mueller)
Followup-To: comp.sys.amiga.programmer
Organization: Departement Informatik, ETH, Zurich
Lines: 56

Recently,  a  Manx  5.0d  bug  report  was  posted on this net.  Before I
explain what happened, a short summary:
 
==> Make sure your Manx 5.0d compiler 'cc' is dated Sep 28 <==
    ( The version of 5.0d dated Sep 20 has a *nasty* bug )
 
The  rest  is  only  for  the interested.  What happens is the following:
Whenever  the destination an addition with a constant in it is an address
register  (this is why the mentioned bug only occured when -sr was turned
on),  Manx  tries  the  following  trick (-sr always set, but it can also
happen when it's not set):
 
Source code              Correct assembler code 5.0d (both versions)
-----------------------+--------------------------------------------
main()                 | move.l  d2,a0    ; i moved to a0
{                      | add.l d2,a0      ; i added to a0
    int i;             | pea   99(a0)     ; a0 + 99 pushed to stack
                       | jsr   _func      ; function call
    func( i+i+99 );    | add.w 4,sp       ; argument popping
}                      |
 
So  far,  so  good.  But when when one part of the addition is a pointer,
this happens with Manx 5.0d Sep 20:
 
Source code              Buggy assembler code by 5.0d Sep 20
-----------------------+------------------------------------
main()                 | move.l  d2,a0    ; i moved to a0
{                      | add.l a2,a0      ; p added to a0
    char *p;           | move.l  a0,-(sp) ; result pushed, but 99 forgotten
    int i;             | jsr   _func
                       | add.w 4,sp
    func( p+i+99 );    |
}
 
The 5.0d version dated Sep 28 does a nice job again (by just forgetting
about that 'pea' trick in that special case):
 
Same source code         Correct assembler code by 5.0d Sep 28
-----------------------+--------------------------------------
main()                 | move.l  d2,a0    ; i moved to a0
{                      | add.l a2,a0      ; p added to a0
    char *p;           | add.l 99,a0      ; 99 added to a0
    int i;             | move.l  a0,-(sp) ; a0 pushed
                       | jsr   _func
    func( p+i+99 );    | add.w 4,sp
}                      |
 
Hope this helped some people. IMHO it's up to Manx to tell you bugs like
this one. There are many people who can't call their BBS. At least I must
say that their update service is good, I got that special update for free
(hadn't even got to pay any postage).
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