From: buers AT gmx DOT de (Dieter Buerssner)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: inline trouble
Date: 3 Feb 2000 02:55:52 GMT
Lines: 54
Message-ID: <87aqnn$3i1ll$1@fu-berlin.de>
References: <86i0tf$jnf$1 AT inf6serv DOT rug DOT ac DOT be> <86i2ub$jn8$1 AT nets3 DOT rz DOT RWTH-Aachen DOT DE> <86pm0u$325jc$1 AT fu-berlin DOT de> <879ri7$a04$1 AT nets3 DOT rz DOT RWTH-Aachen DOT DE>
NNTP-Posting-Host: u-235.karlsruhe.ipdial.viaginterkom.de (62.180.10.235)
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Trace: fu-berlin.de 949546552 3737269 62.180.10.235 (16 [17104])
X-Posting-Agent: Hamster/1.3.8.0
User-Agent: Xnews/2.11.08
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

broeker AT acp3bf DOT physik DOT rwth-aachen DOT de (Hans-Bernhard Broeker) wrote in 
<879ri7$a04$1 AT nets3 DOT rz DOT RWTH-Aachen DOT DE>:

>According to the explanation on the GCC web pages, the old method that
>tolerated this was simply too broken to let it live. It could confuse
>the optimizer into producing incorrect code, for some rare, but
>existing cases. They claim they had no choice but to break backwards
>compatibility, once and for all.

Yes, this really seems to be their claim. And I know, this also is
getting off topic here. Anyway, before I am going to write to the
gcc maintainers, I might hear some comments from this forum about
my suggestion.

My naive algorithom to solve the dilemma would be: for any input in an
asm construct, that is not on the output list, but is in the clobbered
list, allocate a new variable, assign the input to that new
variable and treat the input as if it was refering to that new variable.

I.e.: 

/* This worked with older gcc versions, and from my understanding
this was also documented as working */
type someval;
asm(
    /* Use somereg, and modify somereg */
    : /* output is not interesting in this example */ 
    : ("somereg"), someval 
    : (somereg) /* yes, somereg will be modified */
   );

translate this to

/* This works with gcc 2.95 */
type someval, tempval;
tempval = someval;
asm(
    /* Use somereg, and modify somereg */
    : ("=somereg"), "tempval" 
    : ("0"), "someval"
    /* no clobbered registers needed here */
   )
  
This "translation", should be easy to code. But I must have overlooked
something, otherwise this incompatible change in gcc behaviour would 
not make any sense. 

[I aske for an URL, that discusses this issue]
>http://gcc.gnu.org/fom_serv/cache/23.html

Thank you.

Regards
Dieter